To a solution of (2S)-2-(5-chloro-2-methoxybenzyl)-3-[(2,4,6-trimethoxybenzyl)amino]propionic acid (1g) in acetonitrile (10 ml), glycine ethyl ester hydrochloride (345 mg), 1-hydroxy benzotriazole (478 mg), and triethylamine (0.35 ml) were added at room temperature, and the mixture was stirred at room temperature for 40 minutes. At room temperature, N-(3-dimethylaminopropyl)-N′-ethylcarbodiimide hydrochloride (678 mg) was added to the reaction solution, and the mixture was stirred for 3 hours. The reaction solution was concentrated in vacuo, and ethyl acetate was added to the obtained residue. Then the mixture was washed with saturated aqueous sodium bicarbonate and saturated brine, an the organic layer was concentrated. To the obtained residue, isopropyl alcohol (5 ml) and 5N aqueous sodium hydroxide solution were added, and the mixture was stirred at room temperature for 3 hours. The reaction solution was adjusted with 5N hydrochloric acid to pH 5, then the precipitated crystals were obtained by filtration and dried to obtain the title compound (978 mg) as a colorless crystal. The various types of spectral data match with those of Example 326.
