Reaction Steps
To a stirred solution of 69 (0.41 g, 0.37 mmol) in THF (1.5 ml) at 0° C. was added MeOH (0.015 ml) and LiBH4 (0.81 ml, 2.0 M soln in THF) dropwise. After stirring 2 h at 0° C., saturated sodium potassium tartrate (10 ml) was added dropwise. The reaction mixture was warmed to room temperature and extracted with CH2Cl2 (10 ml×2). The combined organic layer were washed with brine (10 ml) and dried over anhydrous MgSO4, evaporated and the residue was chromatographed (hexane/EtOAc 4:1) to yield 70 (0.30 g, 87%) as a colorless oil: IR (CHCl3) 3400, 2956, 2928, 2856, 1613, 1514, 1449, 1377, 1249, 1074, 836, 774, 706 cm−1; 1H NMR (300 MHz, CDCl3) δ 7.48 (m, 6H), 7.29 (m, 11H), 6.84 (m, 2H), 5.78 (dd, J=15.7, 6.0 Hz, 1H), 5.58 (dt, J=15.7, 5.2 Hz, 1H), 5.46 (m, 1H), 5.35 (m, 1H), 4.59 (t, J=9.5, Hz, 1H), 4.48 (q, J=10.9 Hz, 2H), 3.92 (m, 1H), 3.79 (s, 3H), 3.57 (d, J=5.5 Hz, 2H), 3.25 (m 2H), 3.03 (t, J=4.5 Hz, 1H), 2.75 (m 1H), 2.41 (m, 1H), 1.75 (m, 1H), 1.55 (m, 2H), 1.32 (m, 2H), 1.17 (m, 2H), 1.07 (d, J=6.7 Hz, 3H), 0.97 (d, J=6.8 Hz, 3H), 0.94 (s, 9H), 0.91 (m, 12H), 0.72 (d, J=6.6 Hz, 3H), 0.13 (s, 3H), 0.12 (s, 3H), 0.09 (s, 3H), 0.07 (s, 3H); 13C NMR (75 MHz, CDCl3) δ 158.9, 144.4, 134.4, 133.4, 131.5, 131.4, 129.1, 128.7, 127.7, 126.8, 126.5, 113.6, 87.6, 86.8, 74.1, 73.0, 68.9, 66.5, 65.4, 55.2, 42.7, 42.4, 37.1, 35.0, 33.1, 26.0, 25.9, 18.9, 18.1, 15.8, 14.9, 14.7, −2.8, −4.0, −4.06, −4.10; HRMS (ESI) calcd for C58H86O6Si2K 973.6301 (M+K)+, found 973.6264; [α]20D −31.7 (c 1.3, CHCl3).
