Triethylamine (0.94 mL, 6.74 mmol) was added to a solution of trans(±)-1-(Diphenylmethyl)-2-ethylazetidin-3-ol obtained in Example (234b) (1.20 g, 4.49 mmol) in dichloromethane (8 mL). Then, a solution of methanesulfonyl chloride (0.45 mL, 5.83 mmol) in dichloromethane (1.5 mL) was added dropwise at room temperature, followed by stirring for four hours. The reaction solution was diluted with ethyl acetate, washed with water and brine, and then 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=5/1) to obtain 1.41 g of the title compound as a pale yellow oily substance (91%).
