Reaction Steps
A catalytic amount of tetrakis(triphenylphosphine)palladium (44.0 mg, 38.0 μmol) was added to a stirred solution of the Alloc-protected carbinolamine 41 (0.66 g, 1.53 mmol), triphenylphosphine (20.0 mg, 77.0 mmol) and pyrrolidine (114 mg, 1.60 mmol) in CH2Cl2, (100 mL). After 2 hours stirring at room temperature under a nitrogen atmosphere, TLC (99% CHCl3/MeOH) revealed the complete consumption of starting material. The solvent was evaporated in vacuo and the crude residue was purified by flash chromatography (98% CHCl3/MeOH) to afford the PBD (42, AN-SJG, UP2065) as an orange glass which was repeatedly evaporated in vacuo with CHCl3 in order to provide the N10-C11 imine form (481 mg, 95%): [α]22D+401.84° (c=1.00, CHCl3); 1H NMR (270 MHz, CDCl3) δ 7.87-7.85 (m, 1H), 7.49 (s, 1H), 6.93 (s, 1H), 6.81 (s, 1H), 4.34-4.27 (m, 1H), 3.95 (s, 3H), 3.93 (s, 3H), 3.74 (s, 3H), 3.34 (d, 1H, J=16.85 Hz), 3.24 (s, 2H), 3.19-3.10 (m, 1H); 13C NMR (67.8 MHz, CDCl3) δ 170.6, 162.7, 161.4, 151.8, 147.7, 140.4, 126.5, 119.0, 117.4, 111.5, 109.8, 56.2, 56.1, 53.8, 52.1, 37.4, 33.6; MS (EI), m/z (relative intensity) 332 (M+.+2, 5), 331 (M+.+1, 9), 330 (M+., 41), 329 (28), 328 (100), 313 (18), 272 (8), 271 (24), 270 (14), 269 (27), 262 (7), 257 (12), 255 (5), 242 (6), 225 (7), 197 (4), 192 (16), 191 (16), 183 (6), 164 (14), 136 (11), 135 (9), 106 (9), 80 (17), 53 (5); IR (CHCl3) 3329 (br), 3112, 2952, 2842, 1737, 1626, 1602, 1512, 1453, 1436, 1381, 1356, 1246, 1213, 1173, 1096, 1069, 1008, 875, 840, 786, 666, 620, 574, 537 cm−1; exact mass calcd for C17H18N2O5 m/e 330.1216, obsd m/e 330.1237.
