Efficient Synthesis of Clovibactin and Its Analogues: Promoting the Discovery of More Potent Antibiotics via Multiple Screenings

Increasingly, antimicrobial resistance has become a major concern for public health. The recently discovered cyclic depsipeptide, clovibactin, is a potential antibiotic candidate with potent activities against multidrug-resistant pathogens. It contains three d-amino acids, including a rare d-hydroxyasparagine residue. Herein, we present the efficient synthesis of the suitably protected d-hydroxyasparagine building block and the natural product clovibactin. Efforts have also been made by us to establish the structure-activity relationship (SAR) of clovibactin and to hunt for more active analogues. After three rounds of screening, the new compounds <b>30</b>, <b>40,</b> and <b>42</b> were found to exhibit higher antibacterial activity than clovibactin and were able to eradicate methicillin-resistant <i>Staphylococcus aureus</i> (MRSA). Their substantial efficacy was also demonstrated in a bactericidal activity assay, an in vitro time-killing assay, a hemolysis assay, and a potential resistance development evaluation. The improved antibacterial activity, low hematotoxicity, and resistance-resistant properties of analogues <b>30</b>, <b>40,</b> and <b>42</b> make them promising for further evaluation of drug-likeness and the development of next-generation antibiotics.