The compound (173.5 mg) obtained in Example 102-4 was dissolved in anhydrous methanol (7.0 ml). Then, the solution was added with cyclohexanone (0.083 ml) and sodium cyanoborohydride (75.4 mg) and adjusted to pH 5 with acetic acid, followed by stirring at room temperature for 16.5 hours. After the reaction, the solvent was distilled off. Subsequently, the residue was added with a 1 mol/l sodium hydroxide aqueous solution (7.0 ml), followed by extraction with chloroform. The extract was dried with magnesium sulfate and the solvent was then distilled off. The residue was purified through silica gel column chromatography (chloroform/methanol) and then treated with hydrochloric acid, thereby obtaining hydrochloride (161.6 mg) of the subject compound as a white solid.
