By using an analogous procedure to that described for Reference Example 13, N-(carbobenzyloxy)-L-phenylalanine (2 g, 6.68 mmol), hydroxybenzotriazole (903 mg, 6.68 mmol), 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride 1.28 g, 6.68 mmol), 1-amino-3,3-diethoxypropane (935 mg, 6.36 mmol) and N,N-diisopropylethylamine (1.16 mL, 6.68 mmol) were reacted in anhydrous tetrahydrofuran (32 mL) at room temperature for 16 h, to provide benzyl (1S)-1-benzyl-2-[(3,3-diethoxypropyl)amino]-2-oxoethylcarbamate (2.5 g, 92%) as a white solid.
