To a mixture of 1-[2-(4,4-dimethylcyclohexyl)phenyl]piperazine (30 mg, 0.11 mmol) produced in Example (3c), furan-3-carbaldehyde (21 mg, 0.22 mmol) and tetrahydrofuran (2 mL) was added sodium triacetoxyborohydride (119 mg, 0.559 mmol), followed by stirring for 1 hour and 50 minutes at room temperature. Saturated aqueous solution of sodium hydrogencarbonate was added to the reaction mixture and extraction was performed with ethyl acetate. The separated organic layer was filtered through Celite. The solvent was distilled off by nitrogen stream to the filtrate. The resultant residue was purified by NH silica gel column chromatography (ethyl acetate/heptane) to give 1-[2-(4,4-dimethylcyclohexyl)phenyl]-4-furan-3-ylmethylpiperazine. 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. Hexane was added to the obtained residue to produce a solid, which was then triturated by sonication. The supernatant hexane solution was removed and the resulting solid was dried to give 31 mg of the title compound as colorless crystals.
