X-ray Crystallographic Structure of α-Helical Peptide Stabilized by Hydrocarbon Stapling at i,i + 1 Positions

Abstract

Hydrocarbon stapling is a useful tool for stabilizing the secondary structure of peptides. Among several methods, hydrocarbon stapling at i,i + 1 positions was not extensively studied, and their secondary structures are not clarified. In this study, we investigate i,i + 1 hydrocarbon stapling between cis-4-allyloxy-l-proline and various olefin-tethered amino acids. Depending on the ring size of the stapled side chains and structure of the olefin-tethered amino acids, E- or Z-selectivities were observed during the ring-closing metathesis reaction (E/Z was up to 8.5:1 for 17–14-membered rings and up to 1:20 for 13-membered rings). We performed X-ray crystallographic analysis of hydrocarbon stapled peptide at i,i + 1 positions. The X-ray crystallographic structure suggested that the i,i + 1 staple stabilizes the peptide secondary structure to the right-handed α-helix. These findings are especially important for short oligopeptides because the employed stapling method uses two minimal amino acid residues adjacent to each other.

E-Selective Ring-Closing Metathesis in α-Helical Stapled Peptides Using Carbocyclic α,α-Disubstituted α-Amino Acids

“…Because an α-helix is the most abundant secondary structure, α-helix-inducing i , i + 4-stapled peptides are frequently used for peptide-based drug discovery and an E / Z configuration of stapled peptides is a key to their biological activity . Accordingly, E -selective hydrocarbon stapling at positions i and i + 4 is in demand …”