Reaction Steps
4-Nitrobenzyl chloroformate (52 mg, 0.24 mmol) was added to a solution of 8 (48 mg, 0.12 mmol) in dry pyridine (6 mL) and the yellow solution was stirred at 20° C. More 4-nitrobenzyl chloroformate (52 mg, 0.24 mmol) was added after 30 min. After a further 1 h water was added and the mixture stirred for 30 min until the oil that separated had solidified. The solid was filtered off, washed with water, dried, and triturated with hot EtOAc to give 1-[(E)-4-butyramido-1-methyl-2-pyrroleacryloyl]-3-(chloromethyl)-6-[(4-nitrobenzyloxy)carbonyl]aminoindoline (8a) (49 mg, 71%) as a yellow solid, mp 207-209.5° C. 1H NMR [(CD3)2SO] δ6 9.91 (s, 1 H, NH), 9.76 (s, 1 H, NH), 8.40 (s, 1 H, H-7), 8.27 (d, J=8.7 Hz, 2 H, ArHo to NO2), 7.70 (d, J=8.7 Hz, 2 H, ArHm to NO2), 7.54 (d, J=15.0 Hz, 1 H. H-β) 7.28 (d, J=8.2 Hz, 1 H, H-4), 7.22 (d, J=1.5 Hz, 1 H, H-5′), 7.16 (d, J=8.2 Hz, 1 H, H-6), 6.71 (d, J=1.4 Hz, 1 H. H-3′), 6.64 (d, J=15.0 Hz, 1 H, H-α), 5.30 (s, 2 H, ArCH2O), 4.48-4.39 (m, 1 H, H-2), 4.12 (dd, J=10.5, 4.1 Hz, 1 H, ArCH2O), 4.48-4.39 (m, 1 H, H-2), 4.12 (dd, J=10.5, 4.1 Hz, 1 H, H-2), 3.98-3.92 (m, 1 H, CHCH2Cl), 3.85-3.76 (m, 2 H, CHCH2Cl), 3.68 (s, 3H, NCH3), 2.20 (t, J=7.3 Hz, 2 H, CH2CH2CH3), 1.58 (sx, J=7.4 Hz, 2 H, CH2CH2CH3), 0.89 (t, J=7.4 Hz, 3 H, CH2CH2CH3).
