The compound (552 mg) obtained in Example 11-8 was dissolved in DMF (1.67 ml) and added with zinc cyanide (94.3 mg) and tetrakistriphenyl phosphine palladium (61.8 mg), followed by stirring at 80° C. for 48 hours. The reaction solution was added with chloroform and washed with a 7% aqueous ammonium solution and a saturated saline solution. The resultant was dried with anhydrous sodium sulfate and concentrated under reduced pressure. The residue was purified through silica gel column chromatography (chloroform/methanol), thereby obtaining the subject compound (436.8 mg) as a yellow oily substance.
