To a solution of (3aR,6aS)-octahydrocyclopenta[c]pyrrol-5-ylmethanol hydrochloride (862 mg) and potassium carbonate (1.68 g) in DMF (10 mL) was added 1-fluoro-2,4-bis(trifluoromethyl)benzene (1.24 g). The reaction mixture was stirred at 80° C. for 3 hr, water was added, and the mixture was extracted with ethyl acetate. The extract was washed with water and saturated brine, and dried over anhydrous magnesium sulfate, and the solvent was evaporated under reduced pressure. The residue was purified by silica gel column chromatography (ethyl acetate/hexane). To a solution of the obtained oil (1.71 g) and triethylamine (2.03 mL) in DMSO (10 mL) and ethyl acetate (10 mL) was added sulfur trioxide pyridine complex (2.32 g) under cooling to 0° C. The reaction mixture was stirred at room temperature for 1 hr. To the reaction mixture was added saturated aqueous sodium hydrogen carbonate solution, and the mixture was extracted with ethyl acetate. The extract was washed with water and saturated brine, and dried over anhydrous magnesium sulfate, and the solvent was evaporated under reduced pressure. The residue was purified by silica gel column chromatography (ethyl acetate/hexane) to give the title compound (215 mg).
