General procedure for the synthesis of 5-amino-1H-imidazole-4-carboxylic acid methyl ester from 5-nitro-1H-imidazole-4-carboxylic acid methyl ester: 5-nitro-1H-imidazole-4-carboxylic acid methyl ester (1.24 g, 7.55 mmol) was dissolved in a 1:1 solvent mixture of ethanol:methanol (60 ml) and 10% palladium/carbon catalyst was added. The hydrogenation reaction was carried out under hydrogen balloon atmosphere. After 4 hours of reaction, the catalyst was removed by filtration, the filtrate was concentrated and azeotroped with ethanol to remove residual water. The resulting product was ground with ethyl acetate and dried to give methyl 5-amino-1H-imidazole-4-carboxylate as a white solid (0.98 g, 96% yield). The product was characterized by 1H NMR (400 MHz, DMSO): δ 12.0 (1H, brs), 7.32 (1H, s), 5.56 (2H, s), 3.70 (3H, s). Mass spectrum (ES+) showed m/z 142 ([M+H]+).
