Process for preparation of (3R,5R)-7-[2-(4-fluorophenyl)-5-isopropyl-3-phenyl-4-[(4-hydroxy methyl phenyl amino) carbonyl]-pyrrol-1-yl]-3,5-dihydroxy-heptanoic acid hemi calcium salt

This application is a national stage application under 35 U.S.C. §371 of PCT Application No. PCT/IB2006/003153 having an international filing date of Nov. 8, 2006, which designated the United States, which claims the benefit of priority to Indian Patent Application No. 2964/DEL/2005, filed Nov. 8, 2005; Indian Patent Application No. 2967/DEL/2005, filed Nov. 8, 2005, and Indian Patent Application No. 3033/DEL/2005, filed Nov. 14, 2005. The entire disclosure of these patent documents is hereby by reference.

The present invention relates to processes for the preparation of (3R,5R)-7-[2-(4-fluorophenyl)-5-isopropyl-3-phenyl-4-[(4-hydroxy methyl phenyl amino)carbonyl]-pyrrol-1-yl]-3,5-dihydroxy-heptanoic acid hemi calcium salt.

(3R,5R)-7-[2-(4-fluorophenyl)-5-isopropyl-3-phenyl-4-[(4-hydroxy methyl phenyl amino)carbonyl]-pyrrol-1-yl]-3,5-dihydroxy-heptanoic acid hemi calcium salt acts an inhibitor of 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase, a coenzyme catalyzing the intracellular synthesis of cholesterol, and thus is useful as hypolipidemic and hypocholesterolemic agent, as discussed in PCT Publication No. 04/106299.

Cardiovascular disease and its associated maladies, dysfunctions and complications are a principal cause of disability and the chief cause of death. One specific factor significantly contributing to this pathophysiologic process is atherosclerosis, which has been generally recognized as the leading health care problem both with respect to mortality and health care costs.

Atherosclerosis is characterized by the deposition of fatty substances, primarily cholesterol, resulting in plaque formation on the inner surface of the arterial wall and degenerative change to the arteries. It is now well established that cardiovascular disorders including myocardial infarction, coronary heart disease, hypertension and hypotension, cerebrovascular disorders including stroke, cerebral thrombosis and memory loss due to stroke; peripheral vascular disease and intestinal infarction are caused by blockage of arteries and arterioles by atherosclerotic plaque. Atherosclerotic plaque formation is multi-factorial in its production. Hypercholesterolemia, especially elevated levels of low-density lipoprotein cholesterol (LDL), is an important risk factor for atherosclerosis and arteriosclerosis and associated diseases.

The HMG-CoA reductase inhibitors (statins) have been used in reducing blood levels of LDL cholesterol. Cholesterol is produced via the mevalonic acid pathway. Reducing the formation of mevalonic acid, a precursor to cholesterol, leads to a corresponding decrease in hepatic cholesterol biosynthesis with a reduction in the cellular pool of cholesterol.

A synthetic procedure for preparing (3R,5R)-7-[2-(4-fluorophenyl)-5-isopropyl-3-phenyl-4-[(4-hydroxy methyl phenyl amino) carbonyl]-pyrrol-1-yl]-3,5-dihydroxy-heptanoic acid hemi calcium salt has been disclosed in PCT Publication No. WO 04/106299. The aforementioned procedure involves multiple steps involving selective hydrolysis of two chemically similar functionalities e.g. hydrolysis of methyl ester in the presence of tert. -butyl ester, and reduction with sodium borohydride in the presence of iodine or with borane dimethyl sulphide which are expensive reagents and are air- and moisture-sensitive, hence difficult to handle.

Accordingly, herein are provided processes for preparing (3R,5R)-7-[2-(4-fluorophenyl)-5-isopropyl-3-phenyl-4-[(4-hydroxy methyl phenyl amino) carbonyl]-pyrrol-1-yl]-3,5-dihydroxy-heptanoic acid hemi calcium salt by using synthetic procedure incorporating particular intermediates.

Further, herein are provided processes which are simple and economical, avoid the use of expensive and air- and moisture-sensitive reagents, and avoid selective hydrolysis of methyl ester in the presence of tert-butyl ester.

Further, herein are provided processes for the preparation of a compound of Formula I

which processes comprise:

(a) reacting an amine of Formula II with methyl isobutyryl acetate of Formula III

to form a compound of Formula of IV (wherein R is a hydroxy protecting group, for example, acetyl, benzoyl, tetrahydropyranyl, methoxy methyl, methoxy ethoxymethyl, benzyl);

b) reacting the compound of Formula IV with benzaldehyde to form a compound of Formula V;

c) reacting the compound of Formula V with 4-fluorobenzaldehyde to form a compound of Formula VI;

d) reacting the compound of Formula VI with a compound of Formula VII

to form a compound of Formula VIII;

e) subjecting the compound of Formula VIII simultaneously to acid-catalyzed cleavage of ketal and hydroxy protecting group (when R is tetrahydropyranyl) to form a compound of Formula IX;

f) subjecting the compound of Formula IX to base-catalyzed hydrolysis to form a compound of Formula X; and

g) reacting the compound of Formula X with an aqueous solution of calcium acetate to form a compound of Formula I.

This process may involve one or more of the following features. For example, reaction of an amine of Formula II can be carried out in the presence of one or more organic bases such as, for example, triethylamine, pyridine, 1,2-ethylenediamine or mixtures thereof, in one or more aromatic solvents, for example, xylene, toluene or mixtures thereof. In another feature, the reaction of a compound of Formula IV can be carried out in the presence of one or more organic bases such as, for example, piperidine, pyridine, β-alanine or mixtures thereof, one or more organic acids such as, for example, glacial acetic acid or benzoic acid or mixture of organic bases and organic acids, in one or more solvents such as, for example, hydrocarbon solvents (e.g., hexane or heptane), halogenated solvents (e.g., dichloromethane, dichloroethane or chloroform), aromatic solvents (e.g., toluene or xylene) or mixtures thereof. In another feature, the reaction of a compound of Formula V can be carried out in the presence of one or more catalysts such as, for example, sodium cyanide, 3-ethyl-5-(2-hydroxyethyl)-4-methyl thiazolium bromide, 3-benzyl-5-(2-hydroxyethyl)-4-methyl thiazolium chloride or mixtures thereof, one or more organic bases such as, for example, triethylamine, pyridine or mixtures thereof, in a solvent-free condition or in one or more solvents such as, for example, protic polar solvents (e.g., methanol, ethanol, propanol, isopropanol or water), ethers (e.g., dioxan or tetrahydrofuran) or mixtures thereof. In another feature, the reaction of a compound of Formula VI can be carried out in the presence of one or more organic acids such as, for example, pivalic acid, p-toluene sulfonic acid or mixtures thereof, in one or more solvents such as, for example, aromatic solvents (e.g., xylene or toluene), hydrocarbon solvents (e.g., hexane or heptane), ethers (e.g., tetrahydrofuran, dioxane or diethyl ether) or mixtures thereof. In another feature, the cleavage of ketal and hydroxy protecting group of a compound of Formula VIII can be carried out in the presence of one or more mineral acids such as, for example, hydrochloric acid, hydrobromic acid, hydroiodic acid or mixtures thereof, in one or more solvents such as, for example, protic polar solvents (e.g., methanol, ethanol, propanol or water), ethers (e.g., tetrahydrofuran or diethyl ether) or mixtures thereof. In yet another feature, the hydrolysis of a compound of Formula IX can be carried out in the presence of one or more bases such as, for example, lithium hydroxide, sodium hydroxide, potassium hydroxide or mixtures thereof, in one or more solvents such as, for example, protic polar solvents (e.g., methanol, ethanol, propanol, isopropanol or water), ethers (e.g., tetrahydrofuran or diethyl ether) or mixtures thereof.

(3R,5R)-7-[2-(4-fluorophenyl)-5-isopropyl-3-phenyl-4-[(4-hydroxy methyl phenyl amino) carbonyl]-pyrrol-1-yl]-3,5-dihydroxy-heptanoic acid hemi calcium salt described herein may be prepared by following, for example, reaction sequences as depicted in Scheme I.

(3R,5R)-7-[2-(4-fluorophenyl)-5-isopropyl-3-phenyl-4-[(4-hydroxy methyl phenyl amino) carbonyl]-pyrrol-1-yl]-3,5-dihydroxy-heptanoic acid hemi calcium salt of Formula I can be prepared, for example, according to Scheme I. Thus, an amine of Formula I can be reacted with methyl isobutyryl acetate of Formula III to form a compound of Formula of IV (wherein R is the same as defined earlier). The compound of Formula IV can be reacted with benzaldehyde to form a compound of Formula V. The compound of Formula V can be reacted with 4-fluorobenzaldehyde to form a compound of Formula VI. The compound of Formula VI can be reacted with a compound of Formula VII to form a compound of Formula VIII. The compound of Formula VIII can be simultaneously subject to acid catalyzed cleavage of ketal and hydroxy protecting group (when R is tetrahydropyranyl) to form a compound of Formula IX. The compound of Formula IX can be subject to alkali base catalyzed hydrolysis to form a compound of Formula X. The compound of Formula X can be further converted to hemi calcium salt of Formula I by following procedures known to those of skill in the art.

The reaction of an amine of Formula II can be carried out in one or more aromatic solvents, for example, xylene, toluene or mixtures thereof. The reaction can also be carried out in the presence of one or more organic bases, for example, triethylamine, pyridine, 1,2-ethylenediamine or mixtures thereof.

The reaction of a compound of Formula IV can be carried out in one or more solvents, for example, hydrocarbon solvents (e.g., hexane or heptane), or halogenated solvents (e.g., dichloromethane, dichloroethane or chloroform), aromatic solvents (e.g., toluene or xylene) or mixtures thereof. The reaction can also be carried out in the presence of one or more organic bases, for example, piperidine, pyridine or β-alanine, one or more organic acids, for example, glacial acetic acid or benzoic acid or mixtures of organic bases and organic acids.

The reaction of a compound of Formula V can be carried out in the presence of one or more catalysts, for example, sodium cyanide, 3-ethyl-5-(2-hydroxyethyl)-4-methyl thiazolium bromide, 3-benzyl-5-(2-hydroxyethyl)-4-methyl thiazolium chloride or mixtures thereof. The reaction can also be carried out in the presence of one or more organic bases, for example, triethylamine, pyridine or mixture thereof, in a solvent-free condition or in one or more solvents, for example, protic polar solvents (e.g., methanol, ethanol, propanol, isopropanol or water), ethers (e.g., dioxan or tetrahydrofuran) or mixtures thereof.

The reaction of a compound of Formula VI can be carried out in one or more solvents, for example, aromatic solvents (e.g., xylene or toluene), hydrocarbon solvents (e.g., hexane or heptane), ethers (e.g., tetrahydrofuran, dioxane or diethyl ether) or mixtures thereof. The reaction can also be carried out in the presence of one or more organic acids, for example, pivalic acid, p-toluene sulfonic acid or mixtures thereof.

The cleavage of ketal and hydroxy protecting group of a compound of Formula VIII can be carried out in the presence of one or more mineral acids, for example, hydrochloric acid, hydrobromic acid, hydroiodic acid or mixtures thereof. The reaction can also be carried out in one or more solvents, for example, protic polar solvents (e.g., methanol, ethanol, propanol or water), ethers (e.g., tetrahydrofuran or diethyl ether) or mixtures thereof. The cleavage of ketal and hydroxy protecting group can also be carried out by any other cleavage method known to those of skill in the art.

The hydrolysis of a compound of Formula IX can be carried out in the presence of one or more bases, for example, lithium hydroxide, sodium hydroxide, potassium hydroxide or mixtures thereof. The reaction can also be carried out in one or more solvents, for example, protic polar solvents (e.g., methanol, ethanol, propanol, isopropanol or water), ethers (e.g., tetrahydrofuran or diethyl ether) or mixtures thereof.

The compound of Formula X can be converted into its corresponding hemi calcium salt of Formula I by following procedure known to those of skill in the art.

In the above schemes, where specific reducing agents, solvents, bases, catalysts, acids etc., are mentioned, it is to be understood that other reducing agents, solvents, bases, catalysts, acids etc., known to those skilled in the art may be used. Similarly, the reaction temperature and duration may be adjusted.

While the present invention has been described in terms of its specific embodiments, certain modifications and equivalents will be apparent to those skilled in the art and are within the scope of the present invention.