Cyanomethyl 3-[(2 acetylthiomethyl-3-phenylpropionyl)amino]benzoate (compound of Example 116) (4 g), 2-phenoxyethanol (3 g), 4-dimethylaminopyridine (0.1 g) and triethylamine (2 g) are mixed, and the mixture is stirred at 60° C. for 15 hours and extracted with ethyl acetate (50 ml). The extract is washed with 10% hydrochloric acid and water, and ethyl acetate is distilled off under reduced pressure. The residue is dissolved in 50% aqueous acetonitrile and purified by a column chromatography using Diaion HP-20 (eluant, water-acetonitrile). The fractions containing the desired compound are collected, and acetonitrile is distilled off under reduced pressure. The aqueous solution is extracted with ethyl acetate (100 ml). The extract is dried over anhydrous magnesium sulfate, and ethyl acetate is distilled off under reduced pressure to give the title compound (2.5 g).
