A mixture of 1-[2-(4-cyclopropylmethylpiperazin-1-yl)phenyl]-3,3,5,5-tetramethylcyclohexanol (250 mg, 0.675 mmol) produced in Example (108b), water (0.12 mL) and trifluoroacetic acid (1.04 mL, 13.5 mmol) was stirred for 21 hours at an external temperature of room temperature. Aqueous solution of potassium carbonate was added to the reaction mixture and then extraction was performed with ethyl acetate. Organic layer was concentrated under reduced pressure to give a residue, which was purified by NH silica gel column chromatography (ethyl acetate/heptane) to give 218 mg of the title compound as a colorless solid.
