[Br:1][C:2]1[CH:3]=[C:4]([N:8]2[CH:12]=[CH:11][C:10](C(O)=O)=[N:9]2)[CH:5]=[CH:6][CH:7]=1.[C:16]([O-])(=O)C.[NH4+].C[N:22]([CH:24]=[O:25])C>>[Br:1][C:2]1[CH:3]=[C:4]([N:8]2[C:12]([CH3:16])=[CH:11][C:10]([C:24]([NH2:22])=[O:25])=[N:9]2)[CH:5]=[CH:6][CH:7]=1To a solution of the carboxylic acid (3.79 g, 14.1 mmol) in DMF (47 ml) was added 1,1-carbonyldiimidazole (3.45 g, 21.2 mmol) and the mixture was stirred at room temperature for 3 hours. Anhydrous ammonium acetate (10.9 g, 141 mmol) was then added and the reaction was stirred at room temperature for an additional 16 hours. The reaction mixture was partitioned between ethylacetate and saturated sodium bicarbonate. The organic phase was washed with water, brine, then dried over sodium sulfate and concentrated. The crude product obtained was purified by silica-gel column chromatography (2:3 hexanes/ethyl acetate) to give the product as a white solid (3.23 g, 82%).
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