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Hydrocarbon stapling is a useful tool for stabilizing the secondary structure of peptides. Among several methods, hydrocarbon stapling at <i>i</i>,<i>i</i> + 1 positions was not extensively studied, and their secondary structures are not clarified. In this study, we investigate <i>i</i>,<i>i</i> + 1 hydrocarbon stapling between <i>cis</i>-4-allyloxy-<span style="font-variant: small-caps;">l</span>-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, <i>E-</i> or <i>Z</i>-selectivities were observed during the ring-closing metathesis reaction (<i>E</i>/<i>Z</i> 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</i>,<i>i</i> + 1 positions. The X-ray crystallographic structure suggested that the <i>i</i>,<i>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.