Substituted nucleosides, nucleotides and analogs thereof

2′-C-Methyl-4′-Fluorouridine 1

To a stirred suspension of 1-1 (20 g, 77.5 mmol), PPh 3 (30 g, 114.5 mmol), imidazole (10 g, 147 mmol) and pyridine (90 mL) in anhydrous THF (300 mL) was added a solution of 12 (25 g, 98.4 mmol) in THF (100 mL) dropwise at 0° C. The mixture was warmed to room temperature (R.T.) and stirred at R.T. for 10 h. The reaction was quenched by MeOH (100 mL). The solvent was removed, and the residue was re-dissolved in a mixture ethyl acetate (EA) and THF (2 L, 10:1). The organic phase was washed with saturated Na 2 S 2 O 3 aq., and the aqueous phase was extracted with a mixture of EA and THF (2 L, 10:1). The organic layer was combined and concentrated to give a residue, which was purified on a silica gel column (0-10% MeOH in DCM) to give 1-2 (22.5 g, 78.9%) as a white solid. 1 H NMR: (DMSO-d 6 , 400 MHz) δ 11.42 (s, 1H), 7.59 (d, J=8.4 Hz, 1H), 5.82 (s, 1H), 5.63 (d, J=8.0 Hz, 1H), 5.50 (s, 1H), 5.23 (s, 1H), 3.77-3.79 (m, 1H), 3.40-3.62 (m, 3H), 0.97 (s, 3H).

To a stirred solution of 1-2 (24.3 g, 66.03 mmol) in anhydrous MeOH (240 mL) was added NaOMe (10.69 g, 198.09 mmol) at R.T. under N 2 . The mixture was refluxed for 3 h. The solvent was removed, and the residue was re-dissolved in anhydrous pyridine (200 mL). To the mixture was added Ac 2 O (84.9 g, 833.3 mmol) at 0° C. The mixture was warmed to 60° C. and stirred for 10 h. The solvent was removed, and the residue was diluted with DCM, washed with saturated NaHCO 3 and brine. The organic layer was concentrated and purified on a silica gel column (10-50% EA in PE) to give 1-3 (15 g, 70.1%) as a white solid. 1 H NMR: (CDCl 3 , 400 MHz) δ 8.82 (s, 1H), 7.23 (d, J=2.0 Hz, 1H), 6.54 (s, 1H), 5.85 (s, 1H), 5.77 (dd, J=8.0, 2.0 Hz, 1H), 4.69 (d, J=2.4 Hz, 1H), 4.58 (d, J=2.8 Hz, 1H), 2.07 (d, J=5.2 Hz, 6H), 1.45 (s, 3H).

To an ice-cooled solution of 1-3 (15 g, 46.29 mmol) in anhydrous DCM (300 mL) was added AgF (29.39 g, 231.4 mmol). I 2 (23.51 g, 92.58 mmol) in anhydrous DCM (1.0 L) was added dropwise to the solution. The reaction mixture was stirred at R.T. for 5 h. The reaction was quenched with saturated Na 2 S 2 O 3 and NaHCO 3 , and extracted with DCM. The organic layer was separated, dried and evaporated to dryness. The residue was purified on a silica gel column (10-30% EA in PE) to give 1-4 (9.5 g, 43.6%) as a white solid. 1 H NMR: (Methanol-d4, 400 MHz) δ 7.52 (d, J=8.0 Hz, 1H), 6.21 (s, 1H), 5.80 (d, J=17.2 Hz, 1H), 5.73 (d, J=8.0 Hz, 1H), 3.58 (s, 1H), 3.54 (d, J=6.8 Hz, 1H), 2.17 (s, 3H), 2.09 (s, 3H), 1.58 (s, 3H).

To a solution of 1-4 (7.0 g, 14.89 mmol) in anhydrous DMF (400 mL) were added NaOBz (21.44 g, 148.9 mmol) and 15-crown-5 (32.75 g, 148.9 mmol). The reaction mixture was stirred at 130° C. for 6 h. The solvent was removed, diluted with EA and washed with water and brine. The organic layer was evaporated and purified on a silica gel column (10-30% EA in PE) to give 1-5 (2.8 g, 40.5%). 1 H NMR: (CDCl 3 , 400 MHz) δ 8.84 (s, 1H), 8.04-8.06 (m, 2H), 7.59 (t, J=7.2 Hz, 1H), 7.44-7.47 (m, 2H), 7.21-7.26 (m, 1H), 6.21 (s, 1H), 5.85 (d, J=18 Hz, 1H), 5.67 (d, J=8.0 Hz, 1H), 4.59-4.72 (m, 2H), 2.14 (s, 6H), 1.64 (d, J=6.0 Hz, 3H). ESI-MS: m/z 444.9 [M-F+H] + .

A mixture of 1-5 (4.0 g; 8.6 mmol) and liquid ammonia was kept overnight at R. T. in a high-pressure stainless-steel vessel. Ammonia was then evaporated, and the residue purified on silica (50 g column) with a CH 2 Cl 2 /MeOH solvent mixture (4-12% gradient) to yield compound 1 as a colorless foam (2.0 g; 84% yield). ESI-MS: m/z 275.1 [M−H] − .

Compound 2

To a solution of 1 (1.2 g; 4.3 mmol) in dioxane (30 mL) were added p-toluenesulphonic acid monohydrate (820 mg; 1 eq.) and trimethyl orthoformate (14 mL; 30 eq.). The mixture was stirred overnight at R.T. The mixture was then neutralized with methanolic ammonia and the solvent evaporated. Purification on silica gel column with CH 2 Cl 2 -MeOH solvent system (4-10% gradient) yielded 2-1 (1.18 g, 87%).

To an ice cold solution of 2-1 (0.91 g; 2.9 mmol) in anhydrous THF (20 mL) was added iso-propylmagnesium chloride (2.1 mL; 2 M in THF). The mixture was stirred at 0° C. for 20 mins. A solution of phosphorochloridate reagent (2.2 g; 2.5 eq.) in THF (2 mL) was added dropwise. The mixture was stirred overnight at R.T. The reaction was quenched with saturated aq. NH 4 Cl solution and stirred at R.T. for 10 mins. The mixture was then diluted with water and CH 2 Cl 2 , and the two layers were separated. The organic layer was washed with water, half saturated aq. NaHCO 3 and brine, and dried with Na 2 SO 4 . The evaporated residue was purified on silica gel column with CH 2 Cl 2 -iPrOH solvent system (4-10% gradient) to yield Rp/Sp-mixture of 2-2 (1.59 g; 93%).

A mixture of 2-2 (1.45 g; 2.45 mmol) and 80% aq. HCOOH (7 mL) was stirred at R.T. for 1.5 h. The solvent was evaporated and coevaporated with toluene. The obtained residue was dissolved in MeOH, treated with Et 3 N (3 drops) and the solvent was evaporated. Purification on silica gel column with CH 2 Cl 2 -MeOH solvent system (4-10% gradient) yielded Rp/Sp-mixture of compound 2 (950 mg; 70%). 31 P-NMR (DMSO-d 6 ): δ 3.52, 3.47. MS: m/z=544 [M−1] − .

Compound 3

To an ice cold solution of 3-1 (80 mg; 015 mmol) in anhydrous THF (2 mL) was added isopropylmagnesium chloride (0.22 mL; 2 M in THF). The mixture was stirred at 0° C. for 20 mins. A solution of the phosphorochloridate reagent (0.16 g; 0.45 mmol) in THF (0.5 mL) was added dropwise. The mixture was stirred overnight at R.T. The reaction was quenched with saturated aq. NH 4 Cl solution and stirred at R.T. for 10 mins. The mixture was diluted with water and CH 2 Cl 2 , and the two layers were separated. The organic layer was washed with water, half saturated aq. NaHCO 3 and brine, and dried with Na 2 SO 4 . The evaporated residue was purified on silica gel column with CH 2 C 12 -MeOH solvent system (2-10% gradient) to yield Rp/Sp-mixture of 3-2 (102 mg; 80%).

A mixture of 3-2 (100 mg; 0.12 mmol) in EtOH (3 mL) and 10% Pd/C (10 mg) was stirred under the H 2 atmosphere for 1.5 h. The mixture was filtered through a Celite pad, evaporated and purified on silica gel column with CH 2 C 12 -MeOH solvent system (4-10% gradient) to yield Rp/Sp-mixture of compound 3 (52 mg, 74%). 31 P-NMR (DMSO-d 6 ): δ 3.51, 3.48. MS: m/z=584 [M−1] − .

Compounds 4 and 6

Dry 1 (14 mg, 0.05 mmol) was dissolved in the mixture of PO(OMe) 3 (0.750 mL) and pyridine (0.5 mL). The mixture was evaporated in vacuum for 15 mins at bath temperature 42 OC, and then cooled down to R.T. N-Methylimidazole (0.009 mL, 0.11 mmol) was added followed by POCl 3 (0.009 mL, 0.1 mmol). The mixture was kept at R.T. for 45 mins. Tributylamine (0.065 mL, 0.3 mmol) and N-tetrabutyl ammonium salt of pyrophosphate (100 mg) was added. About 1 mL of dry DMF was added to get a homogeneous solution. In 1 h, the reaction was quenched with 2M ammonium acetate buffer (1 mL, pH=7.5), diluted water (10 mL) and loaded on a column HiLoad 16/10 with Q Sepharose High Performance. The separation was done in linear gradient of NaCl from 0 to 1N in 50 mM TRIS-buffer (pH7.5). The fractions eluted at 60% buffer B contained Compound 4 and at 80% buffer B contained Compound 6. The corresponding fractions were concentrated, and the residue purified by RP HPLC on Synergy 4 micron Hydro-RP column (Phenominex). A linear gradient of methanol from 0 to 30% in 50 mM triethylammonium acetate buffer (pH 7.5) was used for elution. The corresponding fractions were combined, concentrated and lyophilized 3 times to remove excess of buffer. Compound 4: 31 P-NMR (D 2 O): −3.76 (s); MS: m/z 355.3 [M−H] − . Compound 6: 31 P-NMR (D 2 O): −9.28 (d, 1H, Pa), −12.31 (d, 1H, Pγ), −22.95 (t, 1H, Pβ); MS: m/z 515.0 [M−1] − .

Compound 5

Compound 5 was synthesized as described for 2 on 0.1 mmol scale and with neopentyl ester of phosphorochloridate reagent. Yield was 36 mg (63%). 31 P-NMR (CDCl 3 ): δ 2.57 (s), 2.43 (s). MS: 572.6 [M−1] − .

Compound 7

Dry 1 (14 mg, 0.05 mmol) was dissolved in the mixture of PO(OMe) 3 (0.750 mL) and pyridine (0.5 mL). The mixture was evaporated in vacuum for 15 mins at bath temperature 42 OC, and then cooled down to R.T. N-Methylimidazole (0.009 mL, 0.11 mmol) was added followed by PSCl 3 (0.01 mL, 0.1 mmol). The mixture was kept at R.T. for 1 h. Tributylamine (0.065 mL, 0.3 mmol) and N-tetrabutyl ammonium salt of pyrophosphate (200 mg) was added. About 1 mL of dry DMF was added to get a homogeneous solution. In 2 h, the reaction was quenched with 2M ammonium acetate buffer (1 mL, pH=7.5), diluted with water (10 mL) and loaded on a column HiLoad 16/10 with Q Sepharose High Performance. Separation was done in linear gradient of NaCl from 0 to 1N in 50 mM TRIS-buffer (pH7.5). The fractions eluted at 80% buffer B contained 7 (compounds 7a and 7b). The corresponding fractions were concentrated, and the residue purified by RP HPLC on Synergy 4 micron Hydro-RP column (Phenominex). A linear gradient of methanol from 0 to 20% in 50 mM triethylammonium acetate buffer (pH 7.5) was used for elution. Two peaks were collected. The corresponding fractions were combined, concentrated and lyophilized 3 times to remove excess of buffer. Peak 1 (more polar): 31 P-NMR (D 2 O): +42.68 (d, 1H, Pα), −9.05 (d, 1H, Pγ), −22.95 (t, 1H, Pβ); MS 530.90 [M−1] − . Peak 2 (less polar): 31 P-NMR (D 2 O): +42.78 (d, 1H, Pa), −10.12 (bs, 1H, Pγ), −23.94 (t, 1H, Pβ); and MS 530.90 [M−1] − .

Compound 23

To a stirred suspension of 23-1 (20.0 g, 81.3 mmol), imidazole (15.9 g, 234.0 mmol), PPh 3 (53.5 g, 203.3 mmol) and pyridine (90 mL) in anhydrous THF (100 mL) was added a solution of 12 (41.3 g, 162.6 mmol) in THF (150 mL) dropwise at 0° C. The mixture was slowly warmed to R.T. and stirred for 14 h. The reaction was quenched with sat. aq. Na 2 S 2 O 3 (150 mL) and extracted with THF/EA (1/1) (100 mL×3). The organic layer was dried over Na 2 SO 4 , and concentrated at a low pressure. The residue was recrystallized from EtOH to afford pure 23-2 (23 g, 79%) as a white solid.

To a stirred solution of 23-2 (23 g, 65 mmol) in anhydrous MeOH (200 mL) was added NaOCH 3 (10.5 g, 195 mmol) in MeOH (50 mL) at R.T. The mixture was stirred at 60° C. for 3 h, and quenched with dry ice. A solid precipitated and removed by filtration. The filtrate was concentrated at a low pressure. The residue was purified on column silica gel column (MeOH in DCM from 1% to 10%) to provide 23-3 (13.1 g, 92.5%) as a white foam solid.

To a stirred solution of 23-3 (12.0 g, 53 mmol) in anhydrous CH 3 CN was added TEA.3HF (8.5 g, 53 mmol) and NIS (10.2 g, 63.6 mmol) at 0° C. The mixture was stirred for 30 mins, and slowly warmed to R.T. The mixture was stirred for another 30 mins. The solid was removed by filtration, and washed with DCM to give 23-4 (14 g, 73%) as a yellow solid. ESI-MS: m/z 373.0 [M+H] + .

To a stirred solution of 23-4 (12.0 g, 32 mmol) and DMAP (1.2 g, 9.6 mmol) in pyridine (100 mL) was added Bz 2 O (21.7 g, 96 mmol) at R.T. The mixture was stirred at 50° C. for 16 h. The resulting solution was quenched with water, and concentrated to dryness at low pressure. The crude was purified on silica gel column (50% EA in PE) to give 23-5 (15 g, 81%) as a white solid. ESI-TOF-MS: m/z 581.0 [M+H] + .

Tetra-butylammonium hydroxide (288 mL as 54-56% aqueous solution, 576 mmol) was adjusted to pH-4 by adding TFA (48 mL). The resulting solution was treated with a solution of 23-5 (14 g, 24 mmol) in DCM (200 mL). m-Cloroperbenzoic acid (30 g, 60-70%, 120 mmol) was added portion wise with vigorous stirring, and the mixture was stirred overnight. The organic layer was separated and washed with brine. The resulting solution was dried over magnesium sulfate and concentrated under reduced pressure. The residue was purified by column chromatography to give 23-6 (7.5 g, 68%)

Compound 23-6 (5.0 g, 10.6 mmol) was treated with 7N NH 3 .MeOH (100 mL), and the mixture was stirred for 5 h. The mixture was then concentrated to dryness at low pressure. The residue was washed with DCM, and the solid was filtered to give 23-7 (2.1 g, 75%) as a white foam. ESI-MS: m/z 263.0 [M+H] + .

To a solution of 23-7 (2.1 g, 8.0 mmol) in pyridine was added TIDPSCl (2.5 g, 8.0 mmol) dropwise at 0° C., and stirred for 12 h. at R.T. The solution was quenched with water, and concentrated to dryness at low pressure. The crude was purified by column chromatography (EA in PE from 10% to 50%) to give pure 23-8 (1.6 g, 40%) as a white foam.

A solution of 23-8 (1.5 g, 3.0 mmol) and IBX (1.69 g, 6.0 mmol) in anhydrous CH 3 CN (10 mL) was stirred at 80° C. for 3 h. The mixture was cooled down to R.T. and filtered. The filtrate was concentrated to dryness at low pressure. The residue was purified by column chromatography (EA in PE from 2% to 50%) to give pure 23-9 (1.2 g, 80%) as a white foam. ESI-MS: m/z 503.0 [M+H] +

Compound 23-9 (500 mg, 1 mmol) was dissolved in dry THF (8 mL). Ethynyl magnesium bromide (8 mL of 0.5M solution in cyclohexane) was added at R.T. After 30 mins, additional ethynyl magnesium bromide (8 mL) was added. The mixture was left for 30 mins, and then quenched with sat. solution of ammonium chloride. The product was extracted with EA. The organic extracts were washed with brine, dried, and concentrated. The residue was purified by flash chromatography on silica gel in EA to remove the dark color. The yellow compound was dissolved in THF (3 mL) and treated with TBAF (1 mL, 2M solution in THF) for 30 mins. The solvent was evaporated, and the residue was subjected to silica gel chromatography on a Biotage cartridge (25 g). EA saturated with water was used for isocratic elution. Each fractions were analyzed by TLC in DCM-MeOH (9:1 v/v). Fractions containing only the isomer with a high Rf were concentrated to give pure compound 23 (110 mg). MS: 285.1 [M−1] − .

Compound 22

Compound 23 (57 mg, 0.2 mmol) was dissolved in CH 3 CN (2 mL), containing N-methylimidazole (40 uL). The phosphorochloridate (207 mg, 0.6 mmol) was added, and the mixture was kept overnight at 40° C. The mixture was distributed between water and EA. The organic layer was separated, washed with brine, dried and evaporated. The product was isolated by silica gel chromatography in gradient of methanol in DCM from 0% to 15%. Compound 22 was obtained (46 mg, 39%). MS: m/z 593.9 [M−1] − .

Compound 51

To a solution of triethylammonium bis(isopropyloxycarbonyloxymethyl)phosphate (0.74 mmol) in THF was added 51-1 (0.16 gg; 0.49 mmol). The mixture evaporated and rendered anhydrous by coevaporating with pyridine follow by toluene. The residue was dissolved in anhydrous THF and cooled in an ice-bath. Diisopropylethyl amine (0.34 mL) was added, followed by BOP-Cl (250 mg) and 3-nitro-1,2,4-triazole (112 mg) in THF (5 mL). The mixture was stirred at 0° C. for 90 mins, diluted with EtOAc, washed with sat. aq. NaHCO 3 and brine, and dried (Na 2 SO 4 ). The residue was purified on silica column with 3-10% i-PrOH in DCM to give 51-2 (0.2 g, 64%).

A solution of 51-2 (0.20 g; 0.31 mmol) in 80% aq. HCOOH was stirred at R.T. for 2 h, and then concentrated. The residue was coevaporated with toluene and then with MeOH containing a small amount of Et 3 N (2 drops). Purification on silica gel (10 g column) with CH 2 Cl 2 /MeOH (4-10% gradient) was followed by RP-HPLC purification in 5 runs on a Synergi Hydro RP column 250×30 mm (Phenomenex P/N 00G-4375-U0-AX) using H 2 O and ACN both 50 mM TEAA. The Gradient was 25-75% ACN in 20 mins at 24 mL/mins, 254 nM detection. The compound eluted at 16.0 minutes; and the pure fractions were pooled and lyophilized. TEAA was removed by dissolving the compound in DMSO (2 mL) and using the same column and same gradient, using only H 2 O and ACN. Pure fractions were pooled and lyophilized to give compound 51 (18 mg). MS: m/z=1197 [2M+1] + .

Compound 8

Compound 8-1 (5.0 g, 8.5 mmol) and 2-amino-6-chloropurine (3.0 g, 17.7 mmol) were co-concentrated with anhydrous toluene for 3 times. To a stirred suspension of the above mixtures in anhydrous MeCN (50 mL) was added DBU (7.5 g, 49 mmol) at 0° C. The mixture was stirred at 0° C. for 15 mins, and then TMSOTf (15 g, 67.6 mmol) was added dropwise at 0° C. The mixture was stirred at 0° C. for 15 mins. The mixture was heated at 70° C. overnight. The mixture was cooled to R.T., and diluted with EA (100 mL). The solution was washed with sat. NaHCO 3 solution and brine. The organic layer was dried over Na 2 SO 4 and concentrated at low pressure. The residue was purified by column on silica gel (PE/EA: from 15/1 to 3/1) to give 8-2 (2.5 g, 46.3%) as a white foam.

To a solution of 8-2 (10 g, 15.7 mmol), AgNO 3 (8.0 g, 47 mmol) and collidine (10 mL) in anhydrous DCM (20 mL) was added MMTrCl (14.5 g, 47 mmol) in small portions under N 2 . The mixture was stirred at R.T. overnight. The mixture was filtered, and the filtrate was washed with sat. aq. NaHCO 3 and brine. The organic layer was dried over anhydrous Na 2 SO 4 , and concentrated at low pressure. The residue was purified by silica gel column (PE/ME=20/1 to 8/1) to give 8-3 (10 g, 70%) as a yellow solid.

To a solution of 3-hydroxy-propionitrile (3.51 g, 49.4 mmol) in anhydrous THF (100 mL) was added NaH (2.8 g, 70 mmol) at 0° C., and the mixture was stirred at R.T. for 30 mins. A solution of 8-3 (8.5 g, 9.35 mmol) in anhydrous THF (100 mL) at 0° C. was added, and the mixture was stirred at R.T. overnight. The reaction was quenched with water, and extracted with EA (100 mL). The organic layer was dried over anhydrous Na 2 SO 4 , and concentrated at low pressure. The residue was purified by silica gel column (DCM/MeOH=100/1 to 20/1) to give 8-4 (4.5 g, 83%) as a white solid.

Compound 8-4 (1.5 g, 2.6 mmol) was co-concentrated with anhydrous pyridine 3 times. To an ice-cooled solution of 8-4 in anhydrous pyridine (30 mL) was added TsCl (1.086 g, 5.7 mmol), and the mixture was stirred at 0° C. for 1 h. The reaction was quenched with water, and extracted with EA (80 mL). The organic layer was dried over anhydrous Na 2 SO 4 , and concentrated at low pressure. The residue was purified by silica gel column (DCM/MeOH=100/1 to 15/1) to give 8-5 (1.4 g, 73%) as a white solid.

To a solution of 8-5 (4.22 g, 5.7 mmol) in acetone (60 mL) was added NaI (3.45 g, 23 mmol), and the mixture was refluxed overnight. The reaction was quenched with sat. aq. Na 2 S 2 O 3 and extracted with EA (100 mL). The organic layer was dried over anhydrous Na 2 SO 4 , and concentrated at low pressure. The residue was purified by silica gel column (DCM/MeOH=100/1 to 15/1) to give 8-6 (4 g, 73%) as a white solid.

To a solution of 8-6 (4.0 g, 5.8 mmol) in anhydrous THF (60 mL) was added DBU (3.67 g, 24 mmol), and the mixture was stirred at 60° C. overnight. The mixture was diluted with EA (80 mL), and the solution was washed with brine. The organic layer was dried over anhydrous Na 2 SO 4 , and concentrated at low pressure. The residue was purified by silica gel column (DCM/MeOH=100/1 to 20/1) to give 8-7 (2 g, 61%) as a white solid.

To an ice-cooled solution of 8-7 (500 mg, 0.89 mmol) in anhydrous DCM (20 mL) was added AgF (618 mg, 4.9 mmol) and a solution of 12 (500 mg, 1.97 mmol) in anhydrous DCM (20 mL). The mixture was stirred at R.T. for 3 h. The reaction was quenched with sat Na 2 S 2 O 3 and NaHCO 3 aqueous, and the mixture was extracted with DCM (50 mL). The organic layer was separated, dried over anhydrous Na 2 SO 4 , and concentrated to give the crude 8-8 (250 mg) as a yellow solid.

To a solution of crude 8-8 (900 mg, 1.28 mmol) in anhydrous DCM (50 mL) was added DMAP (1.0 g, 8.2 mmol) and BzCl (795 mg, 5.66 mmol). The mixture was stirred at R.T. overnight. The mixture was washed with sat. aq. NaHCO 3 and brine. The organic layer was dried over anhydrous Na 2 SO 4 , and concentrated at low pressure. The residue was purified by prep-TLC (DCM/MeOH=15:1) to give 8-9 (300 mg, 26%) as a white solid.

To a solution of crude 8-9 (750 mg, 0.82 mmol) in anhydrous HMPA (20 mL) was added NaOBz (1.2 g, 8.3 mmol) and 15-crown-5 (1.8 g, 8.3 mmol). The mixture was stirred at 60° C. for 2 d. The mixture was diluted with EA, and the solution was washed with brine. The organic layer was dried over anhydrous Na 2 SO 4 , and concentrated at low pressure. The residue was purified by prep-TLC (PE/EA=1:1) to give crude 8-10 (550 mg, 73%) as a white solid.

The crude 8-10 (550 mg, 0.6 mmol) was dissolved in NH 3 /MeOH (7N, 50 mL). The mixture was stirred at R.T. overnight. The mixture was concentrated, and the residue was purified by silica gel column (DCM/MeOH from 100/1 to 20/1) to give 8-11 (62 mg, 17%) as a white solid. ESI-MS: m/z 598.0 [M+H] +

A solution of 8-11 (12 mg) in 80% formic acid (0.5 mL) stood at R.T. for 3.5 h and then was concentrated. The residue was co-evaporated with MeOH/toluene 4 times in a vial, and triturated with EtOAc at 40° C. The EtOAc solution removed with pippet. The trituration step was repeated several times, and the remaining solid was dissolved in MeOH. The solution was concentrated and dried to give compound 8 as off white solid (4.7 mg). ESI-MS: m/z 326.6 [M+H] + .

Compounds 34 and 35

To a stirred suspension of 8-1 (50 g, 84.8 mmol) and 2-amino-6-chloropurine (28.6 g, 169.2 mmol) in anhydrous MeCN (500 mL) was added DBU (77.8 g, 508 mmol) at 0° C. The mixture was stirred at 0° C. for 30 mins, and TMSOTf (150.5 g, 678 mmol) was added dropwise at 0° C. The mixture was stirred at R.T. for 20 mins until a clear solution was formed. The mixture was stirred at 90-110° C. overnight. The mixture was cooled to R.T., and diluted with EA. The solution was washed with sat. NaHCO 3 solution and brine. The organic layer was dried over Na 2 SO 4 and then concentrated at low pressure. The residue was purified by silica gel column (PE/EA=2/1) to give 34-1 (30 g, 55.5%) as a white solid.

To a solution of 34-1 (30 g, 47.1 mmol) in anhydrous DCM (300 mL) was added collidine (30 mL), AgNO 3 (24 g, 141.4 mmol) and MMTrCl (43.6 g, 141.4 mmol). The mixture was stirred at R.T. overnight. The mixture was filtered, and the filtrate was washed with water and brine. The organic layer was dried over anhydrous Na 2 SO 4 , and concentrated at low pressure. The residue was purified by silica gel column (PE/EA=4/1) to give 34-2 (35 g, 82%) as a white solid.

To a stirred solution of 34-2 (35 g, 38.5 mmol) in anhydrous EtOH (150 mL) was added a solution of EtONa in EtOH (2N, 150 mL). The mixture was stirred at R.T. overnight, and then concentrated at low pressure. The residue was dissolved in EA (200 mL) and the solution was washed with water and brine. The organic layer was dried over Na 2 SO 4 , and concentrated at low pressure. The residue was purified by silica gel column (DCM/MeOH=100/2) to give 34-3 (19 g, 81%) as a white solid.

Compound 34-3 (19 g, 31.3 mmol) was co-concentrated with anhydrous pyridine for 3 times. To an ice-cooled solution of 34-3 in anhydrous pyridine (120 mL) was added a solution of TsCl (6.6 g, 34.6 mmol) in pyridine (40 mL) dropwise at 0° C. The mixture was stirred at 0° C. for 16 h. The mixture was quenched with water, and the reaction mixture was concentrated. The residue was re-dissolved in EA (200 mL). The solution was washed with sat. aq. NaHCO 3 and brine. The organic layer was dried over anhydrous Na 2 SO 4 and filtered, and the filtrate was concentrated. The residue was purified by silica gel column (DCM/MeOH=100/1) to give 34-4 (16 g, 67%) as a yellow solid.

To a solution of 34-4 (15 g, 19.7 mmol) in acetone (100 mL) was added NaI (30 g, 197 mmol). The mixture was refluxed overnight, and then concentrated at low pressure. The residue was purified by silica gel column (DCM/MeOH=100/1) to give 34-5 (9 g, 63.7%) as a white solid.

To a solution of 34-5 (8 g, 11.2 mmol) in anhydrous THF (60 mL) was added DBU (5.12 g, 33.5 mmol), and the mixture was heated at 60° C. overnight. The mixture was diluted with EA, and washed with water and brine. The organic layer was dried over anhydrous Na 2 SO 4 and filtered, and the filtrate was concentrated. The residue was purified by silica gel column (PE/acetone=4/1) to give 34-6 (5.7 g, 86%) as a white solid. 1 H-NMR (CD 3 OH, 400 MHz) δ=8.18 (s, 1H), 7.17-7.33 (m, 12H), 6.80 (d, J=8.8 Hz, 2H), 5.98 (s, 1H), 5.40 (d, J=8.6 Hz, 1H), 3.87 (m, 5H), 3.75 (s, 3H), 2.69 (s, 1H), 1.05 (s, 3H).

To an ice-cooled solution of 34-6 (4.44 g, 7.5 mmol) in anhydrous MeCN (45 mL) was added TEA.3HF (1.23 g, 7.6 mmol) and NIS (2.16 g, 9.5 mmol). The mixture was stirred at R.T. for 2-3 h. The reaction was quenched with sat. Na 2 SO 3 and NaHCO 3 solution. The mixture was extracted with EA (3×100 mL). The organic layer was separated, dried over anhydrous Na 2 SO 4 and concentrated at low pressure. The residue was purified by silica gel column (DCM/acetone=100/2) to give 34-7 (4.4 g, 79.8%) as a white solid.

To a solution of 34-7 (5.36 g, 7.3 mmol) in anhydrous DCM (50 mL) was added DMAP (3.6 g, 29.8 mmol) and BzCl (3.1 g, 22.1 mmol) at 0° C. The mixture was stirred at R.T. overnight. The mixture was washed with sat. aq. NaHCO 3 and brine. The organic layer was concentrated, and the residue was purified by silica gel column (PE/EA=5/1) to give 34-8 (5.6 g, 81.3%) as a white solid.

To a solution of 34-8 (5.0 g, 5.3 mmol) in anhydrous DMF (150 mL) was added NaOBz (7.64 g, 53 mmol) and 15-crown-5 (14 g, 68 mmol). The mixture was stirred at 90-100° C. for 48 h. The mixture was diluted with EA, and washed with water and brine. The organic layer was concentrated, and the residue was purified by silica gel column (PE/EA=5/1) to give 34-9 (3.9 g, 78.5%) as a white solid.

Compound 34-9 in NH 3 in MeOH (7N, 60 mL) was stirred at R.T. for 18 h. The mixture was concentrated at low pressure. The residue was purified by silica gel column (DCM/acetone=50/1) to give 34-10 (500 mg, 74.7%) as a white solid. ESI-MS: m/z 626.3 [M+H] + .

To a solution of 34-10 (350 mg, 0.56 mmol) in anhydrous pyridine (4 mL) was added imidazole (50 mg, 0.72 mmol) and TBSCl (108 mg, 0.72 mmol) at 0 to 5° C., and stirred at R.T. for 15 h. The reaction was quenched with absolute EtOH (0.5 mL). The solution was concentrated to dryness under reduced pressure. The residue was dissolved in EA (150 mL), and washed with water, sat. NaHCO 3 and brine. The combined organic layers were dried over Na 2 SO 4 , filtered and evaporated at low pressure. The residue was purified by silica gel column (10-30% EA in hexanes) to give 34-11 (338 mg, 81.8%) as a white solid.

To a solution of compound 34-11 (328 mg, 0.44 mmol), AgNO 3 (226 mg, 1.33 mmol) and collidine (0.59 mL, 4.84 mmol) in anhydrous DCM (4 mL) was added MMTrCl (410 mg, 1.33 mmol) under N 2 . The mixture was stirred at R.T. overnight under N 2 , and monitored by TLC to completion. The mixture was filtered through pre-packed Celite filter, and the filtrate was washed with water, 50% aqueous citric acid, and brine. The organic layer was separated, dried over anhydrous Na 2 SO 4 , filtered and concentrated at low pressure. The residue was purified by silica gel column (EA in hexanes from 0% to 30%) to give 34-12 (337 mg).

To a solution of 34-12 (337 mg, 0.33 mmol) in anhydrous THF (4 mL) was added 1.0 M solution of TBAF (0.66 ML, 0.66 mmol) at 0 to 5° C. The reaction was slowly warmed to R.T., and stirred for 1 h. The mixture was quenched with silica gel, and filtered. The solvents were evaporated to give the crude product, which was purified by silica gel column (EA in hexanes from 0% to 50%) to give 34-13 (188 mg).

To a stirred solution of 34-13 (180 mg, 0.16 mmol) in anhydrous CH 3 CN (2.5 mL) was added N-methylimidazole (132 μL, 1.6 mmol) at 0-5° C. (ice/water bath) followed by solution of phenyl (cyclohexanoxy-L-alaninyl) phosphorochloridate (207 mg, 0.6 mmol, dissolved in 2 mL of CH 3 CN). The solution was stirred at R.T. for 2.5 h, and the mixture was diluted with EA followed by addition of water (15 mL). The solution was washed H 2 O, 50% aqueous citric acid solution and brine. The organic layer was separated, dried over anhydrous MgSO 4 and filtered. The filtrate was concentrated in vacuum to give a residue, which was purified on silica gel with 0 to 40% EA/hexanes to give 34-14 (75.8 mg) and 34-15 (108 mg) as a slower eluting isomer.

Compound 34-14 (76 mg, 0.063 mmol) was dissolved in_anhydrous CH 3 CN (0.5 mL), and 4N HCl in dioxane (47 μL) was added at 0 to 5° C. (ice/water bath). The mixture was stirred at R.T. for 40 mins, and anhydrous EtOH (200 μL) was added. The solvents were evaporated at R.T. and co-evaporated with toluene 3 times. The residue was dissolved in 50% CH 3 CN/H 2 O, purified on a reverse-phase HPLC (C18) using acetonitrile and water, and lyophilized to give compound 34 (26.6 mg). ESI-LCMS: m/z=663.3 [M+H] + .

Compound 34-15 (108 mg, 0.089 mmol) was dissolved in_anhydrous CH 3 CN (0.7 mL), and 4N HCl in dioxane (67 μL) was added at 0 to 5° C. (ice/water bath). The mixture was stirred at R.T. for 60 mins, and anhydrous EtOH (200 μL) was added. The solvents were evaporated at R.T. and co-evaporated with toluene 3 times. The residue was dissolved in 50% CH 3 CN/H 2 O, purified on a reverse-phase HPLC (C18) using acetonitrile and water, and lyophilized to give compound 35 (40.3 mg). ESI-LCMS: m/z=663.2 [M+H] + .

Compound 25

To a solution of 25-1 (260 mg, 1 mmol), PPh 3 (780 mg, 3 mmol) and pyridine (0.5 mL) in anhydrous THF (8 mL) were added 12 (504 mg, 2 mmol) at R.T., and the mixture was stirred at R.T. for 12 h. The mixture was diluted with EtOAc and washed with 1M HCl solution. The organic layer was dried over Na 2 SO 4 , filtered and concentrated at low pressure. The residue was purified by silica gel column (5% MeOH in DCM) to give 25-2 (190 mg, 85%) as a white solid.

To a solution of 25-2 (190 mg, 0.52 mmol) in THF (4 mL) was added DBU (760 mg, 5 mmol) at R.T., and the mixture was heated at 50° C. overnight. The mixture was diluted with EtOAc, and washed with water. The organic layer was dried over anhydrous Na 2 SO 4 and concentrated at low pressure. The residue was purified by silica gel column (30% EA in PE) to give 25-3 (75 mg, 52%) as a white solid.

To a solution of 25-3 (200 mg, 0.82 mmol) in MeCN (anhydrous, 4 mL) was added NIS (337 mg, 1.5 mmol) and TEA.3HF (213 mg, 1.25 mmol) at R.T., and the mixture was stirred at R.T. for 7 h. The reaction was quenched with sat. Na 2 SO 3 solution and sat. aq. NaHCO 3 solution. The mixture was extracted with EA. The organic layer was separated, dried over anhydrous Na 2 SO 4 , and concentrated at low pressure. The residue was purified by silica gel column (20% EA in PE) to give 25-4 (300 mg, 62%) as a white solid.

To a solution of 25-4 (194 mg, 0.5 mmol) in pyridine (5 mL) was added BzCl (92 mg, 0.55 mmol) at 0° C. The mixture was stirred at R.T. for 5 h, and the reaction was quenched with water. The mixture was concentrated at low pressure, and the residue was purified by silica gel column (20% EA in PE) to give 25-5 (397 mg, 81%) as a white solid.

To a solution of 25-5 (1.05 g, 2.13 mmol) in DCM (12 mL) was added a mixture of TFA (0.5 mL) and Bu 4 NOH (1 mL), followed by addition of m-CPBA (1.3 g, 6 mmol) at R.T. The mixture was stirred at R.T. for 5 h. The mixture was washed with sat. Na 2 SO 3 solution and aq. NaHCO 3 solution. The organic layer was dried over anhydrous Na 2 SO 4 , and concentrated at low pressure. The residue was purified by silica gel column (30% EA in PE) to give 25-6 (450 mg, 63%) as a white solid.

Compound 25-6 (250 mg, 0.65 mmol) was dissolved in NH 3 /MeOH (5 mL). The mixture was stirred at R.T. for 5 h, and then concentrated at low pressure. The residue was purified by silica gel column (5% MeOH in DCM) to give compound 25 (120 mg, 66%) as a white powder. ESI-MS: m/z 279.0 [M+H] + .

Compound 31

To a stirred solution of compound 25 (100 mg, 0.36 mmol) in anhydrous THF (3.0 mL) was added N-methylimidazole (236 μL, 2.87 mmol) at 0° C. (dry ice/acetone bath) followed by a solution of the phosphorochloridate (329 mg, 1.08 mmol, dissolved in 2 mL of THF). The solution was stirred at 0° C. for 1 h, the reaction temperature was raised up-to 10° C. during the next 1 h, and the solution was left at 10° C. for the next 4 h. The mixture was cooled to 0 to 5° C., diluted with EA, and water was added (15 mL). The solution was washed H 2 O, 50% aqueous citric acid solution and brine. The organic layer was separated, dried over anhydrous MgSO 4 and filtered. The filtrate was concentrated in vacuum to give a residue, which dissolved in 25% CH 3 CN/H 2 O. The residue was purified on a reverse-phase HPLC (C18) using acetonitrile and water, followed by lyophilization to give a mixture of two isomers of compound 31 (17.5 mg). MS: m/z 546.05 [M−H] − .

Compound 27

To a solution of compound 25 (139 mg, 0.5 mmol) in pyridine (5 mL) was added BzCl (92 mg, 0.55 mmol) at 0° C. The mixture was stirred at R.T. for 5 h, diluted with EtOAc and washed with 1N HCl solution. The organic layer was dried over anhydrous Na 2 SO 4 , and concentrated at low pressure. The residue was purified by silica gel column (20% EA in PE) to give 27-1 (274 mg, 79%) as a white solid.

To a solution of 27-1 (490 mg, 1 mmol), DMAP (244 mg, 2 mmol) and TEA (205 mg, 2.1 mmol) in MeCN (10 mL) were added TPSCl (604 mg, 2 mmol) at 0° C. The mixture was stirred at R.T. for 2 h., and then NH 4 OH aq. was added at R.T. The mixture was stirred for 0.5 h, diluted with EtOAc and washed with sat. aq. NaHCO 3 and brine. The organic layer was dried over anhydrous Na 2 SO 4 , and concentrated at low pressure. The residue was purified by silica gel column (30% EA in PE) to give 27-2 (250 mg, 41%) as a white solid.

Compound 27-2 (250 mg, 0.51 mmol) was dissolved in NH 3 /MeOH (15 mL). The mixture was stirred at R.T. for 5 h. and then concentrated at low pressure. The residue was purified by silica gel column (5% DCM in DCM) to give compound 27 (95 mg, 66%) as a white powder. ESI-MS: m/z 278.1 [M+H] + .

Compound 29

To a solution of compound 29-1 (30 g, 0.08 mol) in anhydrous THF (300 mL) was added a solution of lithium tri-tert-butoxyaluminohydride (120 mL, 0.12 mol) dropwise at −78° C. under N 2 . The mixture was stirred at −20° C. for 1 h. The reaction was quenched with sat. aq. NH 4 Cl and then filtered. The filtrate was extracted with EA (3×300 mL). The organic layer was dried over anhydrous Na 2 SO 4 , and concentrated at low pressure. The residue was purified by silica gel column (10% EA in PE) to give 29-2 (26 g, 86%) as a colorless oil.

To a stirred solution of PPh 3 (37.7 g, 0.144 mol) in DCM (100 mL) was added compound 29-2 (27 g, 0.072 mol) at −20° C. under N 2 . After the mixture was stirred at R.T. for 15 mins, CBr 4 (42 g, 0.129 mol) was added while maintaining the reaction temperature between −25 and −20° C. under N 2 . The mixture was then stirred below −17° C. for 20 mins. Silica gel was added into the solution, and then purified by flash silica gel column separation to give the crude oil product. The crude was purified by silica gel column (EA in PE from 2% to 20%) to give 29-3 (α-isomer, 17 g, 55%) as a colorless oil.

A mixture of 6-Cl-guanine (11.6 g, 68.8 mmol) and t-BuOK (8.2 g, 73 mmol) in t-BuOH (200 mL) and MeCN (150 mL) was stirred at 35° C. for 30 mins, and then 29-3 (10 g, 22.9 mmol) in MeCN 100 mL) was added at R.T. The mixture was heated at 50° C. overnight. The reaction was quenched with a solution of NH 4 Cl (5 g) in water (40 mL), and the mixture was filtered. The filtrate was evaporated at low pressure. The residue was purified by silica gel column (20% EA in PE) to give 29-4 (6 g, 42%) as a yellow solid.

To a solution of 29-4 (12.5 g, 23.8 mol) in DCM (50 mL) was added AgNO 3 (8.1 g, 47.6 mmol), collidine (5.77 g, 47.6 mmol) and MMTrCl (11 g, 35.7 mmol). The mixture was stirred at R.T. overnight. The reaction was quenched with MeOH (5 mL), filtered and concentrated at low pressure. The residue was purified by silica gel column (5% MeOH in DCM) to give the intermediate (16 g, 86%) as a yellow solid. To a solution of HOCH 2 CH 2 CN (4.7 g, 66 mmol) in THF (200 mL) was added NaH (3.7 g, 92 mmol) at 0° C. The mixture was stirred at R.T. for 30 mins. A solution of the intermediate (10.5 g, 13 mmol) in THF (50 mL) was added, and the reaction mixture was stirred at R.T. for 12 h. The reaction was quenched with MeOH (2 mL), diluted with EA (100 mL), and washed with brine. The organic layer was dried over anhydrous Na 2 SO 4 , and concentrated at low pressure. The residue was purified by silica gel column (5% MeOH in DCM) to give 29-5 (5.8 g, 77%) as a yellow solid.

To a solution of PPh 3 (7.0 g, 26.6 mmol) in anhydrous pyridine (100 mL) was added 12 (6.3 g, 24.9 mmol), and stirred at R.T. for 30 mins. The mixture was treated with a solution of 29-5 (9.5 g, 16.6 mmol) in pyridine (40 mL). The mixture was stirred at R.T. overnight. The reaction was quenched with sat. Na 2 S 2 O 3 solution, and the mixture was extracted with EA. The organic layer was washed with brine, dried over anhydrous Na 2 SO 4 , and concentrated at low pressure. The residue was purified by silica gel column (30% EA in PE) to give 29-6 (7 g, 66%) as a yellow solid.

To a solution of 29-6 (7.5 g, 11 mmol) in dry THF (50 mL) was added DBU (5.4 g, 33 mmol), and the mixture was heated to reflux for 4 h. The mixture was diluted with EA (3×100 mL), and washed with brine. The organic layer was dried over anhydrous Na 2 SO 4 , and concentrated at low pressure. The residue was purified by silica gel column (30% EA in PE) to give 29-7 (4.0 g, 67%) as a white solid.

To an ice-cooled solution of 29-7 (3.0 g, 5.4 mmol) in anhydrous MeCN (20 mL) was added TEA.3HF (0.65 g, 4.1 mmol) and NIS (1.53 g, 6.78 mmol) at R.T., and the reaction mixture was stirred at R.T. for 2 h. The mixture was diluted with EA (50 mL), and washed with sat. Na 2 S 2 O 3 solution and NaHCO 3 aq. The organic layer was dried over anhydrous Na 2 SO 4 , and concentrated to dryness at low pressure. The residue was purified by prep-HPLC (0.1% HCOOH in water and MeCN) to separate the two isomers (about 1:1). NOE showed the polar one was 29-8 (0.6 g, 16%) as a white solid.

To a solution of 29-8 (0.7 g, 1 mmol) in dry pyridine (10 mL) was added BzCl (147 mg, 1.05 mmol) at 0° C. The mixture was stirred at R.T. for 3 h. The mixture was then diluted with EA, and washed with sat. NaHCO 3 aq. and brine. The organic layer was dried over Na 2 SO 4 , and evaporated at low pressure. The residue was purified by silica gel column (20% EA in PE) to give 29-9 (0.65 g, 81%) as a white solid.

To a solution of 29-9 (0.65 g, 0.8 mmol) in dry DMF (40 mL) was added NaOBz (1.15 g, 8 mmol) and 15-crown-5 (1.77 g, 8 mmol). The mixture was stirred at 100° C. for 48 h. The solvent was evaporated at low pressure, and the residue was dissolved in EA (30 mL), and washed with water and brine. The organic layer was dried over Na 2 SO 4 and concentrated at low pressure. The residue was purified by silica gel column (20% EA in PE) to give 29-10 (500 mg, 78%) as a white solid.

Compound 29-10 (400 mg, 0.5 mmol) in NH 3 /MeOH (7N, 100 mL) was stirred at R.T. for 18 h. The mixture was concentrated at low pressure, and the residue was purified by silica gel column (5% MeOH in DCM) to give 29-11 (220 mg, 63%) as a white solid. ESI-MS: m/z 590.3 [M+H] + .

Compound 29-11 (59 mg, 0.1 mmol) was dissolved in 50% TFA in methanol (10 mL), and the mixture was kept at R.T. for 2 h. The solvent was evaporated and co-evaporated with a methanol/toluene mixture to remove traces of the acid. The residue was suspended in CH 3 CN (1 mL) and centrifuged. The precipitate was washed with CH 3 CN (1 mL) and dried. Compound 29 was obtained as a colorless solid (21 mg, 65%. MS: m/z 316.2 [M−1] − .

Compounds 42 and 43

A freshly prepared EtONa in dry EtOH (2N, 150 mL) was added to a solution of 29-4 (13.67 g, 17.15 mmol) in EtOH (50 mL) at 0° C. The mixture was stirred at R.T. for 1 h, and then concentrated at low pressure. The residue was purified by silica gel column (5% MeOH in DCM) to give 42-1 (10 g, 98%) as a yellow solid.

To a solution of PPh 3 (2.73 g, 10.4 mol) in anhydrous pyridine (60 mL) was added 12 (2.48 g, 9.76 mmol) at R.T., and the reaction mixture was stirred R.T. for 30 mins. A solution of 42-1 (3.9 g, 6.51 mmol) in pyridine (10 mL) was added. The mixture was stirred at R.T. overnight. The reaction was quenched with sat. Na 2 S 2 O 3 solution and NaHCO 3 aq., and then extracted with EA (100 mL). The organic layer was dried over anhydrous Na 2 SO 4 , and evaporated at low pressure. The residue was purified by silica gel column (2% MeOH in DCM) to give 42-2 (3.0 g, 75%) as a yellowed solid.

To a solution of 42-2 in dry THF (300 mL) was added DBU (14.0 g, 91.8 mmol), and the mixture was heated to reflux for 3 h. The mixture was concentrated at low pressure. The residue was dissolved in EA (100 mL), and washed with brine. The organic layer was dried over anhydrous Na 2 SO 4 , and evaporated at low pressure. The residue was purified by silica gel column (20% EA in PE) to give 42-3 (0.6 g, 37.5%) as a white solid.

To an ice-cooled solution of 42-3 (2.0 g, 3.44 mmol) in anhydrous MeCN (20 mL) was added NIS (0.975 g, 4.3 mmol) and TEA.3HF (0.82 g, 5.16 mmol) at 0° C. The mixture was stirred at R.T. for 2 h. The reaction was quenched with sat. Na 2 SO 3 and NaHCO 3 aqueous solution, and then concentrated at low pressure. The residue was dissolved in EA (50 mL), washed with brine, dried over anhydrous Na 2 SO 4 , and evaporated at low pressure. The residue was purified by silica gel column (20% EA in PE) to give 42-4 (1.5 g, 60%) as a white solid.

To a solution of 42-4 (1 g, 1.37 mmol) in dry pyridine (100 mL) was added BzCl (0.23 g, 1.65 mmol) at 0° C. The reaction was stirred for 30 mins and checked by LCMS. The mixture was concentrated at low pressure, and the residue was dissolved in EA (50 mL). The solution was washed with brine. The organic layer was dried over MgSO 4 , and evaporated at low pressure. The residue was purified by silica gel column chromatography (10% EA in PE) to give 42-5 (0.9 g, 78%) as a white solid.

To a solution of 42-5 (2 g, 2.4 mmol) in dry DMF (40 mL) was added NaOBz (3.46 g, 24 mmol) and 15-crown-5 (4.5 mL). The mixture was stirred at 95° C. for 72 h. The mixture was then diluted with EA (100 mL), and washed with water and brine. The organic phase was dried over MgSO 4 , and concentrated at low pressure. The residue was purified by silica gel column (15% EA in PE) to give 42-6 (1.5 g, 75%) as a white solid.

Compound 42-6 (1.35 g, 1.64 mmol) in NH 3 /MeOH (150 mL) was stirred at R.T. for 18 h. The mixture was concentrated at low pressure, and the residue was purified by silica gel column (5% MeOH in DCM) to give 42-7 (0.9 g, 90%) as a white solid. ESI-MS: m/z 618.3 [M+H] + .

To a solution of 42-7 (99 mg, 0.16 mmol) in DCM (1.0 mL), triethylamine (92.7 μL, 0.64 mmol) was added at R.T. The mixture was cooled to 0 to 5° C. (ice/water bath), and freshly prepared and distilled isopropyl phosphorodichloridate (36.6 μL, 0.2 mmol, prepared according to a procedure, Reddy et al. J. Org. Chem. 2011, 76 (10), 3782-3790) was added to the mixture. The mixture was stirred 0 to 5° C. (ice/water bath) for 15 mins, followed by addition of N-methylimidazole (26.3 μL, 0.32 mmol). The mixture was then stirred for 1 h at 0 to 5° C. TLC showed absence of 42-7. EA (100 mL) was added, followed by water. The organic layer was washed H 2 O, saturated aqueous NH 4 Cl solution and brine. The organic layer was separated, dried over anhydrous MgSO 4 and filtered. The filtrate was concentrated in vacuum to give a residue, which was purified on silica gel with 0 to 10% iPrOH/DCM to give a mixture of 42-a and 42-b (61.5 mg).

A mixture of 42-a and 42-b (61.5 mg, 0.085 mmol) was dissolved in anhydrous CH 3 CN (0.5 mL), and 4N HCl in dioxane (64 μL) was added at 0 to 5° C. (ice/water bath). The mixture was stirred at R.T. for 40 mins, and anhydrous EtOH (200 μL) was added. The solvents were evaporated at R.T. and co-evaporated with toluene 3 times. The residue was dissolved in 50% CH 3 CN/H 2 O, was purified on a reverse-phase HPLC (C18) using acetonitrile and water, followed by lyophilization to give compound 42 (1.8 mg) and compound 43 (14.5 mg).

Compound 42: 1 H NMR (CD 3 OD-d 4 , 400 MHz) δ 8.0 (s, 1H), 6.69 (d, J=16.0 Hz, 1H), 5.9-5.6 (br s, 1H), 4.94-4.85 (m, 1H), 4.68-4.52 (m, 3H), 1.49-1.3 (m, 12H); 19 F NMR (CD 3 OD-d 4 ) δ −122.8 (s), −160.06 (s); 31 P NMR (CD 3 OD-d 4 ) δ −7.97 (s). ESI-LCMS: m/z=450.1 [M+H] + ; Compound 43: 1 H NMR (CD 3 OD-d 4 , 400 MHz) δ 7.96 (s, 1H), 6.68 (s, 1H), 6.69 (d, J=16.8 Hz, 1H), 6.28-6.1 (br s, 1H), 4.81-4.5 (m, 4H), 1.45-1.39 (m, 12H); 31 P NMR (CD 3 OD-d 4 ) δ −5.84 (s). ESI-LCMS: m/z=450.0 [M+H] + .

Compounds 32 and 33

To a solution of 42-7 (0.47 g, 0.65 mol) in DCM (3 mL) was added AgNO 3 (0.22 g, 1.29 mmol), collidine (0.15 g, 1.29 mmol) and MMTrCl (0.3 g, 0.974 mmol) at 0° C. The mixture was stirred at R.T. overnight. The mixture was filtered, and the filter was washed with sat. aq. NaHCO 3 solution and brine. The organic layer was separated, dried over anhydrous Na 2 SO 4 and concentrated at low pressure. The residue was purified by silica gel column to give 32-1 (0.55, 85%) as a white solid.

To a solution of 32-1 (0.5 g, 0.5 mmol) in dry DMF (10 mL) was added NaOBz (0.72 g, 5 mmol) and 15-crown-5 (0.9 mL). The mixture was stirred at 95° C. for 72 h. The mixture was diluted with EA, and washed with water and brine. The organic phase was dried over MgSO 4 and concentrated at low pressure. The residue was purified by silica gel column (10% EA in PE) to give 32-2 (0.3 g, 60%) as a white solid.

Compound 32-2 (0.3 g, 0.3 mmol) in NH 3 /MeOH (30 mL) was stirred at R.T. for 18 h. The mixture was concentrated at low pressure, and the residue was purified by silica gel column (20% EA in PE) to give 32-3 (145 mg, 56%) as a white solid. ESI-LCMS: m/z 890.5 [M+H] + .

To a stirred solution of 32-3 (161 mg, 0.16 mmol) in anhydrous CH 3 CN (2.0 mL) was added N-methylimidazole (118 μL, 2.87 mmol) at 0 to 5° C. (ice/water bath) followed by solution of 32-4 (186 mg, 0.54 mmol, dissolved in 2 mL of CH 3 CN). The solution was stirred at 0 to 5° C. for 4 h. The mixture was diluted with EA, and water was added (15 mL). The solution was washed H 2 O, 50% aqueous citric acid solution and brine. The organic layer was separated, dried over anhydrous MgSO 4 and filtered. The filtrate was concentrated in vacuum to give a residue, which was purified on silica gel with 0 to 40% EA/hexanes to give as 32-5 (82.6 mg) as the faster eluting isomer and 32-6 (106 mg) as the slower eluting isomer.

Compound 32-5 (82.6 mg, 0.07 mmol) was dissolved in_anhydrous CH 3 CN (0.5 mL), and 4N HCl in dioxane (35 μL) was added at 0 to 5° C. The mixture was stirred at R.T. for 1 h, and anhydrous EtOH (100 μL) was added. The solvents were evaporated at R.T. and co-evaporated with toluene 3 times. The residue was dissolved in 50% CH 3 CN/H 2 O, and purified on a reverse-phase HPLC (C18) using acetonitrile and water, followed by lyophilization to give compound 32 (19.4 mg). 1 H NMR (CD 3 OD-d 4 , 400 MHz) δ 7.9 (s, 1H), 7.32-7.28 (t, J=8.0 Hz, 2H), 7.2-7.12 (m, 3H), 6.43 (d, J=17.6 Hz, 1H), 4.70-4.63 (m, 2H), 4.55-4.4 (m, 3H), 3.94-3.9 (m, 1H), 1.79-1.67 (m, 4H), 1.53-1.49 (m, 1H), 1.45-1.22 (m, 15H); 31 P NMR (CD 3 OD-d 4 ) δ 4.06 (s); ESI-LCMS: m/z=655.2 [M+H] + , 653.15 [M−H] − .

Compound 32-6 (100 mg, 0.083 mmol) was dissolved in_anhydrous CH 3 CN (0.5 mL), and 4N HCl in dioxane (50 μL) was added at 0 to 5° C. Following the procedure for obtaining compound 32, compound 33 (31.8 mg) was obtained. 1 H NMR (CD 3 OD-d 4 , 400 MHz) δ 7.93 (s, 1H), 7.33-7.29 (m, 2H), 7.24-7.14 (m, 3H), 6.41 (d, J=17.6 Hz, 1H), 4.70-4.60 (m, 2H), 4.54-4.49 (m, 2H), 4.44-4.39 (m, 1H), 3.92-3.89 (m, 1H), 1.77-1.66 (m, 4H), 1.54-1.24 (m, 16H); 31 P NMR (CD 3 OD-d 4 ) δ 3.91 (s); ESI-LCMS: m/z=655.2 [M+H] + , 653.1 [M−H] − .

Compound 53

Compound 53-1 (70 mg, 58%) was prepared from 32-3 (90 mg; 0.1 mmol) and triethylammonium bis(isopropyloxycarbonyloxymethyl)phosphate (0.2 mmol) with DIPEA (87 μL), BopCl (44 mg), and 3-nitro-1,2,4-triazole (29 mg) in THF (2 mL) according to a method described for compound 51-2. Purification was done with hexanes/EtOAc solvent system, 20-80% gradient.

Compound 53 (25 mg, 64%) was prepared from 53-1 (70 mg) in acetonitrile (0.6 mL) and 4 N HCl/dioxane (50 μL) according to a method described for compound 51. MS: m/z=658 [M+1] + .

Compounds 40 and 41

To a mixture of pre-silylated 6-Cl-guanine (using HMDS and (NH 4 ) 2 SO 4 ) (25.2 g, 150 mmol) in DCE (300 mL) was added 40-1 (50 g, 100 mmol) and TMSOTf (33.3 g, 150 mmol) at 0° C. The mixture was stirred at 70° C. for 16 h, and then concentrated at low pressure. The residue was re-dissolved in EA, and washed with sat. aq. NaHCO 3 and brine. The organic layer was dried over anhydrous Na 2 SO 4 , and concentrated at low pressure. The residue was purified on silica gel column (PE/EA=2/1) to give pure 40-2 (45 g, 73%) as a white solid.

To a solution of 40-2 (45 g, 73.4 mmol) in EtOH (73 mL) was added with EtONa (1N in EtOH, 360 mL). The mixture was stirred at R.T. for 16 h. The mixture was then concentrated to give a residue, which was purified by silica gel column (DCM/MeOH=10/1) to give pure 40-3 (19 g, 83%) as a white solid.

To a solution of 40-3 (19 g, 61.1 mmol) in pyridine (120 mL) was added with TIPDSCl 2 (19.2 g, 61 mmol) dropwise at 0° C. The mixture was stirred at R.T. for 16 h, and then concentrated at low pressure. The residue was re-dissolved in EA, and washed with sat. aq. NaHCO 3 . The organic layer was dried over anhydrous Na 2 SO 4 , and concentrated at low pressure. The residue was purified by silica gel column (DCM/MeOH=20/1) to give pure 40-4 (22 g, 65%) as a white solid.

To a solution of 40-4 (22 g, 39.8 mmol) in DMF/pyridine (5/1, 100 mL) was added TMSCl (12.9 g, 119 mmol) dropwise at 0° C. The mixture was stirred at R.T. for 1 h and then treated with isobutyryl chloride (5.4 g, 50 mmol). The mixture was stirred at R.T. for 3 h and then quenched by NH 4 OH. The mixture was concentrated at low pressure. The residue was dissolved in EA (200 mL). The solution was washed with sat. aq. NaHCO 3 , and then the organic layer was dried and concentrated at low pressure. The residue was purified by silica gel column (DCM/MeOH=50/1) to give pure 40-5 (15 g, 60%) as a white solid.

To a solution of 40-5 (15 g, 24.1 mmol) in DCM (100 mL) was added PDC (13.5 g, 26 mmol) and Ac 2 O (9.8 g, 96 mmol) at 0° C. The mixture was stirred at R.T. for 16 h. The reaction was quenched by sat. aq. NaHCO 3 , and then extracted with EA. The organic layer was dried over anhydrous Na 2 SO 4 , and concentrated at low pressure. The residue was dissolved in anhydrous THF (100 mL). To a solution of TMSCCH (12 g, 112 mmol) in THF (200 mL) was added n-BuLi (2.5 N, 44 mL) at −78° C. The mixture was stirred at −78° C. for 15 mins and 0° C. for 15 mins. The mixture was treated with a solution of crude ketone in THF at −78° C. and stirred at −30° C. for 2 h. The reaction was quenched by sat. aq. NH 4 Cl, and then extracted by EA. The combined organic layer was dried over anhydrous Na 2 SO 4 , and concentrated at low pressure. The residue was purified by silica gel column (PE/EA=10/1) to give pure 40-6 (3.1 g, 18%) as a white solid.

To a solution of 40-6 (7 g, 7.5 mmol) and pyridine (1.4 g, 17 mmol) in DCM (35 mL) was added with DAST (5.6 g, 35 mmol) at −78° C. The mixture was stirred at −78° C. for 3 h. The reaction was quenched by sat. aq. NaHCO 3 , and then extracted with EA. The combined organic layer was dried over anhydrous, and concentrated at low pressure. The residue was purified by silica gel column (PE/EA=10/1) to give pure 40-7 (3.1 g, 18%) as a white solid.

Compound 40-7 (4.1 g, 5.7 mmol) in sat. NH 3 /MeOH (100 mL) was stirred at R.T. for 16 h, and concentrated at low pressure. The residue was re-dissolved in anhydrous DCM (300 mL), and was treated with AgNO 3 (27.0 g, 160 mmol), collidine (22 mL) and MMTrCl (23.0 g, 75.9 mmol) in small portions under N 2 . The mixture was stirred at R.T. for 16 h. The mixture was filtered, and the filtrate was washed with sat. NaHCO 3 solution and brine. The organic layer was separated, dried over anhydrous Na 2 SO 4 , and concentrated at low pressure. The residue was purified by silica gel column (PE/EA=10/1) to give the pure intermediate. The intermediate was dissolved in a solution of TBAF/THF (1N, 20 mL). The mixture was stirred at R.T. for 2 h and then concentrated at low pressure. The residue was purified by silica gel column (DCM/MeOH=50/1) to give pure 40-8 (3.0 g, 86%) as a white solid.

To a solution of 40-8 (3.0 g, 4.9 mmol) in THF (50 mL) was added imidazole (840 mg, 12 mmol), PPh 3 (3.2 g, 12 mmol), and 12 (2.4 g, 9.2 mmol) at 0° C. The mixture was stirred at R.T. for 16 h. The reaction was quenched by sat. aq. Na 2 S 2 O 3 , and then extracted with EA. The combined organic layer was dried over anhydrous Na 2 SO 4 , and concentrated at low pressure. The residue was purified by silica gel column (PE/EA=2/1) to give crude 40-9 (4.2 g, >100%, containing TPPO) as a white solid.

To a solution of crude 40-9 in anhydrous THF (30 mL) was added DBU (2.7 g, 18 mmol), and heated to 80° C. The mixture was stirred for 1 h and checked by LCMS. The mixture was quenched by water, and extracted with EA. The organic layer was dried over anhydrous Na 2 SO 4 and filtered, and the filtrate was concentrated at low pressure. The residue was purified by silica gel column (PE/EA=2/1) to give 40-10 (2.0 g, 69%) as a white solid.

To an ice-cooled solution of 40-10 (2.0 g, 3.38 mmol) in anhydrous MeCN (15 mL) was added NIS (777 mg, 3.5 mmol) and NEt 3 .3HF (536 g, 3.3 mmol) at 0° C. The mixture was stirred at R.T. for 16 h and checked by LCMS. After completion, the mixture was quenched by sat. Na 2 SO 3 and sat. NaHCO 3 solution, and extracted with EA. The organic layer was separated, dried over anhydrous Na 2 SO 4 and concentrated at low pressure. The residue was purified by silica gel column chromatography (PE/EA=10/1 to 3/1) to give 40-11 (2.1 g, 84.0%) as a white solid.

To a solution of crude 40-11 (2.1 g, 2.85 mmol) in anhydrous DCM (100 mL) was added DMAP (490 mg, 4 mmol), and BzCl (580 mg, 4 mmol) at 0° C. The mixture was stirred overnight and checked by LCMS. The reaction was washed with sat. NaHCO 3 solution. The organic layer was dried over anhydrous Na 2 SO 4 , and concentrated at low pressure. The residue was purified by silica gel column chromatography (PE/EA=8/1 to 3/1) to give 40-12 (2.0 g, 83.4%) as a white solid.

To a solution of 40-12 (2.0 g, 2.4 mmol) in anhydrous DMF (60 mL) was added NaOBz (3.3 g, 23.0 mmol) and 15-crown-5 (5.11 g, 23 mmol). The mixture was stirred at 110° C. for 36 h. The reaction was quenched by water, and the mixture was extracted with EA. The organic layer was dried over anhydrous Na 2 SO 4 , and concentrated at low pressure. The residue was purified by silica gel column (PE/EA=5/1 to 3/1) to give 40-13 (830 mg, 42.0%) as a white solid. ESI-MS: m/z 836.11 [M+H] + .

A solution of 40-13 (831 mg, 1.0 mmol) in anhydrous n-butylamine (4 mL) was stirred at R.T. for 3 h under N 2 atmosphere. The reaction was monitored by TLC. The solvent was evaporated in vacuo, and the residue was purified by silica gel column (MeOH in DCM from 0% to 10%) to give the crude product, which as re-purified using silica gel column to give 40-14 as a light pink solid (563 mg).

To a solution of 40-14 (560 mg, 0.89 mmol) in anhydrous pyridine (5 mL) was added imidazole (78.6 mg, 1.16 mmol) and TBSCl (202 mg, 1.34 mmol) at 0 to 5° C. The mixture was stirred at R.T. for 15 h. The reaction was quenched by adding absolute EtOH (0.3 mL). The solution was concentrated to dryness under reduced pressure, and co-evaporated with toluene 3 times. The residue was dissolved in EA (150 mL), and washed with water, sat. NaHCO 3 , and brine. The combined organic layer was dried over Na 2 SO 4 , filtered and evaporated at low pressure. The residue was purified by silica gel column (0-20% EA in hexanes) to give 40-15 (303 mg) as a white solid.

To a solution of 40-15 (303 mg, 0.41 mmol), AgNO 3 (208 mg, 1.23 mmol) and collidine (0.55 mL, 4.51 mmol) in anhydrous DCM (4 mL) was added MMTrCl (378 mg, 1.3 mmol) under N 2 . The mixture was stirred at R.T. overnight under N 2 , and monitored by TLC. The mixture was filtered through pre-packed celite filter, and the filtrate was washed with water and, 50% aqueous citric acid, and brine. The organic layer was separated, dried over anhydrous Na 2 SO 4 , filtered and concentrated at low pressure. The residue was purified by silica gel column (EA in hexanes from 0% to 30%) to give 40-16 (374 mg, 90%).

To a solution of 40-16 (374 mg, 0.37 mmol) in anhydrous THF (4 mL) was added 1.0 M solution of TBAF (0.74 mL, 0.74 mmol) at 0 to 5° C. The mixture was stirred at R.T. for 1 h. The mixture was quenched with silica gel, and filtered. The solvents were evaporated to give the crude product, which was purified by silica gel column (EA in hexanes from 0% to 50%) to give 40-17 (265 mg).

To a stirred solution of 40-17 (187.5 mg, 0.16 mmol) in anhydrous CH 3 CN (2.5 mL) was added N-methylimidazole (136 μL, 1.66 mmol) at 0-5° C. (ice/water bath) followed by solution of phenyl (cyclohexanoxy-L-alaninyl) phosphorochloridate (214 mg, 0.62 mmol, dissolved in 0.5 mL of CH 3 CN). The solution was stirred at R.T. for 3 h, and then diluted with EA followed by the addition of water (15 mL). The solution was washed with H 2 O, 50% aqueous citric acid solution and brine. The organic layer was separated, dried over anhydrous MgSO 4 and filtered. The filtrate was concentrated in vacuum to give a residue, which was purified on silica gel with 0 to 40% EA/hexanes to give (single isomers) of 40-18 (108 mg) Elution of the latter fraction gave (single isomers) of 40-19 (120 mg) as glassy solid.

Compound 40-18 (108 mg, 0.089 mmol) was dissolved in_anhydrous CH 3 CN (0.5 mL), and 4N HCl in dioxane (67 μL) was added at 0 to 5° C. (ice/water bath). The mixture was stirred at R.T. for 40 mins, and anhydrous EtOH (200 μL) was added. The solvents were evaporated at R.T. and co-evaporated with toluene 3 times. The residue was dissolved in 50% CH 3 CN/H 2 O, was purified on a reverse-phase HPLC (C18) using acetonitrile and water, followed by lyophilization to give compound 40 (26.6 mg) as a white foam. 1 H NMR (CD 3 OD-d 4 , 400 MHz) δ 7.89 (s, 1H), 7.33-7.29 (m, 2H), 7.20-7.13 (m, 3H), 7.17 (m, 1H), 6.62 (d, J=15.6 Hz, 1H), 5.39 (t, J=25.2 Hz, 1H), 4.75-4.42 (m, 6H), 3.92 (t, J=8.8 Hz, 1H), 3.24 (d, J=5.6 Hz, 1H), 1.76-1.51 (m, 5H), 1.45-1.25 (m, 12H); 31 P NMR (CD 3 OD-d 4 ) δ4.04 (s); ESI-LCMS: m/z=665.2 [M+H] + .

Compound 41 (44.4 mg, single isomer) was obtained according to the procedure described for compound 40 using 40-19. 1 H NMR (CD 3 OD-d 4 , 400 MHz) δ 7.93 (s, 1H), 7.32 (t, J=8.0 Hz, 1H), 7.24 (d, J=7.6 Hz, 2H), 7.16 (t, J=7.6 Hz, 1H), 6.61 (d, J=16.0 Hz, 1H), 4.68-4.60 (m, 2H), 4.54-4.39 (m, 3H), 3.93-3.89 (m, 1H), 3.24 (d, J=5.6 Hz, 1H), 1.75-1.5 (m, 5H), 1.48-1.23 (m, 12H); 19 F NMR (CD 3 OD-d 4 ) δ −122.95 (s), −155.84-155.99 (m); 31 P NMR (CD 3 OD-d 4 ) δ3.94 (s); ESI-LCMS: m/z=665.15 [M+H] + .

Compound 49

To a solution of triethylammonium bis(isopropyloxycarbonyloxymethyl)phosphate (0.33 mmol, prepared from 110 mg of bis(POC)phosphate and 46 μL of Et 3 N) in THF was added 49-1 (91 mg, 0.11 mmol). The mixture evaporated and rendered anhydrous by co-evaporating with pyridine follow by toluene. The residue was dissolved in anhydrous THF (1.5 mL) and cooled in an ice-bath. Diisopropylethyl amine (0.19 mL, 10 eq.) was added, followed by BOP-Cl (0.14 g, 5 eq.), and 3-nitro-1,2,4-triazole (63 mg, 5 eq.). The mixture was stirred 0° C. for 90 mins, diluted with EtOAc (30 mL), washed with sat. aq. NaHCO 3 , brine, and dried (Na 2 SO 4 ). The residue was purified on silica (10 g column) with CH 2 Cl 2 /i-PrOH solvent system (2-10% gradient) to obtain 49-2 (13 mg, 10%) and 49-3 (95 mg, 58%).

A solution of 49-2 and 49-3 (13 mg and 95 mg, respectively) in 80% aq. HCOOH (3 mL) was stirred at R.T. for 3 h, then evaporated and co-evaporated with toluene. The residue was purified on silica (10 g column) with CH 2 Cl 2 /MeOH (4-10% gradient) to obtain compound 49 in (42 mg, 94%) yield. MS: m/z=628 [M+1] + .

Compound 52

Compound 52-2 (158 mg, 50%) was from 52-1 (0.21 g; 0.35 mmol) and triethylammonium bis(isopropyloxycarbonyloxymethyl)phosphate (0.54 mmol) with DIPEA (0.18 mL), BopCl (178 mg), and 3-nitro-1,2,4-triazole (80 mg) in THF (4 mL).

A solution of 52-2 (158 mg) in acetonitrile (1 mL) and HCl (4 N/dioxane; 85 μL) was stirred at R.T. for 30 mins. The reaction was quenched with MeOH and concentrated. The residue was purified on silica gel (10 g column) with CH 2 Cl 2 /i-PrOH (3-10% gradient) to give compound 52 (85 mg, 76%). MS: m/z=656 [M+1] + .

Compound 11

A mixture of 11-1 (170 mg, 0.19 mmol) and methanolic ammonia (7 N; 3 mL) was stirred at R.T. for 8 h, concentrated and purified on silica gel (10 g column) with CH 2 Cl 2 /MeOH (4-11% gradient) to give 11-2 (100 mg, 90%).

Compound 11-2 was rendered anhydrous by co-evaporating with pyridine, followed by toluene. To a solution of 11-2 (24 mg, 0.04 mmol), and N-methylimidazole (17 μL, 5 eq.) in acetonitrile (1 mL) was added the phosphorochloridate (50 mg, 3.5 eq.) in 2 portions in 6 h intervals. The mixture was stirred at R.T. for 1 d and evaporated. Purification on silica (10 g column) with CH 2 Cl 2 /MeOH (4-12% gradient) yielded 11-3 (10 mg, 28%).

A solution of 11-3 (9 mg, 0.01 mmol) in 80% formic acid was stirred 3 h at R.T. The mixture was evaporated and purified on silica (10 g column) with CH 2 Cl 2 /MeOH (5-15% gradient) to give compound 11 (3 mg, 50%). MS: m/z=624 [M−1] − .

Compound 14

A mixture of 14-1 (1.2 g, 4.3 mmol), PTSA monohydrate (0.82 g, 1 eq.), and trimethyl orthoformate (14 mL, 30 eq.) in dioxane (30 mL) was stirred overnight at R.T. The reaction was neutralized with 7 N NH 3 /MeOH and a white solid removed by filtration. The residue was dissolved in THF (10 mL) and treated with 80% aq. AcOH (5 mL). The mixture was kept at R.T. for 45 mins and then evaporated. The residue was purified on silica gel (25 g column) with CH 2 Cl 2 /MeOH (4-10% gradient) to give 14-2 (1.18 g, 87%).

Compound 14-3 (137 mg, 75%) was prepared from 14-2 (93 mg, 0.29 mmol) and triethylammonium bis(isopropyloxycarbonyloxymethyl)phosphate (0.44 mmol) with DIPEA (0.2 mL), BopCl (147 mg), and 3-nitro-1,2,4-triazole (66 mg) in THF (3 mL). Purification was done with CH 2 Cl 2 /i-PrOH solvent system (3-10% gradient).

A solution of 14-3 (137 mg) in 80% aq. HCOOH was stirred at R.T. for 2 h, and then concentrated. The residue was co-evaporated with toluene and then MeOH containing a small amount of a small amount of Et 3 N (2 drops). Purification on silica (25 g column) with CH 2 Cl 2 /MeOH (4-10% gradient) gave compound 14 (100 mg, 77%). MS: m/z=1175 [2M−1] − .

Compound 16

Compound 16-1 (50 g, 86.0 mmol) and 6-Cl-guanine (16.1 g, 98.2 mmol) were co-evaporated with anhydrous toluene 3 times. To a solution of 10-1 in MeCN (200 mL) was added DBU (39.5 g, 258.0 mmol) at 0° C. The mixture was stirred at 0° C. for 30 mins, and then TMSOTf (95.5 g, 430.0 mmol) was added dropwise at 0° C. The mixture was stirred at 0° C. for 30 mins. The mixture was heated to 70° C., and stirred overnight. The solution was cooled to R.T. and diluted with EA (100 mL). The solution was washed with sat. NaHCO 3 solution and brine. The organic layer was dried over Na 2 SO 4 , and concentrated at low pressure. The residue was purified by column on silica gel (EA in PE from 10% to 40%) to give 16-2 (48.0 g, yield: 88.7%) as a yellow foam. ESI-MS: m/z 628 [M+H] + .

To a solution of 16-2 (48.0 g, 76.4 mol), AgNO 3 (50.0 g, 294.1 mmol) and collidine (40 mL) in anhydrous DCM (200 mL) was added MMTrCl (46.0 g, 149.2 mmol) in small portions under N 2 . The mixture was stirred at R.T. for 3 h under N 2 . The reaction was monitored by TLC. The mixture was filtered, and the filter was washed with sat. NaHCO 3 solution and brine. The organic layer was dried over anhydrous Na 2 SO 4 , and concentrated at low pressure. The residue was purified by silica gel column (EA in PE from 5% to 50%) to the give crude 16-3 (68 g, 98%). ESI-MS: m/z 900.1 [M+H] + .

Sodium (8.7 g, 378.0 mmol) was dissolved in dry EtOH (100 mL) at 0° C., and slowly warmed to R.T. Compound 16-3 (68.0 g, 75.6 mmol) was treated with freshly prepared NaOEt solution, and stirred overnight at R.T. The reaction was monitored by TLC, and the mixture was concentrated at low pressure. The mixture was diluted with H 2 O (100 mL), and extracted with EA (3×100 mL). The organic layer was dried over anhydrous Na 2 SO 4 , and evaporated at low pressure. The residue was purified by silica gel column chromatography (MeOH in DCM from 1% to 5%) to give 16-4 (34.0 g, 75.2%) as a yellow solid. ESI-MS: m/z 598 [M+H] + .

Compound 16-4 (32.0 g, 53.5 mmol) was co-evaporated with anhydrous pyridine 3 times. To an ice-cooled solution of 16-4 in anhydrous pyridine (100 mL) was added TsCl (11.2 g, 58.9 mmol) in pyridine (50 mL) dropwise at 0° C. The mixture was stirred for 18 h. at 0° C. The reaction was checked by LCMS (about 70% was the desired product). The reaction was quenched with H 2 O, and the solution was concentrated at low pressure. The residue was dissolved in EA (100 mL), and washed with sat. NaHCO 3 solution. The organic layer was dried over anhydrous Na 2 SO 4 , and evaporated at low pressure. The residue was purified by silica gel column chromatography (MeOH in DCM from 1% to 5%) to give crude 16-5 (25.0 g, 62.2%) as a yellow solid. ESI-MS: m/z 752 [M+H] + .

To a solution of 16-5 (23.0 g, 30.6 mmol) in acetone (150 mL) was added NaI (45.9 g, 306.0 mmol) and TBAI (2.0 g), and refluxed overnight. The reaction was monitored by LCMS. After the reaction was complete, the mixture was concentrated at low pressure. The residue was dissolved in EA (100 mL), washed with brine, and dried over anhydrous Na 2 SO 4 . The organic solution was evaporated at low pressure. The residue was purified by silica gel column chromatography (DCM:MeOH=100:1 to 20:1) to give the crude product. To a solution of the crude product in dry THF (200 mL) was added DBU (14.0 g, 91.8 mmol), and heated to 60° C. The mixture was stirred overnight, and checked by LCMS. The reaction was quenched with sat. NaHCO 3 , and the solution was extracted with EA (100 mL). The organic layer was dried over anhydrous Na 2 SO 4 , and evaporated at low pressure. The residue was purified by silica gel column chromatography (MeOH in DCM from 1% to 5%) to give 16-6 (12.0 g, 67.4%) as a yellow solid. ESI-MS: m/z 580 [M+H] + .

To an ice-cooled solution of 16-6 (8.0 g, 13.8 mmol) in dry MeCN (100 mL) was added NIS (3.9 g, 17.2 mmol) and TEA.3HF (3.3 g, 20.7 mmol) at 0° C. The mixture was stirred at R.T. for 18 h and checked by LCMS. After the reaction was complete, the reaction was quenched with sat Na 2 SO 3 and sat. NaHCO 3 solution. The solution was extracted with EA. The organic layer was dried over anhydrous Na 2 SO 4 , and evaporated at low pressure. The residue was purified by silica gel column chromatography (EA in PE from 10% to 50%) to give 16-7 (7.2 g, 72.0%) as a solid. ESI-MS: m/z 726 [M+H] + .

To a solution of crude 16-7 (7.2 g, 9.9 mmol) in dry DCM (100 mL) was added DMAP (3.6 g, 29.8 mmol), and BzCl (2.8 g, 19.8 mmol) at 0° C. The mixture was stirred overnight, and checked by LCMS. The mixture was washed with sat. NaHCO 3 solution. The organic layer was dried over anhydrous Na 2 SO 4 , and evaporated at low pressure. The residue was purified by silica gel column chromatography (EA in PE from 10% to 30%) to give 16-8 (8.0 g, 86.4%) as a solid. ESI-MS: m/z 934 [M+H] + .

To a solution of 16-8 (7.5 g, 8.0 mmol) in dry DMF (100 mL) was added NaOBz (11.5 g, 80.0 mmol) and 15-crown-5 (15.6 mL). The mixture was stirred for 36 h. at 90° C. The mixture was diluted with H 2 O (100 mL), and extracted with EA (3×150 mL). The organic layer was dried over anhydrous Na 2 SO 4 , and evaporated at low pressure. The residue was purified by silica gel column chromatography (EA in PE from 10% to 30%) to give crude 16-9 (6.0 g, 80.0%) as a solid. ESI-MS: m/z 928 [M+H] + .

Compound 16-9 (4.0 g, 4.3 mmol) was co-evaporated with anhydrous toluene 3 times, and treated with NH 3 /MeOH (50 mL, 4N) at R.T. The mixture was stirred for 18 h at R.T. The reaction was monitored by LCMS, and the mixture was concentrated at low pressure. The residue was purified by silica gel column chromatography (EA in PE from 30% to 50%) to give 16-10 (1.9 g, 71.7%) as a solid. ESI-MS: m/z 616 [M+H] + .

Compound 16-10 (300.0 mg, 0.49 mmol) was co-evaporated with anhydrous toluene 3 times, and was dissolved in MeCN (2 mL). The mixture was treated with NMI (120.5 mg, 1.47 mmol) and the phosphorochloridate reagent (338.1 mg, 0.98 mmol) in MeCN (1 mL) at 0° C. The mixture was stirred for 18 h at R.T. The reaction was monitored by LCMS. The mixture was diluted with 10% NaHCO 3 solution, and extracted with EA. The residue was purified by silica gel column chromatography (EA in PE from 30% to 50%) to give 16-11 (240 mg, 53.3%) as a solid. ESI-MS: m/z 925 [M+H] + .

Compound 16-11 (240.0 mg, 0.26 mmol) was treated with 80% AcOH (10 mL), and the mixture was stirred for 18 h at R.T. The reaction was monitored by LCMS. The mixture was concentrated at low pressure. The residue was purified by silica gel column chromatography (MeOH in DCM from 1% to 3%) to give compound 16 (87.6 mg, 51.7%) as a solid. ESI-MS: m/z 653 [M+H] + .

Compound 30

To a stirred solution of compound 25 (60 mg, 0.22 mmol) in anhydrous THF (2.0 mL) was added N-methylimidazole (0.142 mL, 1.73 mmol) at 0° C. (dry ice/acetone bath) followed by solution of phenyl (cyclohexanoxy-L-alaninyl) phosphorochloridate (235 mg, 0.68 mmol, dissolved in THF (2 mL). The resulting solution was stirred at 0° C. for 1 h, and the temperature was raised up-to 10° C. over the next 1 h. The reaction left at 10° C. for 3 h. The mixture was cooled to 0 to 5° C., diluted with EA, and water (5 mL) was added. The solution was washed with H 2 O and brine. The organic layer was separated, dried over anhydrous Na 2 SO 4 and filtered. The filtrate was concentrated in vacuum to give a residue, which dissolved in 25% CH 3 CN/H 2 O. The compound was purified on a reverse-phase HPLC (C18) using acetonitrile and water, followed by lyophilization gave a white foam. The produce was re-dissolved in EtOAc, washed with 50% aqueous citric acid solution, dried over anhydrous MgSO 4 and filtered. The filtrate was concentrated in vacuum, and lyophilized to give two isomers (Rp/Sp) of compound 30 (6.3 mg). MS: m/z 586.05 [M−H] − .

Compound 17

Compound 17-1 (50 g, 86.0 mmol) and 6-Cl-guanine (16.1 g, 98.2 mmol) were co-evaporated with anhydrous toluene 3 times. To a solution of 17-1 (50 g, 86.0 mmol) and 6-Cl-guanine (16.1 g, 98.2 mmol) in MeCN (200 mL) was added DBU (39.5 g, 258.0 mmol) at 0° C. The mixture was stirred at 0° C. for 30 mins, and TMSOTf (95.5 g, 430.0 mmol) was added dropwise at 0° C. The mixture was stirred at 0° C. for 30 mins until a clear solution was observed. The mixture was heated to 70° C., and stirred overnight. The solution was cooled to R.T., and diluted with EA (100 mL). The solution was washed with sat. NaHCO 3 solution and brine. The organic layer was dried over Na 2 SO 4 , and concentrated at low pressure. The residue was purified by column on silica gel (EA in PE from 10% to 40%) to give 17-2 (48.0 g, 88.7%) as a yellow foam. ESI-MS: m/z 628 [M+H] + .

To a solution of 17-2 (48.0 g, 76.4 mol), AgNO 3 (50.0 g, 294.1 mmol) and collidine (40 mL) in anhydrous DCM (200 mL) was added MMTrCl (46.0 g, 149.2 mmol) in small portions under N 2 . The mixture was stirred at R.T. for 3 h under N 2 . Completion of the reaction was determined by TLC. After filtration, the filtrate was washed with sat. NaHCO 3 solution and brine. The organic layer was dried over anhydrous Na 2 SO 4 , and concentrated at low pressure. The residue was purified by silica gel column (EA in PE from 5% to 50%) to the give crude 17-3 (68 g, 98%). ESI-MS: m/z 900.1 [M+H] + .

Sodium (8.7 g, 378.0 mmol) was dissolved in dry EtOH (100 mL) at 0° C., and slowly warmed to R.T. Compound 17-3 (68.0 g, 75.6 mmol) was treated with freshly prepared NaOEt solution, and stirred overnight at R.T. Completion of the reaction was determined by TLC and LCMS. The mixture was concentrated at a low pressure, diluted with H 2 O (100 mL), and extracted with EA (3×100 mL). The organic layer was dried over anhydrous Na 2 SO 4 , and evaporated at low pressure. The residue was purified by silica gel column chromatography (MeOH in DCM from 1% to 5%) to give 17-4 (34.0 g, 75.2%) as a yellow solid. ESI-MS: m/z 598 [M+H] + .

Compound 17-4 (32.0 g, 53.5 mmol) was co-evaporated with anhydrous pyridine 3 times. To an ice-cooled solution of 17-4 (32.0 g, 53.5 mmol) in anhydrous pyridine (100 mL) was added a solution of TsCl (11.2 g, 58.9 mmol) in pyridine (50 mL) dropwise at 0° C. The mixture was stirred for 18 h. at 0° C. The reaction was monitored by LCMS, and quenched with H 2 O. The solution was concentrated at low pressure, and the residue was dissolved in EA (100 mL), and washed with sat. NaHCO 3 solution. The organic layer was dried over anhydrous Na 2 SO 4 , and evaporated at a low pressure. The residue was purified by silica gel column chromatography (MeOH in DCM from 1% to 5%) to give crude 17-5 (25.0 g, 62.2%) as a yellow solid. ESI-MS: m/z 752 [M+H] + .

To a solution of 17-5 (23.0 g, 30.6 mmol) in acetone (150 mL) was added NaI (45.9 g, 306.0 mmol) and TBAI (2.0 g), and the mixture was refluxed overnight. Completion of the reaction was determined by LCMS. The mixture was concentrated at low pressure, and the residue was dissolved in EA (100 mL). The solution was washed with brine, and dried over anhydrous Na 2 SO 4 . The organic solution was evaporated at low pressure, and the residue was purified by silica gel column chromatography (DCM:MeOH=100:1 to 20:1) to give a crude product. To a solution of the crude product in dry THF (200 mL) was added DBU (14.0 g, 91.8 mmol), and the mixture was heated to 60° C. and stirred overnight. The reaction was monitored by LCMS. The reaction was quenched with sat. NaHCO 3 solution, and the solution was extracted with EA (100 mL). The organic layer was dried over anhydrous Na 2 SO 4 , and evaporated at low pressure. The residue was purified by silica gel column chromatography (MeOH in DCM from 1% to 5%) to give 17-6 (12.0 g, 67.4%) as a yellow solid. ESI-MS: m/z 580 [M+H] + .

To an ice-cooled solution of 17-6 (8.0 g, 13.8 mmol) in anhydrous MeCN (100 mL) was added NIS (3.9 g, 17.2 mmol) and TEA.3HF (3.3 g, 20.7 mmol) at 0° C. The mixture was stirred at R.T. for 18 h, and the reaction was checked by LCMS. After the reaction was completed, the reaction was quenched with sat. Na 2 SO 3 solution and sat. NaHCO 3 solution. The solution was extracted with EA (3×100 mL). The organic layer was dried over anhydrous Na 2 SO 4 , and evaporated at low pressure. The residue was purified by silica gel column chromatography (EA in PE from 10% to 50%) to give 17-7 (7.2 g, 72.0%) as a solid. ESI-MS: m/z 726 [M+H] + .

To a solution of 17-7 (7.2 g, 9.9 mmol) in dry DCM (100 mL) was added DMAP (3.6 g, 29.8 mmol), and BzCl (2.8 g, 19.8 mmol) at 0° C. The mixture was stirred overnight, and checked by LCMS. The mixture was washed with sat. NaHCO 3 solution. The organic layer was dried over anhydrous Na 2 SO 4 , and evaporated at low pressure. The residue was purified by silica gel column chromatography (EA in PE from 10% to 30%) to give 17-8 (8.0 g, 86.4%) as a solid. ESI-MS: m/z 934 [M+H] + .

To a solution of 17-8 (7.5 g, 8.0 mmol) in dry DMF (100 mL) was added NaOBz (11.5 g, 80.0 mmol) and 15-crown-5 (15.6 mL). The mixture was stirred for 36 h. at 90° C. The mixture was diluted with H 2 O (100 mL), and extracted with EA (3×150 mL). The organic layer was dried over anhydrous Na 2 SO 4 , and evaporated at low pressure. The residue was purified by silica gel column chromatography (EA in PE from 10% to 30%) to give crude 17-9 (6.0 g, 80.0%) as a solid. ESI-MS: m/z 928 [M+H] + .

Compound 17-9 (4.0 g, 4.3 mmol) was co-evaporated with anhydrous toluene 3 times, and treated with NH 3 /MeOH (50 mL, 4N) at R.T. The mixture was stirred for 18 h. at R.T. Completion of the reaction was determined by LCMS. The mixture was concentrated at low pressure, and the residue was purified by silica gel column chromatography (EA in PE from 30% to 50%) to give product 17-10 (1.9 g, 71.7%) as a solid. ESI-MS: m/z 616 [M+H] + .

Compound 17-10 (300.0 mg, 0.49 mmol) was co-evaporated with anhydrous toluene 3 times, and was dissolved in MeCN (2 mL). The mixture was treated with NMI (120.5 mg, 1.47 mmol) and the phosphorochloridate reagent (326.3 mg, 0.98 mmol) in MeCN (1 mL) at 0° C. The mixture was stirred for 18 h at R.T. and monitored by LCMS. The mixture was diluted with 10% NaHCO 3 solution, and extracted with EA (3×30 mL). The residue was purified by silica gel column chromatography (EA in PE from 30% to 50%) to give 17-11 (210 mg, 47.5%) as a solid. ESI-MS: m/z 913.0 [M+H] + .

Compound 17-11 (210 mg, 0.26 mmol) was treated with 80% of AcOH (15 mL), and the mixture was stirred for 18 h at R.T. Completion of the reaction was determined by LCMS. The mixture was concentrated at low pressure, and the residue was purified by silica gel column chromatography (MeOH in DCM from 1% to 3%) to give compound 17 (71.8 mg, 48.7%) as a solid. ESI-MS: m/z 641.3 [M+H] + .

Compounds 9, 12, 15, 26, 28, 38, 44, 46, 50, 63, 64, 69 and 76

Compounds 9, 12, 15, 26, 28, 38, 44, 46, 50, 63, 64, 69 and 76 were prepared in a manner similar to method for preparing compound 6. After the addition of POCl 3 , the mixture was kept at R.T. for 20-40 mins. The reaction was controlled by LCMS and monitored by the appearance of corresponding nucleoside 5′-monophosphate. After completion of the reaction, tetrabutylammonium salt of pyrophosphate (150 mg) was added, followed by DMF (0.5 mL) to get a homogeneous solution. After 1.5 h at ambient temperature, the reaction was diluted with water (10 mL). The triphosphate (eluted at 75-80% B) were obtained as described for compound 6.

28

556.2

−10.92 −11.03 (d)

−23.18 (t)

−11.86 −11.98 (d)

38

516.1

−7.49  −7.61 (d)

−22.42 (t)

−12.17 −12.30 (d)

9

554.0

−10.94 −11.06 (d)

−23.25 (t)

−11.85 −11.97 (d)

12

525.2

−8.53 (bs)

−22.61 (bs)

−12.17 −12.29 (d)

15

564.4

−11.05 (bs)

−23.25 (bs)

−11.96 −12.08 (d)

44

566.0

−10.92 −11.04 (d)

−23.18 (t)

−11.93  −1 (d)

46

533.3

−10.89 −11.01 (d)

−23.31 (t)

−12.49  −1 (d)

50

513.8

−8.66 (bs)

−22.80 (t)

−12.17 −12.29 (d)

26

517.7

−13.73 −13.60 (d)

−25.98 (t)

−15.18 −15.06 (d)

63

539.5

−7.42 (br · s)

−22.57 (t)

−12.23 −12.34 (d)

64

513.1

−6.36  −6.49 (d)

−22.49 (t)

−12.20 −12.33 (d)

69

526.8

−10.96 −11.08 (d)

−23.33 (t)

−12.41 −12.53 (d)

76

533.4

−10.78 (br · s)

−23.22 (t)

−12.24 −12.36 (d)

The following compounds can also be prepared using a method similar to the method described in Example 27:

Compound 10

Compound 10-1 (5 g, 8.79 mmol) was co-evaporated with anhydrous pyridine. To an ice-cooled solution of 10-1 in anhydrous pyridine (15 mL) was added TsCl (3.43 g, 17.58 mmol), and stirred for 1 h at 0° C. The reaction was checked by LCMS and TLC. The reaction was quenched with H 2 O, and extracted with EA. The organic phase was dried over anhydrous Na 2 SO 4 , and evaporated at low pressure. Compound 10-2 (6.35 g, 100%) was used for next step directly.

To a solution of 10-2 (31.77 g, 43.94 mmol) in acetone (300 mL) was added NaI (65.86 g, 439.4 mmol), and heated to reflux overnight. The reaction was checked by LCMS. The reaction was quenched with sat. Na 2 S 2 O 3 solution, and extracted with EA. The organic layer was dried over anhydrous Na 2 SO 4 , and evaporated at low pressure. The residue was purified by silica gel column chromatography (MeOH in DCM from 1% to 6%) to give 10-3 (11.5 g, 38%) as a white solid.

To a solution of 10-3 (11.5 g, 16.94 mmol) in dry THF (120 mL) was added DBU (12.87 g, 84.68 mmol), and heated to 60° C. The reaction was stirred overnight and checked by LCMS. The reaction was quenched with sat. NaHCO 3 solution, and extracted with EA. The organic phase was dried over anhydrous Na 2 SO 4 , and evaporated at low pressure. The residue was purified by silica gel column chromatography (MeOH in DCM from 1% to 5%) to give 10-4 (5.5 g, 54%) as a white solid.

To an ice-cooled solution of 10-4 (500 mg, 0.90 mmol) in dry DCM (20 ml) was added AgF (618 mg, 4.9 mmol) and a solution of 12 (500 mg, 1.97 mmol) in dry DCM (20 mL). The reaction was stirred for 3 h., and checked by LCMS. The reaction was quenched with sat Na 2 S 2 O 3 solution and sat. NaHCO 3 solution, and the mixture was extracted with DCM. The organic layer was dried by anhydrous Na 2 SO 4 , and evaporated at low pressure to give crude 10-5 (420 mg, 66%).

To a solution of crude 10-5 (250 mg, 0.36 mmol) in dry DCM (8 mL) was added DMAP (0.28 g, 2.33 mmol), TEA (145 mg, 1.44 mmol) and BzCl (230 mg, 1.62 mmol) in a solution of DCM (2 mL). The reaction was stirred overnight, and checked by LCMS. The mixture was washed with sat. NaHCO 3 solution and brine. The organic layer was evaporated at low pressure. The residue was purified by prep-TLC to give crude 10-6 (150 mg, 46%).

To a solution of crude 10-6 (650 mg, 0.72 mmol) in dry HMPA (20 mL) was added NaOBz (1.03 g, 7.2 mmol) and 15-crown-5 (1.59 g, 7.2 mmol). The reaction was stirred for 2 d at 60° C. The mixture was diluted with H 2 O, and extracted with EA. The organic layer was evaporated at low pressure. The residue was purified by prep-TLC to give 10-7 (210 mg, 32.4%). ESI-MS: m/z: 900.4 [M+H] + .

A mixture of 10-7 (25 mg) and BuNH 2 (0.8 mL) was stirred overnight at R.T. The mixture was evaporated and purified on silica gel (10 g column) with CH 2 Cl 2 /MeOH (4-15% gradient) to yield 10-8 (15 mg, 91%).

A mixture of 10-8 (15 mg, 0.02 mmol) in ACN (0.25 mL) and 4 N HCL/dioxane (19 uL) was stirred at R.T. for 45 mins. The mixture was diluted with MeOH and evaporated. The crude residue was treated with MeCN, and the solid was filtered to yield compound 10 (7 mg). MS: m/z=314 [M−1] − .

Compounds 36 and 37

To a solution of 36-1 (150 mg, 0.24 mmol) in DCM (2.0 mL), triethylamine (141 μL, 2.0 mmol) was added at R.T. The mixture was cooled to 0 to 5° C. (ice/water bath), and freshly prepared and distilled isopropyl phosphorodichloridate (45 μL, 0.26 mmol, prepared according to a procedure, Reddy et al. J. Org. Chem. 2011, 76 (10), 3782-3790) was added. The mixture was stirred at 0 to 5° C. (ice/water bath) for 15 mins, followed by N-methylimidazole (40 μL, 0.49 mmol). The mixture was stirred for 1 h at 0 to 5° C. TLC showed the absence of starting material 36-1. EA (100 mL) was added, followed by water. The organic layer was washed with H 2 O, sat. aq. NH 4 Cl solution and brine. The organic layer was separated, dried over anhydrous MgSO 4 and filtered. The filtrate was concentrated in vacuum to give a residue, which was purified on silica gel with 0 to 10% iPrOH/DCM to give 36-2a (16.9 mg, faster eluting isomer) and 36-2b (72.7 mg, slower eluting isomer).

Compounds 36-2a and 36-2b were deprotected using a procedure described herein. Compound 36 (7.3 mg, single isomers from 36-2a (16.5 mg, 0.0235 mmol)) and compound 37 (29.0 mg. single isomers from 36-2b (72.7 mg, 0.1 mmol)) were obtained.

Compound 36: 1 H NMR (CD 3 OD-d 4 , 400 MHz) δ 7.94 (s, 1H), 6.32 (s, 1H), 6.00-5.9 (br s, 1H), 4.9-4.487 (m, 1H), 4.83-4.77 (m, 1H), 4.65-4.50 (m, 3H), 1.45-1.39 (s, 9H), 1.2 (s, 3H); 19 F NMR (CD 3 OD-d 4 ) δ −120.3 (s); 31 P NMR (CD 3 OD-d 4 ) δ −5.19 (s); ESI-LCMS: m/z=448.05 [M+H] + . Compound 37: 1 H NMR (CD 3 OD-d 4 , 400 MHz) δ 7.98 (s, 1H), 6.34 (s, 1H), 5.78-5.64 (br s, 1H), 4.95-4.48 (m, 2H), 4.62-4.52 (m, 3H), 1.48-1.42 (s, 9H), 1.1 (s, 3H); 19 F NMR (CD 3 OD-d 4 ) δ −121.3 (s); 31 P NMR (CD 3 OD-d 4 ) δ −7.38 (s); ESI-LCMS: m/z=448.05 [M+H] + .

Compound 48

To a solution of 48-1 (600 mg, 1.29 mmol) in anhydrous CH 3 CN (4 mL) was added DMAP (315 mg, 2.59 mmol), TEA (391 mg, 3.87 mmol) and TPSCl (782 mg, 2.58 mmol). The mixture was stirred for 3 h. under N 2 . A solution of NH 3 in THF (2 mL) was added, and stirred for 1 h. The reaction was quenched with sat. NH 4 Cl solution, and extracted with EA. The organic layer was dried over anhydrous Na 2 SO 4 , and concentrated to dryness at low pressure. The residue was purified by column chromatography to provide 48-2 (370 mg, 62%) as a white foam solid.

Compound 48-2 (370 mg, 1.48 mmol) in methanolic ammonium was stirred at R.T. for 4 h. The solution was concentrated to dryness to give compound 48 (200 mg, 91%) as a white solid. ESI-MS: m/z 275.9 [M+H] + .

Compounds 18 and 19

The diastereomers of compound 2 were separated by RP-HPLC. A gradient of 10-43% ACN in H 2 O over 26 mins on a Synergi Hydro RP 30×250 m 4 u particle column (Phenomenex PN 00G-4375-U0-AX) eluted compound 19 (29.5 mins) and compound 18 (30.1 mins). Pure fractions were lyophilized to produce a white powder. Compound 19: 31 P-NMR (DMSO-d6) 3.448 ppm; MS: m/z: 544 [M−1] − ; Compound 18: 31 P-NMR (DMSO-d6) 3.538 ppm; MS: m/z: 544 [M−1] − .

Compounds 20 and 21

The diastereomers of compound 3 were separated by RP-HPLC. A gradient of 25-52% ACN in H 2 O over 26 mins on a Synergi Hydro RP 30×250 m 4 u particle column (Phenomenex PN 00G-4375-U0-AX) eluted compound 21 (24.8 mins) and compound 20 (25.3 mins). Pure fractions were lyophilized to produce a white powder. Compound 21: 31 P-NMR (DMSO-d6) 3.492 ppm; MS: m/z: 584 [M−1] − . Compound 20: 31 P-NMR (DMSO-d6) 3.528 ppm; MS: m/z: 584 [M−1] − .

Compound 13

Compound 2-1 (32 mg, 0.1 mmol) was dissolved in dry THF (3 mL) and 2M solution of isopropylmagnesium bromide in THF (0.1 mL) was added at 0° C. The reaction was left for 1 h at R.T., and phenyl(isopropyl-L-alaninyl) thiophosphorochloridate was added (0.3 mmol). The mixture was left overnight at R.T. LSMS analysis showed about 20% of unreacted starting material. The same amount of Grignard reagent and thiophosphorochloridate were added, and the mixture was heated at 37° C. for 4 h. The reaction was quenched with NH 4 Cl. The product was extracted with EA, washed with brine, dried over Na 2 SO 4 , and evaporated. The resulting oil was dissolved in 80% formic acid (4 mL) and in 1 h evaporated. Compound 13 was purified by RP HPLC in gradient of methanol in water from 30% to 95% on Synergy 4 u Hydro-RP column (Phenominex) yielding a colorless solid. Compound 13 (7 mg, yield 12.5%). MS: m/z: 560.0 [M−1] − .

Compound 39, Bis-Lithium Salt

Compound 39-1 was synthesized using a procedure similar for preparing compound 2 using alanine benzyl ester hydrochloride. LCMS: m/z 592 [M−1] − .

To a solution of 39-1 (1.1 g, 1.85 mmol) in dioxane (15 mL) and water (3 mL) was added aqueous triethylammonium acetate (2M, 2 mL, 4 mmol) followed by Pd—C (10%, 100 mg). The mixture was hydrogenated (balloon) for 2 h, and monitored by HPLC. The catalyst was filtered off, and the filtrate was concentrated to dryness. The residue was suspended in 3% solution of lithium perchlorate in acetone (25 mL). The solid was isolated by filtration, rinsed with acetone and dried under vacuum to give compound 39 (bis-lithium salt) (731 mg, 90%). LCMS: m/z 426 [M−1] − .

Compound 55

Compound 1 (40 mg, 0.14 mmol) and triethylammonium bis(pivaloyloxymethyl)phosphate (0.21 mmol, prepared from 80 mg of bis(pivaloyloxymethyl)phosphate and 30 μL of Et 3 N) were rendered anhydrous by coevaporating with pyridine, followed by toluene. The evaporated residue was dissolved in anhydrous THF (2 mL) and cooled in an ice-bath. Diisopropylethyl amine (73 μL, 3 eq.), BopCl (71 mg, 2 eq.), and 3-nitro-1,2,4-triazole (32 mg, 2 eq.) were added. The mixture was stirred at 0° C. for 90 mins. The mixture was then diluted with EtOAc, washed with sat. aq. NaHCO 3 and brine, and dried (Na 2 SO 4 ). Purification on silica gel column with CH 2 Cl 2 /i-PrOH solvent system (4-10% gradient) followed by RP-HPLC purification (A: water, B: MeCN) yielded compound 55 (13 mg, 16%). MS: m/z=1167 [2M−1].

Compound 45

Compound 45-1 (15.0 g, 25.55 mmol) was treated with 90% HOAc (150 mL) at R.T. The mixture was stirred at 110° C. for 12 h, and then concentrated at a low pressure. The residue was dissolved in DCM, and the solution was washed with brine. The organic phase was dried over anhydrous Na 2 SO 4 , and then concentrated at a low pressure. The residue was purified by column chromatography (5% MeOH in DCM) to give 45-2 (11.0 g, 88.9%) as a white solid.

Compound 45-2 (12.0 g, 24.79 mmol) was treated with NH 3 in MeOH (200 mL, 7 M) at R.T. The solution was stirred at R.T. for 12 h, and then concentrated at a low pressure. The residue was purified by column chromatography (10% MeOH in DCM) to give 45-3 (6.5 g, 95.0%) as a white solid.

To a stirred suspension of 45-3 (4.3 g, 15.58 mmol), PPh 3 (8.16 g, 31.15 mmol), imidazole (2.11 g, 31.15 mmol) and pyridine (15 mL) in anhydrous THF (45 mL) was added a solution of 12 (7.91 g, 31.15 mmol) in THF (100 mL) dropwise at 0° C. The mixture was slowly warmed to R.T. and stirred overnight. The mixture was quenched with MeOH (100 mL). The solvent was removed at a low pressure, and the residue was re-dissolved in a mixture of EA and THF (0.2 L, 10:1). The organic phase was washed with sat. Na 2 S 2 O 3 aq. (2×). The aqueous phase was extracted with a mixture of EA and THF (0.2 L, 10:1, 2×). The concentrated organic phase was dried over anhydrous Na 2 SO 4 . The residue was purified on a silica gel column (0-10% MeOH in DCM) to afford 45-4 (5.1 g, 85.0%) as a white solid.

Compound 45-4 (800 mg, 2.07 mmol) was dissolved in a mixture of DBU (4 mL) and THF (4 mL) at R.T. under N 2 . The solution was stirred at R.T. for 1 h. The mixture was neutralized with HOAc, and extracted with a mixture of EA and THF (10:1, 40 mL). The organic phase was washed with brine, and dried over anhydrous Na 2 SO 4 . The concentrated organic phase was purified by column chromatography (0-10% MeOH in DCM) to give 45-5 (240 mg, 44.9%) as a white solid.

To an ice-cooled solution of 45-5 (1.20 g, 4.65 mmol) in anhydrous MeCN (12 mL) was added NIS (1.57 g, 6.97 mmol) and TEA.3HF (1.12 g, 6.97 mmol) under N 2 . The mixture was stirred at R.T. for 5 h. The reaction was quenched with sat. NaHCO 3 solution, and extracted with EA (3×100 mL). The organic phase was dried over anhydrous Na 2 SO 4 , and evaporated to dryness at low pressure. The residue was purified on a silica gel column (0-5% MeOH in DCM) to give 45-6 (0.91 g, 48.6%) as a white solid.

To a stirred solution of 45-6 (1.2 g, 2.97 mmol) in anhydrous DCM (12 mL) was added BzCl (0.83 g, 5.94 mmol), TEA (0.6 g, 5.94 mmol) and DMAP (0.72 g, 5.94 mmol) successively at R.T. The mixture was stirred at R.T. for 12 h. The reaction was quenched with water, and extracted with EA (3×60 mL). The organic phase was concentrated at low pressure. The residue was purified by column chromatography (0-5% MeOH in DCM) to give 45-7 (1.2 g, 66.2%) as a white solid.

Tetra-butyl ammonium hydroxide (25.78 mL, 51.78 mmol) was neutralized with TFA (4.3 mL) to pH=4, and the solution was added to a solution of 45-7 (1.09 g, 2.14 mmol) in DCM (30 mL). m-CPBA (1.85 g, 10.74 mmol) was added portion-wise under vigorous stirring, and the mixture was stirred for 12 h. The mixture was diluted with EA (100 mL), and washed with sat. sodium bicarbonate. The organic phase was concentrated at low pressure. The residue was purified by column chromatography (50% EA in PE) to give 45-8 (350 mg, 41.1%) as a white solid.

Compound 45-8 (280 mg, 0.704 mmol) was treated with NH 3 in MeOH (10 mL, 7 M) at R.T. The mixture was stirred at R.T. for 2 h. The mixture was concentrated at a low pressure. The residue was purified by column chromatography (0-10% MeOH in DCM) to give compound 45 (110 mg, 53.1%) as a white solid. ESI-LCMS: m/z 295.1 [M+H] + .

Compound 54

To an ice-cooled solution of 54-1 (10 g, 42 mmol) in anhydrous MeCN (200 mL) was added TEA.3HF (10 g, 62.5 mmol) and NIS (28 g, 126 mmol). The mixture was stirred at R.T. for 1.5 h, and monitored by LCMS. After the reaction was completed, the mixture was concentrated at a low pressure. The residue was purified by silica gel column chromatography (15% MeCN in DCM) to give 54-2 (12 g, 74%) as a yellow solid.

To a solution of 54-2 (22 g, 57 mmol) in anhydrous DCM (200 mL) was added DMAP (21 g, 171 mmol) and BzCl (17.6 g, 125 mol). The mixture was stirred for 5 h at R.T., and monitored by LCMS. The solution was washed with sat. NaHCO 3 solution, brine and extracted with EA. The organic phase was dried over anhydrous Na 2 SO 4 and filtered. The filtrate was concentrated at low pressure. The residue was purified by silica gel column chromatography (20% EA in PE) to give 54-3 (30 g, 88%) as a white foam.

To a solution of 54-3 (6.5 g, 11 mmol) in anhydrous DMF (270 mL) was added NaOBz (15.8 g, 110 mmol) and 15-crown-5 (29 g, 132 mmol). The mixture was stirred at 95° C. for 48 h. The precipitate was removed by filtration, and the organic solvent was removed at low pressure. The residue was dissolved in EA (200 mL), and the solution was washed with sat. NaHCO 3 solution, and brine. The organic layer was dried over anhydrous Na 2 SO 4 and filtered. The filtrate was concentrated at low pressure. The residue was purified by silica gel column chromatography (20% EA in PE) to give 54-4 (3 g crude, 46.1%) as an oil.

Compound 54-4 (3 g, crude) was treated with NH 3 in MeOH (120 mL, 7 M). The mixture was stirred for 3 h and monitored by TLC. The solution was concentrated at low pressure. The residue was purified by silica gel column chromatography (10% isopropanol in DCM) to give 54-5 (1.0 g, 67%) as a white solid. 1 H-NMR (CD 3 OD, 400 MHz) δ=1.19 (s, 3H), 3.76-3.82 (m, 2H), 4.02 (d, J=19.8 Hz, 1H), 5.70 (d, J=8.07 Hz, 1H), 6.27 (s, 1H), 7.89 (d, J=8.07 Hz, 1H).

Compound 54-5 (100 mg, 0.36 mmol) was co-evaporated with toluene 3 times. To a stirred solution of 54-5 (100 mg, 0.36 mmol) in a mixture of MeCN (1.0 mL) and NMI (295 mg, 3.6 mmol) was added a solution of 54-C (255.6 mg, 0.72 mmol, preparation described below) in MeCN (0.5 mL) at 0° C. The mixture was stirred at R.T. overnight. The reaction was quenched with water, and diluted with EA (20 mL). The organic layer was washed with water and brine. The organic layer was dried over anhydrous Na 2 SO 4 . The organic phase was concentrated at low pressure. The residue was purified on a silica gel column (5% i-PrOH in DCM) to give the crude product. The product was purified by prep-HPLC (0.1% HCOOH in water and MeCN) to give compound 54 (46.7 mg, 23.3%) as a white solid. ESI-LCMS: m/z 618 [M+Na] + .

To a stirred solution of 54-A (2.0 g, 13.16 mmol) and naphthalen-1-ol (1.89 g, 13.16 mmol) in anhydrous DCM (100 mL) was added a solution of TEA (1.33 g, 13.16 mmol) in DCM (20 mL) dropwise at −78° C. After addition, the mixture was gradually warmed to R.T., and stirred for 2 h. The solution was cooled to −78° C., and (S)-isopropyl 2-aminopropanoate hydrochloride (2.20 g, 13.16 mmol) in DCM (20 mL) was added, followed by TEA (2.66 g, 26.29 mmol) in DCM (20 mL) dropwise. The mixture was gradually warmed to R.T., and stirred for 2 h. The organic solvent was removed at low pressure. The residue was dissolved in methyl-butyl ether. The precipitate was filtered, and the filtrate was concentrated at low pressure. The residue was purified on a silica gel column (anhydrous DCM) to give 54-C (1.0 g, 24.8%) as a colorless oil.

Compounds 56 and 57

To a solution of 54-5 (300 mg, 1.08 mmol) and NMI (892 mg, 10 mmol) in anhydrous MeCN (4 mL) was added a solution of 57-C (736 mg, 2.17 mmol, preparation described below) in anhydrous MeCN (1 mL) dropwise at 0° C. The mixture was stirred at R.T. overnight. The reaction was quenched with water, and diluted with EA (30 mL). The organic layer was washed with water and brine. The organic phase was dried over anhydrous Na 2 SO 4 and concentrated at low pressure. The residue was purified by a silica gel column (iPrOH in DCM from 1% to 5%) to give crude compound 56 (276 mg, crude). Crude compound 56 (96 mg) was purified by prep-HPLC (0.1% HCOOH in water and MeCN) to give pure compound 56 (46 mg, 47.9%) as a white solid. ESI-LCMS: m/z 560 [M−F] + .

To a solution of compound 56 (180 mg, 0.31 mmol) in anhydrous pyridine (6 mL) was added acetic anhydride (158 mg, 1.54 mmol) dropwise at 0° C. The mixture was stirred at R.T. overnight. The solution was quenched with water and concentrated at a low pressure. The residue was dissolved in EA (10 mL), and washed with brine. The organic layer was dried over anhydrous Na 2 SO 4 . The organic phase was concentrated at low pressure. The residue was purified by silica gel column (i-PrOH in DCM from 1% to 3%) to give crude compound 57 (172 mg). Crude compound 57 was purified by prep-HPLC (0.1% HCOOH in water and MeCN) to give pure compound 57 (46 mg, 23.8%) as a white solid. ESI-LCMS: m/z 602.3 [M−F] + .

Compound 56-C (1.02 g, 23%, a colorless oil) was prepared using a procedure similar to the preparation of 54-C using 54-A (2.00 g, 13.16 mmol) and 4-chlorophenol (1.68 g, 13.16 mmol).

Compound 61

Compound 25 (109 mg, 0.39 mmol) and triethylammonium bis(isopropyloxycarbonyloxymethyl)phosphate (0.6 mmol, prepared from 195 mg of bis(isopropyloxycarbonyloxymethyl)phosphate and 85 μL of Et 3 N) were rendered anhydrous by coevaporating with pyridine, followed by toluene. The residue was dissolved in anhydrous THF (3 mL) and cooled in an ice-bath. Diisopropylethyl amine (0.2 mL, 3 eq.), BopCl (190 mg, 2 eq.), and 3-nitro-1,2,4-triazole (81 mg, 2 eq.) were added, and the mixture was stirred at 0° C. for 90 mins. The mixture was diluted with EtOAc, washed with sat. aq. NaHCO 3 and brine, and dried (Na 2 SO 4 ). Purification on silica gel column with CH 2 Cl 2 /i-PrOH (4-10% gradient) followed by RP-HPLC purification (A: 0.1% HCOOH in water, B: 0.1% HCOOH in MeCN) yielded compound 61 (28 mg, 12%). 1 H-NMR (CDCl 3 ): δ 7.24 (d, 1H), 6.6 (br, 1H), 5.84 (d, 1H), 5.65-5.73 (m, 4H), 4.94 (m, 2H), 4.38 (m, 2H), 4.1 (b, 1H), 2.88 (d, 1H), 1.47 (d, 3H), 1.33 (m, 12H).

Compound 74

Dry nucleoside (0.05 mmol) was dissolved in a mixture of PO(OMe) 3 (0.7 mL) and pyridine (0.3 mL). The mixture was evaporated in vacuum for 15 mins. at 42° C., then cooled to R.T. N-Methylimidazole (0.009 mL, 0.11 mmol) was added followed by POCl 3 (0.009 mL, 0.11 mmol). The mixture was kept at R.T. for 20-40 mins and monitored for the formation of compound 74 by LCMS. The reaction was quenched with water and isolated by RP HPLC on Synergy 4 micron Hydro-RP column (Phenominex). A linear gradient of methanol from 0 to 30% in 50 mM triethylammonium acetate buffer (pH 7.5) was used for elution. The corresponding fractions were combined, concentrated and lyophilized 3 times to remove excess of buffer. MS: m/z 396.5 [M−1] − .

Compound 68

The nucleoside (140 mg, 0.42 mmol) was dissolved in n-butylamine (0.5 mL). The mixture was kept for 2 h at R.T., and the amine was then evaporated. The residue was dissolved in EtOAc, and the organic layer was washed twice with 10% citric acid, dried over Na 2 SO 4 , and evaporated. The residue purified by column chromatography on silica gel in linear gradient of methanol in DCM from 0% to 12% over 10 column volumes. The fractions containing the product were concentrated and treated with 80% HCOOH for 1 h at R.T. The mixture was evaporated to dryness, and suspended in CH 3 CN. The precipitate was separated, washed with CH 3 CN (1 mL) and dried to yield compound 68 (27 mg, 50%). MS: m/z 326.5 [M−1] − .

Compound 62

Compound 45 (30 mg, 0.1 mmol) was dissolved in a mixture of CH 3 CN (2 mL) and N-methylimidazole (200 uL). Phosphorochloridate (100 mg, 0.3 mmol) was added, and the mixture was kept for 5 d at R.T. The mixture was distributed between water and EA. The organic layer was separated, washed with brine, dried and evaporated. The phosphoroamidate was isolated by silica gel chromatography in a gradient of methanol in DCM from 3% to 10%. The corresponding fractions were concentrated and re-purified by RP HPLC on Synergy 4 micron Hydro-RP column (Phenominex). A linear gradient of methanol in DCM from 3% to 95% containing 0.1% formic acid was used for elution. Compound 62 was obtained as a mixture Rp and Rs isomers (9 mg, 16%). MS: m/z 562.1 [M−1] − .

Compound 72

Compound 47 (30 mg, 0.1 mmol) was dissolved in a mixture of CH 3 CN (2 mL) and N-methylimidazole (200 uL). Phosphorochloridate (100 mg, 0.3 mmol) was added, and the mixture was kept overnight at 40° C. The temperature was increased to 65° C. and heated for 1 h. The mixture was distributed between water and EA. The organic layer was separated, washed with brine, dried and evaporated. The azido-phosphoramidate was purified by RP HPLC on Synergy 4 micron Hydro-RP column (Phenominex). A linear gradient of methanol from 30% to 100% in 50 mM triethylammonium acetate buffer (pH 7.5) was used for elution. The azido-phosphoramidate (8 mg) was dissolved in pyridine/Et 3 N (3 mL, 8:1 v/v) and cooled to 0° C. H 2 S gas was bubbled through the solution for 10 min, and the reaction was kept for 1 h at R.T. The solvents were evaporated, and the residue isolated by RP HPLC. The corresponding fractions were combined, concentrated and lyophilized 3 times to remove excess of buffer, to provide compound 72 (1.2 mg) as mixture Rp and Rs isomers. MS: m/z 544.1 [M+1] + .

Compound 65

To a solution of 65-1 (23.0 g, 39.5 mmol) in anhydrous toluene (200 mL) was added DAST (31.9 g, 198 mmol) dropwise at −78° C., and the solution was stirred at −78° C. for 3 h. The mixture was quenched with sat. NaHCO 3 , extracted with EA (2×200 mL) and dried over with anhydrous Na 2 SO 4 . The solution was concentrated to dryness under low pressure. The residue was purified on a silica gel column (50% EA in PE) to give 65-2 (16.5 g, 71%) as a yellow foam.

A mixture of 65-2 (16.0 g, 27.4 mmol) and NH 4 F (3.0 g, 82.2 mmol) in methanol (100 mL) was stirred at 70° C. for 12 h. The reaction was cooled, and the salt was removed by filtration. The filtrate was concentrated to dryness at low pressure. The residue was purified on a silica gel column (3% MeOH in DCM) to give 65-3 (5.1 g, 69.0%) as a white foam.

To a stirred suspension of 65-3 (4.1 g, 15.2 mmol), PPh 3 (8.0 g, 30.4 mmol), imidazole (2.1 g, 30.4 mmol) and pyridine (18.2 mL) in anhydrous THF (40 mL) was added dropwise a solution of 12 (5.8 g, 22.8 mmol) in THF (20 mL) at 0° C. The mixture was stirred at R.T. for 12 h. The reaction was quenched with MeOH (100 mL), and the solvent was removed under reduced pressure. The residue was purified on a silica gel column (4% MeOH in DCM) to give pure 65-4 (4.4 g, 77%) as a white solid. ESI-MS: m/z 381.1 [M+1] + .

To a stirred solution of 65-4 (2.5 g, 0.7 mmol) in anhydrous THF (3 mL) was added DBU (2.1 g, 14 mmol) at R.T., and the mixture was stirred at R.T. for 1 h. The reaction was quenched with HOAc, and diluted with 2-Me-tetrahydrofuran. The solution was washed with brine, dried over with anhydrous Na 2 SO 4 and concentrated to dryness at low pressure. The residue was purified on a silica gel column (MeOH 5% in DCM) to give 65-5 (1.1 g, 68.9%) as a white foam.

To a stirred solution of 65-5 (800 mg, 3.17 mmol) in anhydrous CH 3 CN (10 mL) was added TEA.3HF (510 mg, 3.17 mmol) and NIS (785 mg, 3.49 mmol) at 0° C. The mixture was stirred for 30 mins, gradually warmed to R.T., and stirred for 1 h. The mixture was quenched with sat. NaHCO 3 solution and Na 2 S 2 O 3 solution, and extracted with EA (2×20 mL). The organic layer was dried over with anhydrous Na 2 SO 4 , and concentrated to dryness at low pressure. The residue was purified on a silica gel column to give pure 65-6 (695 mg, 57.9%) as a yellow solid.

To a stirred solution of 65-6 (650 mg, 1.63 mmol) in pyridine (3 mL) was added BzCl (507 mg, 3.59 mmol) at 0° C., and stirred at R.T. for 12 h. The mixture was quenched with water, and concentrated to dryness under reducing pressure. The residue was purified on a silica gel column (EA 50% in PE) to yield 65-7 (550 mg, 67%) as a white foam.

Tetra-butylammonium hydroxide (9 mL as 54-56% aqueous solution, 72 mmol) was neutralized with TFA to pH-4 (1.5 mL), and the mixture was added to a solution of 65-7 (375 mg, 0.75 mmol) in DCM (9 mL). m-Chloroperbenzoic acid (924 mg, 60-70%, 3.75 mmol) was added in portions with vigorous stirring, and the mixture was stirred overnight. The mixture was washed with brine, dried over magnesium sulfate and concentrated under reduced pressure. The residue was purified by column chromatography (EA 50% in PE) to give 65-8 (230 mg, 78.8%) as a white foam. ESI-MS: m/z 393.1 [M+1] + .

Compound 65-8 (120 mg, 0.24 mmol) was treated with 7N NH 3 .MeOH (20 mL), and stirred for 5 h. The mixture was concentrated to dryness at low pressure. The residue was purified on a silica gel column (propan-2-ol 15% in DCM) to yield compound 65 (53 mg, 60.2%) as a white solid. ESI-MS: m/z 288.8 [M+1] + .

Compound 70

To a solution of 70-1 (3.0 g, 18.0 mmol) and POCl 3 (1.35 g, 9.0 mmol) in DCM (80 mL) was added TEA (3.6 g, 36.0 mmol) in DCM (20 mL) dropwise at 0° C. The mixture was stirred at 0° C. for 2 h. A solution of pentafluorophenol (1.65 g, 9.0 mmol) and TEA (0.9 g, 9.0 mmol) in DCM (20 mL) was added dropwise at 0° C., and the mixture was stirred at 0° C. for 15 h. After the reaction was completed, the mixture was concentrated under reduced pressure. The residue was washed by TBME and filtered. The filtrate was concentrated under reduced pressure, and the residue was purified by silica gel chromatography (20% EA in PE) to give 70-2 (2.7 g, 62.7%) as a white solid. ESI-MS: m/z 491.1 [M+1] + .

To a stirred solution of 1-((3aR,4R,6S,6aS)-6-fluoro-6-(hydroxymethyl)-2-methoxy-3a-methyltetrahydrofuro [3,4-d][1,3]dioxol-4-yl)pyrimidine-2,4(1H,3H)-dione (150 mg, 0.47 mmol) in anhydrous THF (2 mL) was added a solution of t-BuMgCl (0.46 mL, 1M in THF) dropwise at 0° C. The mixture was stirred at R.T. for 40 mins, and re-cooled to 0° C. A solution of 70-2 (462 mg, 0.94 mmol) was added, and the mixture was stirred at R.T. for 4 h. The mixture was quenched with H 2 O, and extracted with EA. The organic layer was dried over Na 2 SO 4 and concentrated under reducing pressure. The residue was purified on a silica gel column (50% EA in PE) to give 70-3 as a white foam (230 mg, 78%).

Compound 70-3 (230 mg, 0.37 mmol) was dissolved in 80% HCOOH aqueous solution (20 mL), and the mixture was stirred at R.T. for 24 h. The solvent was removed at low pressure. The residue was purified on a silica gel column to give the crude product, which was purified by RP HPLC (HCOOH system) to give compound 70 as a mixture of two P-isomers (75 mg, 33%). ESI-TOF-MS: m/z 583.0 [M+H] + .

Compound 75

To a solution of 75-1 (120 g, 0.26 mol) in CH 3 CN (2.0 L) was added IBX (109 g, 0.39 mol), and refluxed for 12 h. The reaction was monitored by TLC and LCMS. After cooling to R.T., the mixture was filtered, and the filtrate was concentrated at low pressure. The crude product was used directly for the next step.

Compound 75-2 (130 g, 0.26 mol) was co-evaporated with anhydrous toluene three times to remove H 2 O. To a solution of 75-2 in THF (300 mL) was added dropwise vinyl magnesium bromide (700 mL, 0.78 mol, 1N in THF) over 30 min at −78° C. The mixture was stirred for about 1 h at R.T. After the starting material was consumed, the mixture was poured into a sat. NH 4 Cl solution. The organic layer was washed with brine, dried with anhydrous Na 2 SO 4 and filtered. The solution was concentrated at low pressure to get the crude product. To a solution of this crude product (170 g, 0.346 mol) in anhydrous CH 2 Cl 2 was added TEA (105 g, 1.04 mol) and DMAP (84 g, 0.69 mol). Benzoyl chloride (146 g, 1.04 mol) was added slowly at R.T. for 12 h. The mixture was diluted with CH 2 C 12 and then washed with sat. aq. NaHCO 3 . The combined aq. phase was extracted with DCM (100 mL), and the combined organic phase was dried with Na 2 SO 4 . After filtration, the solution was evaporated to dryness under reduced pressure, and the residue was purified by column chromatography to give 75-3 (107 g, 52%).

Uracil (44.8 g, 0.4 mol) (co-evaporated with toluene twice) and NOBSA (81.4 g, 0.4 mol) were dissolved in CH 3 CN (500 mL). The mixture was refluxed for 1.5 h and then slowly cooled to R.T. The mixture was treated with 75-3 (59 g, 0.1 mol) and TMSOTf (155 g, 0.7 mol), and then warmed to 60-70° C. for 12 h. The mixture was neutralized with a sat. NaHCO 3 solution, and extracted with EA (3×1000 mL). The solution was dried over anhydrous MgSO 4 , and evaporated at low pressure. The residue was purified using a silica gel column to give pure 75-4 (40 g, 69%) as a white solid.

To a solution of 75-4 (50 g, 0.086 mol) in DMF was added PMBCl (16 g, 0.1 mol) and K 2 CO 3 (17.8 g, 0.13 mol) at 0° C., and the mixture was stirred at R.T. for 12 h. The mixture was quenched with water (100 mL), and extracted with EA (3×200 mL). The organic phase was concentrated at low pressure to give crude 75-5 (65 g) which was used in the next step without further purification.

To a solution of crude 75-5 (65 g, 0.086 mol) in MeOH/DCM (4/1) (200 mL) was added NaOMe (16.8 g, 0.3 mol), and the mixture was stirred at R.T. for 2.5 h. The reaction was quenched with dry ice, and then concentrated at low pressure. The residue was dissolved in EA (200 mL) and washed with brine. The organic layer was concentrated at low pressure, and the residue was purified using a silica gel column using 1% MeOH in CH 2 C 12 to give 75-6 as a yellow foam (25 g, 75%).

To a solution of 75-6 (25.5 g, 0.065 mol) in DMF was added NaH (10.5 g, 0.26 mol) slowly at 0° C., and the mixture was stirred for 30 mins. BnBr (36.3 g, 0.21 mol) was added, and the mixture was stirred at R.T. for 12 h. The reaction was quenched with sat. NH 4 Cl (aq.), and then extracted with EA (3×100 mL). The solution was dried over anhydrous MgSO 4 , and evaporated at low pressure. The residue was purified by a silica gel column using 10% EA in PE to give 75-7 (20 g, 46%) as a white solid.

To a solution of 75-7 (20 g, 0.03 mol) and NMMO (7 g, 0.06 mol) in THF:H 2 O (5:1) (100 mL) was added OsO 4 (2.6 g, 0.01 mol) at R.T., and the mixture was stirred at R.T. for 24 h. The mixture was quenched with a sat. Na 2 S 2 O 3 solution, and extracted with EA (3×100 mL). The organic layer was washed with brine, and dried over anhydrous MgSO 4 . The solution was evaporated at low pressure to give the crude compound, which was used in the next step without further purification.

To a solution of the crude diol (0.03 mol) in MeOH:H 2 O:THF (170 mL:30 mL:50 mL) was added NaIO 4 (9.6 g, 0.045 mol), and the mixture was stirred at R.T. for 2 h. After filtration, the filtrate was used directly in the next step. This solution was treated with NaBH 4 (1.8 g, 0.048 mol) at 0° C., and the mixture was stirred at R.T. for 30 mins. The mixture was quenched with MeOH, and evaporated at low pressure. The residue was dissolved in EA (100 mL), and washed with brine. The solution was evaporated at low pressure, and the residue was purified by a silica gel column using 20% EA in EA to give 75-8 (12 g, 61% over three steps).

To a solution of 75-8 (14 g, 21 mmol) and DMAP (5.1 g, 42 mmol) in DCM (100 mL) was added MsCl (3.1 g, 27 mmol) at 0° C., and the mixture was stirred at R.T. for 40 mins. The reaction was quenched with sat. NaHCO 3 (aq.), and washed with HCl (0.2 N) solution. The organic phase was dried over anhydrous MgSO 4 , and evaporated at low pressure. The residue was purified by a silica gel column using 5% EA in PE to give mysolate product (14 g, 90%). The MsO-product (41 g, 55 mmol) was treated with TBAF (1 N in THF, 500 mL), and the mixture was stirred at 70-80° C. for 3 d. The mixture was concentrated at low pressure, and the residue was dissolved in EA (200 mL). The solution was washed with brine, dried over anhydrous MgSO 4 and evaporated at low pressure. The residue was purified by chromatography using 10% EA in PE to give 75-9 (9.9 g, 27%).

To a solution of 75-9 (6.3 g, 9.45 mmol) in CH 3 CN:H 2 O (3:1, 36 mL:12 mL) was added CAN (15.5 g, 28.3 mmol), and the mixture was stirred at R.T. overnight. The mixture was extracted with EA (3×50 mL). The solution was dried over anhydrous MgSO 4 , and evaporated at low pressure. The residue was purified by chromatography using 20% EA in PE to give 75-10 (3.6 g, 71%) as a white solid.

To a solution of 75-10 (2.4 g, 4.4 mmol) in anhydrous DCM (10 mL) was added slowly BCl 3 (1 N, 30 mL CH 2 Cl 2 ) at −70° C., and the mixture was stirred for 2 h. at −70° C. The mixture was quenched with the slow addition of MeOH at −70° C., and the mixture was concentrated at low pressure. The residue was purified by chromatography using 50% EA in PE to give 75-11 (1.2 g, 86%) as a white solid. ESI-MS: m/z 277.1 [M+H] + .

To a solution of PPh 3 (3.37 g, 12.8 mmol) in pyridine (15 mL) was added 12 (3.06 g, 12 mmol) at 0° C., and the mixture was stirred at R.T. for 30-40 mins. The mixture was cooled to 0° C., and then treated with 75-11 (2.2 g, 8 mmol) in Py. (5 mL). The mixture was stirred at R.T. under N 2 for 12 h. The mixture was quenched with sat. Na 2 S 2 O 3 (aq.) and extracted with CH 2 Cl 2 (3×50 mL). The organic phase was dried over anhydrous MgSO 4 , and then concentrated at low pressure. The residue was purified by chromatography using 1-2% MeOH in CH 2 Cl 2 to yield 75-12 (1.8 g, 58%) as a white solid.

To a solution of 75-12 (1.35 g, 3.5 mmol) in THF:CH 3 CN (10 mL:5 mL) was added DBU (1.06 g, 7 mmol), and the mixture was stirred at 60-70° C. for 2 h. The mixture was concentrated at low pressure, and the residue was dissolved in EA (20 mL). The solution was washed with 10% HCl solution and brine. The organic phase was dried over anhydrous MgSO 4 and concentrated at low pressure. The residue was purified by chromatography using 30% EA in PE to give 75-13 (0.5 g, 55%).

To a solution of 75-13 (670 mg, 2.6 mmol) in CH 3 CN (6 mL) was added NIS (730 mg, 3.25 mmol) and 3HF.TEA (335 mg, 2.1 mmol) at 0° C., and the mixture was stirred at R.T. for 2 h. The mixture was quenched with sat. NaHCO 3 (aq.) and Na 2 S 2 O 3 (aq.) solution. The mixture was extracted with EA (3×20 mL), dried over anhydrous MgSO 4 and concentrated at low pressure. The residue was purified by chromatography using 1-2% MeOH in CH 2 Cl 2 to give 75-14 (1.2 g, 80%).

To a solution of 75-14 (1.0 g, 2.47 mmol), DMAP (0.75 g, 6.2 mmol) and TEA (0.75 g, 7.42 mmol) in DCM (10 mL) was added BzCl (1.15 g, 8.16 mmol) in DCM (1 mL) at 0° C., and the mixture was stirred at R.T. for 12 h. The mixture was diluted with CH 2 Cl 2 (10 mL), and then washed with HCl (0.1 N, 20 mL) solution and brine. The organic phase was dried over anhydrous MgSO 4 , and concentrated at low pressure. The residue was purified by chromatography using 20% EA in PE to afford 75-15 (850 mg, purity-80%).

To a solution of 75-15 (600 mg, 1 mmol) in DMF (25 mL) was added BzONa (1.45 g, 10 mmol), 15-crown-5 (2.2 g, 10 mmol), and the mixture was stirred at 90-100° C. for 24 h. The mixture was concentrated at low pressure, and the residue was dissolved in EA (20 mL), and washed with brine. The organic phase was dried over anhydrous MgSO 4 , and then concentrated at low pressure. The residue was purified by chromatography using 15% EA in PE to give 75-16 (275 mg, 37%) as a light yellow foam.

Compound 75-16 (250 mg, 0.41 mmol) was treated with NH 3 .MeOH (7 N, 5 mL), and the mixture stirred at R.T. for 15 h. The mixture was concentrated at low pressure, and the residue was purified by prep-HPLC to give compound 75 (33 mg, 25%) as a white solid. ESI-MS: m/z 295.1 [M+H] + .

Compound 73

To a solution of IBX (133.33 g, 476 mmol) in dry CH 3 CN (2 L) was added 73-1 (100.0 g, 216 mol) at R.T. The mixture was refluxed and stirred for 12 h. The mixture was filtered, and the filtrate was concentrated at low pressure to give 73-2 as a yellow oil (90.0 g, 90.4%).

Compound 73-2 (50.0 g, 108.70 mmol) was coevaporated with anhydrous toluene twice to remove H 2 O. Ethynyl magnesium bromide, (800 mL, 400.0 mmol) was added dropwise into a solution of 73-2 in THF (500 mL) over 20 mins at −78° C. The mixture was stirred for about 10 mins at −78° C. When the starting material was consumed, the ice-acetone cooling bath was removed. The mixture was quenched with a sat. NH 4 Cl solution with stirring, and then warmed to R.T. The mixture was extracted with EA, filtered through Celite and washed with brine. The combined organic phase was dried over anhydrous Na 2 SO 4 , filtered and concentrated at low pressure to give crude 73-3 as a deep yellow oil (48.0 g, yield: 90.8%).

Compound 73-3 (200.0 g, 411.52 mmol) was dissolved in anhydrous CH 2 Cl 2 (2000 mL) and then DMAP (100.41 g, 823.05 mmol) and Et 3 N (124.94 g, 1.23 mol) were added at R.T. The mixture was treated with benzoyl chloride (173.46 g, 1.23 mol) at 0° C. After stirring for 12 h at R.T., the reaction was quenched with H 2 O. The combined aq. phase was extracted with DCM. The combined organic phase was dried over anhydrous Na 2 SO 4 , filtered and evaporated to dryness under reduced pressure to give a black oil. The oil was purified by column chromatography using 7%-20% EA in PE as the eluent to give a yellow oil. The residue triturated with CH 3 OH and filtered. The filter cake was concentrated in vacuo to give 73-4 as a white solid (30.0 g, 36.4%).

Uracil (34.17 g, 305.08 mmol) were coevaporated with anhydrous toluene twice to remove H 2 O. To a stirred suspension of uracil in anhydrous MeCN (150 mL) was added N,O-BSA (123.86 g, 610.17 mmol) at R.T. The mixture was refluxed for 1.5 h and then cooled to R.T. Compound 73-4 (90 g, 152.54 mmol, which were coevaporated with anhydrous toluene twice to remove H 2 O) was added. TMSOTf (237.05 g, 1.07 mol) was then added at R.T. The mixture was heated to 70° C., and then stirred overnight and then monitored by LCMS. The mixture was cooled to R.T., and quenched with a sat. NaHCO 3 solution. The solution was extracted with EA. The organic layer was dried over Na 2 SO 4 , and then concentrated at low pressure. The residue was purified using a silica gel column eluted with 10%-50% EA in PE to give 73-5 as a white solid (45 g, 50.9%).

Compound 73-5 (50 g, 86.21 mmol) was treated with NH 3 in MeOH (1 L) at R.T., and then stirred for 48 h. The mixture was concentrated at low pressure, and the residue was purified by column chromatography (10% MeOH in DCM) to give 73-6 (12.6 g, 54.55%) as a white solid.

To a solution of cyclopentanone (100 g, 1.189 mmol) and trimethyl orthoformate (150 mL) in MeOH (600 mL) was added TsOH.H 2 O (1.13 g, 5.9 mmol), and the mixture was stirred at R.T. for 30 mins. The reaction was quenched with NaOMe (0.32 g, 5.9 mmol) and H 2 O, and the solution was extracted by n-hexane. The organic layer was dried over anhydrous Na 2 SO 4 , and then concentrated at low pressure. The cyclopentyl dimethoxy acetal and 73-6 (20 g, 74.63 mmol) was dissolved in DCE (200 mL), and then treated with TsOH.H 2 O (0.71 g, 3.73 mmol). The mixture was stirred at 50° C. for 12 h, and then concentrated at low pressure. The residue was purified by silica gel column chromatography (1-10% MeOH in DCM) to give 73-7 (15.4 g, 61.8%) as a white solid.

Compound 73-7 (20.0 g, 0.06 mol) was coevaporated with anhydrous pyridine three times to remove H 2 O. To an ice-cold solution of 73-7 in anhydrous pyridine (100 ml) was added TsCl (22.8 g, 0.12 mol) at 0° C., and the mixture was stirred overnight and monitored by LCMS and TLC. The reaction was quenched with H 2 O and extracted with EA. The organic phase was dried over anhydrous NaSO 4 and evaporated at low pressure. The residue was purified by silica gel column chromatography (DCM:MeOH=100:1 to 15:1) to give 78-8 (20.0 g, 69.0%) as a white solid.

To a solution of 73-8 (20.0 g, 0.04 mol) in acetone (200 ml) was added NaI (31.0 g, 0.2 mol) and heated to reflux overnight and monitored by LCMS. The mixture was quenched with a sat. Na 2 S 2 O 3 solution, and extracted with EA. The organic phase was dried over anhydrous Na 2 SO 4 and evaporated at low pressure. The residue was purified by silica gel column chromatography (DCM:MeOH=100:1 to 15:1) to give 73-9 (15.0 g, 83.3%) as a white solid.

To 73-9 (30.0 g, 0.068 mol) in dioxane (60 mL) in sealed tube was added CuBr (4.9 g, 0.034 mol), i-Pr 2 NH (13.6 g, 0.135 mol) and (CH 2 O) n (5.1 g, 0.17 mol) under N 2 . The mixture was heated at reflux for 16 h. The mixture was diluted with EtOAc, and washed with a sat. NH 4 Cl solution and brine. The solution was dried over anhydrous MgSO 4 , and concentrated under reduced pressure. The residue was purified by column chromatography (DCM:MeOH=100:1 to 15:1) to give 73-10 (10.0 g, 32.3%) as a white solid.

Compound 73-10 (10 g, 21.83 mmol) was treated with HCOOH (80%) in H 2 O at R.T. The solution was stirred at 60° C. for 2 h, and then concentrated at a low pressure. The residue was purified by column chromatography (1%-10% MeOH in DCM) to give 73-11 (5.1 g, 58.55%) as a white solid.

Compound 73-11 (5 g, 12.79 mmol) was dissolved in anhydrous MeOH (100 mL) and treated with NaOMe (4.83 g, 89.5 mmol) at R.T. The solution was stirred at 60° C. for 36 h. The mixture was quenched with CO 2 and then concentrated at low pressure. The residue was purified by column chromatography (0-10% MeOH in DCM) to give 73-12 (2.3 g, 68.05%) as a yellow solid. 1 H-NMR (CDCl 3 , 400 MHz) δ=7.29 (d, J=8 Hz 1H), 6.10 (s, 1H), 5.71 (d, J=8.0 Hz 1H), 5.18 (t, J=6.4 Hz, 1H), 4.79-4.84 (m, 1H), 4.61 (d, J=8.0 Hz, 2H), 4.39 (s, 1H), 3.45 (s, 1H).

To an ice-cold solution of 73-12 (1.5 g, 5.68 mmol) in anhydrous MeCN (15 mL) was added NIS (1.66 g, 7.39 mmol) and TEA.3HF (0.73 g, 4.55 mmol) under N 2 . The mixture was stirred at R.T. for 1 h. The reaction was quenched with sat. NaHCO 3 and sat. Na 2 SO 3 solution, and extracted with EA (3×100 mL). The organic phase was dried over anhydrous Na 2 SO 4 , and evaporated to dryness at low pressure. The residue was purified on a silica gel column (0-5% MeOH in DCM) to give 73-13 (1.08 g, 46.2%) as a yellow solid.

To a stirred solution of 73-13 (1 g, 2.44 mmol) in anhydrous DCM (10 mL) was added DMAP (0.60 g, 4.88 mmol) and Et 3 N (0.74 g, 7.32 mmol) at R.T. The mixture was treated with benzoyl chloride (0.79 g, 5.61 mmol) at 0° C. and then stirred at R.T. for 3 h. The reaction was quenched with water, and extracted with EA (3×60 mL). The organic phase was concentrated at low pressure, and the residue was purified by column chromatography (0-10% MeOH in DCM) to give 73-14 (0.9 g, 59.6%) as a white solid.

Bu 4 NOH (55% in H 2 O, 13.74 mL) was treated with TFA (to adjust pH=3-4). The mixture was cooled to R.T. To a solution of 73-14 (0.9 g, 1.46 mmol) in DCM (9 mL) was added m-CPBA (80%, 1.57 g, 7.28 mmol) at R.T. The mixture was stirred at 25° C. for 48 h. The mixture was washed with sat. aq. NaHCO 3 . The organic layer was passed through an anhydrous Al 2 O 3 column, and the solution was concentrated at low pressure. The residue was purified by a silica gel column (30% EA in PE) to give 73-15 (0.26 g, 35.1%) as a yellow solid.

Compound 73-15 (0.25 g, 0.49 mmol) was dissolved in NH 3 /MeOH (5 mL, 7 M), and the mixture was stirred at R.T. for 24 h under N 2 . The mixture was concentrated at low pressure at R.T., and the residue was purified by a silica gel column (5% MeOH in DCM) to give 73-16 (100 g, 67.75%) as a white solid. 1 H-NMR (CD 3 OD, 400 MHz) δ=7.83 (d, J=8 Hz 1H), 6.29 (s, 1H), 5.67 (d, J=6.0 Hz 1H), 5.12 (t, J=6.8 Hz, 1H), 4.99-5.01 (m, 1H), 4.38 (d, J=19.6 Hz 1H), 3.74-3.81 (m, 2H), 3.35 (s, 1H).

Compound 73-16 (100 mg, 0.33 mmol) was co-evaporated with toluene three times to remove H 2 O. To a stirred solution of 73-16 (100 mg, 0.33 mmol) in a mixture of MeCN (1.0 mL) and NMI (271 mg, 3.3 mmol) was added a solution of 73-C (216.5 mg, 0.66 mmol) in MeCN (0.5 mL) at 0° C. The mixture was stirred at R.T. overnight and then reaction was quenched with water. The mixture was diluted with EA (20 mL), and the organic layer was washed with water and brine, and dried over anhydrous Na 2 SO 4 . The organic phase was concentrated at low pressure, and the residue was purified on a silica gel column (5% i-PrOH in DCM) to give the crude product. The crude product was purified by prep-HPLC (0.1% HCOOH in water and MeCN) to give compound 73 (35.6 mg, 19.0%) as a white solid. ESI-LCMS: m/z 592 [M+Na] + .

To a stirred solution of 73-A (2.0 g, 13.16 mmol) and phenol (1.22 g, 13.16 mmol) in anhydrous DCM (100 mL) was added a solution of TEA (1.33 g, 13.16 mmol) in DCM (20 mL) dropwise at −78° C. The mixture was warmed gradually to R.T., and then stirred for 2 h. The solution was re-cooled to −78° C., and (S)-isopropyl 2-aminopropanoate hydrochloride (2.20 g, 13.16 mmol) in DCM (20 mL) was added, followed by the dropwise addition of TEA (2.66 g, 26.29 mmol) in DCM (20 mL). The mixture was warmed gradually to R.T., and then stirred for 2 h. The organic solvent was removed at low pressure, and the residue was dissolved in methyl-butyl ether. The precipitate was filtered, and the filtrate was concentrated at low pressure. The residue was purified on a silica gel column (anhydrous DCM) to give 73-C (0.9 g, 22.3%) as a colorless oil.

Compound 66

Compound 66-2 (2648 g, 7.3 mol) was dissolved in anhydrous dichloromethane (10 L), and the solution was cooled to −40° C. with stirring under N 2 . Compound 66-1 (1 kg, 7.69 mol) was dissolved in anhydrous CH 2 Cl 2 (3 L) and added to the solution of 66-2 over 30 mins at −40 OC. The stirred mixture was allowed to warm to R.T. overnight. The mixture was concentrated under reduced pressure to dryness, and the residue was suspended in TMBE (6 L). The suspension was filtered to remove Ph 3 PO, and the filtrate was concentrated under reduced pressure to afford crude 66-3 (1230 g, 78.6%). 1 H NMR (400 Hz) (CDCl 3 ): δ 6.65 (dt, J=7.6 Hz, 1H), 4.82 (dd, J=14.8, 7.6 Hz, 1H), 4.20-4.10 (m, 3H), 3.59 (t, J=8.0 Hz, 1H), 1.86 (d, J=1.2 Hz, 3H), 1.41 (s, 3H), 1.37 (s, 3H), 1.26 (t, J=6.8 Hz, 3H).

Crude 66-3 (1230 g, 5.74 mol) was dissolved in acetone (30 L) at 0-5° C. KMnO 4 (1107 g, 5.17 mol) was added in one portion. After being stirred at 0-5° C. for 5 h, the reaction was quenched with sat. aq. sodium sulfite (20 L). After 30 mins, a colorless suspension was formed. The solid was removed by filtration and washed with EA (6 L). The filtrate was extracted with EA (3×2 L). The combined extracts were dried over Na 2 SO 4 , filtered, and concentrated under reduced pressure to give a white solid residue. The residue was dissolved in EA, and PE was added to give a precipitate. The solid was collected by filtration and recrystallization was 3 times to give 66-4 (770 g, 53.6%) as a white solid.

To a stirred solution of 66-4 (770 g, 3.1 mol) in anhydrous DCM (5 L) and triethylamine (1.1 L, 8.05 mol) at 0° C. was added slowly sulfuryl chloride (300 mL, 3.6 mmol). The mixture was stirred at R.T. for 2 h, diluted with DCM (3 L), and washed with sat. NaHCO 3 aq. and brine. The organic phase was dried over anhydrous Na 2 SO 4 , filtered, and concentrated under reduced pressure. The residue was purified by a silica gel column using PE:EA=1:0 to 10:1 as the eluent to give 66-5 (490 g, 50.6%) as an oil.

Tetraethylammonium fluoride hydrate (650 g, 3.7 mol) was added into a solution of 66-5 (490 g, 1.6 mol) in anhydrous dioxane (3 L), and the mixture was heated to 120° C. for 16 h. The mixture was then cooled to ambient temperature. 2,2-Dimethoxypropane (3 L) was added followed by conc. aq hydrochloric acid (200 mL). The mixture was stirred for 3 h at ambient temperature. The solvent was concentrated to ⅓ of the original volume, and then diluted with EA (3 L). The mixture was washed with cold sat. aq. sodium bicarbonate and brine. The combined aqueous layer was back-extracted with EA (1 L). The combined organic layer was dried over anhydrous Na 2 SO 4 , filtered, and concentrated at low pressure to give crude 66-6 (220 g, 70.8%).

Crude 66-6 (220 g, 0.89 mol) was dissolved in ethanol (2 L) and cone. aq. HCl (60 mL). The solution was stirred at ambient temperature for 48 h. and then concentrated under reduced pressure followed by co-evaporations with toluene 3 times to give 66-7 as a pale yellow solid (110 g).

Compound 66-7 (110 g) was dissolved in anhydrous pyridine (1 L). Benzoyl chloride (200 mL, 1.67 mol) was added slowly at 0-5° C. The mixture was stirred at ambient temperature for 45 mins. The reaction was quenched with ice and MeOH to form a precipitate. After filtration, the filtrate was washed with MeOH to give 66-8 (200 g, 61.2%) as a white solid.

To a solution of 66-8 (100 g, 269 mmol) in anhydrous THF (1000 ml) was added dropwise a solution of lithium tri-tert-butoxyaluminohydride (400 ml, 1M, 0.4 mol) at −78° C. under N 2 for 30 mins. The solution was stirred at −20° C. for 1 h, and TLC (PE:EA=3:1) showed that the reaction was complete. The mixture was quenched with sat.NH 4 Cl, and diluted with EA. After filtration, the filtrate was extracted with EA. The combined layers were dried over Na 2 SO 4 , and concentrated at low pressure. The residue was purified by a silica column gel (PE:EA=20:1) to give 66-9 (100 g, 100%) as a colorless oil.

To a stirred solution of PPh 3 (140 g, 382 mol) in CH 2 Cl 2 (1000 ml) was added 66-9 (100 g, 269 mmol) at −20° C. under N 2 . After stirring for 15 mins, CBr 4 (177 g, 382 mol) was added dropwise while maintaining the temperature between −25 and −20° C. under N 2 . The mixture was stirred below −17° C. for 20 mins. Silica gel was added to the mixture. The mixture was filtered through cold silica column gel and washed with PE:EA (50:1 to 4:1). The combined filtrates were concentrated under reduced pressure at R.T. to give the crude oil product. The residue was purified by a silica column gel a second time (PE:EA=50:1 to 4:1) to give 66-10 (α-isomer, 64 g, yield: 55%) as a colorless oil.

A mixture of 6-chloro-guanine (55.8 g, 316.5 mol) and t-BuOK (39.5 g, 352.7 mmol) in t-BuOH (500 mL) and MeCN (280 mL) was stirred for 30 mins. Compound 66-10 (48 g, 105.5 mmol) was added at R.T., and the mixture was heated to 50° C. and stirred overnight. The reaction was monitored by TLC (PE:EA=2:1). The mixture was quenched with solid NH 4 Cl. After stirring for 1 h, the mixture was filtered and washed with MeCN. The filtrate was evaporated at low pressure, and the residue was purified by a silica gel column to give 66-11 (33 g, 57%).

To a solution of 66-11 (49 g, 93.1 mol) in CH 2 Cl 2 (200 mL) was added AgNO 3 (31.7 g, 186 mmol), collidine (22.5 g, 186 mmol) and MMTrCl (43 g, 140 mmol) in small portions under N 2 at 0° C. The mixture was stirred at R.T., and monitored by TLC (PE:EA=4:1). After filtration, the organic phase was washed with NaHCO 3 aqueous and brine. The organic layer was dried over anhydrous Na 2 SO 4 and concentrated at low pressure. The residue was purified by a silica gel column (PE:ME=20:1 to 1:1) to give 66-12 (70 g, 94.2%).

Sodium (10.1 g, 439 mmol) was dissolved in dry EtOH (600 mL) at 70° C. and then cooled to 0° C. To a solution of 66-12 (70 g, 87.7 mmol) was added a freshly prepared NaOEt solution in portions at 0° C., and the mixture was stirred for 1 h. at R.T. After TLC and LCMS showed the reaction was completed, the reaction was quenched with carbon dioxide. The mixture was evaporated at low pressure, and the residue was purified using silica gel column chromatography (DCM:MeOH=100:1 to 20:1) to give 66-13 (50 g, yield 5%) as a yellow solid.

A mixture of PPh 3 (35 g, 133.5 mol) and 12 (31.75 g, 125 mmol) in anhydrous pyridine (600 mL) was stirred for 30 mins, and then a solution of 66-13 (50 g, 83.3 mmol) in pyridine (100 mL) was added at 0° C. The mixture was stirred overnight at R.T. and monitored by TLC (DCM:MeOH=50:1). The reaction was quenched with a sat. NaHCO 3 solution, and extracted with DCM (3×50 mL). The organic phase was dried over anhydrous MgSO 4 , and evaporated at low pressure. The residue was purified using silica gel column chromatography (DCM:MeOH=200:1 to 50:1) to give 66-14 (50 g, 84.7%).

To a solution of 66-14 (37 g, 52.1 mmol) in dry THF (400 mL) was added DBU (16 g, 105 mmol). The mixture was heated to reflux and stirred for 3 h. The reaction was monitored by LCMS. The reaction was quenched with a sat. NaHCO 3 solution, and extracted with EA. The combined organic layers were dried over anhydrous Na 2 SO 4 , and evaporated at low pressure. The residue was purified using silica gel column chromatography (PE:EA=10:1 to 5:1) to give 66-15 (25 g, 61.1%) as a white solid.

To an ice-cold solution of 66-15 (26 g, 44.6 mmol) in dry MeCN (300 mL) was added NIS (12.68 g, 56 mmol) and NEt 3 .3HF (10.6 g, 67 mmol) at 0° C. The reaction was stirred at R.T. for 2 h. and monitored by LCMS. After the reaction was completed, the reaction was quenched with a sat Na 2 SO 3 and sat. NaHCO 3 solution, and extracted with EA. The organic layer was separated, dried over anhydrous Na 2 SO 4 , and evaporated at low pressure. The residue was purified using silica gel column chromatography (PE:EA=8:1 to 1:1) to give 66-16 (21 g, 64.4%) as a white solid.

To a solution of 66-16 (21 g, 28.8 mol) in CH 2 Cl 2 (150 mL) was added AgNO 3 (9.8 g, 59.6 mmol) and collidine (7 g, 59.8 mmol) and MMTrCl (13.1 g, 42.5 mmol) in small portions under N 2 at 0° C. The mixture was stirred at R.T., and the reaction was monitored by TLC (PE:EA=2:1). After filtration, the solution was washed with sat. aq. NaHCO 3 and brine. The organic layer was separated, dried over anhydrous Na 2 SO 4 and concentrated at low pressure. The residue was purified by a silica gel column to give 66-17 (25 g, yield 86.5%).

To a solution of 66-17 (22 g, 22 mmol) in dry DMF (500 mL) was added NaOBz (31.9 g, 220 mmol) and 15-crown-5 (48.4 g, 220 mmol), and the mixture was stirred for 72 h. at 95° C. The mixture was diluted with EA, washed with water and brine, and dried over MgSO 4 . The organic layer was evaporated at low pressure, and the residue was purified using a silica gel column chromatography to give 66-18 (15 g, 68.8%) as a white solid.

Compound 66-18 (15.2 g, 15.3 mmol) was co-evaporated with anhydrous toluene 3 times to remove H 2 O. The compound was treated with NH 3 in MeOH (7 N, 200 mL) at R.T. The mixture was stirred for 18 h at R.T., and the reaction was monitored by LCMS. The residue was concentrated at low pressure, and purified using silica gel column chromatography to give 66-19 (11 g, 81%) as a white solid.

To a stirred solution of 66-20 (14 g, 15.73 mmol) in anhydrous CH 3 CN (150 mL) was added N-methylimidazole (23.5 g, 283.9 mmol) at 0 to 5° C. (ice/water bath) followed by a solution of phenyl(cyclohexanoxy-L-alaninyl)phosphorochloridate (16.33 g, 47.2 mmol, dissolved in 50 mL of CH 3 CN). The solution was stirred at 0 to 5° C. for 12 h and then diluted with EA. The solution was washed 50% aqueous citric acid solution and brine. The organic layer was separated, dried over anhydrous MgSO 4 and filtered. The filtrate was concentrated at low pressure, and the residue was purified on silica gel with PE:EA=5:1 as the eluent to give 66-20 (17.62 g, 93.4%) as a white solid.

Compound 66-20 (17.62 g, 14.7 mmol) was dissolved in 80% AcOH (200 mL), and the mixture was stirred overnight at R.T. After removal of the solvents, the reside was purified on silica gel using PE:EA=2:1 to eluent to give the crude product, which was purified on via reverse-phase HPLC using acetonitrile and water to give compound 66 (5.25 g, yield 66%) as a white solid. ESI-LCMS: m/z 655 [M+H] + .

Compound 67

To a solution of the nucleoside (300 mg, 1.09 mmol) and proton-sponge (467 mg, 2.18 mmol) in anhydrous CH 3 CN (5 mL) at 0° C. under N 2 was added dropwise a solution of phosphorus oxychloride (330 mg, 2.18 mmol) in anhydrous CH 3 CN (1 mL). The mixture was stirred at 0° C. for 30 mins, and the hydrogen chloride salt of (S)-ethyl 2-aminopropanoate (998 mg, 6.52 mmol) and triethylamine (1.5 mL, 10.87 mmol) at 0° C. were added. The mixture was stirred overnight at 30° C. The reaction was quenched with water, and extracted with EA (3×20 mL). The organic layer was concentrated at low pressure, and the residue was purified by reverse phase HPLC to give compound 67 (20 mg, 3%) as a white solid. ESI-LCMS: m/z 535 [M−F] + .

Compound 59

To a solution of sodium hydrosulfide (4.26 g, 76.0 mmol) in EtOH (100 mL) was added t-butyryl chloride (76.2 mmol; 9.35 mL) dropwise at 0° C., and the mixture was stirred at R.T. for 1 h. A solution of 2-(2-chloroethoxy)ethanol (57 mmol; 6.0 mL) and TEA (21 mL, 120 mmol) was added, and the mixture was heated at reflux for 60 h. The mixture was filtered, and then concentrated to a small volume. The residue was dissolved in EA, and then washed with water, sat. aq. NaHCO 3 and brine. The organic phase was dried over Na 2 SO 4 , filtered and concentrated in vacuo. The crude product (10.0 g) was isolated and 5 grams were purified by silica gel flash column chromatography using a gradient of 0 to 100% EA in hexane to give 59-3 (4.5 g, 22 mmol) as a clear, colorless oil. 1 H-NMR (CDCl 3 ): 3.70-3.74 (m, 2H), 3.5-3.65 (m, 4H), 3.1 (t, 2H), 1.25 (s, 9H).

A solution 59-3 (4.5 g; 21.8 mmol) and triethylamine (6.7 mL, 87.2 mmol) in tetrahydrofuran (50 mL) was added dropwise over 1 h to a stirred solution of N,N-diisopropylphosphorodichloridite (2.0 mL, 10.9 mmol) in THF (50 mL) under argon at −78° C. The mixture was stirred at R.T. for 2 h, and then diluted with EA (200 mL). The mixture was washed with sat. aq. NaCl and dried over Na 2 SO 4 . After filtration, the filtrate was evaporated under reduced pressure to give a pale yellow oil. Purification by flash column chromatography using a gradient of EA (0-5%) in hexane containing 5% triethylamine afforded 59-4 (2.5 g, 4.25 mmol) as a clear, colorless oil. 1 H-NMR (CDCl 3 ): 3.70-3.82 (m, 4H), 3.57-3.65 (m, 10H), 3.1 (t, 4H), 1.25 (s, 18H), 1.17 (t, 12H); 31 P-NMR (CDCl 3 ): 148.0 ppm.

Compound 59-5 (285 mg, 0.9 mmol) and DCI (175 mg, 1.5 mmol) were coevaporated twice with ACN and then dissolved in ACN (5 mL). Compound 59-4 (790 mg, 1.35 mmol) in ACN (4 mL) was added, and the reaction was monitored by TLC. After 15 mins, tert-butylhydroperoxide (0.5 mL of 5.5M solution in decane) was added, and the mixture was stirred for 10 mins. The mixture was diluted with EA (25 mL), washed with sat. aq. NaHCO 3 and sat. aq. NaCl solution, dried over Na 2 SO 4 , filtered and concentrated. Purification by flash column chromatography using a gradient of EA (0-100%) in hexane afforded 59-6 (0.17 g, 0.22 mmol) as a white solid. Compound 59-6 was dissolved in 80% aq. HCOOH (5 mL). After 30 mins at R.T., the solvent was removed and coevaporated twice with toluene. The residue was dissolved in methanol (10 mL) and TEA (0.2 mL) was added. After 2 mins at R.T., the solvent was removed in vacuo. Purification by flash column chromatography using a gradient of methanol (0-15%) in DCM afforded compound 59 (90 mg). 1 H-NMR (CDCl 3 ): 7.40 (d, 1H), 6.1 (s, 1H), 5.83 (d, 1H), 4.3 (t, 2H), 4.1-4.2 (m, 6H), 3.70-3.82 (m, 4H), 3.57-3.65 (m, 4H), 3.1 (t, 4H) 1.61 (s, 8H), 1.3 (s, 3H), 1.23 (s, 18H). 31 P-NMR (CDCl 3 ): −1.55 ppm.

Compound 60

Compound 60-1 (6.0 g, 31.6 mmol) was prepared using a similar procedure to the one used to prepared 59-3 using 4-chlorobutanol. Compound 60-1 was obtained as a clear, colorless oil. 1 H-NMR (CDCl 3 ): 3.67 (s, 2H), 2.86 (m, 2H), 1.65 (m, 4H), 1.25 (s, 9H).

Compound 60-2 (2.14 g, 4.0 mmol) was prepared using a similar procedure to the one used to prepared 59-4. Compound 60-2 was obtained as a clear, colorless oil. 1 H-NMR (CDCl 3 ): 3.67 (m, 6H), 2.86 (t, 4H), 1.65 (m, 8H), 1.25 (s, 18H), 1.17 (t, 12H). 31 P-NMR (CDCl 3 ): 143.7 ppm.

Compound 60-3 (0.23 g, 0.22 mmol) was prepared using a similar procedure to the one used to prepared 59-6 using 59-5 and 60-2. Compound 60-3 was obtained as a white solid. Using a similar procedure to the one used to prepared compound 59, 60-3 was used to prepare compound 60 (170 mg). 1 H-NMR (CDCl 3 ): 7.40 (d, 1H), 6.1 (s, 1H), 5.83 (d, 1H), 4.3 (t, 2H), 4.1-4.2 (m, 6H), 2.8 (t, 4H), 1.78 (m, 4H), 1.69 (s, 8H), 1.3 (s, 3H), 1.23 (s, 18H). 31 P-NMR (CDCl 3 ): −1.56 ppm.

Compound 58

Compound 58-1 was prepared according to the procedure described in Lefebre et al. J. Med. Chem. (1995) 38:3941-3950, which is hereby incorporated by reference for the limited purpose of its description of the preparation of 58-1.

Compound 58-2 (0.33 g, 0.5 mmol) was prepared using a similar procedure to the one used to prepared 59-6 using 59-5 and 58-1. Compound 58-2 was obtained as a white solid. Using a similar procedure to the one used to prepared compound 59, 58-2 was used to prepare compound 58 (130 mg). 1 H-NMR (CDCl 3 ): 7.40 (d, 1H), 6.1 (s, 1H), 5.83 (d, 1H), 4.3 (t, 2H), 4.1-4.2 (m, 6H), 3.2 (t, 4H), 1.69 (s, 4H), 1.3 (s, 3H), 1.23 (s, 18H); 31 P-NMR (CDCl 3 ): −2.4 ppm.

Compound 47

Compound 47-1 (1.0 g, 3.53 mmol) was coevaporated with anhydrous pyridine 3 times to remove H 2 O. To an ice-cold solution of 47-1 in anhydrous pyridine (9 mL) was added TsCl (808 mg, 4.24 mmol) in pyridine (3 mL) drop-wise at 0° C., and the mixture was stirred for 18 h. at 0° C. The reaction was monitored by LCMS, and then quenched with H 2 O. After concentration at low pressure, the residue was dissolved in EA (50 mL). The solution was washed with sat. NaHCO 3 solution and brine. The organic layer was dried over anhydrous Na 2 SO 4 and filtered. The filtrate was evaporated at low pressure, and the residue was purified by silica gel column chromatography (1% MeOH in DCM) to give 47-2 (980 mg, 63%) as a white solid.

To a solution of 47-2 (980 mg, 2.24 mmol) in acetone (10 mL) was added NaI (1.01 g, 6.73 mmol), and the mixture was heated to reflux overnight. The reaction was monitored by LCMS. After the reaction was completed, the mixture was concentrated at low pressure. The residue was dissolved in EA (50 mL). The solution was washed with brine, and dried over anhydrous Na 2 SO 4 . The solution was evaporated at low pressure, and the residue was purified by silica gel column chromatography (1% MeOH in DCM) to give 47-3 (700 mg, 79%) as a solid.

To a solution of 47-3 (700 mg, 1.78 mmol) in dry THF (9 mL) was added DBU (817 mg, 5.34 mmol), and the mixture was heated to 60° C. The mixture was stirred overnight, and monitored by LCMS. The reaction was quenched with sat. NaHCO 3 and extracted with EA (3×50 mL). The organic phase was dried over anhydrous Na 2 SO 4 , and filtered. The filtrate was evaporated at low pressure, and the residue was purified by silica gel column chromatography (1% MeOH in DCM) to give 47-4 (250 mg, 53%) as a white solid.

To an ice-clod solution of 47-4 (250 mg, 0.94 mmol) in dry MeCN (5 mL) was added NEt 3 -3HF (151 mg, 0.94 mmol) and NIS (255 mg, 1.13 mmol). The mixture was stirred at R.T., for 3 h., and checked by LCMS. The reaction was quenched with sat Na 2 S 2 O 3 and sat. NaHCO 3 solution, and extracted with EA (3×50 mL). The organic layer was separated, dried over anhydrous Na 2 SO 4 , and evaporated at low pressure. The residue was purified by silica gel column chromatography (2% acetone in DCM) to give 47-5 (170 mg, 44%).

To a solution of 47-5 (270 mg, 0.65 mmol) in dry DCM (4 mL) was added DMAP (158.6 mg, 1.3 mmol), and BzCl (137 mg, 0.98 mmol). The mixture was stirred for 4-5 h. at R.T., and checked by LCMS. The mixture was diluted with CH 2 Cl 2 , and washed with sat. NaHCO 3 solution and brine. The organic layer was evaporated at low pressure, and the residue was purified by silica gel column chromatography (20% EA in PE) to give 47-6 (290 mg, 86%) as a solid.

To a solution of 47-6 (900 mg, 1.74 mmol) in dry DMF (45 mL) was added NaOBz (2.5 g, 17.4 mmol) and 15-crown-5 (4.5 g, 20.9 mmol). The mixture was stirred for 48 h at 90-100° C. The mixture was diluted with EA (100 mL), and washed with brine. The organic layer was evaporated at low pressure, and the residue was purified by silica gel column chromatography (20% EA in PE) to give 47-7 (500 mg, 56%) as a solid.

To a solution of 47-7 (500 mg, 0.98 mmol) in anhydrous CH 3 CN (5 mL) was added TPSCl (741 mg, 2.45 mmol), DMAP (299.6 mg, 2.45 mmol) and NEt 3 (248 mg, 2.45 mmol) at R.T., and the mixture was stirred overnight. The mixture was then treated with NH 3 in THF (5 mL) and then stirred for another 30 mins. The mixture was diluted with EA (100 mL). The solution was washed with 0.5% AcOH solution. The organic solvent was dried over anhydrous MgSO 4 , and concentrated at low pressure. The crude product was purified by silica gel column chromatography (2% Acetone in DCM) to give 47-8 (257 mg, 51.6%) as a white solid. ESI-MS: m/z 509 [M+H] + .

Compound 47-8 (80 mg, 0.16 mmol) was dissolved in n-butylamine (3 mL). The mixture was kept overnight at R.T. and evaporated. The residue was crystallized from methanol to give compound 47 (30 mg). The mother liquor was purified by RP HPLC on Synergy 4 micron Hydro-RP column (Phenominex). A linear gradient of methanol from 0 to 30% in 50 mM triethylammonium acetate buffer (pH 7.5) was used for elution. The corresponding fractions were combined, concentrated and lyophilized 3 times to remove excess of buffer to yield additional compound 47 (13 mg). Compound 47 (total yield 43 mg, 73%). MS: m/z 299.7 [M−1] − .

Compound 83

To a stirred solution of POCl 3 (2.0 g, 13 mmol) in anhydrous DCM (10 mL) was added 1-naphthol (1.88 g, 13 mmol) at −70° C., and TEA (1.31 g, 13 mmol) in DCM (3 mL) dropwise at −70° C. The mixture was gradually warmed to R.T. and stirred for 1 h. Crude 83-1 was obtained.

To a stirred solution of (S)-isopropyl 2-aminopropanoate hydrochloride (2.17 g, 13 mmol) in DCM (10 mL) was added crude 83-1 at −70° C. TEA (2.63 g, 26 mmol) was added to the stirred solution dropwise at −70° C. The mixture was gradually warmed to R.T. and stirred for 2 h. The reaction was monitored by LCMS and quenched with n-propylamine. The mixture was concentrated at low pressure, and the residue was purified by a silica gel column (PE:MTBE=5:1˜1:1) to give pure 83-2 (1.6 g, 35%).

To a solution of 83-(A) (300 mg, 0.337 mmol) and NMI (276 mg, 3.37 mmol) in anhydrous CH 3 CN (4 mL) was added 83-2 (240 mg, 0.674 mol, in DCM (5 mL)) at 0° C. The mixture was stirred at R.T. for 10 h. The reaction was monitored by LCMS. The reaction was quenched with water, and extracted with CH 2 Cl 2 (3×20 mL). The organic phase was dried over anhydrous MgSO 4 , and concentrated at low pressure. The residue was purified by sil-gel (PE:EA=5:1˜2:1) to give 83-3 (380 mg, 93%).

Compound 83-3 (380 mg, 0.314 mmol) was dissolved in CH 3 COOH (80%, 8 mL), and stirred at 40-50° C. for 2.5 h. The reaction was monitored by LCMS. The mixture was concentrated at low pressure, and the residue was purified by chromatography (PE:EA=1:1˜EA) to give crude compound 83. The crude product was purified by prep-HPLC (neutral system, NH 4 HCO 3 ) to give pure compound 83 (70 mg, 80%) as a white solid. ESI-MS: m/z 665.1 [M+H] + .

Compound 79

A solution of 79-1 (16.70 g, 0.363 mol) and TEA (36.66 g, 0.363 mol) in CH 2 Cl 2 (150 mL) was added dropwise to a stirred solution of POCl 3 (55.65 g, 0.363 mol) in DCM (100 mL) over 25 mins at −78° C. After the mixture was stirred for 2 h. at R.T., the triethylamine hydrochloride salt was filtered, and washed with CH 2 Cl 2 (100 mL). The filtrate was concentrated at low pressure, and the residue was distilled under high vacuum (˜10 mm Hg) with a cow-head fraction collector. The product was collected between 45° C. (distillation head temperature) as a colorless liquid (30.5 g, 50% yield). 1 H-NMR (400 MHz, CDCl 3 ) δ=4.44 (dq, J=10.85, 7.17 Hz, 2H), 1.44-1.57 (m, 3H); 31 P-NMR (162 MHz, CDCl 3 ) δ=6.75 (br. s., 1 P).

To a stirred suspension of 83-A (93 mg, 0.15 mmol) in CH 2 Cl 2 (1 mL) was added TEA (61 mg, 0.15 mmol) at R.T. The mixture was cooled to −20° C., and then was treated with a 79-2 (35 mg, 0.21 mmol) solution dropwise over a period of 10 mins. The mixture was stirred at this temperature for 15 min., and then was treated with NMI (27 mg, 0.33 mmol). The mixture was stirred at −20° C., and then slowly warmed to R.T. The mixture was stirred overnight. The mixture was suspended in EA (15 mL), washed with brine (10 mL) and dried over anhydrous sodium sulfate. The solution was concentrated at low pressure, and the residue was purified by chromatography (DCM:MeOH=100:1) to give 79-3 (60 mg, yield: 56%) as a solid.

A solution of 79-3 (60 mg, 0.085 mmol) in 80% AcOH aqueous (2 mL) was stirred at R.T. for 2 h. The mixture was concentrated under reduced pressure, and the residue was purified by a silica gel column eluting DCM/MeOH=50/land prep-HPLC to give compound 79 (23 mg, 62%) as a white solid. ESI-MS: m/z 436.3 [M+H] + .

Compound 80

Compound 80-2 was prepared using a similar procedure as for the preparation of 79-2 using a solution of iso-butanol (23.9 g, 322.98 mmol) and POCl 3 (49.5 g, 322.98 mmol). Compound 80-2 (26 g, 42% yield) was obtained as a colorless liquid. 1 H-NMR (400 MHz, CDCl 3 ) δ=4.10 (dd, J=9.04, 6.39 Hz, 2H), 2.09 (dq, J=13.24, 6.67, 6.67, 6.67, 6.67 Hz, 1H), 1.01 (d, J=6.62 Hz, 6H); 31 P-NMR (162 MHz, CDCl 3 ) δ=7.06 (br. s., 1 P).

To a stirred suspension of 83-A (310 mg, 0.5 mmol) in CH 2 Cl 2 (3 mL) was added TEA (202 mg, 2 mmol) at R.T. The mixture was cooled to −20° C., and then was treated with 80-2 (134 mg, 0.7 mmol). The mixture was stirred at this temperature for 15 mins and then was treated with NMI (90 mg, 1.1 mmol). The mixture was stirred at −20° C. for 1 h., and then slowly warmed to R.T. overnight. The mixture was suspended in EA (15 mL), washed with brine (10 mL), and dried over anhydrous sodium sulfate. The organic phase was concentrated at low pressure, and the residue was purified by silica column gel (DCM:MeOH=100:1) to give 80-3 (310 mg, yield: 84%) as a solid.

A solution of 80-3 (310 mg, 0.43 mmol) in 80% AcOH aqueous (4 mL) was stirred at R.T. for 2 h. The mixture was concentrated at low pressure, and the residue was purified by a silica gel column eluting DCM/MeOH=50/1 and prep-HPLC to give compound 80 (79 mg, 50%) as a white solid. ESI-MS: m/z 464.0 [M+H] + .

Compound 81

Compound 81-2 was prepared using a similar procedure as for the preparation of 79-2 using a solution of isopropyl alcohol (21 g, 350 mmol) and POCl 3 (53.6 g, 350 mmol). Compound 81-2 (40.5 g, 65% yield) was obtained as a colorless liquid. 1 H-NMR (400 MHz, CDCl 3 ) δ=4.94-5.10 (m, 1H), 1.48 (d, J=6.17 Hz, 6H); 31 P-NMR (162 MHz, CDCl 3 ) δ=5.58 (br. s., 1 P).

Compound 81-3 was prepared using a similar procedure as for the preparation of 80-3 using 81-2 (124 mg, 0.7 mmol) and 83-A (310 mg, 0.5 mmol). Compound 81-3 (300 mg, 83%) was obtained as a solid.

Compound 81 was prepared using a similar procedure as for the preparation of compound 80 using 81-3 (300 mg, 0.41 mmol) in 80% AcOH aqueous (4 mL). Compound 81 (80 mg, 43%) was obtained as a white solid. ESI-MS: m/z 450.0 [M+H] + .

Compound 82

To an ice cooled solution of 82-1 (50 g, 204.9 mmol) in dry Py (400 mL) was added TIPDSCl (70.78 g, 225.4 mmol) dropwise. The mixture was stirred at R.T. for 16 h, and then concentrated at low pressure. The residue was purified by chromatography using 20% EA in PE to generate 82-2 (111.5 g, 100%) as a white solid.

To a solution of 82-2 (50 g, 103 mmol) in anhydrous CH 3 CN (400 mL) was added IBX (43 g, 153 mmol) at R.T. The mixture was refluxed overnight and monitored by TLC (PE:EA=1:1). The precipitate was filtered off, and the filtrate was concentrated to give the crude 82-3 (50 g, 99%) as a white solid.

To a solution of trimethylsilylacetylene (20 g, 200 mmol) in anhydrous THF (400 mL) was added dropwise n-BuLi (80 mL, 200 mL) at −78° C. The mixture was stirred at −78° C. for 30 mins, and then warmed to R.T for 10 mins. Compound 82-3 (30 g, 60 mmol) in THF (100 mL) was added to the mixture dropwise at −78° C. The mixture was stirred at −78° C. for 1 h and then slowly warmed to R.T. The mixture was stirred for 20 mins, and then the reaction was quenched with a sat. NH 4 Cl solution at −78° C. The mixture was diluted with EA. The organic phase was washed with brine, dried over anhydrous Na 2 SO 4 , and concentrated at low pressure. The residue was purified by silica gel column chromatography (15% EA in PE) to give 82-4 as a white solid (14 g, 50%).

Compound 82-4 (14 g, 24 mmol) was dissolved in anhydrous toluene (100 mL) under N 2 and cooled to −78° C. DAST (19 g, 120 mmol) was added dropwise at −78° C. and stirring was continued for 1.5 h. The mixture was diluted with EA and poured into a sat. NaHCO 3 solution. The organic layer was washed with brine, dried over anhydrous Na 2 SO 4 , and concentrated at low pressure. The residue was purified by silica gel chromatography (20% EA in PE) to give 82-5 as a white solid (12 g, 81%).

A mixture of 82-5 (12 g, 20 mmol) and NH 4 F (11 g, 30 mmol) in MeOH (150 mL) was refluxed for 2 h. After cooling to R.T, the mixture was concentrated at low pressure, and the residue was purified by silica gel column chromatography (5% MeOH in DCM) to give 82-6 (3.1 g, 58%) as a white solid.

To a solution of 82-6 (3.1 g, 11.6 mmol) in dry Py (50 mL) was added imidazole (3.1 g, 46.4 mmol) and TBSCl (5.2 g, 34.8 mmol). The mixture was stirred at 50-60° C. for 3 h. The mixture was concentrated at low pressure, and the residue was dissolved in EA (100 mL). The solution was washed with brine, dried over anhydrous Na 2 SO 4 , and concentrated at low pressure. The residue was purified by silica gel chromatography (20% EA in PE) to give 82-7 as a white solid (5 g, 86%).

To a solution of 82-7 (4.5 g, 9 mmol) in 1,4-dioxane (45 mL) was added CuBr (643 mg, 4.5 mmol), dicyclohexylamine (3.3 g, 18 mmol) and paraformaldehyde (675 mg, 22.5 mmol). The mixture was refluxed for 24 h and then cooled to R.T. The reaction was quenched with a sat. NH 4 Cl solution. The mixture was extracted with EA (3×100 mL). The organic layer was washed with brine, dried over anhydrous Na 2 SO 4 , and concentrated at low pressure. The residue was purified by silica gel column chromatography (15% EA in PE) to give 82-8 as a white solid (2.0 g, 43%).

A mixture of 82-8 (2 g, 4 mmol) and NH 4 F (2.2 g, 60 mmol) in MeOH (20 mL) was refluxed overnight. After cooling to R.T., the mixture was concentrated at low pressure, and the residue was purified by silica gel column chromatography (5% MeOH in DCM) to give 82-9 (946 mg, 83%) as a white solid.

To a stirred suspension of 82-9 (946 mg, 3.33 mmol), PPh 3 (1.3 g, 5 mmol), imidazole (453 mg, 6.66 mmol) and pyridine (3 mL) in anhydrous THF (12 mL) was added a solution of I 2 (1 g, 4.33 mmol) in THF (4 mL) dropwise at 0° C. The mixture was warmed to R.T. and stirred for 16 h. The reaction was quenched with a sat. Na 2 S 2 O 3 aq. solution and extracted with EA (3×60 mL). The organic layer was dried over Na 2 SO 4 and concentrated at low pressure. The residue was purified on a silica gel column (2% MeOH in DCM to 5% MeOH in DCM) to afford 82-10 (2.1 g, crude) as a white solid.

To a solution of 82-10 (2.1 g, 5.3 mmol) in THF (15 mL) was added DBU (15 g, 100 mmol) and the mixture stirred for 30 mins. The mixture was diluted with EA and neutralized with acetic acid. The solution was washed with brine, dried over anhydrous Na 2 SO 4 , and concentrated at low pressure. The residue was purified by silica gel column chromatography (1.5% MeOH in DCM) to give 82-11 as a white solid (800 mg, 90%).

To an ice-cooled solution of 82-11 (800 mg, 3 mmol) in dry MeCN (1.5 mL) was added NEt 3 3HF (484 mg, 3 mmol) and NIS (1.68 g, 7.5 mmol). The mixture was stirred at R.T. for 30 mins., and the reaction was monitored by LCMS. The reaction was quenched with sat. Na 2 S 2 O 3 and sat. NaHCO 3 solution, and extracted with EA (3×50 mL). The organic layer was dried over anhydrous Na 2 SO 4 , and concentrated at low pressure. The residue was purified by a silica gel column (25% EA in PE) to afford 82-12 (850 mg, 68%) as a white solid.

To a solution of 82-12 (850 mg, 2 mmol) in dry DCM (10 mL) was added DMAP (488 mg, 4 mmol) and BzCl (422 mg, 3 mol). The mixture was stirred for 4-5 h at R.T., and the reaction was monitored by LCMS. The mixture was diluted with CH 2 Cl 2 (40 mL), and washed with a sat. NaHCO 3 solution. The organic layer was dried over anhydrous Na 2 SO 4 , and filtered. The filtrate was evaporated at low pressure, and the residue was purified by silica gel column chromatography (20% EA in PE) to give 82-13 (900 mg, 87%) as a white foam.

Tetra-butylammonium hydroxide (21 mL as 54-56% aqueous solution, 42 mmol, 24 eq.) was adjusted with TFA to pH˜4 (˜3.5 mL), and the solution was treated with a solution of 82-13 (900 mg, 1.7 mmol) in DCM (21 mL). m-Cloroperbenzoic acid (2.1 g, 60-70%, ˜8.75 mmol, ˜5 eq.) was added portionwise under vigorous stirring, and the mixture was stirred overnight. The mixture was diluted with CH 2 Cl 2 (30 mL), and washed with a saturated NaHCO 3 solution. The organic layer was washed with brine, dried over anhydrous magnesium sulfate and concentrated under reduced pressure. The residue was purified by column chromatography in (40-70% EA in PE) to give 82-14 as an oil. The residue was purified by TLC (50% EA in PE) to give pure 82-14 (350 mg 50%).

Compound 82-14 (350 mg, 0.86 mg) was treated with 7N NH 3 in MeOH (15 mL). The mixture was stirred for 2-3 h and monitored by TLC. The mixture was concentrated at low pressure, and the residue was purified by silica gel column chromatography (5% isopropanol in DCM) to give 82-15 (250 mg, 96%) as a white solid. 1 H NMR (CD 3 OD, 400 M Hz) δ=7.75 (d, J=7.9 Hz, 1H), 6.60-6.35 (m, 1H), 5.72 (d, J=8.2 Hz, 1H), 5.37-5.25 (m, 1H), 5.17-5.06 (m, 1H), 5.04-4.94 (m, 1H), 4.59-4.29 (m, 1H), 3.87-3.70 (m, 2H).

To a stirred solution of 82-16 (3.79 g, 18 mmol) and 82-17 (3 g, 18 mmol) in anhydrous DCM (60 mL) was added with a solution of TEA (4 g, 39 mmol) in DCM (40 mL) dropwise at −78° C., and the mixture was stirred for 2 h. The mixture was concentrated at low pressure, and the residue was dissolved in methyl-butyl ether. The precipitate was removed by filtration, and the filtrate was concentrated to give the crude product. The residue was purified by dry column chromatography (anhydrous DCM) to give pure 82-18 as a colorless oil (3 g, 54%).

Compound 82-15 (200 mg, 0.66 mmol) was coevaporated with toluene 3 times to remove H 2 O. Compound 82-15 was treated with MeCN (1.5 mL) and NMI (541 mg, 6.6 mmol). The mixture was stirred at R.T., and then 82-18 (403 mg, 1.32 mmol) in MeCN (0.5 mL) was added. The residue was purified by a silica gel column (5% iPrOH in DCM) to give the crude product, which was purified by HPLC (0.1% HCOOH in water and MeCN) to give compound 82 (33 mg, 9%). ESI-LCMS: m/z 594 [M+Na] + .

Compound 84

To a stirred solution of POCl 3 (2.0 g, 13 mmol) in anhydrous DCM (10 mL) was added 1-naphthol (1.88 g, 13 mmol) at −70° C. and TEA (1.31 g, 13 mmol) in DCM (3 mL) dropwise at −70° C. The mixture was gradually warmed to R.T., and stirred for 1 h. A crude solution of 84-1 was obtained.

To a stirred solution of (S)-isobutyl 2-aminopropanoate hydrochloride (2.35 g, 13 mmol) in DCM (20 mL) was added TEA (2.63 g, 26 mmol) and a crude solution of 84-1 at −70° C. The mixture was gradually warmed to R.T., and stirred for 2 h. The reaction was monitored by LCMS and quenched with n-propylamine. The solvent was evaporated at low pressure, and the residue was purified by chromatography (PE:MTBE=5:1˜1:1) to give pure 84-2 (1.8 g, 37%).

To a solution of 83-A (300 mg, 0.337 mmol) and NMI (276 mg, 3.37 mmol) in anhydrous CH 3 CN (4 mL) was added 84-2 (249 mg, 0.674 mol, in DCM (5 mL)) at 0° C. The mixture was stirred at R.T. for 10 h. The reaction was monitored by LCMS, and then quenched with H 2 O. The mixture was extracted with CH 2 Cl 2 (3×20 mL). The organic phase was dried over anhydrous MgSO 4 , and concentrated at low pressure. The residue was purified by chromatography using PE:EA=5:1˜2:1 as the eluent to give 84-3 (360 mg, 87%).

Compound 84-3 (360 mg, 0.294 mmol) was dissolved in CH 3 COOH (80%, 8 mL), and stirred at 40-50° C. for 2.5 h. The reaction was monitored by LCMS and then quenched with MeO. The mixture was concentrated at low pressure, and the residue was purified by chromatography using PE:EA=1:1 as the eluent to generate crude compound 84. The product purified by prep-HPLC (neutral system, NH 4 HCO 3 ) to give compound 84 (70 mg, 75%) as a white solid. ESI-MS: m/z 679.2 [M+H] + .

Compound 85

To a stirred solution of POCl 3 (2.0 g, 13 mmol) in anhydrous DCM (10 mL) was added phenol (1.22 g, 13 mmol) at −70° C. and TEA (1.31 g, 13 mmol) in DCM (3 mL) dropwise at −70° C. The mixture was gradually warmed to R.T., and stirred for 1 h. A crude solution of 85-1 was obtained.

Compound 85 was prepared using a similar procedure as for the preparation of compound 84 using 85-2 (205 mg, 0.674 mol, in DCM (5 mL) obtained from (S)-isopropyl 2-aminopropanoate hydrochloride and 85-1) and 83-A (300 mg, 0.337 mmol). Compound 85 (50 mg, 74%) was obtained as a white solid. ESI-MS: m/z 615.2 [M+H] + .

Compound 86

Compound 86 was prepared using a similar procedure as for the preparation of compound 84 using 86-2 (214 mg, 0.674 mol, in DCM (5 mL) obtained from (S)-isobutyl 2-aminopropanoate hydrochloride and 86-1) and 83-A (300 mg, 0.337 mmol). Compound 86 (70 mg, 87%) was obtained as a white solid. ESI-MS: m/z 629.2 [M+H] + .

Compound 87

Compound 87 was prepared using a similar procedure as for the preparation of compound 84 using 87-2 (223 mg, 0.674 mol, DCM (5 mL) obtained from (S)-cyclopentyl 2-aminopropanoate hydrochloride and 87-1) and 83-A (300 mg, 0.337 mmol). Compound 87 (62 mg, 71%) was obtained as a white solid. ESI-MS: m/z 641.2 [M+H] + .

Compound 88

Compound 88 was prepared using a similar procedure as for the preparation of compound 84 using 88-2 (223 mg, 0.674 mol, DCM (5 mL), obtained from (S)-3-pentyl 2-aminopropanoate hydrochloride and 88-1) and 83-A (300 mg, 0.337 mmol). Compound 88 (42 mg, 60%) was obtained as a white solid. ESI-MS: m/z 643.2 [M+H] + .

Compound 89

A stirred solution of phosphoryl trichloride (1.00 g, 6.58 mmol) and 5-quinoline (955 mg, 6.58 mmol) in anhydrous DCM (50 mL) was treated with a solution of TEA (665 mg, 6.58 mmol) in DCM (10 mL) at −78° C. The mixture was gradually warmed to R.T., and stirred for 2 h. The solution was cooled to −78° C. and then treated with (S)-neopentyl 2-aminopropanoate hydrochloride (1.28 g, 6.58 mmol). TEA (1.33 g, 13.16 mmol) was added dropwise at −78° C. The mixture was gradually warmed to R.T., and stirred for 2 h. The mixture was concentrated at low pressure, and the residue was dissolved in methyl-butyl ether. The precipitate was filtered off, and the filtrate was concentrated at low pressure. The residue was purified by a silica gel column (pure AcOEt) to give 89-1 as colorless oil (500 mg, 20%).

To a solution of 89-2 (300 mg, 0.337 mmol) and NMI (276.6 mg, 3.37 mmol) in anhydrous CH 3 CN (0.9 mL) was added 89-1 (388 mg, 1.011 mmol) in CH 3 CN (0.3 mL) dropwise at 0° C. The mixture was stirred at R.T. overnight. The reaction was quenched with water, and extracted with AcOEt. The organic phase was washed with brine, dried over anhydrous sodium sulfate, and concentrated at low pressure. The residue was purified by silica gel column (33% EA in PE) to give 89-3 as a yellow powder (300 mg, 71.9%).

Compound 89-3 (300 mg, 0.243 mmol) was dissolved in 80% CH 3 COOH (3 mL), and the mixture was stirred at 60° C. for 2.5 h. The mixture was partitioned between AcOEt and water. The organic layer phase was washed by brine, dried over sodium sulfate and concentrated at low pressure. The residue was purified by silica gel column (50% EA in PE) to give compound 89 as a yellow powder (81 mg, crude product). The crude product (81 mg) was purified by RP HPLC to give compound 89 as a white solid. (28.7 mg, 17.1%). ESI-LCMS: m/z 694.1 [M+H] + .

Compound 90

Compound 90-1 was prepared using a similar procedure as for the preparation of compound 89-1 using phosphoryl trichloride (2.00 g, 13.16 mmol), 1-naphthol (1.882 g, 13.16 mmol) and (S)-neopentyl 2-aminopropanoate hydrochloride (2.549 g, 13.16 mmol). Compound 90-1 (600 mg, 12%) was obtained as a colorless oil.

A solution of 90-2 (230 mg 0.26 mmol) and NMI (212 mg 2.60 mmol) in anhydrous CH 3 CN (1 mL) was treated with a solution of 90-1 (300 mg 0.78 mmol) in anhydrous CH 3 CN (0.5 mL) at R.T. The mixture was stirred at R.T. overnight. The reaction was quenched with water, and extracted with EA (3×20 mL). The organic layer was washed with brine, dried by anhydrous sodium sulfate, and concentrated at low pressure. The residue was purified by a silica gel column (CH 3 OH in CH 2 Cl 2 from 1% to 5%) to give 90-3 (300 mg, 93%) as a white solid.

Compound 90-3 (300 mg, 0.24 mmol) was dissolved in CH 3 COOH (80%, 5 mL). The mixture was stirred at 60° C. for 2.5 h. The mixture was diluted with EA (30 mL) and washed with brine. The organic phase was dried over anhydrous sodium sulfate, and concentrated at low pressure. The residue was purified by a silica gel column (CH 3 OH in CH 2 Cl 2 from 1% to 5%) to give crude compound 90 (105 mg). The crude product was purified by HPLC (0.1% NH 4 HCO 3 in water and CH 3 CN) to give compound 90 (45 mg, 26%) as a white solid. ESI-LCMS: m/z 693.2 [M+H] + .

Compound 91

A stirred solution of 91-1 (2.00 g, 13.99 mmol) and 91-2 (2.00 g, 13.99 mmol) in anhydrous DCM (8 mL) was treated with a solution of TEA (3.11 g, 30.8 mmol) in DCM (20 mL) dropwise at −78° C. The mixture was stirred for 2 h. at −78° C. and then gradually warmed to R.T. The organic solvent was removed at low pressure, and the residue was dissolved in methyl-butyl ether. The precipitate was filtered off, and the filtrate was concentrated at low pressure. The residue was purified on a silica gel column (dry DCM) to give 91-3 as colorless oil (1 g, 20.96%).

Compound 91-4 (260 mg, 0.29 mmol) was coevaporated with toluene 3 times to remove H 2 O. Dried 91-4 was treated with MeCN (0.8 mL) and NMI (240 mg, 2.9 mmol) and then stirred for 10 mins. The mixture was treated with a solution of 91-3 (291 mg, 0.87 mmol) in MeCN (0.4 mL), and then concentrated at low pressure. The residue was purified on a silica gel column (75% EA in PE)) to give 91-5 (300 mg, 86%) as a white solid.

Compound 91-5 (300 mg, 0.25 mmol) was treated with CH 3 COOH (5 mL, 80%), and stirred at 50° C. for 3 h. The mixture was diluted with EA. The solution was washed with brine, dried over anhydrous Na 2 SO 4 , and concentrated at low pressure. The residue was purified by silica gel column chromatography (67% EA in PE) to give crude compound 91, which was purified by HPLC. The product was dried by lyophilization to give compound 91 (30 mg, 18.5%) as a white solid. ESI-LCMS: m/z 643 [M+H] + .

Compound 77

To a solution of 1,1-dimethoxycyclopentane (19.3 g, 148.52 mmol) and 77-1 (10.0 g, 37.13 mmol) in DCE (100 mL) was added TsOH.H 2 O (0.7 g, 3.71 mmol). The mixture was stirred at 50° C. for 12 h. The mixture was neutralized with Et 3 N, and concentrated at low pressure. The residue was purified by silica gel column chromatography (1-10% MeOH in DCM) to give 77-2 (8.7 g, 70.1%) as a white solid.

Compound 77-2 (20.0 g, 0.06 mol) was coevaporated with anhydrous pyridine 3 times to remove H 2 O. To an ice-cold solution of 77-2 in anhydrous pyridine (100 mL) was added TsCl (22.8 g, 0.12 mol) at 0° C., and the mixture was stirred overnight. The reaction was monitored by LCMS and TLC. The reaction was quenched with H 2 O, and the mixture extracted with EA (3×200 mL). The solution was dried over anhydrous Na 2 SO 4 and evaporated at low pressure. The residue was purified by silica gel column chromatography (DCM:MeOH=100:1 to 15:1) to give 77-3 (20.0 g, 69.0%) as a white solid.

To a solution of 77-3 (20.0 g, 0.04 mol) in acetone (200 mL) was added NaI (31.0 g, 0.2 mol), and the mixture was heated to reflux overnight. The reaction was monitored by LCMS. The reaction was quenched with a sat. Na 2 S 2 O 3 solution. The solution was extracted with EA (3×200 mL). The organic layer was dried over anhydrous Na 2 SO 4 , and evaporated at low pressure. The residue was purified by silica gel column chromatography (DCM:MeOH=100:1 to 15:1) to give 77-4 (15.0 g, 83.3%) as a white solid.

Compound 77-4 (13.4 g, 30.16 mmol) was treated with HCOOH (80%) in H 2 O at R.T. The solution was stirred at 60° C. for 2 h. The mixture was concentrated at low pressure. The residue was purified by column chromatography (1%-10% MeOH in DCM) to give 77-5 (9.1 g, 80.0%) as a white solid.

To a solution of 77-5 (5.0 g, 13.22 mmol) in anhydrous CH 3 CN/THF (50 mL, 1:1, v:v) was added DBU (6.0 g, 39.66 mmol) at R.T. The solution was stirred at 50° C. for 1.5 h. The reaction was quenched with HCOOH at 0° C., and then concentrated at low pressure. The residue was purified by column chromatography (50%-70% EA in PE) to give 77-6 (3.3 g, 48.1%) as a white solid.

To an ice-cold solution of 77-6 (2.1 g, 8.39 mmol) in anhydrous MeCN (21 mL) was added NIS (2.4 g, 10.49 mmol) and TEA.3HF (1.0 g, 6.29 mmol) under N 2 . The mixture was stirred at R.T. for 1 h. The reaction was quenched with sat. NaHCO 3 and sat. Na 2 SO 3 solution, and extracted with EA (3×100 mL). The organic phase was dried over anhydrous Na 2 SO 4 , and evaporated to dryness at low pressure. The residue was purified on a silica gel column (30%-50% EA in PE) to give 77-7 (1.3 g, 39.3%) as a light yellow solid.

To a stirred solution of 77-7 (3.2 g, 8.08 mmol) in anhydrous DCM (32 mL) was added DMAP (2.5 g, 20.20 mmol) and Et 3 N (2.5 g, 24.24 mmol) at R.T. The mixture was treated with BzCl (3.7 g, 26.66 mmol) at 0° C. and then stirred at R.T. overnight. The reaction was quenched with water, and extracted with EA (3×60 mL). The organic phase was concentrated at low pressure, and the residue was purified by column chromatography (20%-30% EA in PE) to give 77-8 (1.8 g, 31.6%) as a white solid.

Bu 4 NOH (8.0 g, 13.74 mL, 55% in H 2 O) was adjusted to pH=3-4 with TFA, and then cooled to R.T. To a solution of 77-8 (600 mg, 0.85 mmol) in DCM (10 mL) was added the Bu 4 NOH solution and m-CPBA (917 mg, 4.25 mmol, 80%) at R.T. The mixture was stirred at 25° C. for 48 h and then washed with a sat. NaHCO 3 solution. The organic layer was directly passed through basic Al 2 O 3 column, and the solvent was concentrated at low pressure. The residue was purified by a silica gel column (20%-30% EA in PE) to give 77-9 (123 mg, 24.3%) as a white solid.

To a solution of 77-9 (300 mg, 0.50 mmol) in EA/hexane (20 mL, 1:1, v:v) was added Lindlar catalyst (200 mg) under N 2 . The mixture was stirred under H 2 (40 Psi) at 2° C. for 1.5 h. The suspension was filtered, and the filtrate was treated with Lindlar catalyst (200 mg) under N 2 , and stirred under H 2 (40 Psi) at 25° C. for 1.5 h. The mixture was filtered, and the filtrate was concentrated at low pressure to give crude 77-10 (287 mg) as a white solid.

Compound 77-10 (287 mg, 0.48 mmol) was dissolved in NH 3 /MeOH (30 mL, 7 M). The mixture was stirred at R.T. for 24 h under N 2 and then concentrated at low pressure. The residue was purified by prep-HPLC (0.1% HCOOH in water and MeCN) to give 77-11 (50 mg, 34.7% over two steps) as a white solid. 1 H-NMR (CD 3 OD, 400 MHz) δ=7.86 (d, J=8.0 Hz 1H), 6.26 (s, 1H), 5.62-5.86 (m, 1H), 5.49 (d, J=17.1 Hz, 1H), 5.30 (d, J=10.5 Hz, 1H), 4.41 (d, J=19.3 Hz, 1H), 3.71-3.86 (m, 1H).

Compound 77-11 (113 mg, 0.39 mmol) was co-evaporated with toluene 3 times to remove H 2 O. To a stirred solution of 77-11 (113 mg, 0.39 mmol) in a mixture of MeCN (0.5 mL) and NMI (320 mg, 3.90 mmol) was added a solution of 73-C (256 mg, 0.66 mmol) in MeCN (0.5 mL) at 0° C. The mixture was stirred at R.T. overnight and then concentrated at low pressure. The residue was purified on a silica gel column (5% MeOH in DCM) to give crude compound 77, which purified by prep-HPLC (0.1% HCOOH in water and MeCN) to give compound 77 (45 mg, 20.1%) as a white solid. ESI-MS: m/z 538.2 [M−F] + ESI-MS: m/z 580.2 [M+Na] + .

Compound 78

To a solution of 77-9 (300 mg, 0.50 mmol) in MeOH (30 mL) was added wet Pd/C (300 mg, 10%) under N 2 . The mixture was stirred under H 2 (1 atm) at 25° C. for 1.5 h. The suspension was filtered, and then concentrated at low pressure to give crude 78-1 (307 mg) as a white solid.

Compound 78-1 (307 mg, 0.48 mmol) was dissolved in NH 3 /MeOH (30 mL, 7 M). The mixture was stirred at R.T. for 24 h under N 2 then concentrated at low pressure. The residue was purified by prep-HPLC (0.1% HCOOH in water and MeCN) to give 78-2 (30 mg, 21% over two steps) as a white solid.

Compound 78-2 (91 mg, 0.31 mmol) was co-evaporated with toluene 3 times to remove H 2 O. To a stirred solution of 78-2 (91 mg, 0.31 mmol) in a mixture of MeCN (0.5 mL) and NMI (254 mg, 3.90 mmol) was added a solution 73-C (203 mg, 0.66 mmol) in MeCN (0.5 mL) at 0° C. The mixture was stirred at R.T. overnight and then concentrated at low pressure. The residue was purified on a silica gel column (5% MeOH in DCM) to the crude compound 78, which purified by prep-HPLC (0.1% HCOOH in water and MeCN) to give compound 78 (30 mg, 17%) as a white solid. ESI-MS: m/z 540.1 [M−F] + .

Additional Compounds of Formula (I)

The foregoing syntheses are exemplary and can be used as a starting point to prepare a large number of additional compounds. Examples of compounds of Formula (I) that can be prepared in various ways, including those synthetic schemes shown and described herein, are provided below. Those skilled in the art will be able to recognize modifications of the disclosed syntheses and to devise routes based on the disclosures herein; all such modifications and alternate routes are within the scope of the claims.

HCV Replicon Assay

Cells

Huh-7 cells containing the self-replicating, subgenomic HCV replicon with a stable luciferase (LUC) reporter were cultured in Dulbecco's modified Eagle's medium (DMEM) containing 2 mM L-glutamine and supplemented with 10% heat-inactivated fetal bovine serum (FBS), 1% penicillin-streptomyocin, 1% nonessential amino acids, and 0.5 mg/mL G418.

Determination of Anti-HCV Activity

Determination of 50% inhibitory concentration (EC 50 ) of compounds in HCV replicon cells were performed by the following procedure. On the first day, 5,000 HCV replicon cells were plated per well in a 96-well plate. On the following day, test compounds were solubilized in 100% DMSO to 100× the desired final testing concentration. Each compound was then serially diluted (1:3) up to 9 different concentrations. Compounds in 100% DMSO are reduced to 10% DMSO by diluting 1:10 in cell culture media. The compounds were diluted to 10% DMSO with cell culture media, which were used to dose the HCV replicon cells in 96-well format. The final DMSO concentration was 1%. The HCV replicon cells were incubated at 37° C. for 72 h. At 72 h, cells were processed when the cells are still subconfluent. Compounds that reduce the LUC signal are determined by Bright-Glo Luciferase Assay (Promega, Madison, Wis.). % Inhibition was determined for each compound concentration in relation to the control cells (untreated HCV replicon) to calculate the EC 50 .

Compounds of Formula (I) are active in the replicon assay. The antiviral activity of exemplary compounds is shown in Table 2, where ‘A’ indicates an EC 50 <1 μM, ‘B’ indicates an EC 50 ≥1 μM and <10 μM, and ‘C’ indicates an EC 50 ≥10 μM and <100 μM.

NS5B Inhibition Assay

The enzyme activity of NS5B570-Con1 (Delta-21) was measured as an incorporation of tritiated NMP into acid-insoluble RNA products. The complementary IRES (cIRES) RNA sequence was used as a template, corresponding to 377 nucleotides from the 3′-end of HCV (−) strand RNA of the Con-1 strain, with a base content of 21% Ade, 23% Ura, 28% Cyt, and 28% Gua. The cIRES RNA was transcribed in vitro using a T7 transcription kit (Ambion, Inc.) and purified using the Qiagen RNeasy maxi kit. HCV polymerase reactions contained 50 nM NS5B570-Con1, 50 nM cIRES RNA, about 0.5 μCi tritiated NTP, 1 μM of competing cold NTP, 20 mM NaCl, 40 mM Tris-HCl (pH 8.0), 4 mM dithiothreitol, and 4 mM MgCl 2 . Standard reactions were incubated for 2 h at 37° C., in the presence of increasing concentration of inhibitor. At the end of the reaction, RNA was precipitated with 10% TCA, and acid-insoluble RNA products were filtered on a size exclusion 96-well plate. After washing of the plate, scintillation liquid was added and radio labeled RNA products were detected according to standard procedures with a Trilux Topcount scintillation counter. The compound concentration at which the enzyme-catalyzed rate was reduced by 50% (IC 50 ) was calculated by fitting the data to a non-linear regression (sigmoidal). The IC 50 values were derived from the mean of several independent experiments and are shown in Table 3. Compounds of Formula (I) showed activity in this assay. A value of ‘A’ in the table below indicates an IC 50 of <1 μM, a value of ‘B’ indicates an IC 50 ≥1 μM and <10 μM, and a value of ‘C’ indicates an IC 50 value of ≥10 μM and <100 μM.

Assessment of Inhibition of Mitochondrial Function

Drug-associated dysfunction of mitochondria is believed to play a role in the etiology of the various adverse symptoms that occur in patients treated with antiviral nucleoside/nucleotides. For this reason, evaluation of compounds for their potential to inhibit mitochondrial function is useful. To assess the potential for nucleotide/nucleoside analogs to interfere with normal mitochondrial functions and exhibit mitochondrial toxicity, the following were measured: (1) the ability of nucleotides to be incorporated by human mitochondrial RNA polymerase in vitro and (2) the cellular inhibition of the synthesis of the mitochondrial DNA (mtDNA)-encoded protein, cytochrome c oxidase (COX-I), relative to the nuclear DNA (nDNA)-encoded mitochondrial protein succinate dehydrogenase subunit A (SDH-A) in HepG2 cells. Control compounds and compounds of Formula (I) were studied in these assays.

Biochemical Assay

Arnold et al. “Sensitivity of Mitochondrial Transcription and Resistance of RNA Polymerase II Dependent Nuclear Transcription to Antiviral Ribonucleosides” PLoS Pathog (2012) 8(11): e1003030. doi:10.1371/journal.ppat.1003030, which is hereby incorporated by reference in its entirety.

Assessment of Incorporation of Nucleotides by Human Mitochondrial RNA Polymerase (HMRP)

DdRp Assay with Human Mitochondrial RNA Polymerase

The DdRp assay with human mitochondrial RNA polymerase was performed under single turnover conditions where enzyme concentration is in excess of the primer/template. The 33 P-RNA/DNA primer/template was used at a concentration of 100 nM, together with 320 nM enzyme. The standard 10-μL reactions were carried out at 30° C. for 1 minute with 100 μM of each nucleotide 5′-triphosphate (NTP), 10 mM MgCl 2 , 50 mM NaCl, 40 mM Tris, pH 7.5, and 1 mM DTT. The reaction was stopped by adding 20 μL of formamide loading dye containing 50 mM EDTA. RNA products were resolved by electrophoresis on 22.5% TBE Urea polyacrylamide sequencing gels that were scanned using a TYPHOON PhosphorImager.

Results

As shown in both FIGS. 10 and 11 , the appropriate natural nucleotides were shown to be good substrates for incorporation by HMRP in each template. The template in FIG. 10 was designed to measure incorporation of UTP analogs. Primer/Template: (SEQ ID NO: 1) UUUUGCCGCGCC and (SEQ ID NO: 2) GGGAATGCTAGGCGCGGC. In the control water lanes, wherein no nucleotides were added, no incorporation was observed as indicated by the lack of product band. As shown in FIG. 10 , UTP and 3′-deoxy-UTP were efficient substrates for incorporation as indicated by the prominent product band. The potential for misincorporation was assessed using the control nucleotide CTP. As provided in FIG. 10 , CTP was incorporated to a lesser extent relative to UTP. In contrast to UTP and 3′-deoxy-UTP, compounds of Formula (I) and 2′-Me-2′-F-UTP were not efficient substrates for incorporation by HMRP as demonstrated by the lack of product band.

The template strand shown in FIG. 11 was designed to measure the incorporation of GTP analogs. Primer/Template: (SEQ ID NO: 3) UUUUGCCGCGCC and (SEQ ID NO: 4) GGGAATGCACGGCGCGGC. In the control water lanes, no incorporation was observed as indicated by the lack of product band. GTP and 3′-deoxy-GTP were found to be efficient substrates for incorporation as demonstrated by the significant product bands. The potential for misincorporation was assessed using the control nucleotide ATP. As shown by the lack of product band in FIG. 11 , control ATP was a poor substrate for incorporation. Nucleotide analog 2′-Me-GTP (the nucleotide metabolite of monophosphate prodrug INX-0189/BMS-986094) was tested and found to be a good substrate for incorporation by HMRP as indicated by the product band. Nucleotide analog 2′-Me-2′-F-GTP (nucleotide metabolite of monophosphate prodrug GS-938) was tested and also found to be incorporated by HMRP. In contrast, compounds of Formula (I) were not efficient substrates for incorporation into the template strand by HMRP as indicated by the lack of product bands in FIG. 11 .

Assessment of Inhibition of Mitochondrial Protein Synthesis—Cell Based Assay

Assay Principle

MitoBiogenesis™ In Cell ELISA kits (Cat. # MS643) were obtained from Mitosciences, OR, USA. The MitoBiogenesis™ In Cell ELISA kit is a duplexing 96 well assay that ratios both an mtDNA and an nDNA encoded mitochondrial protein. Cells were seeded in 96 microplates and after exposure to compounds for several cell doublings, the levels of the two mitochondrial proteins were measured simultaneously in each well. The two proteins assayed were each subunits of different oxidative phosphorylation enzyme complexes, one protein being subunit I of Complex IV (cytochrome c oxidase; COX I) that is mtDNA encoded and the other being the 70 kDa subunit of Complex II (succinate dehydrogenase subunit A; SDH A) that is nDNA encoded. Complex IV includes several proteins that are encoded by the mtDNA while the proteins of Complex II are entirely encoded by nDNA. To control for the density of cells present at the end of the culture period, the number of cells were assessed by staining with Janus Green and the levels of COX I/SDH A normalized to the final cell density.

96 Well Plate Assay Format for HepG2 Cells

On the first day, 1000 HepG2 cells per well were plated in a 96 well plate. On the following day, compounds to be tested were solubilized in 100% DMSO to 100× the desired final testing concentration. Each compound was serially diluted (1:3) up to 9 distinct concentrations. Compounds in 100% DMSO were reduced to 10% (v/v) DMSO by diluting 1:10 in cell culture media. A 10 μL aliquot of the compounds diluted to 10% (v/v) DMSO with cell culture media was used to dose the cells in duplicate. The final DMSO concentration was 1% (v/v). Untreated cells and wells containing no cells were included on the plate to serve as controls. Cells were then incubated with compounds and observed for 8 days at 37° C. and 5% CO 2 . Plates were processed as described below in the assay procedure.

Batch Assay Format for HepG2 Cells

An alternate cell culture procedure was employed to test the potential to mediate mitochondrial toxicity at higher concentrations than achievable in the 96 well plate format. HepG2 cells were grown either in media/DMSO alone or in a series of compound concentrations in 15 cm 2 dishes or 6 well plates at an initial cell seeding density of 5×10 6 and 5×10 4 cells/mL, respectively. Cells were then incubated and observed for 8 days at 37° C. and 5% CO 2 . After 8 days, the cells were harvested by trypsinization, counted, and seeded in 96 well plates at a density of 25,000 cells/well in 16 replicate wells. Cells were allowed to adhere overnight and then the plates were processed as described below in the assay procedure.

Assay Procedure

The assay was performed according to the manufacturer's instructions. Briefly, after the end of the culture period the cell culture media was gently aspirated from the wells of the plate and replaced with 100 μL of 4% (v/v) paraformaldehyde solution in phosphate buffered saline (PBS, Electron Microscopy Sciences Cat. #15713). After a 20 mins incubation at R.T., the solution was removed and the wells washed 3× with 300 μL of PBS. After the final wash, the PBS was removed and the wells overlayed with 100 μL PBS. The plates were then sealed and stored at 4° C. until used. To perform the assay, the PBS overlay was removed by blotting on a paper towel and 100 μL of 0.5% (v/v) acetic acid added to each well to block endogenous alkaline phosphatase activity. After a 5 mins incubation at R.T., the acetic acid solution was removed and the cells washed once with 200 μL PBS. Then, 100 μL of permeabilization buffer (0.1% (v/v) Triton X 100) was added to each well. After 30 mins incubation at R.T., the permeabilization buffer was removed and each well was blocked with 200 μL of 2× blocking solution for 2 h at R.T. The 2× blocking solution was then removed and 100 μL of primary antibody solution containing anti COX I and anti SDH A antibodies in 1× blocking solution was added to each well. Plates were then sealed and incubated overnight at 4° C. The primary antibody/blocking solution was removed and the plate washed 3× with 250 μL 0.05% (v/v) Tween 20 in PBS. Then, 100 μL of secondary antibody solution containing alkaline phosphatase (AP) labeled anti SDH A antibody and horseradish peroxidase (HRP) labeled anti COX I antibody was added and incubated for 1 h at R.T. The plate was then washed 4× with 250 μL 0.05% (v/v) Tween 20 in PBS. After blotting the plate dry 100 μL of AP detection reagent was added to each well, and the plate incubated in the dark for 30 mins at R.T. The optical density of each well was then measured at 405 nm. The AP detection reagent was then removed and replaced with 100 μL of HRP detection reagent, and the plate incubated in the dark for a further 30 mins at R.T. The optical density of each well was then measured at 600 nm. The HRP detection reagent was then removed and each well was then stained with 50 μL of 1× Janus Green Stain for 5 mins at R.T. After removal of the dye, the plates were washed 5× in ultrapure water to remove any remaining dye. The Janus Green stain was then solubilized by the addition of 100 μL of 0.5 M HCl and incubated for 10 mins. The optical density of each well was then measured at 595 nm.

Data Analysis

The average of all replicate background measurements from each experimental condition was calculated and subtracted from the experimental values of the same condition. The SDH A and COX I signals were then plotted as a ratio (COX I/SDH A) and normalized to the Janus Green staining intensity to correct for differences in cell density.

Results

Control compound d4T was tested and found not to inhibit mitochondrial protein synthesis at concentrations up to 100 μM as shown in FIGS. 12A-D . Control compound ddC was tested and found to strongly inhibit mitochondrial protein synthesis. See FIGS. 12A-D . As demonstrated in FIG. 12A , nucleoside monophosphate prodrug INX-08189/BMS-986094 (which delivers 2′-Me-GTP) was tested in the assay and found to strongly inhibit mitochondrial protein synthesis. In contrast, compounds of Formula (I) were tested and found to not inhibit mitochondrial protein synthesis at concentrations up to 100 μM as shown in FIGS. 12B-D .

Combination of Compounds

Combination Testing

Two or more test compounds were tested in combination with each other using an HCV genotype 1b HCV replicon harbored in Huh7 cells with a stable luciferase (LUC) reporter. Cells were cultured under standard conditions in Dulbecco's modified Eagle's medium (DMEM; Mediatech Inc, Herndon, Va.) containing 10% heat-inactivated fetal bovine serum (FBS; Mediatech Inc, Herndon, Va.) 2 mM L-glutamine, and nonessential amino acids (JRH Biosciences). HCV replicon cells were plated in a 96-well plate at a density of 10 4 cells per well in DMEM with 10% FBS. On the following day, the culture medium was replaced with DMEM containing either no compound as a control, the test compounds serially diluted in the presence of 2% FBS and 0.5% DMSO, or a combination of compound 18 with one or more test compounds serially diluted in the presence of 2% FBS and 0.5% DMSO. The cells were incubated with no compound as a control, with the test compounds, or the combination of compounds for 72 h. The direct effects of the combination of the test compounds were examined using a luciferase (LUC) based reporter as determined by the Bright-Glo Luciferase Assay (Promega, Madison, Wis.). Dose-response curves were determined for individual compounds and fixed ratio combinations of two or more test compounds.

The method utilized for evaluating combination effects used a program called MacSynergy II. MacSynergy II software was kindly provided by Dr. M. Prichard (University of Michigan). The Prichard Model allows for a three-dimensional examination of drug interactions and a calculation of the synergy volume (units: μM 2 %) generated from running the replicon assay using a checkerboard combination of two or more inhibitors. The volumes of synergy (positive volumes) or antagonism (negative volumes) represent the relative quantity of synergism or antagonism per change in the concentrations of the two drugs. Synergy and antagonism volumes are defined based on the Bliss independence model. In this model, synergy volumes of less than −25 indicate antagonistic interactions, volumes in the −25-25 range indicate additive behavior, volumes in the 25-100 range indicate synergistic behavior and volumes >100 indicate strong synergistic behavior. Determination of in vitro additive, synergistic and strongly synergistic behavior for combinations of compounds can be of utility in predicting therapeutic benefits for administering the combinations of compounds in vivo to infected patients.

The synergy volume results for the combinations are provided in Table 4.

Although the foregoing has been described in some detail by way of illustrations and examples for purposes of clarity and understanding, it will be understood by those of skill in the art that numerous and various modifications can be made without departing from the spirit of the present disclosure. Therefore, it should be clearly understood that the forms disclosed herein are illustrative only and are not intended to limit the scope of the present disclosure, but rather to also cover all modification and alternatives coming with the true scope and spirit of the invention.