To a mixture of 1-[3-piperazin-1-yl-4-(3,3,5,5-tetramethylcyclohexyl)phenyl]ethanone (19 mg, 0.0555 mmol) produced in Example (82b), propionaldehyde (0.0119 mL, 0.166 mmol) and tetrahydrofuran (0.3 mL) was added sodium triacetoxyborohydride (35 mg, 0.166 mmol), followed by stirring for 1 hour at room temperature. Saturated aqueous solution of sodium hydrogencarbonate was added to the reaction mixture and extraction was performed with diethyl ether. The solvent was distilled off by nitrogen stream to the separated organic layer. The resultant residue was purified by NH silica gel column chromatography (ethyl acetate/heptane) to give 1-[3-(4-propylpiperazin-1-yl)-4-(3,3,5,5-tetramethylcyclohexyl)phenyl]ethanone.
