摘要 |
A novel crystalline form of quinapril hydrochloride of formula (I). An amorphous form of quinapril hydrochloride substantially free of impurities, specially diketopiperazine compound, and conforming to pharmacopoeial specifications formed from the said novel crystalline form of quinapril hydrochloride of formula (I). The crystalline quinapril hydrochloride is in the form nitroalkane solvate in which the nitroalkane is nitromethane, nitroethane and nitropropane. Each such nitroalkane solvate having particula r characteristic X- ray diffraction patterns. A process for preparation of amorphous from of quinapril hydrochloride, substantially free of impurities, specially diketopiperazine compound, and conforming to pharmacopoeial specifications, using the novel crystalline quinapril hydrochloride as an intermediate. The process involves obtaining free base compound of formula ( V) by adjusting the pH of a solution of the benzyl ester maleate salt of quinapril of formula (V) between 7.5-8.5 in a mixture of water and an organi c solvent; catalytic hydrogenation of this compound (V) in an alcoholic solven t in the presence of concentrated hydrochloric acid or hydrogen chloride dissolved in an alcoholic solvent and in the presence of catalytic amounts o f Pd/C to obtain a residue containing formula (I);crystallization of the said residue by evaporating the alcoholic solvent from a nitroalkane solvent to give crystalline quinapril hydrochloride, associated with a solvate of the nitroalkane solvent, and drying the crystalline quinapril hydrochloride nitroalkane solvate at a temperature between 40~C and 45~C under vacuum to give amorphous quinapril hydrochloride of formula (I).
|