A mixture of N-[(3R*,4R*)-3-(3,4-dichlorophenyl)piperidin-4-yl]-N-methyl-3,5-bis(trifluoromethyl)benzamide monohydrochloride (0.90 g) obtained in Example 2, N-Boc-isonipecotic acid (1.52 g), WSC.HCl (0.82 mg) and HOBt (0.65 mg) was stirred at room temperature for 2 hr. The reaction mixture was poured into water, and the resultant product was extracted with ethyl acetate. The organic layer was washed with saturated aqueous sodium hydrogen carbonate solution and brine and dried, and the solvent was evaporated under reduced pressure. The obtained residue was purified by silica gel column chromatography (solvent gradient; 50→100% ethyl acetate/hexane, then 0→10% methanol/ethyl acetate) to give the title compound (1.19 g, 59%) as a white powder.
