Improved recrystallization processes for obtaining anhydrous optically active lansoprazole

Abstract From the Canadian patent

The present invention relates to a production method of a crystal of (R)-2-3-methyl-4-(2,2,2-trifluoroethoxy)-2pyridylmethylsulfinylbenzimidazole . n'H2O (wherein n' is about 0 to about 0.1) or a salt thereof which , characteristically includes crystallization from an organic solvent solution or suspension in which (R)-2-3-methyl-4- (2,2,2-trifluoroethoxy)-2-pyridylmethylsulfinylbenzimidazole . nH2O (wherein n is about 0.1 to about 1.0) or a salt thereof has been dissolved or suspended and the like, and , provides a convenient method for efficiently producing an optically active sulfoxide derivative having an extremely high enantiomer excess in high yield at an industrial large scale.