[NH:1]1[C:9]2[C:4](=[CH:5][CH:6]=[C:7]([NH:10][C:11](=[O:18])[C:12]3[CH:17]=[CH:16][CH:15]=[CH:14][CH:13]=3)[CH:8]=2)[CH:3]=[CH:2]1.[CH3:19][N:20]1[C:24](=[O:25])[CH:23]=[CH:22][C:21]1=[O:26]>C(O)(=O)C>[CH3:19][N:20]1[C:24](=[O:25])[CH2:23][CH:22]([C:3]2[C:4]3[C:9](=[CH:8][C:7]([NH:10][C:11](=[O:18])[C:12]4[CH:17]=[CH:16][CH:15]=[CH:14][CH:13]=4)=[CH:6][CH:5]=3)[NH:1][CH:2]=2)[C:21]1=[O:26]Compound 114 (3.5 g, 14.813 mmol) and N-methylmaleimide (4.07 g, 37.033 mmol) in glacial acetic acid (100 mL) was refluxed for 56 h. The reaction was brought to room temperature and acetic acid was evaporated. The crude solid was taken into ethyl acetate (100 mL), washed with sat. NaHCO3 solution (3×20 mL), brine (20 mL) and dried (Na2SO4). Solvent was evaporated and crude was purified by column chromatography (EtOAc: Hexanes, 1:3 to 1:1) to obtain compound 115 (2.32 g, 45%) as a foam. 1H NMR (DMSO-d6) δ 2.80 (dd, 1H, J=5.1, 18.0 Hz), 2.92 (s, 3H), 3.23 (dd, 1H, J=9.3, 18.0 Hz), 4.34 (dd, 1H, J=5.1, 9.3 Hz), 7.26-7.36 (m, 2H), 7.45-7.60 (m, 4H), 7.95-7.98 (m, 2H), 8.07 (s, 1H), 10.17 (s, 1H), 11.02 (s, 1H); ESI-MS (m/z, %) 370 (M+Na, 100), 348 (MH+, 58).
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