Reaction Steps
NaHMDS (1.0 M in THF, 1.68 ml) was added at −78° C. to a solution of 68 (1.67 g) in THF (4 ml). After 30 min, the reaction mixture was treated with MeI (0.29 ml) at −78° C., stirred for an additional 4 h, quenched with sat'd aqueous NH4Cl, and extracted with ether (2×10 ml). The combined organic layers were dried (MgSO4), concentrated and purified by flash column chromatography (EtOAc/hexane 1:9) to give product 69 (1.05 g, 62%) as a colorless oil: IR (CHCl3) 2957, 2929, 2856, 1783, 1697, 1513, 1449, 1385, 1249, 1074, 836, 774, 705 cm−1; 1H NMR (300 MHz, CDCl3) δ 7.49 (m, 6H), 7.29 (m, 16H), 6.80 (m, 2H), 5.79 (dd, J=15.6, 6.2 Hz, 1H), 5.56 (dt, J=15.6, 5.7 Hz, 1H), 5.42 (m, 2H), 4.62 (m, 2H), 4.56 (d, J=11.3 Hz, 1H), 4.37 (d, J=11.1 Hz, 1H), 4.17 (m, 1H), 4.05 (m, 1H), 3.92 (m, 1H), 3.77 (s, 3H), 3.58 (d, J=5.2 Hz, 1H), 3.27 (m, 1H), 3.08 (dd, J=6.3, 2.5 Hz, 1H), 2.77 (m, 2H), 2.38 (m, 1H), 1.76 (m, 1H), 1.64 (m, 2H), 1.46 (m, 4H), 1.10 (d, J=6.7 Hz, 3H), 1.00 (d, J=6.3 Hz, 3H), 0.98 (d, J=6.7 Hz, 3H), 0.93 (m, 21H), 0.14 (s, 3H), 0.11 (s, 6H), 0.10 (s, 3H); 13C NMR (75 MHz, CDCl3) δ 177.3, 158.7, 152.8, 144.4, 135.3, 134.9, 133.6, 132.3, 131.3, 129.4, 128.9, 128.8, 128.6, 127.6, 127.2, 126.7, 126.3, 113.5, 86.6, 86.5, 74.0, 72.8, 66.5, 65.8, 65.2, 43.0, 42.5, 37.8, 35.4, 35.3, 33.0, 26.3, 26.0, 25.9, 18.3, 18.1, 17.4, 14.5, 14.2, −2.9, −4.0, −4.1, −4.2; HRMS (ESI) calcd for C68H93NO8Si2K 1146.6077 (M+K)+, found 1146.6079; [α]20D +16.70 (c 1.1, CHCl3).
