Thia-Michael Stapling of Allenamide-Incorporated α-Helical Antimicrobial Peptides

Herein is presented a chemoselective thia-Michael stapling approach, mediated by a highly electrophilic allenamide group, occurring spontaneously in a mixture of aqueous buffer and 2,2,2-trifluoroethanol (TFE). Leveraging the commercially available homologs of Lys and Cys, the staple length and stereochemistry are readily interchangeable, presenting a facile strategy to introduce i, i + 3, i, i + 4 and i, i + 7 conformational constraints to α-helical peptides. Harnessing this approach, a number of stapled antimicrobial peptides (StAMPs) were prepared from amphibian-derived defense peptides. A stapled temporin-1Ta analog demonstrated markedly improved helicity, enhanced potency toward Gram-positive pathogens, and low cytotoxicity toward mammalian cells. This StAMP was further demonstrated to be well-tolerated and possess in vivo efficacy toward lethal and sublethal Streptococcus pyogenes in vivo infection models in the wax worm, Galleria mellonella.