Synthesis
In a three-necked flask, 5 g of ethyl 2-aminonicotinate (0.0302 mol) and 80 mL of tetrahydrofuran were added, and 13 g of sodium borohydride (0.2416 mol) powder was slowly added under stirring. The reaction mixture was stirred at 65 °C for 15 min before 65 mL of methanol was added dropwise, followed by heating and refluxing the reaction. The reaction process was monitored by thin layer chromatography (TLC, unfolding agent ratio of trichloromethane: methanol = 4:1). Upon completion of the reaction, vacuum concentration was performed while hot. To the concentrate, 40 mL of the mixture and 1 g of sodium hydroxide were added and hydrolyzed at 70-80 °C for 7-8 hours. After completion of the reaction, the organic phase was separated and dried with anhydrous sodium sulfate and subsequently concentrated to give Intermediate A (2-amino-3-pyridinecarboxylic acid ethanol) as a light yellow solid powder 2.7 g in 75% yield with a melting point of 67.5-68 °C.
References
[1] Patent: CN104892608, 2017, B. Location in patent: Paragraph 0040; 0041; 0047; 0048
[2] Polish Journal of Chemistry, 2003, vol. 77, # 5, p. 535 - 545
[3] Patent: US2005/20587, 2005, A1. Location in patent: Page 17
