Stable solid compositions comprising quinapril magnesium can be made using quinapril or an acid addition salt thereof by reacting the quinapril or acid addition salt with an alkaline magnesium compound in the presence of a solvent so as to convert all or substantially all of the quinapril or acid addition salt to quinapril magnesium.

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 ...

Disclosed herein a process for preparing a pure amorphous quinapril hydrochloride and its other pharmaceutically acceptable salts and packing the same. The process comprises of dissolving or suspending crystalline or solvate form of quinapril hydrochloride in a suitable solvent adding a second solvent solvent followed by gradual cooling and isolating the pure amorphous quinapril hydrochloride.

Methods and materials for preparing quinapril its pharmaceutically acceptab le salts including quinapril hydrochloride are disclosed. The method includes reacting (2S4S)-2-(4-methyl-25-dioxo-oxazolidin-3-yl)-4-phenyl-butyric aci d ethyl ester with (3S)-1234-tetrahydro-isoquinoline-3-carboxylic acid tert - butyl ester toyield quinapril tert-butyl ester which is subsequently reactedwith an acid to yield quinapril or an acid addition salt of quinapril .

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 nitropropanae. Each such nitroalkane solvate having p...