Potent Analogues of Clovibactin from Commercially Available Amino Acid Building Blocks

This paper reports highly active analogues of clovibactin in which the rare, noncanonical amino acid d-hydroxyasparagine is replaced with the commercially available amino acid d-threonine. Sequential mutation of leucines 2, 7, and 8 to the more hydrophobic homologue cyclohexylalanine dramatically increases the antibiotic activity of d-Thr(5)-clovibactin. The resulting analogues (d-Cha(2),d-Thr(5)-clovibactin, Cha(7),d-Thr(5)-clovibactin, and Cha(8),d-Thr(5)-clovibactin) are readily prepared by standard peptide synthesis techniques and exhibit excellent activity (≤1 μg/mL) against the Gram-positive, drug-resistant pathogens MRSA and VRE.