tert-Butyl dicarbonate (202 mg, 0.93 mmol) and triethylamine (0.27 mL, 1.93 mmol) were added to a solution of cis(±)-1-(diphenylmethyl)-2-ethylazetidin-3-amine obtained in Example (235d) (206 mg, 0.77 mmol) in dichloromethane (4 mL), followed by stirring for two hours. The reaction solution was diluted with ethyl acetate, and the organic layer was washed with water and brine. The organic layer was dried over anhydrous magnesium sulfate. Following filtration, the filtrate was concentrated under reduced pressure. The resulting residue was purified by silica gel column chromatography (elution solvent: hexane/ethyl acetate=4/1) to obtain 161 mg of the title compound as a colorless oily substance (57%).
