4-[9-(t-Butyldimethylsilyloxy)nonyl]-7-methoxy-3-(4-methoxyphenyl)-3-methylthiochroman (2.2 g, 3.95 mmol) was dissolved in tetrahydrofuran (150 ml), and 3N-HCl (11 ml) was added thereto. The reaction mixture was stirred at room temperature for 140 minutes. After the reaction was completed, water was added to the reaction solution, and the resulting mixture was extracted with ethyl acetate. The extract was dried over anhydrous magnesium sulfate, and concentrated under reduced pressure. The residue was subjected to flash chromatography on silica gel (n-hexane:ethyl acetate=8:2 and 1:1) to give the title compound (1.61 g, yield 92%) as a white solid.
