Process for preparing amorphous rosuvastatin calcium free of impurities

摘要

A pure amorphous form of rosuvastatin calcium having purity of more than 99.5%, preferably a purity of more than 99.8%, more preferably a purity of more than 99.9% as determined by HPLC area percentage, and free from any traces of alkali metal impurities is disclosed. A process of preparing said pure amorphous form of rosuvastatin calcium is disclosed, which comprises hydrolysis of C 1 -C 5 alkyl esters of rosuvastatin, preferably tert- butyl ester of rosuvastatin, with an organic nitrogen base, notably tert- butylamine , in the presence of water, optionally containing aprotic solvent, following the conversion of thus obtained rosuvastain salt with a source of calcium to desired rosuvastatin calcium, which is then isolated. An alternative process is disclosed, which comprises the conversion of novel ammonium salt of rosuvastatin notably tert-butyl salt of rosuvastatin, with the source of calcium to desired commercial rosuvastatin calcium. Rosuvastatin calcium is HMG CoA reductase, useful in the treatment of hyperlipidemia, hypercholesterolemia and atherosclerosis.