PROCESS FOR PREPARATION OF SALTS OF S-ENATIOMER OF 5-METHOXY-2-(4-METHOXY-3,5-DIMETHYL-2-PYRIDINYLMETHYL)SULFINYL -1H-BENZIMIDAZOLE SUBSTANTIALLY FREE OF SULFONE IMPURITY

摘要

The present provides alkali and 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, and a process for prparation thereof comprising a) enantioselective oxidation of the prochiral sulfide, 5-methoxy-2-(4-methoxy-3,5-dimethyl-2-pyridinylmethylthio-1H-bezimidazole to form S-enantiomer of 5-methoxy-2-[(4-methoxy-3,5-dimethyl-2-pyridinylmethyl)sulfinyl]-1H-benzimidazole; b) reacting the S-enantiomer formed in step 'a' with salts alkali or alkaline earth metals to form the salt of S-enantiomer of 5-methoxy-2-[(4-methoxy-3,5-dimethyl-2-pyridinylmethyl)sulfinyl]-1H-benzimidazole; c) removing the sulfone impurity from the alkali or alkaline earth metal salt formed in step 'b' by treatment with a solvent system, said solvent system comprising an organic solvent selected from ketone and nitrile, d) 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, by conventional means. The solvent system of the process of the present invention can further comprise an aqueous salt solution of a neutral salt of alkali or alkaline earth metal.