Synthetic Studies with Bacitracin A and Preparation of Analogues Containing Alternative Zinc Binding Groups

The growing threat of drug‐resistant bacteria is a global concern, highlighting the urgent need for new antibiotics and antibacterial strategies. In this light, practical synthetic access to natural product antibiotics can provide important structure‐activity insights while also opening avenues for the development of novel analogues with improved properties. To this end, we report an optimised synthetic route for the preparation of the clinically used macrocyclic peptide antibiotic bacitracin. Our combined solid‐ and solution‐phase approach addresses the problematic, and previously unreported, formation of undesired epimers associated with the stereochemically fragile N‐terminal thiazoline moiety. A number of bacitracin analogues were also prepared wherein the thiazoline motif was replaced by other known zinc‐binding moieties and their antibacterial activities evaluated. An improved synthetic route is reported for the clinically used natural product antibiotic bacitracin A. This new route provides access to the bacitracin scaffold with confidence in the stereochemical purity of the product and enables studies involving structural variation of the bacitracin framework.