The compound (103 mg) obtained in Example 51, diethyl ethoxymethylenemalonate (108 mg) and tetrahexylammonium chloride (29 mg) were dissolved in dichloromethane (1 ml). After adding potassium carbonate (138 mg), the mixture was stirred at room temperature for 22 hours. After the completion of the reaction, the residue was filtered off and the solvent was evaporated. Then the residue thus obtained was subjected to silica gel column chromatography to thereby give 147 mg (78%) of the title compound as a colorless solid. The 1H-NMR and IR spectral data of this product was identical with those of the compound obtained in Example 63.
