Reaction Steps
A stirred solution of alcohol 47 (25 mg, 24 μmol) in 3.4 mL of 12:5 EtOH/THF was treated with 1N aqueous KOH (0.24 mL) and the mixture was refluxed gently for 3 h. The ethanolic solution was concentrated and then diluted with Et2O (4 mL). After the solution was acidified to pH3 with 1N aqueous HCl, the organic phase was separated and aqueous phase was extracted with Et2O (2×5 mL). The combined organic phase was dried with MgSO4, filtered, concentrated and the residue was used without further purification: IR (CHCl3) 2956, 2929, 2857, 1693, 1635, 1600, 1471, 1462, 1254, 1088, 836, 773 cm−1; 1H NMR (300 MHz, CDCl3) δ 7.33 (dd, J=15.2, 11.3 Hz, 1H), 6.61 (t, J=11.4 Hz, 1H), 6.61 (m, 1H), 6.07 (t, J=11.0 Hz, 1H), 6.02 (dd, J=15.8, 7.2 Hz, 1H), 5.58 (d, J=11.3 Hz, 1H), 5.39 (m, 2H), 5.23 (dd, J=11.0, 8.2 Hz, 1H), 5.18 (d, J=16.8 Hz, 1H), 5.09 (d, J=10.2 Hz, 1H), 4.50 (m, 1H), 3.92 (m, 1H), 3.73 (m, 1H), 3.46 (dd, J=7.3, 2.6 Hz, 1H), 3.34 (m, 1H), 2.78 (m, 1H), 2.54 (m, 2H), 1.66 (m, 4H), 1.42 (m, 4H), 1.24 (m, 3H), 1.01 (d, J=6.8 Hz, 3H), 0.95 (d, J=6.7 Hz, 3H), 0.94 (d, J=6.7 Hz, 3H), 0.88 (m, 30H), 0.84 (m, 15H), 0.09 (s, 3H), 0.07 (s, 3H), 0.06 (s, 6H), 0.02 (s, 6H), 0.01 (s, 6H); 13C NMR (75 MHz, CDCl3) δ 171.2, 148.2, 147.3, 135.2, 133.2, 132.7, 132.3, 123.0, 127.0, 117.7, 115.2, 79.9, 77.6, 76.5, 72.1, 66.4, 43.5, 42.6, 41.6, 37.8, 36.0, 35.8, 34.9, 32.1, 31.5, 30.6, 26.2, 25.93, 25.87, 20.3, 19.4, 18.4, 18.10, 18.05, 17.7, 15.3, 13.6, 6.9 −3.0, −3.4, −3.7, −4.1, −4.19, −4.24, −4.4; LRMS (ESI) 1029.7 [M+Na]+, 875.6, 743.6, 611.4, 593.4, 393.3; HRMS (ESI) calcd for C56H110O7Si4Na 1029.7226 [M+Na]+, found 1029.7274; [α]20D−25.7 (c 0.54, CHCl3).
