0.73 g (0.00722 mole) of triethylamine and 0.41 g (0.0043 mole) of magnesium chloride were added, at room temperature, to a solution of 0.73 g (0.0043 mole) of monopotassium ethyl malonate dissolved in :10 ml of acetonitrile, followed by stirring. Thereto was added 0.8 g (0.00287 mole) of 2-[1-(4-chlorophenyl)ethyl]-4-isopropyl-4-methyl-1,3-oxazol-5-one. The mixture was stirred at 60° C. for 5 hours to give rise to a reaction. After the completion of the reaction, the reaction mixture was cooled. Thereto were added 50 ml of water and diluted hydrochloric acid to adjust the mixture to a pH of 4 or less. The mixture was subjected to extraction with ethyl acetate. The organic layer was washed with a saturated aqueous sodium bicarbonate solution and a saturated aqueous sodium chloride solution, then dried over anhydrous sodium sulfate, and concentrated. The concentrate was subjected to separation by column chromatography to obtain 0.5 g (0.00136 mole) of ethyl 4-[2-(4-chlorophenyl)propanoylamino]-4,5-dimethyl-3-oxohexanoate (yield=48%).
