Using a reducing agent such as lithiumaluminium hydride, sodium borohydride or the like, the ketone moiety may be reduced in a conventional known method.For example, when sodium borohydride is used, methanol, ethanol or the like is used as the reaction solvent, and the compound 3 is reduced with from 1 to 3 mols, per mol of the compound 3, of sodium borohydride at room temperature for 1 to 6 hours