Recent Studies on Gramicidin S Analog Structure and Antimicrobial Activity

Gramicidin-S-Inspired Cyclopeptidomimetics as Potent Membrane-Active Bactericidal Agents with Therapeutic Potential

Antimicrobial peptides (AMPs) are promising antibacterial agents often hindered by their undesired hemolytic activity. Inspired by gramicidin S (GS), a well-known cyclodecapeptide, we synthesized a panel of antibacterial cyclopeptidomimetics using β,γ-diamino acids (β,γ-DiAAs). We observed that peptidomimetic CP-2 displays a bactericidal activity similar to that of GS while possessing lower side-effects. Moreover, extensive studies revealed that CP-2 likely kills bacteria through membrane disruption. Altogether, CP-2 is a promising membrane-active antibiotic with therapeutic potential.

Synthesis and Biological Studies of Dodecameric Cationic Antimicrobial Peptides Containing Tetrahydrofuran Amino Acids

We report here a concise route to synthesize various stereoisomers of tetrahydrofuran amino acids (TAAs) and the synthesis of TAA-containing linear cationic dodecapeptides. Some of these linear peptides show slightly better antimicrobial activities than their tetra- and octameric congeners, but no activity against Mycobacterium tuberculosis, for which octapeptides exhibited by far the best results; this implies that antibacterial activity is dependent on the length of these linear peptides. All the dodecapeptides described here were found to be toxic in nature against Vero cells. The study helps to delineate the optimal length of this series of linear peptides and select potential leads in the development of novel cationic peptide-based antibiotics.

Stabilization of Cyclic β-Hairpins by Ugi-Reaction-Derived N-Alkylated Peptides: The Quest for Functionalized β-Turns

A solid-phase approach including on-resin Ugi reactions was developed for the construction of β-hairpins. Various N-alkylated dipeptide fragments proved capable of aligning antiparallel β-sheets in a macrocyclic scaffold, thus serving as β-hairpin templates. Gramicidin S was used as the model β-hairpin to compare the Ugi-derived β-turns with the type-II' β-turn. The results show that the multicomponent incorporation of such N-alkylated residues allows for the simultaneous stabilization and exo-cyclic functionalization of cyclic β-hairpins.