C(C[N:5]1[C:14]2[C:9](=[CH:10][CH:11]=[CH:12][CH:13]=2)[NH:8][C:7](=[O:15])[C:6]1=[O:16])(O)=O.[N+]([C:20]1[CH:26]=[CH:25][C:23]([NH2:24])=[CH:22][CH:21]=1)([O-])=O.[CH2:27]1CCC(N=C=NC2CCCCC2)CC1.C[N:43]([CH:45]=[O:46])C>>[C:25]1([CH3:27])[CH:26]=[CH:20][CH:21]=[CH:22][C:23]=1[NH:24][C:45]([NH:43][N:5]1[C:14]2[C:9](=[CH:10][CH:11]=[CH:12][CH:13]=2)[NH:8][C:7](=[O:15])[C:6]1=[O:16])=[O:46]To a stirred solution of N-carboxymethyl-1,4-dihydroquinoxaline-2,3-dione (250 mg, 1.140 mmol) and p-nitroaniline (156 mg, 1.140 mmol) in DMF (3 mL) under N2 at 0° C., DCC (233 mg, 1.140 mmol) was added in one portion. The solution was allowed to warm to 28° C. and stirred at that temperature overnight. The precipitated solid was filtered and the clear filtrate was poured into water (30 mL). The solid thus obtained was filtered and dried under vacuum (water aspirator) to obtain 100 mg crude product as a yellow powder. The crude product was purified by Soxhlet extraction in boiling ethanol (20 mL), keeping the oil bath temperature at 120° C., for 4 h. The insoluble material (in the thimble) was dried under vacuum to obtain 23 mg pure (1H NMR) N-(N'-(p-nitrophenyl)carboxamidyl)methyl-1,4-dihydroquinoxaline-2,3-dione as a light yellow powder (some of the product also ends up being extracted by hot ethanol which accounts for the low yield of the pure product). M.p. >300° C. (decomposes). 1H NMR: δ 5.02 (s, 1H), 7.13-7.3 (m, 4H), 7.78 (d, 1H, J=8.4 Hz), 8.21 (d, 1H, J=8.4 Hz), 10.92 (s, 1H), 12.16 (s, 1H). IR (KBr, cm-1): 3453, 1701, 1684, 1625, 1572, 1509. HRMS: Calculated for C16H12N4O5, 340.0808; Observed, 340.0811.
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