Synthesis
A suspension of methanol (150 mL, 0.5 M) of 3-hydroxy-2-pyridinecarboxylic acid (10 g, 72 mmol, 1 eq.) was slowly added dropwise to concentrated sulfuric acid (12 mL, 216 mmol, 3 eq.) at 0 °C. The reaction mixture was stirred under reflux conditions for 6 hours. Upon completion of the reaction, the mixture was cooled to room temperature and concentrated under reduced pressure. Subsequently, the pH was adjusted to 8.5 with saturated aqueous NaHCO3 and solid NaHCO3. The aqueous layer was extracted with EtOAc, and the combined organic layers were washed with brine, dried over MgSO4, and concentrated under reduced pressure to afford methyl 3-hydroxy-2-pyridinecarboxylate as a white solid (10.9 g, 99%). Thin layer chromatography (TLC) showed Rf = 0.3 (petroleum ether/EtOAc 1:1, v/v). Melting point was 74°C. 1H NMR (300 MHz, CDCl3): δ (ppm) = 4.06 (s, 3H), 7.34 (dd, J = 3.9,8.4 Hz, 1H), 7.38 (dd, J = 1.5,8.4 Hz, 1H), 8.38 (dd, J = 1.5,3.9 Hz, 1H), 10.64 (s, 1H). 13C NMR (75 MHz, CDCl3): δ= 53.2,126.3,129.8,130.2,141.6,158.9,169.9. mass spectra (ESI+): m/z (%): 154 (100) [M + H]+.
References
[1] Journal of Controlled Release, 2018, vol. 290, p. 102 - 111
[2] Tetrahedron, 2011, vol. 67, # 11, p. 2118 - 2124
[3] Patent: WO2018/5662, 2018, A1. Location in patent: Paragraph 0290
[4] Patent: EP3255042, 2017, A2. Location in patent: Paragraph 0180; 0181
[5] Patent: WO2014/121418, 2014, A1. Location in patent: Page/Page column 44
