General procedure for the synthesis of 2-amino-5-bromo-4-carboxylic acid pyridine from 2-amino-5-bromoisonicotinic acid methyl ester: 2-amino-5-bromoisonicotinic acid methyl ester (10.0 g, 43.28 mmol) and lithium hydroxide (LiOH, 5.46 g, 129.8 mmol) were reacted with 2-amino-5-bromo-4-carboxylic acid methyl ester (10.0 g, 43.28 mmol) and 2-amino-5-bromoisonicotinic acid methyl ester (10.0 g, 43.28 mmol) and lithium hydroxide (LiOH, 5.46 g, 129.8 mmol) in a water (100 mL) in a solvent mixture of tetrahydrofuran (THF, 400 mL), methanol (MeOH, 200 mL), and water (100 mL), and the reaction was stirred at 70 °C for 2 h under nitrogen (N2) protection. Upon completion of the reaction, the reaction mixture was cooled to 0 °C and the pH was adjusted to 6 by dropwise addition of concentrated aqueous hydrochloric acid (HCl).Subsequently, the resulting suspension was filtered and the solid was dried under vacuum to afford pyridine 2-amino-5-bromo-4-carboxylic acid (7.8 g, 83% yield). The product was analyzed by liquid chromatography-mass spectrometry (LC-MS, ESI) and showed m/z 211 [M + H]+.
