In 8 ml of methylene chloride is dissolved 0.80 g of 3,4-diisopentyloxybenzoic acid. Then, 20 μl of N,N-dimethylformamide is added, and the mixture thus obtained is stirred at ambient temperature for one hour. To the mixture thus obtained are successively added 1.10 g of aluminum chloride and 0.95 g of isopentyl 2-(2-isopentyloxyphenyl)acetate at 5-10° C., and the mixture thus obtained is stirred at 5-10° C. for 10 minutes. The reaction mixture is added to a mixture of chloroform and ice water, and the organic layer is separated. After washing the organic layer with water and saturated aqueous solution of sodium chloride successively and dried over anhydrous magnesium sulfate, the solvent is distilled off under reduced pressure. The residue thus obtained is purified by silica gel column chromatography [eluent; hexane:ethyl acetate=10:1] to obtain 1.20 g of isopentyl 2-[5-(3,4-diisopentyloxybenzoyl)-2-isopentyloxyphenyl]-acetate as a yellow oily product.
