β crystalline form of perindopril tert-butylamine salt

The present invention relates to a new β crystalline form of perindopril tert-butylamine salt of formula (I):

Perindopril and its pharmaceutically acceptable salts, and more especially its tert-butylamine salt, have valuable pharmacological properties.

Their principal property is that of inhibiting angiotensin I converting enzyme (or kininase II), which prevents, on the one hand, conversion of the decapeptide angiotensin I to the octapeptide angiotensin II (a vasoconstrictor) and, on the other hand, degradation of bradykinin (a vasodilator) to an inactive peptide.

Those two actions contribute to the beneficial effects of perindopril in cardiovascular diseases, more especially in arterial hypertension and heart failure.

Perindopril, its preparation and its use in therapeutics have been described in European Patent specification EP 0 049 658.

In view of the pharmaceutical value of this compound, it has been of prime importance to obtain it with excellent purity. It has also been important to be able to synthesise it by means of a process that can readily be converted to the industrial scale, especially in a form that allows rapid filtration and drying. Finally, that form had to be perfectly reproducible, easily formulated and sufficiently stable to allow its storage for long periods without particular requirements for temperature, light, humidity or oxygen level.

The patent specification EP 0 308 341 (equivalent to U.S. Pat. No. 4,914,214, the subject matter of which is hereby incorporated by reference) describes an industrial synthesis process for perindopril. However, that document does not specify the conditions for obtaining perindopril in a form that exhibits those characteristics in a reproducible manner.

The Applicant has now found that a particular salt of perindopril, the tert-butylamine salt, can be obtained in a well defined, perfectly reproducible crystalline form that especially exhibits valuable characteristics for formulation.

More specifically, the present invention relates to the β crystalline form of the compound of formula (I), characterized by the following powder X-ray diffraction diagram, measured using a Siemens D5005 diffractometer (copper anticathode) and expressed in terms of inter-planar distance d, Bragg's angle 2 theta, intensity and relative intensity (expressed as a percentage of the most intense ray):

The invention relates also to a process for the preparation of the β crystalline form of the compound of formula (I), which process is characterized in that:

either, according to a first embodiment, a solution of perindopril tert-butylamine salt in dichloromethane is heated at reflux and is then rapdily cooled to 0° C. and the solid obtained is collected by filtration, or, according to a second embodiment, a solution of perindopril tert-butylamine salt in ethyl acetate is heated at reflux and is then rapidly cooled to 5° C. and the solid obtained is collected by filtration. In the crystallisation process according to the invention it is possible to use the compound of formula (I) obtained by any process. Advantageously, the compound of formula (I) obtained by the preparation process described in patent specification EP 0 308 341 is used. In the first embodiment of the process according to the invention, the concentration of the compound of formula (I) in the dichloromethane is preferably from 100 to 200 g/liter. In the second embodiment of the process according to the invention, the concentration of the compound of formula (I) in the ethyl acetate is preferably from 70 to 90 g/liter.

The invention relates also to pharmaceutical compositions comprising as active ingredient the β crystalline form of the compound of formula (I) together with one or more appropriate, inert, non-toxic excipients. Among the pharmaceutical compositions according to the invention, there may be mentioned more especially those that are suitable for oral, parenteral (intravenous or subcutaneous) or nasal administration, tablets or dragées, sublingual tablets, gelatin capsules, lozenges, suppositories, creams, ointments, dermal gels, injectable preparations, drinkable suspensions etc.

The useful dosage can be varied according to the nature and severity of the disorder, the administration route and the age and weight of the patient. It varies from 1 to 500 mg per day in one or more administrations.

The pharmaceutical compositions according to the invention may also comprise a diuretic such as indapamide.

The following Examples illustrate the invention but do not limit it in any way.

The powder X-ray diffraction spectrum was measured under the following experimental conditions:

Siemens D5005 diffractometer, scintillation detector, copper anticathode (λ=1.5405 Å), voltage 40 kV, intensity 40 mA, mounting θ-θ, measurement range: 5° to 30°, increment between each measurement: 0.02°, measurement time per step: 2 s, variable slits : v6, filter Kβ (Ni), no internal reference, zeroing procedure with the Siemens slits, experimental data processed using EVA software (version 5.0).