Synthesis
General procedure for the synthesis of 2-(tert-butoxycarbonylamino)thiazole-5-carboxylic acid from ethyl 2-(tert-butoxycarbonylamino)thiazole-5-carboxylate: To a vigorously stirred suspension of ethyl 2-(tert-butoxycarbonylamino)thiazole-5-carboxylate (4.2 g, 15 mmol) in methanol (11 mL) was slowly added an aqueous 2 M NaOH solution (22 mL, 44.0 mmol). The reaction mixture was stirred at room temperature overnight. Upon completion of the reaction, the mixture was concentrated under vacuum by rotary evaporator to remove methanol. The pH was adjusted to 1-2 by adding aqueous 6 N HCl dropwise to the residual aqueous suspension. the mixture was stirred for 1 h, during which time it was occasionally sonicated to promote precipitation. The resulting white solid was collected by filtration, washed thoroughly with deionized water and dried in a vacuum drying oven to afford 2-(tert-butoxycarbonylamino)thiazole-5-carboxylic acid (3.7 g, 100% yield). Mass spectrometry analysis showed (M + H-Boc)+ = 145.
References
[1] Patent: WO2009/100171, 2009, A1. Location in patent: Page/Page column 109
[2] Patent: CN106674150, 2017, A. Location in patent: Paragraph 0022-0026
[3] Patent: US2004/54186, 2004, A1. Location in patent: Page 23
[4] Synthetic Communications, 2017, vol. 47, # 17, p. 1610 - 1621
[5] Asian Journal of Chemistry, 2018, vol. 30, # 7, p. 1621 - 1628
