[OH:1][CH:2]1[CH2:7][N:6]([C:8]([O:10][CH2:11][CH3:12])=[O:9])[CH2:5][CH:4]=[CH:3]1.N1C=CN=C1.[Si:18](Cl)([C:21]([CH3:24])([CH3:23])[CH3:22])([CH3:20])[CH3:19]>C(Cl)Cl.CCOCC.O>[Si:18]([O:1][CH:2]1[CH2:7][N:6]([C:8]([O:10][CH2:11][CH3:12])=[O:9])[CH2:5][CH:4]=[CH:3]1)([C:21]([CH3:24])([CH3:23])[CH3:22])([CH3:20])[CH3:19]To a solution of Compound 239C (16 g, 93.5 mmol) in 150 mL of dry CH2Cl2 at 0° C. was added imidazole (9.5 g, 140.0 mmol) and t-butyldimethylsilylchloride (15.5 g, 102.8 mmol) and the mixture was stirred at ambient temperature overnight. The reaction mixture was diluted with ether (500 mL) and water (1 L) at 0° C. The organic phase was separated and washed with 10% LiCl (150 mL×3), dried over anhydrous MgSO4. Concentration in vacuo followed by flash chromatography (hexane-EtOAc: 15:1 to 10:1) afforded 25.2 g (Yield: 94.4%) of 239D as an oil.
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