To a solution of 70 mg (0.11 mmol) of 4-(4,4-Difluorocyclohexyl)-3-{fluoro[4-(trifluoromethyl)phenyl]methyl}-2-[1-(5-formyl pyrimidin-2-yl)piperidin-4-yl]-7,7-dimethyl-5,6,7,8-tetrahydroquinolin-5-ol obtained in Example (36-1) in 1.0 ml of tetrahydrofuran, 6.1 μl (0.11 mmol) of acetic acid, 26 μl (0.32 mmol) of 2-(methylamino)ethanol and 68 mg (0.32 mmol) of sodium triacetoxyborohydride were added, and the reaction solution was stirred at room temperature for 3 hours. After completion of the reaction, saturated sodium hydrogencarbonate aqueous solution was added to the reaction solution and the reaction solution was extracted with dichloromethane. The organic layer was dried with anhydrous sodium sulfate, and then the solvent was distilled off under reduced pressure. The obtained residue was subjected to silica gel column chromatography [dichloromethane/methanol/28% ammonia aqueous solution=95/4.75/0.25-80/19/1 (V/V/V)] to provide 68 mg of the title compound as a white solid (yield: 89%).
