Reaction Steps
A solution of the nitro compound 2 (15.49 g, 40.12 mmol, 1.0 equiv) and tin (II) chloride (45.27 g, 200.64 mol, 5.0 equiv) in methanol (300 mL) was heated at reflux for 4 h. Excess solvent was removed by rotary evaporation under reduced pressure. The residue was treated carefully with a saturated aqueous sodium bicarbonate solution to basify the mixture to pH 9. The resulting suspension was allowed to stir overnight with ethyl acetate (100 mL), and filtrated through Celite to remove precipitated tin salts. The aqueous phase was extracted with EtOAc (2×50 mL), and the combined organic phase washed with brine (50 mL), dried (MgSO4), and evaporated in vavuo to provide 3 as a pink oil, which was used in the subsequent reaction without further purification: [α]20D=−97° (c=0.18, CHCl3); 1H NMR (CDCl3, 400 MHz): δ 1.50-1.81 (m, 3H, 1-H, 2-H), 2.05-2.15 (m, 1H, 1-H), 3.03-3.16 (m, 1H, 3-H), 3.23-3.36 (m, 1H, 3-H), 3.56-3.78 (m, 2H, 11-H), 3.88 (s, 3H, 7-OMe), 4.21-4.38 (m, 1H, 11a-H), 4.47-4.75 (m, 1H, 3-H), 5.03 (d, 1H, J=12.4 Hz, OBn), 5.10 (d, 1H, J=12.4 Hz, OBn), 6.26 (s, 1H, 9-H), 6.66 (s, 1H, 6-H), 7.28-7.41 (m, 5H, Ph); 13C NMR (CDCl3, 400 MHz): δ 24.8, 28.5, 51.1, 55.7, 61.1, 67.5, 72.5, 100.8, 116.9, 127.5, 127.7, 128.4, 137.4, 138.8, 142.6, 153.0, 171.1, 171.7; IR (neat): 3436, 33.52, 29.67, 28.73, 1621, 1589, 1513, 1448, 1402, 1264, 1216, 1172, 1110, 1025 cm−1; MS (FAB) m/z (relative intensity) 379 ([M+Na]+., 5), 357 (M+., 100), 255 (58).
