C12BC(CCC1)CCC2.[CH:10](/[C:18]1[O:19][CH:20]=[C:21]([CH:23]=[CH2:24])[N:22]=1)=[CH:11]\[C:12]1[CH:17]=[CH:16][CH:15]=[CH:14][CH:13]=1.[OH-:25].[Na+].OO>O1CCCC1.C(OCC)(=O)C.O>[OH:25][CH2:24][CH2:23][C:21]1[N:22]=[C:18](/[CH:10]=[CH:11]/[C:12]2[CH:17]=[CH:16][CH:15]=[CH:14][CH:13]=2)[O:19][CH:20]=19-Borabicyclo[3.3.1]nonane (0.5N tetrahydrofuran solution, 158 ml) was added to a solution of 2-(trans-styryl)-4-vinyloxazole (13.0 g) in tetrahydrofuran (500 ml) at 0° C., and the mixture was stirred at room temperature for 15 hours. Water (10 ml), a 3N aqueous solution (80 ml) of sodium hydroxide and aqueous hydrogen peroxide (80 ml) were successively added dropwise to the reaction mixture at 0° C., and the mixture was stirred at room temperature for 6 hours. After water (600 ml) and ethyl acetate (200 ml) were added to the resultant reaction mixture to separate an organic layer, the water layer was extracted with ethyl acetate (200 ml). After the organic layers were collected, washed with saturated saline (200 ml) and dried over anhydrous sodium sulfate, the solvent was distilled off under reduced pressure. The residue was purified by column chromatography on silica gel (hexane:ethyl acetate=2:1→ethyl acetate alone) to obtain the title compound (14.1 g) as a colorless solid.
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