Diethylazodicarboxylate (40% toluene solution 0.55 ml) was added dropwise to a solution of N-trifluoroacetyl-3,5-diiodo-L-tyrosine methyl ester (272 mg, 0.5 mmol), 4-(4-hydroxyphenoxy)benzylalcohol (119 mg, 0.55 mmol) and triphenylphosphine (328 mg, 1.25 mmol) in tetrahydrofuran (5 ml) under argon atmosphere at −15° C., and the mixture was stirred at the same temperature for 1.5 hrs. The solvent of the reaction mixture was distilled off under reduced pressure. The residue was purified by column chromatography on silica gel (n-hexane/ethyl acetate=2) to give N-trifluoroacetyl-O-[4-(4-hydroxy-phenoxy)benzyl]-3,5-diiodo-L-tyrosine methyl ester (280 mg, 76%) as colorless crystals.
