Reaction Steps
The nitro-alcohol 17 (0.637 g, 1.60 mmol), SnCl2 2H2O (1.81 g, 8.0 mmol) and methanol (36 mL) were heated at reflux and monitored by TLC (90% CHCl3/MeOH). After 1 hour the MeOH was evaporated in vacuo and the resulting residue cooled (ice), and treated carefully with saturated NaHCO3 (120 mL). The mixture was diluted with EtOAc (120 mL), and after 16 hours stirring at room temperature the inorganic precipitate was removed by filtration through celite. The organic layer was separated, washed with brine (100 mL), dried (MgSO4), filtered and evaporated in vacuo to give an orange glass. Flash chromatography (EtOAc) afforded the pure amine 18 as a pale yellow glass (0.37 g, 63%): [α]23D=−42.7° (c=3.7, CHCl3); 1H NMR (270 MHz, CDCl3) δ 7.44-7.29 (m, 5Harom), 6.77 (s, 1Harom), 6.27 (s, 1Harom), 5.12 (s, 2H, PhCH2O), 5.06-5.00 (m, 1H, NCH2C═CH2), 4.99-4.92 (m, 1H, NCH2C═CH2), 4.63-4.53 (m, 1H, NCHCH2OH), 4.25-3.60 (m, 10H, NCHCH2OH, NCH2C═CH2, OCH3, OH and NH2), 2.77 (dd, 1H, J=8.52, 15.85 Hz, NCH2C═CH2CH2), 2.43-2.39 (m, 1H, NCH2C═CH2CH2); 13C NMR (67.8 MHz, CDCl3) δ 171.4 (NC═O), 151.0 (Cquat), 143.3 (Cquat), 141.5 (Cquat), 140.6 (Cquat), 136.5 (Cquat), 128.6 and 128.0 (BnC—Harom), 127.8 (Cquat), 127.1 (BnC—Harom), 112.5 (C—Harom), 107.8 (NCH2C═CH2), 103.0 (C—Harom), 70.6 (PhCH2O), 65.9 (NCHCH2OH), 60.0 (NCHCH2OH), 57.1 (OCH3), 53.3 (NCH2C═CH2), 34.4 (NCH2C═CH2CH2); MS (EI), m/z (relative intensity) 368 (M+, 100), 353 (M-CH3, 2), 340 (1), 286 (2), 273 (4), 256 (M-NCH2C═CH2CH2CHCH2OH, 59 ), 249 (8), 226 (4), 200 (2), 196 (2), 166 (5), 138 (17), 112 (NCH2C═CH2CH2CHCH2OH, 39), 91 (PhCH2, 70), 82 (5), 65 (5); IR (NEAT) 3600-3000 (br, NH2 and OH), 3065, 3052, 2932, 2869, 2246, 1668, 1620, 1592, 1513, 1454, 1408, 1264, 1229, 1197, 1176, 1113, 1079, 1002, 909, 733, 698, 645 cm−1; exact mass calcd for C21H24N2O4 m/e 368.1736, obsd m/e 368.1662.
