New Single-Step Radioiodination Technique for Peptides: Cu(I)-Catalyzed Nucleophilic Nonisotopic Displacement Reaction. Synthesis of Radioiodinated Deltorphin and Dermorphin Analogues

摘要

The Cu(I)-catalyzed nucleophilic noniso-topic substitution reaction combines an easy preparation of the [4′-Br-Phe]precursor peptides with high labeling yields. The major limitation is the hydrolysis reaction of a C-terminal peptide-amide, the extent of which appears to be dependent on the C-terminal amino acid. For peptide 3, lowering the acidity of the reaction medium avoids this side reaction but unfortunately decreases the labeling yield to 28%. In comparison with the iododediazonization method, for which the preparation of the precursor requires extra steps, the radio-chemical yield is only slightly lower. Oxidative damage to tryptophan or methionine is not observed. Therefore, this new method may have an application domain for peptides which is complementary to the previously described ones.