METHOD FOR PRODUCING OPTICALLY ACTIVE COMPOUND CONTAINING SULFONAMIDE GROUP, AND INTERMEDIATE FOR ITS SYNTHESIS

PROBLEM TO BE SOLVED: To provide a method for producing an optically active compound (I) or its salt, of industrial excellence. SOLUTION: A diastereomer or its salt of which the configuration of asymmetric carbon in R1 or R2 is R-type or S-type, is produced by dividing diastereomers or their salts shown by formula (I) (wherein, R1 and R2 are a hydrocarbon group that may be substituted in the same or different way, or a heterocycle group that may be substituted, and only one of R1 and R2 contains one asymmetric carbon; Ra is an optically active hydrocarbon group that may be substituted, or an optically active heterocycle group that may be substituted).