2-(Bromomethyl)-1-chloro-3-(trifluoromethyl)benzene (443 mg, 1.62 mmol) and potassium carbonate (244 mg) were added to a solution of tert-butyl 4-[(3R*,4S*)-3-[2-(tert-butoxy)-2-oxoethyl]-4-methylpyrrolidin-3-amido]piperidine-1-carboxylate obtained in Example 3b (345 mg, 0.811 mmol) in N,N-dimethylformamide (dehydrated) (10 mL), which was stirred at 45° C. for six hours and at 40° C. for two days. Ethyl acetate was added to the reaction liquid, which was washed with a 1N aqueous sodium hydroxide solution and brine. This was dried over anhydrous magnesium sulfate and concentrated. The residue was purified by silica gel column chromatography (elution solvent: heptane/ethyl acetate) to give the title compound (320 mg, yield: 63.8%).
