OPTICALLY ACTIVE SUBSTITUTED PYRIDINYLMETHYL-SULPHINYL-BENZIMIDAZOLE AND SALTS

摘要

The present invention relates to an enantioselective catalytic oxidation process for preparation of an optically active enantiomer or an enantiomerically enriched form of substituted pyridinylmethyl-sulphinyl-benzimidazole comprising enantioselective catalytic oxidation of a substituted pyridinylmethyl prochiral sulphide derivative of benzimidazole with an oxidizing agent in an organic solvent in the presence of a base and a catalyst comprising titanium or vanadium complexed with a chiral monodentate ligand. The present invention also relates to alkali or alkaline earth metal salts of S-enantiomer of 5-methoxy-2-[(4-methoxy-3,5-dimethyl-2-pyridinylmethyl)sulfinyl]-1H-benzimidazole substantially free of sulfone impurity. The present invention also relates to a process for purification of alkali or alkaline earth metal salts of S-enantiomer of 5-methoxy-2-[(4-methoxy-3,5-dimethyl-2-pyridinylmethyl)sulfinyl]-1H-benzimidazole comprising treatment of the said alkali or alkaline earth metal salt having a sulfone impurity with a solvent system comprising an organic solvent selected from ketone and nitrile, and isolating the alkali or alkaline earth metal salt of S-enantiomer of 5-methoxy-2-[(4-methoxy-3,5-dimethyl-2-pyridinylmethyl)sulfinyl]-1H-benzimidazole which is substantially free of sulfone impurity.