General procedure for the synthesis of methyl 3-carboxylic acid pyridine-2-carboxylate from methanol and 2,3-pyridinedicarboxylic anhydride: 2,3-pyridinedicarboxylic anhydride (5.0 g, 34 mmol) was dissolved in methanol (25 mL). The reaction mixture was heated to reflux for 2 hours and the solvent was subsequently removed by rotary evaporation. The resulting white solid was dissolved in ethyl acetate (25 mL) under reflux conditions and the insoluble by-products were removed by filtration. The filtrate was concentrated under reduced pressure and recrystallized from ethyl acetate to give the final methyl 3-carboxypyridine-2-carboxylate (4.5 g, 71% yield) as a white solid with a melting point of 157-159 °C.1H NMR (300 MHz, CDCl3) δ 8.84 (dd, J=1.7,5.0 Hz, 1H), 8.34 (dd, J=1.6, 7.9 Hz, 1H), 7.57 (dd, J=5.0,8.1 Hz, 1H), 4.00 (s, 3H).
