To a solution of 150 mg of (S)-3-[(R)-1-(naphthalen-1-yl)ethylamino]pyrrolidine dihydrochloride and 108 mg of 4-fluorophenylethylsulfone in 2 ml of DMSO was added 263 mg of potassium carbonate, and the reaction mixture was stirred at 130° C. for 1 day. To the reaction mixture was added water and chloroform, the mixture was stirred and the liquids were separated. The organic layer was dried and evaporated, and then, the residue was purified by NH silica gel column chromatography (hexane:ethyl acetate=80:20→40:60) to obtain 132.5 mg of 4-[(S)-3-[(R)-1-(naphthalen-1-yl)ethylamino]pyrrolidin-1-yl]phenylethylsulfone.
