A study of 2-component i, i + 3 peptide stapling using thioethers.

Peptides are promising scaffolds for use as therapeutics, targeting interactions previously considered to be "undruggable" by small molecules. While short peptides are generally unstructured in solution and rapidly degraded by proteases in the cell cytosol, peptide stapling offers an effective method to both stabilize peptides in a helical structure and increase resistance to proteolytic degradation. Most studies of peptide stapling have focused on residues with i, i + 4 and i, i + 7 spacing, while stapling of residues with i, i + 3 spacing has been understudied. Herein, we evaluated a suite of bifunctional linkers for stapling between residues with i, i + 3 spacing, comparing the ability of each compound to react with the peptide and the degree of helicity conferred. Finally, we evaluated the ability of the stapling to increase proteolytic resistance in cell lysates, comparing stapling of i, i + 3 and i, i + 4 spacing, with i, i + 3 spacing resulting in a greater increase in peptide half-life in the model system. This presents an effective stapling strategy, adding to the peptide stapling toolbox.