To a stirred solution of 2-(tert-butoxycarbonylamino)-4-methylthiazole-5-carboxylic acid (2.97 g, 11.50 mmol) and diisopropylamine (8.5 mL, 48.70 mmol) in dichloromethane (40 mL) was added N-ethyl-N′-(3-dimethylaminopropyl)carbodiimide hydrochloride (2.25 g, 11.50 mmol) and 1-hydroxybenzotriazole (2.02 g, 14.80 mmol). After 30 min benzylamine (1.7 mL, 15.60 mmol) was added. The resultant mixture was stirred at ambient temperature over 8 h, diluted with ethyl acetate, washed with water and brine, dried over anhydrous sodium sulfate, filtered and concentrated in vacuo. The crude product was purified by flash column chromatography eluting with ethyl acetate/hexanes (5/95 to 100/0) to afford 2-(tert-butoxycarbonylamino)-4-methylthiazole-5-carboxylic acid benzylamide (2.00 g, 50% yield).
