To a mixture of 1-[2-(3,3,5,5-tetramethylcyclohexyl)phenyl]piperazine (50 mg, 0.166 mmol) produced in Example (8b), furan-3-carbaldehyde (0.02 mL, 0.231 mmol) and tetrahydrofuran (3 mL) was added sodium triacetoxyborohydride (43 mg, 0.203 mmol), followed by stirring for 20 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 by nitrogen stream. The resultant residue was purified by NH silica gel column chromatography (ethyl acetate/hexane) to give 1-furan-3-ylmethyl-4-[2-(3,3,5,5-tetramethylcyclohexyl)phenyl]piperazine. This compound was dissolved in dichloromethane, and a 4N solution of hydrogen chloride in ethyl acetate was added. The solvent was distilled off by nitrogen stream. Diethyl ether was added to the obtained residue to produce a solid, and after further adding hexane, the solid was triturated by sonication. The supernatant solution was removed and the obtained solid was dried to give 33 mg of the title compound as colorless crystals.
