Reaction Steps
A solution of Compound 10 (6.55 g, 22.4 mmol) in dichloromethane (40 mL) at zero degrees C was treated with imidazole (3.21 g, 47.2 mmol), and then TBSCl (3.47 g, 23.1 mmol) in dichloromethane (20 mL) and stirred for two hours. The mixture was poured into saturated aqueous sodium bicarbonate solution (100 mL), extracted with dichloromethane (3×50 mL), concentrated, and the residue purified by flash chromatography (ether) to give Compound 10-1 (8.88 g, 98 percent) as a colorless oil; Rf =0.51 (Et2O); [a]D25 =-33.3° (c 5.3, CH2Cl2); IR (thin film) νmax 3490 cm-1 ; 1H NMR (500 MHz, CDCl3) δ 5.77 (m, 1 H, CH=CH2), 5.30-5.26 (m, 2 H, CH=CH2), 4.73 (ABq, J =6.5 Hz, Dn =40 Hz, 2 H, OCH2O), 4.03-3.95 (m, 5 H, CH--OH, ethylene ketal), 3.93 (dd, J =5.4, 10.0 Hz, 1 H, CH--OMEM), 3.82 (m, 1 H, OCHH--CH2 --OMe), 3.61 (m, 1 H, OCHH--CH2 --OMe), 3.55 (ABq, J =10.4 Hz, Dn =23 Hz, 2 H, CH2 --OTBS), 3.53 (m, 2 H, OCH2CH2 -13 OMe), 3.48 (bs, 1 H, OH), 3.37 (s, 3 H, OMe), 1.94 (dd, J =1.4, 14.9 Hz, 1 H, CHH), 1.83 (dd, J =10.0, 14.9 Hz, 1 H, CHH), 0.88 (s, 9 H, tBu), 0.04 (s, 6 H, SiMe2); 13C NMR (125 MHz, CDCl3) δ 134.7, 119.3, 110.4, 92.9, 80.2, 71.7, 69.5, 67.0, 66.2, 65.5, 65.1, 65.1, 58.9, 37.2, 25.8, 18.2, -5.5; FAB HRMS (NBA/CsI) m/e 539.1430, M+Cs+ calcd for C19H38O7Si 539.1441.
