To a solution of N-benzyloxycarbonyl-L-phenyl alanine (0.6 g) and triethylamine (0.28 ml) in dry tetrahydrofuran (12 ml), 2-p-nitrophenyloxycarbonyloxyimino-2-cyanoacetic acid amide (0.6 g) is added, and the resulting mixture is stirred at room temperature for 1.5 hours. The reaction mixture is admixed with water and extracted with ethyl acetate. The organic layer is washed with an aqueous solution of sodium chloride, dried and concentrated. The residue is recrystallized from an ethanol-petroleum ether mixture to give N-benzyloxycarbonyl-L-phenylalanine p-nitrophenyl ester (0.5 g) as crystals.
