Commercially available (2-mercapto-4-methyl-1,3-thiazol-5-yl)acetic acid (15 g) was dissolved in methanol (360 mL) and 1N aqueous sodium hydroxide solution (174 mL), 2-bromo-2-methylpropionic acid tert-butyl ester (19.4 g) was added, and the mixture was stirred at 60° C. for 6 hr. The reaction mixture was concentrated, the residue was dissolved in water, and the mixture was acidified with 10% aqueous citric acid solution. The precipitated solid was collected by filtration, and dried under reduced pressure to give the title compound (25 g) as a white solid.
