Peptide [4]Catenane by Folding and Assembly

A topologically complex peptide [4]catenane with the crossing number of 12 was synthesized by a folding and assembly strategy wherein the folding and metal‐directed self‐assembly of a short peptide fragment occur simultaneously. The latent Ω‐looped conformation of the Pro‐Gly‐Pro sequence was found only when pyridines at the C‐ and N‐termini coordinatively bind metal ions (AgI or AuI). Crystallographic studies revealed that the Ω‐looped motifs formed four M3L3 macrocycles that were intermolecularly entwined to generate an unprecedented peptide [4]catenane topology. It's all about topology: Upon complexation with silver(I) the tripeptide ligand (Pro‐Gly‐Pro) simultaneously folds into an Ω‐looped conformation and self‐assembles into a discrete peptide [4]catenane with the crossing number of 12. Within the [4]catenane each of the four equivalent M3L3 macrocycles is interlocked with the other three rings with tetrahedral symmetry.