Stapled peptides have received increasing attention as potential therapeutic agents. Stapling can enhance essential properties like selectivity, binding affinity, and bioavailability. Presented here are two novel methods of stapling of peptides containing two 1,2-aminothiol groups.

Various strategies have been explored for introducing the 1,2-aminothiol motif into peptides. The motif can either be resembled by canonical N-terminal cysteine in the peptide main chain or introduced in the side chain as a “pseudo-cysteine” residue with varying linker length.¹ The latter can be incorporated either as fully protected amino-acid building block or directly assembled on the solid support during standard Fmoc solid-phase peptide synthesis.

The first stapling technique employs a 2,6-dicyanopyridine linker that reacts with the two 1,2-aminothiol moieties present on the peptide.¹ This reaction converts each 1,2-aminothiol and nitrile combination into a thiazoline, ultimately forming a thiazoline-pyridine-thiazoline bridge that staples the peptide.

The second method utilises a linker with two α-bromoketone moieties that also react with the 1,2-aminothiols on the peptide.² This reaction combines S-alkylation and imine formation, resulting in lanthionine ketenamine linkages at each end of the staple, stapling the peptide.

Both stapling methods function in aqueous solution at pH 7.5, have been tested on a diverse array of peptide substrates, and are fully compatible with standard Fmoc solid-phase peptide synthesis. Furthermore, these stapling techniques have successfully been employed to produce a series of peptide inhibitors targeting the Zika virus protease. In summary, these novel two-component stapling approaches provide simple and effective means to staple peptides containing two 1,2-aminothiol groups.

References

1. Morewood R, Nitsche C. Chem Sci. 2020;12(2):669-674. doi: 10.1039/d0sc05125j.
2. Morewood R, Nitsche C. Chem Commun. 2022;58:10817-10820. doi: 10.1039/d2cc03510c.