To a mixture of benzyl (3-methoxy-4-piperidin-4-ylphenyl)carbamate (Preparation Example 455) (1.52 g) and 1,2-dichloroethane (70 mL), formalin (3.62 mL) and sodium triacetoxyborohydride (1.42 g) were added and stirred overnight at room temperature. After addition of water and saturated aqueous sodium hydrogen carbonate, the reaction liquid was extracted with chloroform, and the organic layer was dried over anhydrous magnesium sulfate. After the solvent was distilled off under reduced pressure, the residue was purified by silica gel column chromatography (eluent; chloroform:methanol:saturated aqueous ammonia=100:0:0 to 10:1:0.1) to give benzyl [3-methoxy-4-(1-methylpiperidin-4-yl)phenyl]carbamate (1.26 g) as a white solid.
