2-(4-Octanoyl phenyl)ethyl p-toluene sulfonate prepared in the step D-1 (500 mg), diethyl acetamide malonate (810 mg) and sodium ethylate (313 mg) were dissolved in anhydrous ethanol (1.5 ml)—anhydrous N,N-dimethylformamide (6 ml) to obtain a solution. The solution was stirred under atmosphere of nitrogen at 60° C. overnight. The reaction solution was poured into ice water, extracted with ether, and washed with saturated saline solution. The extracted solution was dried over anhydrous magnesium sulfate, and concentrated. The residue was subjected to silica gel column chromatography using hexane-ethyl acetate (1:0→3:1) as an eluate to obtain diethyl acetamide-2-(4-octanoyl phenyl)ethyl malonate (417 mg) in the form of colorless crystal.
