Oxidative phenol coupling—tyrosine dimers and libraries containing tyrosyl peptide dimers

The principles of phenol oxidation are outlined and summarized. Various procedures were used to dimerize tyrosine derivatives, especially linear tripeptides and cyclohexapeptides, via cross-linking of their phenolic side-chains. The coupling was performed by potassium hexacyanoferrate(III), phenyliodine(III)-bis(trifluoroacetate), vanadium(V)-oxyfluoride or horseradish peroxidase. The individual dityrosine and isodityrosine derivatives obtained in preparative scale, as well as the peptide-dimer libraries generated, were characterized by HPLC and electrospray ionization mass spectrometry. Further analyses were carried out by NMR spectroscopy, fluorescence spectroscopy and gas chromatography.