4-(9-Hydroxynonyl)-7-methoxy-3-(4-methoxyphenyl)-3-methylthiochroman (131 mg, 0.30 mmol) obtained in Example 30 was dissolved in dichloromethane (12 ml) and then triethylamine (0.2 ml, 1.48 mmol) and methanesulfonyl chloride (0.11 ml, 1.48 mmol) were added thereto. The reaction mixture was stirred for 40 minutes at room temperature. When the reaction is completed, water was added to the reaction solution which was then extracted with ethyl acetate. The organic layer was washed with water and saturated sodium chloride solution and dried over anhydrous magnesium sulfate. The residue was purified with column chromatography (n-hexane:ethyl acetate=7:3) to obtain 141 mg (yield: 91%, 3RS,4RS/3RS,4SR=8.5/1) of the title compound as an oil.
