A solution of 4N-hydrogen chloride in ethyl acetate (5 ml) was added to 2-[2-(N-t-butoxycarbonyl-N-methylamino)ethyl]pyridine at 0° C. The solution was stirred at 0° C. for 1 hour and concentrated under reduced pressure. The residue was dissolved in methylene chloride (10 ml). Triethylamine (304 mg) and (1S)-1-benzyloxycarbonyl-2-phenylethyl isocyanate (281 mg) prepared by reacting L-phenylalanine benzyl ester with trichloromethylchloroformate was added to this solution at 0° C. The solution was stirred at the same temperature for 1 hour and the solvent was evaporated in vacuo. The residue was dissolved in ethyl acetate and the solution was washed with 10% citric acid aqueous solution, saturated sodium bicarbonate solution, and saturated sodium chloride solution successively, dried over magnesium sulfate, and concentrated under reduced pressure to give N-[N-(2-pyridyl)ethyl-N-methylaminocarbonyl]-L-phenylalanine benzyl ester (400 mg) as an oil. Rf: 0.50 ( chloroform:methanol, 20: 1, V/V)
