New peptide architectures through C–H activation stapling between tryptophan–phenylalanine/tyrosine residues

Natural peptides show high degrees of specificity in their biological action. However, their therapeutical profile is severely limited by their conformational freedom and metabolic instability. Stapled peptides constitute a solution to these problems and access to these structures lies on a limited number of reactions involving the use of non-natural amino acids. Here, we describe a synthetic strategy for the preparation of unique constrained peptides featuring a covalent bond between tryptophan and phenylalanine or tyrosine residues. The preparation of such peptides is achieved in solution and on solid phase directly from the corresponding sequences having an iodo-aryl amino acid through an intramolecular palladium-catalysed C–H activation process. Moreover, complex topologies arise from the internal stapling of cyclopeptides and double intramolecular arylations within a linear peptide. Finally, as a proof of principle, we report the application to this new stapling method to relevant biologically active compounds. Macrocyclic, constrained peptides show promise in therapeutic applications due to the stable and defined conformations that can be produced. Here, the authors report a method to form macrocyclic peptides through C–H activation on tryptophan and coupling with iodo-substituted aryl amino acids