Reaction Steps
A mixture of 239 (5.24 g, 12.4 mmol), imidazole (3.72 g, 54.6 mmol), and TBDMSCl (2.07 g, 13.6 mmol) in dry DMF (50 mL) was stirred at 0° C. under N2 for 30 min. The reaction was quenched with ice (20 mL), and the reaction mixture was partitioned between Et2O (200 mL) and H2O (100 mL). The separated organic phase was washed with H2O (100 mL) and brine (100 mL). The organic layer was dried over anhydrous Na2SO4 and concentrated. The residue was purified by flash chromatography (hexanes:EtOAc, 3:1) to give a colorless oil 240 (6.164 g, 93%): [α]D −140.4° (c 0.87, CHCl3); 1H NMR (CDCl3) δ 7.35-7.25 (15H, m, Ar), 4.74 and 4.60 (2H, 2d, Ja,b=11.7 Hz, CH2Ph), 4.69 and 4.51 (2H, 2d, Ja,b=11.9 Hz, CH2Ph), 4.51 and 4.45 (2H, 2d, Ja,b=11.6 Hz, CH2Ph), 4.05 (1H, dddd, J3,4=2.3 Hz, J4,5a=J4,5b=5.9 H,J4,OH=5.9 Hz, H-4), 3.88 (1H, dd, J1a,1b=11.0 Hz, J1a,2=4.2 Hz, H-1a), 3.78 (1H, dd, J1b,2=4.9 Hz, H-1b), 3.77 (1H, dd, J2,3=4.1 Hz, H-3), 3.73 (1H, ddd, H-2), 3.54(1H, dd, H-5a), 3.49 (1H, dd, H-5b), 3.02 (1H, d, OH), 0.891 (9H, s, (CH3)3CSi), 0.05 (6H, s, (CH3)2Si); 13C NMR (CDCl3) δ 149.11, 145.62, 140.95 (3Cipso), 128.35-127.60 (15C, Ar), 80.25 (C-2), 77.25 (C-3), 73.65, 73.26, 72.84 (3CH2Ph), 71.16 (C-5), 69.75 (C-4), 62.04 (C-1), 25.88 (3C, (CH3)3CSi) 18.23 (1C, CSi), −5.40, −5.44 (2C, (CH3)2Si); MALDI-TOF MS: m/e 537.89 (M++H), 559.33 (M++Na). Anal. Calcd for C32H44O5Si: C, 71.60; H, 8.26. Found: C, 71.44; H, 8.34.
