The (+)-7-hydroxy-3-(4-hydroxyphenyl)-3-methylchroman-4-one resolved as Peak 1 in Example 22 (2.0 g, 7.40 mmol) was dissolved in anhydrous tetrahydrofuran (30 ml) and then cooled to −78° C. To this solution, a solution of diisobutylaluminum hydride in toluene (1N, 22.94 ml, 22.94 mmol) was slowly added dropwise, and the resulting mixture was stirred for 35 minutes at −78° C. Methanol (1 ml) was added to the reaction mixture at −78° C., which was then warmed to 0° C. and saturated aqueous ammonium chloride (5 ml) and concentrated hydrochloric acid (7 ml) were added to the mixture followed by stirring for 30 minutes. The reaction mixture was extracted twice with ethyl acetate. The combined organic layers were washed with water and saturated aqueous sodium chloride, and then dried over anhydrous magnesium sulfate. After distilling off the solvent, zinc iodide (2.55 g, 7.98 mmol) was added to a suspension of the residue and allyltrimethylsilane (5.3 ml, 33.2 mmol) in 1,2-dichloroethane (80 ml) followed by stirring for 12 hours at room temperature. Saturated aqueous ammonium chloride (15 ml), methanol (10 ml) and concentrated hydrochloric acid (10 ml) were added to the reaction mixture, followed by stirring for 30 minutes. The reaction mixture was extracted twice with dichloromethane. The combined organic layers were washed with water and saturated aqueous sodium chloride, and then dried over anhydrous magnesium sulfate. After distilling off the solvent, the residue was purified by silica gel column chromatography (eluent: ethyl acetate/hexane=1/4) to give optically active 7-hydroxy-3-(4-hydroxyphenyl)-3-methyl-4-(2-propenyl)chroman (cis-configuration, 859 mg, Yield 44%).
