439109-82-7

477870-14-7

439109-82-7

3) Lithium hydroxide monohydrate (3.072 g) was added to a mixed solution of tetrahydrofuran (150 mL) and methanol (75 mL) containing methyl 5-methoxyoxazole-2-carboxylate (10.26 g). Subsequently, water (75 mL) was added at room temperature and the reaction mixture was stirred for 2 hours. Upon completion of the reaction, the reaction solution was adjusted to be weakly acidic (pH ≈ 4) by dropwise addition of 1 M hydrochloric acid-ethanol solution, followed by concentration under reduced pressure to remove most of the organic solvent. To the residue, chloroform-methanol (10:1, v/v) was added for partition extraction. The aqueous phase was further extracted with chloroform-methanol (10:1, v/v) and the organic phases were combined and dried over anhydrous sodium sulfate. After filtration to remove the desiccant, the solvent was evaporated under reduced pressure to afford 5-methoxyoxazole-2-carboxylic acid [1.06 g, 11% yield; 1H-NMR (400 MHz, DMSO-d6) δ: 3.91 (3H, s), 6.45 (1H, s); EI-MS m/z: 143 (M+)] as a solid. The organic solvent in the aqueous phase was further evaporated under reduced pressure and the precipitated solid was filtered and combined with the previously obtained solid to give the crude product of 5-methoxyoxazole-2-carboxylic acid (15.63 g).