De Novo Cyclic Pseudopeptides Containing Aza-β3-amino Acids Exhibiting Antimicrobial Activities

De novo cyclic pseudopeptides composed of α-amino and aza-β3-amino acids were designed with the aim to obtain potential new antimicrobial agents. Antimicrobial cyclic pseudopeptides (ACPPs) are based on the properties of antimicrobial peptides (AMPs), so they are cationic and amphiphilic. Aza-β3-amino acids enhance the in vivo half-life of these compounds and offer the possibility to incorporate a large variety of side chains. Most of the 13 ACPPs exert antimicrobial activities in rich media with broad spectrum of antibacterial activities. Selectivity for bacterial over mammalian cells was determined by testing the hemolytic activities of ACPPs against sheep red blood cells (sRBC). We examined the ratio of cationic to hydrophobic residues as well as the type of hydrophobic side chains essential for biological activity of this class of ACPPs. These results will be useful for designing potential candidates for a therapeutic application.