Diversity-Oriented Peptide Stapling: A Third Generation Copper-Catalysed Azide-Alkyne Cycloaddition Stapling and Functionalisation Strategy.

The introduction of macrocyclic constraints in peptides (peptide stapling) is an important tool within peptide medicinal chemistry for stabilising and pre-organising peptides in a desired conformation. In recent years, the copper-catalysed azide-alkyne cycloaddition (CuAAC) has emerged as a powerful method for peptide stapling. However, to date CuAAC stapling has not provided a simple method for obtaining peptides that are easily diversified further. In the present study, we report a new diversity-oriented peptide stapling (DOPS) methodology based on CuAAC chemistry. Stapling of peptides incorporating two azide-modified amino acids with 1,3,5-triethynylbenzene efficiently provides (i, i+7)- and (i, i+9)-stapled peptides with a single free alkyne positioned on the staple, which can be further conjugated or dimerised. A unique feature of the present method is that it provides easy access to radiolabelled stapled peptides by catalytic tritiation of the alkyne positioned on the staple.