7-Methoxy-3-(4-methoxyphenyl)-3-methylthiochroman-4-one(2.24 g, 6.823 mmol) prepared according to the known method in WO98/25916 was dissolved in dry tetrahydrofuran(30 ml) and then cooled to −78° C. Lithium aluminum hydride(1N solution in THF, 3.41 ml, 3.412 mmol) was added dropwise thereto and the resulting mixture was stirred overnight at room temperature. The reaction mixture was treated with saturated aqueous ammonium chloride solution(100 ml), extracted twice with ethyl acetate(100 ml), washed with water and saturated saline solution, dried over anhydrous magnesium sulfate, and filtered. The filtrate was concentrated under reduced pressure and the residue was dissolved in 1,2-dichloroethane(30 ml). Zinc iodide(2.61 g, 8.188 mmol) and allyltrimethylsilane(2.17 ml, 13.646 mmol) were added dropwise thereto under cooling to 0° C. and the resulting mixture was stirred overnight at room temperature. The reaction mixture was diluted with water(200 ml), extracted twice with dichloromethane(200 ml), washed with water and saturated saline solution, dried over anhydrous magnesium sulfate, and filtered. The filtrate was concentrated under reduced pressure and the residue thus obtained was purified by silica gel column chromatography(eluent:ethyl acetate/n-hexane=1/4, v/v) to give 1.4 g(Yield 58%) of the title compound.
