To a solution of tert-butyl 4-{[(3R,4R)-4-[{[3,5-bis(trifluoromethyl)phenyl]carbonyl}(methyl)amino]-3-(3,4-dichlorophenyl)piperidin-1-yl]carbonyl}piperidine-1-carboxylate (0.502 g) obtained in Example 87 in ethyl acetate (5 mL) was added 4N hydrogen chloride/ethyl acetate (4 mL), and the mixture was stirred at 50° C. for 2 hr. The reaction mixture was concentrated under reduced pressure and the residue was dissolved in ethyl acetate. This was washed with 1N aqueous sodium hydroxide solution and dried, and the solvent was evaporated under reduced pressure. The obtained residue was treated with 1 equivalent of 4N hydrogen chloride/ethyl acetate to give the title compound (0.405 g, 89%) as a white powder.
