2,4,5-Trichlorophenol → N-(1,1-dimethylethoxycarbonyl)leucine 2,4,5-trichlorophenyl ester

N-(1,1-Dimethylethoxycarbonyl)leucine (6.32 g, 15 mmol) was stirred with 2,4,5-trichlorophenol (3.01 g, 15.2 mmol) and dicyclohexylcarbodiimide (3.14 g, 15.2 mmol) in ethyl acetate (50 mL) at -10° C. for 4 h. The suspension was filtered and the solvent was evaporated under reduced pressure from the filtrate. The residue was dissolved in ethyl acetate. The suspension was filtered and the solvent was evaporated under reduced pressure from the filtrate to give N-(1,1-dimethylethoxycarbonyl)leucine 2,4,5-trichlorophenyl ester (6.2 g, 99%).