Reaction Steps
Trityl chloride (4.1 g, 14.7 mmol) and DMAP (1.8 g, 14.7 mmol) were added to a solution of alcohol 11 (2.75 g, 7.1 mmol) in pyridine (71 mL). The mixture was heated to reflux for 18 h, cooled to ambient temperature and added to a solution of sat'd CuSO4 (200 mL). The mixture was extracted with Et2O (2×20 mL) and the combined organic extracts were washed sat'd CuSO4 (2×20 mL). The organic layer was separated, dried (MgSO4), filtered, and concentrated in vacuo. Flash column chromatography (EtOAc/hexane 1:19) provided 12 (4.46 g, quantitative) as a pale yellow oil: IR (CHCl3) 2954, 2856, 1471, 1448, 1254, 1095, 835, 773, 705 cm−1; 1H NMR (300 MHz, CDCl3) ε7.56 (m, 6H), 7.32 (m, 9H), 5.79 (dd, J=15.6, 6.7 Hz, 1H), 5.65 (dd, J=15.7, 5.0 Hz, 1H), 3.85 (m, 1H), 3.74 (m, 1H), 3.66 (d, J=4.9 Hz, 1H), 2.43 (m, 1H), 1.70 (q, J=6.5 Hz, 2H), 1.21 (d, J=6.9 Hz, 3H), 0.99 (s, 9H), 0.97 (s, 9H), 0.154 (s, 3H), 0.150 (s, 3H), 0.13 (s, 3H), 0.12 (s, 3H); 13C NMR (75 MHz, CDCl3) δ 144.4, 134.2, 128.7, 127.7, 126.9, 126.8, 86.8, 72.6, 65.1, 60.2, 42.1, 36.6, 26.0, 18.3, 18.1, 15.3, −4.4, −5.3; LRMS (EST) 653.3 [M+Na]+, 422.4, 243.2; HRMS (ESI) calcd for C39H58O3Si2Na 653.3822 [M+Na]+, found 653.3851; [α]20D−1.9 (c 0.42, CHCl3).
