Reaction Steps
A solution of THF/AcOH/H2O (2:1:1, 5 mL) was added to the olefin 26 (1.8 g, 3.3 mmol) and the resulting mixture was stirred for 3 h at which point TLC (SiO2, 50% EtOAc-hexane) revealed complete reaction. The mixture was then neutralized with saturated NaHCO3 and extracted with EtOAc (3×30 mL) and the combined organic layers were washed with brine (50 mL) and dried (MgSO4). Removal of excess solvent under reduced pressure gave the crude product. The residue was subjected to flash chromatography (SiO2, 50% EtOAc-hexane) to afford the product 27 (1.34 g, 2.9 mmol, 87% yield, mixture of diastereomers from THP protecting group): [α]27D=+81° (c=0.16, CHCl3); 1H NMR (CDCl3, 400 MHz): δ 1.32 (s, 18H, Boc), 1.45-1.64 (m, 8H, THP), 1.66-1.84 (m, 4H, THP), 2.50-2.58 (m, 1H, 1-H), 2.68-2.80 (m, 1H, 1-H), 2.84-2.96 (m, 2H, 1-H), 3.51-3.67 (m, 4H, 11a-H, THP), 3.87-4.00 (m, 8H, 7-OMe, THP), 4.04-4.18 (m, 2H, 3-H), 4.23-4.38 (m, 2H, 3-H), 4.96-5.19 (m, 6H, 2a-H, THP), 5.65-5.72 (d, 1H, 11-H), 5.75-5.88 (d, 1H, 11-H), 5.97 (s, 1H, 8-OH), 6.00 (s, 1H, 8-OH), 6.63 (s, 1H, 9-H), 6.92 (s, 1H, 9-H), 7.17 (s, 1H, 6-H), 7.21 (s, 1H, 6-H); 13C NMR (CDCl3, 100 MHz): δ 20.0, 20.7, 25.1, 25.2, 28.0, 28.1, 29.7, 30.8, 31.3, 35.1, 35.4, 50.7, 56.1, 56.2, 59.8, 60.0, 63.6, 64.6, 88.0, 91.0, 96.1, 100.7, 109.4, 109.8, 116.4, 117.0, 130.3, 130.5, 142.0, 145.8, 146.0, 147.5, 147.7, 167.3, 167.5; IR (neat): 2940, 2851, 1703, 1630, 1512, 1467, 1440, 1407, 1391, 1367, 1326, 1200, 1161, 1118, 1072, 1019, 910, 730 cm−1; MS (ES+) m/z (relative intensity) 461 (M+., 75), 462 ([M+2H]+., 20), 259 (100), 260 (30), 359 (21).
