6.95 g of 2-(tert-butoxycarbonyl-methyl-amino)-acetic acid, 6.1 g of hydrazine carboxylic acid benzyl ester, 6.18 g of 1-hydroxybenzotriazole monohydrate and 19.2 mL of N,N-diisopropylethylamine were dissolved in 120 mL of N,N-dimethylformamide, and 10.6 g of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride was added under stirring at room temperature. After stirring at room temperature for 17 hours, the reaction solution was added with water and extracted with ethyl acetate, and the resultant organic layer was washed with saturated brine and dried over magnesium sulfate. The solvent was evaporated, followed by purification by silica gel column chromatography (hexane:ethyl acetate=1:1), to obtain 10.9 g of the title compound.
