[CH3:1][O:2][C:3]1[CH:8]=[C:7]([O:9][CH3:10])[CH:6]=[CH:5][C:4]=1[CH:11]=[C:12]([C:18]([O:20][CH2:21][CH3:22])=[O:19])[C:13]([O:15][CH2:16][CH3:17])=[O:14].[CH2:23]([Mg]Br)[CH2:24][CH2:25][CH2:26][CH3:27].Cl>C(OCC)C>[CH3:1][O:2][C:3]1[CH:8]=[C:7]([O:9][CH3:10])[CH:6]=[CH:5][C:4]=1[CH:11]([CH:12]([C:18]([O:20][CH2:21][CH3:22])=[O:19])[C:13]([O:15][CH2:16][CH3:17])=[O:14])[CH2:23][CH2:24][CH2:25][CH2:26][CH3:27]A solution of 9.15 g (29.7 mmol) of ethyl 3-(2,4-dimethoxyphenyl)-2-ethoxycarbonyl-2-propenoate (prepared as described in Preparation 1) in 9 ml of diethyl ether was added to 72 ml (36 mmol) of a 0.5 M ice-cooled solution of pentylmagnesium bromide in diethyl ether, and the resulting mixture was stirred at the same temperature for 1.5 hours. At the end of this time, the reaction mixture was poured into a 10% aqueous solution of hydrochloric acid in ice, and then extracted with ethyl acetate. The extract was washed with water and dried over anhydrous sodium sulfate. The solvent was removed by distillation under reduced pressure, and the resulting residue was purified by column chromatography through 200 g of silica gel, using a 10:1 by volume mixture of hexane and ethyl acetate as the eluent, to give 8.65 g (yield 77%) of the title compound as an oily substance.
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