(2) Preparation of 3-aminopyridine-2-carboxylic acid: 3-nitropyridine-2-carboxylic acid (2.72 g, 16.2 mmol) and sodium bicarbonate (1.34 g, 16.2 mmol) were dissolved in distilled water (20 mL). The atmosphere in the system was replaced with nitrogen to exclude oxygen. After adding 10% palladium carbon catalyst (1.72 g), the atmosphere in the system was replaced with hydrogen and the reaction was stirred at room temperature for 50 hours. After completion of the reaction, the pH of the reaction solution was adjusted to weakly acidic by adding 1N aqueous hydrochloric acid. The solvent was removed by distillation under reduced pressure and a small amount of ethanol and ethyl acetate was added to the residue and the resulting precipitate was collected by filtration. The filtrate was concentrated to afford the target product 3-aminopyridine-2-carboxylic acid (1.50 g, 67% yield) as a light yellow solid.
