General procedure for the synthesis of 4-aminopyridinamide (99B) from 4-nitro-2-pyridine carboxamide (99A): 99A (40 mg) was dissolved in methanol, 10% Pd/C catalyst (40 mg) was added, and the hydrogenation reaction was carried out for 8 hours under the atmosphere of a hydrogen balloon. Upon completion of the reaction, the Pd/C catalyst was removed by filtration. The filtrate was concentrated to give a white solid 99B (80 mg, 87% yield). The product was characterized by 1H NMR (400 MHz, methanol-d4): δ 6.65 (dd, J = 5.71, 2.64 Hz, 1H), 7.27 (d, J = 2.20 Hz, 1H), 8.03 (d, J = 5.71 Hz, 1H).
