A mixture of 2-(acetylamino)-4-(2-{4-[(tert-butoxycarbonyl)amino]phenyl}ethyl)-1,3-thiazole-5-carboxylic acid (80 mg), 30% methylamine in ethanol solution (0.02 ml), 1-hydroxybenzotriazole (29.3 mg) and 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (39.7 mg) in dichloromethane (1 ml) and N,N-dimethylformamide (0.5 ml) was stirred at ambient temperature for 20 hours. The reaction mixture was poured into saturated sodium hydrogen carbonate solution, and extracted with chloroform. The organic layer was washed with water and saturated sodium chloride solution, dried over anhydrous magnesium sulfate, and concentrated in vacuo to give tert-butyl 4-(2-{2-(acetylamino)-5-[(methylamino)carbonyl]-1,3-thiazol-4-yl}ethyl)phenylcarbamate (92.8 mg) as an off-white amorphous substance.
