Reaction Steps
A catalytic amount of tetrakis(triphenylphosphine)palladium (32.4 mg, 28.1 μmol) was added to a stirred solution of the Alloc-protected carbinolamine 73 (0.42 g, 1.12 mmol), triphenylphosphine (14.7 mg, 56.2 μmol) and pyrrolidine (83.9 mg, 1.18 mmol) in CH2Cl2 (55 mL). After 2.5 hours stirring at room temperature under a nitrogen atmosphere, TLC (95% CHCl3/MeOH) revealed the complete consumption of starting material. The solvent was evaporated in vacuo and the crude residue was purified by flash chromatography (CHCl3) to afford the novel PBD (74, MMY-SJG, UP2064) as a yellow oil which was repeatedly evaporated in vacuo with CHCl3 in order to provide the N10-C11 imine form (259 mg, 85%): [α]22D=+583.14° (c=1.42, CHCl3); 1H NMR (270 MHz, CDCl3) δ7.69 (d, 1H, J=4.39 Hz), 7.51 (s, 1H), 6.82 (s, 1H), 5.21-5.17 (m, 2H), 4.44-4.23 (m, 2H), 3.96-3.81 (m, 7H), 3.17-3.08 (m, 1H), 2.95 (d, 1H, J=14.29 Hz); 13C NMR (67.8 MHz, CDCl3) δ164.7, 162.6, 151.5, 147.6, 141.6, 140.8, 119.8, 111.2, 109.4, 109.4, 56.2, 56.1, 53.8, 51.4, 35.5; MS (EI), m/z (relative intensity) 273 (M+. +1, 16), 272 (M+., 100), 271 (35), 270 (9), 255 (5), 243 (7), 241 (7), 230 (6), 228 (6), 226 (5), 212 (3), 192 (4), 191 (16), 165 (4), 164 (19), 163 (4), 136 (22), 93 (6), 82 (7), 80 (3), 53 (3); IR (NEAT) 3312 (br), 3083, 2936, 2843, 1624, 1603, 1505, 1434, 1380, 1264, 1217, 1180, 1130, 1096, 1069, 1007, 935, 895, 837, 786, 696, 666, 594, 542 cm−1; exact mass calcd for C11H16N2O3 m/e 272.1161, obsd m/e 272.1154.
