876 mg of 3(3-bromo-5-[(t-butoxycarbonyl)amino]methyl-4-methoxyphenyl)-2-isopropoxypropionic acid ethyl ester was dissolved in 5 ml of propionitrile. 182 mg of sodium cyanide, 214 mg of tetrakistriphenylphosphine palladium and 70 mg of copper iodide were added, followed by heating under reflux overnight in nitrogen atmosphere. The reaction mixture was cooled down to room temperature, and ethyl acetate was added thereto. The solution was filtered through Celite, and the filtrate was evaporated. The residue was purified by silica gel column chromatography, to give 586 mg of 3-(3-cyano-5-[(t-butoxycarbonyl)amino]methyl-4-methoxyphenyl)-2-isopropoxypropionic acid ethyl ester from fractions eluted with hexane-ethyl acetate (4:1).
