Cesium carbonate (242 mg) and ethyl bromoacetate (103 μl) are added to a solution of (1R,2R)-2-tert-butyldiphenylsilanyloxy-1-(3,4,5-trifluorophenyl)propylamine obtained in Example 26 (274 mg) in DMF (5 ml), and the reaction solution was stirred at room temperature for 11 hours. Ice water and ethyl acetate were added to the reaction solution, and the organic layer was separated. The organic layer was sequentially washed with half-saturated brine and brine and dried over anhydrous magnesium sulfate, and then the solvent was evaporated under reduced pressure. The resulting residue was purified by silica gel column chromatography (hexane:diethyl ether=19:1) to obtain 190 mg of the title compound.
