General procedure for the synthesis of 3-amino-6-bromopyridine-2-carboxylic acid from methyl 3-amino-6-bromopyridinecarboxylate (Step 3): methyl 3-methyl-3-amino-6-bromopyridine-2-carboxylate (10 g, 43.28 mmol) was dissolved in a solvent mixture of THF and methanol (2:1, v/v, 142 mL). To this solution was added 1 M aqueous lithium hydroxide (71 mL) at room temperature and the reaction mixture was stirred for 16 hours at room temperature. Upon completion of the reaction, 1N hydrochloric acid (71 mL) was added to the mixture for acidification. Subsequently, the mixture was concentrated under reduced pressure to remove the solvent. The precipitate was collected by filtration and the crude product was washed with cold water to yield 3-amino-6-bromopyridine-2-carboxylic acid (9.0 g, 96% yield) as an off-white solid. The product was characterized by 1H-NMR (400 MHz, DMSO-D6): δ 6.50-7.05 (1H, broad single peak), 7.18 (1H, d, J=8.76 Hz), 7.42 (1H, d, J=8.76 Hz), 11.20-13.80 (1H, broad single peak). Note: No proton signal was observed for carboxylic acid (CO2H).
