Chemical and ribosomal synthesis of atropisomeric and macrocyclic peptides with embedded quinolines.

Potent peptide ligands for therapeutically relevant targets are regularly returned from screening trillion-member libraries of ribosomally synthesized peptides containing non-canonical amino acids and macrocyclic architectures. Yet the chemical space explored by these peptides is a fraction of that embodied by natural products and pharmaceuticals, and most peptide leads require exhaustive medicinal chemistry optimization to improve potency and physicochemistry. To address the need for strategies to introduce chemical complexity and conformational control into peptide macrocycles, we report here that linear peptides with a reactive N-terminal β-keto or γ-keto amide can be synthesized ribosomally. Subsequent Friedländer reactions generate quinoline-peptide hybrids, some of which contain stable biaryl atropisomeric axes. We also demonstrate intramolecular Friedländer macrocyclization reactions-sufficiently mild to be employed on unprotected and in vitro-translated peptides-that embed a quinoline pharmacophore directly within the peptide backbone. The introduction of N-terminal ketone motifs into genetically encoded materials and their post-translational derivatization provides a paradigm for the programmed synthesis of peptide-derived materials that more closely resemble complex natural products.