At room temperature, KOH (330 mg) and tetrahexylammonium chloride (190.1 mg) were dissolved in DMF (15 ml). After adding a solution (5 ml) of (2S)-2-(2,3,4-trifluoroanilino)propanol (1 g, 99.8% ee) and diethyl ethoxymethylenemalonate (2.09 g) in DMF, the mixture was stirred for 1 hour. Next, it was heated to 60° C. and a solution (5 ml) of KOH (330 mg) and diethyl ethoxymethylenemalonate (120 mg) in DMF was added thereto. The resultant mixture was stirred at the same temperature for 5 hours. After adding water, the liquid reaction mixture was extracted with ethyl acetate. The organic layer was dried over anhydrous magnesium sulfate. After evaporating the solvent, the obtained residue was subjected to silica gel column chromatography. Thus, 1.37 g (99.8% ee) of the title compound was obtained as a yellow oily substance. Various spectral data was identical with those described in Japanese Patent No. 2,769,174.
