[Si](O[N:9]=[C:10]1[CH2:18][C:17]2[C:12](=[CH:13][C:14]([CH3:19])=[CH:15][CH:16]=2)[C:11]1=[O:20])(C(C)(C)C)(C)C.CO.C(N(CC)CC)C.Cl[C:31]([O:33][CH2:34][CH3:35])=[O:32]>O1CCCC1.ClCCl.O>[OH:20][CH:11]1[C:12]2[C:17](=[CH:16][CH:15]=[C:14]([CH3:19])[CH:13]=2)[CH2:18][CH:10]1[NH:9][C:31](=[O:32])[O:33][CH2:34][CH3:35]
The compound (6.00 g, 20.7 mmol) obtained in step B was dissolved in tetrahydrofuran (100 ml), and the mixture was stirred with heating at 63° C. At the same temperature, 1 mol/L borane-tetrahydrofuran complex/tetrahydrofuran solution (41.4 ml, 41.4 mmol) was slowly added dropwise. The mixture was stirred at the same temperature for 2.5 hr, cooled to room temperature and methanol was slowly added dropwise with stirring. The reaction solution was concentrated under reduced pressure, methanol and toluene were added again, and the solution was concentrated under reduced pressure. This was repeated 4 times, and the obtained colorless solid and triethylamine (3.5 ml, 24.8 mmol) were dissolved in dichloromethane (50 ml) and the mixture was stirred under ice-cooling. Then, ethyl chloroformate (2.2 ml, 22.8 mmol) was added, and the mixture was stood at room temperature overnight. The reaction mixture was diluted with water and extracted with ethyl acetate. The organic layer was washed with diluted hydrochloric acid and saturated brine, and dried over anhydrous magnesium sulfate. The solution was concentrated under reduced pressure, and the obtained oil was purified by silica gel column chromatography (methanol-chloroform) to give the title compound (3.30 g, yield 67%) as a colorless oil.
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