To a suspension of 2-amino-4-methylthiazole-5-carboxylic acid (500 mg, 3.20 mmol) in tetrahydrofuran (20 mL) was added pyridine (1.30 mL, 16.0 mmol) and acetyl chloride (0.60 mL, 7.90 mmol) sequentially at 0 °C. The reaction mixture was stirred at 0 °C for 21 h and then brought to room temperature. Upon completion of the reaction, volatiles were removed from the mixture under vacuum, water was added to the residue and the suspension was stirred for 1 hour. The resulting precipitate was collected by filtration, washed with water and dried under vacuum to give 2-acetamido-4-methylthiazole-5-carboxylic acid (585 mg, 91% yield) as a colorless powder.1H NMR (200 MHz, DMSO-d6) δ 2.15 (s, 3H), 2.52 (s, 3H), 12.35 (br s, 1H); MS (ESI) : m/z 201 [M + H]+, 223 [M + Na]+, 199 [M-H]-.
