A 39.4 g quantity of 4-[(dimethoxyphosphoryl)methyl]benzoyl chloride was dissolved in 150 ml of dry dichloromethane. Then 150 ml of a pyridine solution containing 27.7 g of 5'-chloro-2'-hydroxypropiophenone was slowly added dropwise to the reaction mixture with stirring under ice-cooling, and the stirring was continued at room temperature for 10 hours. After addition of 150 ml of water, the reaction mixture was extracted with chloroform. The chloroform layer was washed serially with 300 ml of a 10% aqueous HCl solution and 200 ml of water and dried over Glauber's salt. The solvent was distilled off under reduced pressure, and the residue thus obtained was dissolved in 150 ml of pyridine. A 14.0 g quantity of potassium hydroxide was added to the solution with stirring at room temperature, and the mixture was heated at 50° C. with stirring for 2 hours. After addition of 300 ml of a 10% aqueous HCl solution, the reaction mixture was extracted with chloroform. The chloroform layer was washed with 100 ml of water and dried over Glauber's salt. The solvent was distilled off under reduced pressure and the residue was subjected to silica gel column chromatography (eluent: chloroform:ethyl acetate=1:1). The resulting crude crystals were recrystallized from dichloromethane-n-hexane to provide 3.9 g of the title compound as colorless crystals. Table 1 shows the structure and physical property of the compound obtained.
