A solution of Intermediate 1 (228 mg) obtained in Example 1, Step A and tetramethyltin (0.69 ml, Tokyo Kasei Kogyo) in N,N-dimethylformamide (4 ml) is added with tetrakis(triphenylphosphine)palladium(0) (29 mg, Kanto Chemicals), and the mixture is stirred at 120° C. with heating for 12 hours. The reaction mixture is cooled to room temperature, then added with saturated brine (5 ml), and extracted 3 times with ethyl acetate (5 ml for each time). The combined organic layer is washed with saturated brine (10 ml), and dried over anhydrous magnesium sulfate. The solvent is evaporated under reduced pressure, and then the residue is purified by silica gel chromatography (n-hexane:ethyl acetate=1:1) to obtain the title compound (176 mg (predictive yield)).
