Reaction Steps
LiAl(O-t-Bu)3H (2.0 mL, 1.0 M solution in THF) was added to a solution of 70 (0.80 g, 0.68 mmol) in THF (7 mL). After 30 min of stirring at room temperature, the reaction was quenched with saturated aqueous NH4Cl (1 mL), stirring for 1 h, dried over MgSO4, filtered, concentrated in vacuo, and chromatographed (EtOAc/hexane 3:17) to provide the β isomer of 71 (0.76 g, 95%) as a colorless oil: IR (CHCl3) 3538, 2929, 2855, 1615, 1518, 1461, 1385, 1251, 1072, 835, 773, 734 cm−1; 1H NMR (300 MHz, CDCl3) δ 7.70-7.66 (m, 6H), 7.59-7.56 (m, 2H), 7.52-7.39 (m, 9H), 7.08-7.05 (m, 2H), 5.93-5.77 (m, 2H), 5.71 (s, 1H), 5.67 (t, J=10.2 Hz, 1H), 5.55-5.48 (m, 1H), 4.78 (m, 1H), 4.30 (dd, J=11.4, 4.8 Hz, 1H), 4.15 (m, 1H), 4.09 (m, 1H), 3.94 (s, 3H), 3.88 (dd, J=10.0, 1.5 Hz, 1H), 3.79 (d, J=3.9 Hz, 2H), 3.70 (t, J=11.1 Hz, 1H), 3.64 (m, 1H), 3.38 (br, 1H), 2.84 (m, 1H), 2.65 (m, 1H), 2.33 (m, 1H), 2.22-1.91 (m, 2H), 1.86-1.71 (m, 3H), 1.66-1.54 (m, 4H), 1.49-1.34 (m, 3H), 1.24 (d, J=7.0 Hz, 3H), 1.21 (d, J=6.6 Hz, 3H), 1.15-1.08 (m, 21H), 1.09 (d, J=6.9 Hz, 3H), 1.04 (m, 9H), 0.94 (d, J=6.7 Hz, 3H), 0.34-0.25 (m, 18H); 13C NMR (75 MHz, CDCl3) δ 160.0, 144.4, 144.3, 134.3, 132.8, 132.2, 130.6, 128.6, 127.6, 127.1, 126.7, 113.6, 101.1, 88.9, 86.7, 80.1, 76.2, 73.0, 72.2, 66.4, 65.0, 55.1, 42.3, 41.6, 38.2, 37.4, 35.7, 35.0, 33.6, 30.3, 28.0, 26.5, 26.1, 25.91, 25.87, 19.5, 18.4, 18.05, 17.99, 15.0, 13.2, 11.8, 5.6, −3.0, −3.7, −3.8, −4.2, −4.3; LRMS (ESI) 1199.7 [M+Na]+, 937.6, 782.4, 413.2; HRMS (ESI) calcd for C71H112O8Si3Na 1199.7563 [M+Na]+, found 1199.7538; [α]20D+8.9 (c 0.46, CHCl3).
