Reaction Steps
A mixture of the diol 76 (0.98 g, 1.49 mmol) and SnCl20.2H2O (3.36 g, 14.9 mmol) in MeOH (35 mL) was heated at reflux and the progress of the reaction monitored by TLC (90% CHCl3/MeOH). After 45 minutes, the MeOH was evaporated in vacuo and the resulting residue was 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 a brown solid. Flash chromatography (95% CHCl3/MeOH) afforded the pure bis-amine 77 as an orange solid (0.54 g, 61%): [α]19D=−31.8° (c=0.30, CHCl3); 1H NMR (270 MHz, CDCl3) δ6.74 (s, 2Harom), 6.32 (s, 2Harom), 5.00 (br s, 2H, NCH2C═CH2), 4.93 (br s, 2H, NCH2C═CH2), 4.54 (br s, 2H, NCHCH2OH), 4.24-4.14 (m, 4H, OCH2CH2CH2O), 3.98-3.50 (m, 14H, NCHCH2OH, NCH2C═CH2 and OCH3), 2.76 (dd, 2H, J=8.61, 15.91 Hz, NCH2C═CH2CH2), 2.46-2.41 (m, 2H, NCH2C═CH2CH2), 2.33-2.28 (m, 2H, OCH2CH2CH2O); 13C NMR (67.8 MHz, CDCl3) δ171.0 (NC═O), 151.0 (Cquat), 143.5 (Cquat), 141.3 (Cquat), 140.6 (Cquat), 112.4 (C—Harom), 111.9 (Cquat), 107.8 (NCH2C═CH2), 102.4 (C—Harom), 65.2 (OCH2CH2CH2O), 65.0 (NCHCH2OH), 59.8 (NCHCH2OH), 57.1 (OCH3), 53.3 (NCH2C═CH2), 34.4 (NCH2C═CH2CH2), 29.0 (OCH2CH2CH2O); MS (FAB) (Relative Intensity) 596 (M+., 13), 484 (M—NCH2CCH2CH2CHCH2OH, 14), 389 (10), 371 (29), 345 (5), 224 (8), 206 (44), 166 (100), 149 (24), 112 (39), 96 (34), 81 (28); IR (NUJOL™) 3600-3000 (br, OH), 3349 (NH2), 2922, 2852, 2363, 1615, 1591 (NH2), 1514, 1464, 1401, 1359, 1263, 1216, 1187, 1169, 1114, 1043, 891, 832, 761 cm−1. (2S,4R)&(2S,4S)-1,1′-[[(Propane-1,3-diyl)dioxy]bis[(2-amino-5-methoxy-1,4-phenylene)carbonyl]]bis[2-(hydroxymethyl)-4-methylpyrrolidine] (77).
