[CH3:1][NH2:2].[O:3]=[C:4]1[NH:9][C:8]2[CH:10]=[C:11]([C:14]([N:16]3[C:21]4[CH:22]=[CH:23][CH:24]=[CH:25][C:20]=4[O:19][CH2:18][CH:17]3[CH2:26][C:27](OCC)=[O:28])=[O:15])[CH:12]=[CH:13][C:7]=2[O:6][CH2:5]1>CO>[CH3:1][NH:2][C:27](=[O:28])[CH2:26][CH:17]1[N:16]([C:14]([C:11]2[CH:12]=[CH:13][C:7]3[O:6][CH2:5][C:4](=[O:3])[NH:9][C:8]=3[CH:10]=2)=[O:15])[C:21]2[CH:22]=[CH:23][CH:24]=[CH:25][C:20]=2[O:19][CH2:18]1Methylamine (370 mL) was added slowly into a solution of ethyl {4-[(3-oxo-3,4-dihydro-2H-1,4-benzoxazin-6-yl)carbonyl]-3,4-dihydro-2H-1,4-benzoxazin-3-yl}acetate (Intermediate 4, 10.7 g, 26.9 mmol) in MeOH (640 mL) at rt. The resulting mixture was stirred at rt for 16 h. The organic solvent was removed by evaporation under reduced pressure. The crude product was purified by re-crystallization from MeOH to afford the title compound (10.3 g, 100%) as a white power.
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