A suspension of Intermediate 6 (8.00 g), tri(n-butyl)vinyltin (8.63 ml), tetrakis(triphenylphosphine)palladium(0) (455 mg), and 2,6-di-tert-butyl-p-cresol (8.7 mg) in toluene (120 ml) was stirred at 110° C. for 2 hours. The reaction mixture was cooled to room temperature, then added with 10% aqueous potassium fluoride (120 ml), and stirred for 15 hours. After the precipitates were removed by filtration, the organic layer was separated, and dried over anhydrous magnesium sulfate. The solvent was evaporated under reduced pressure, and then the residue was purified by silica gel column chromatography (n-hexane:ethyl acetate=2:1) to obtain the title compound (6.72 g).
