Structure–Activity Studies on the Antitubercular Natural Product Evybactin

The escalating threat of antibacterial resistance is a pressing global issue that highlights the urgent need for innovative antibiotics. In this regard, the recent discovery of evybactin─a nonribosomal depsipeptide antibiotic that selectively and effectively inhibits the growth of M. tuberculosis ─is notable given its unique structure and mechanism of action. In a previous report, we described the first total synthesis of evybactin and a revision of the originally assigned structure. Building on this, we report here a series of structure–activity relationship studies with evybactin. In doing so, we synthesized a total of 21 novel evybactin analogues by performing an alanine scan and exploring multiple modifications, including variations of the ester-linked macrocycle, substitution of the formylated N-terminus, and removal of positively charged side chains. Our results provide valuable insights into the significance of certain amino acids and other structural features that underscore the potent antitubercular activity of this unique natural product.