To a mixture of 1-[5-methoxy-4-piperidin-1-yl-2-(3,3,5,5-tetramethylcyclohexyl)phenyl]piperazine (5 mg, 0.0121 mmol) produced in Example (72b), propionaldehyde (1.4 mg, 0.0242 mmol) and tetrahydrofuran (0.3 mL) was added sodium triacetoxyborohydride (5 mg, 0.0242 mmol), followed by stirring for 1 hour and 10 minutes at room temperature. Saturated aqueous solution of sodium hydrogencarbonate was added to the reaction mixture and extraction was performed with ethyl acetate. The solvent was distilled off nitrogen stream to the separated organic layer. The resultant residue was purified by NH silica gel column chromatography (ethyl acetate/hexane) to give 1-[5-methoxy-4-piperidin-1-yl-2-(3,3,5,5-tetramethylcyclohexyl)phenyl]-4-propylpiperazine. This compound was dissolved in dichloromethane, and a 4N solution of hydrogen chloride in ethyl acetate was added. The solvent was distilled of by nitrogen stream. Heptane was added to the obtained residue to produce a solid, which was then triturated by sonication. The supernatant heptane solution was removed and the resulting solid was dried to give 6.1 mg of the title compound as a colorless solid.
