PROCESS FOR PRODUCING CRYSTAL

摘要

A process for producing crystals of (R)-2-[[[3-methyl-4-(2,2,2-trifluoroethoxy)-2-pyridyl]methyl]-sulfinyl]benzimidazole <.>n'H2O (wherein n' is about 0 to about 0.1) or of a salt thereof, characterized by subjecting a solution or dispersion in an organic solvent of (R)-2-[[[3-methyl-4-(2,2,2-trifluoroethoxy)-2-pyridyl]methyl]sulfinyl]benz-imidazole <.>nH2O (wherein n is about 0.1 to about 1.0) to crystallization to crystallize out the target compound. This process is a simple process by which an optically active sulfoxide derivative can be efficiently and industrially mass-produced in high yield while attaining an extremely high enantiomer excess.