A 2.1 ml (3.0×1.1 mmole) portion of n-butyllithium·hexane solution was added dropwise to a solution of 0.50 ml (3.0×1.2 mmole) of diisopropylamine in anhydrous tetrahydrofuran (5 ml) under an atmosphere of argon at -20° C. over the period of 5 minutes, followed by stirring at -20 to -5° C. for 10 minutes. The mixed solution was cooled at -20° C. and a solution of 0.38 g (3.0×1.1 mmole) of ethyl isobutyrate in tetrahydrofuran (4 ml) was added dropwise to it over the period of 5 minutes, followed by stirring at -20° to -5° C. for 20 minutes. A solution of 1.36 g (3.0 mmole) of 1-iodo-5-(2,5-dimethoxy-3,4,6-trimethylphenyl)-5-phenylpentane in tetrahydrofuran (14 ml) was added dropwise to the mixed solution over the period of 5 minutes, followed by stirring at -20° to -10° C. for 1.5 hours. After the reaction solution was cooled with ice, the reaction was suspended by adding 1N hydrochloric acid, and isopropyl ether and sodium chloride were added to extract the product. The organic layer was separated out, washed with aqueous saturated sodium chloride solution, dried (magnesium sulfate) and evaporated. The residual solution was chromatographed on a silica gel column to perform purification (elution with hexane/isopropyl ether) to thereby give 1.20 g (91%) of ethyl 7-(2,5-dimethoxy-3,4,6-trimethylphenyl)-2,2-dimethyl-7-phenylheptanoate. Its typical physical properties and nuclear magnetic resonance spectrum data are shown in Table 14.
