Further observations on the oxidation of di-iodotyrosine derivatives

Abstract

The formation of thyroxine peptides from di-iodotyrosine pep-tides has been further investigated. N-Acetyldi-iodotyrosyl-[epsilon]-N-([alpha]-acetyl)-lysine gives rise to high yields of the corresponding thyroxine derivative during aerobic incubation at pH 7.5. The side chain lost during incubation of the peptide was characterized through its p-bromophenylhydrazone as [epsilon]-N-hydroxypyruvoyl-[alpha]-N-acetyl-lysine. The side chain lost from N-acetyl-L-di-iodotyrosine during oxidative coupling has not been satisfactorily characterized. It has not been possible to demonstrate the presence of pyruvic acid. The side chain lost during the formation of tetraidothyroacetic acid from 4-hydroxy-3, 5-di-iodophenylacetic acid has been identified as glyoxylic acid.