Reaction Steps
A flame-dried 25-mL round-bottomed flask was charged with alcohol 11 (1.0 g, 1.9 mmol, 1.0 equiv) and CH2Cl2 (9.5 mL). NEt3 (0.8 mL, 5.7 mmol, 3.0 equiv) and DMAP (0.023 g, 0.19 mmol, 0.1 equiv) were added and the solution was cooled 0° C. TBDPSCl (1.47 mL, 5.7 mmol, 3.0 equiv) was added dropwise and the reaction was warmed to rt and stirred for 8 h. Saturated NH4Cl(aq.) (10 mL) was added and the mixture was extracted with Et2O (3×15 mL). The combined organic extracts were washed with brine (10 mL), dried with magnesium sulfate, and concentrated in vacuo. The crude product was purified via flash chromatography (70:30 hexanes:EtOAc) to give the title compound as a pale yellow oil (1.1 g, 76%). Analytical data: [α]D19 −4.4 (c=0.70, CHCl3); 1H NMR (600 MHz, CDCl3): δ 7.67 (d, J=7.2 Hz, 2H), 7.62 (d, J=7.2 Hz, 2H), 7.44-7.30 (m, 11H), 5.68 (d, J=10.2 Hz, 1H), 5.23 (d, J=12.0 Hz, 1H), 4.97 (d, J=12.6 Hz, 1H), 4.74 (dd, J=3.0, 7.2 Hz, 1H), 4.70 (br s, 1H), 4.26 (d, J=12, 6 Hz, 1H), 4.11 (d, J=3.0 Hz, 1H), 4.03 (q, J=6.0 Hz, 1H), 3.92 (d, J=12.0 Hz, 1H), 2.68 (s, 6H), 1.19 (d, J=6.0 Hz, 3H), 1.01 (s, 9H), 0.92 (s, 9H), 0.13 (s, 6H); 13C NMR (150 MHz, CDCl3): δ 203.9, 156.8, 156.0, 136.7, 135.5, 135.4, 132.6, 132.3, 129.8, 129.7, 128.3, 128.1, 127.9, 127.8, 127.7, 74.1, 69.4, 66.4, 66.2, 60.8, 57.5, 52.2, 36.1, 26.6, 25.6, 19.1, 18.3, 17.8, −3.8, −4.8; LRMS (ESI+) Calcd. for C41H57N3O7Si2+H, 760.38. Found, 760.31. IR (thin film, cm−1) 3419, 2931, 2857, 2359, 1716, 1651, 1507, 1226, 1113, 828, 733; TLC (70:30 hexanes/EtOAc): Rf=0.30.
