Establishing the Comprehensive Structure-Activity Relationship of the Natural Antibiotic Kibdelomycin/Amycolamicin.

Kibdelomycin (KBD) and amycolamicin (AMM) are potent natural antibiotics effective against antibiotic-resistant Gram-positive pathogens, including vancomycin-intermediate Staphylococcus aureus (S. aureus, VISA), methicillin-resistant S. aureus (MRSA), and quinolone-resistant S. aureus (QRSA). Their antibacterial activity stems from an unprecedented dual mechanism: the lower binding sites occupy the adenosine triphosphate (ATP) binding pocket of bacterial type II topoisomerases, while the upper binding sites disrupt the enzyme dimer interface. This dual action, combined with their unique chemical structures, positions KBD and AMM as promising scaffolds for developing new antibiotics. However, the structure-activity relationship (SAR) of KBD/AMM remains underexplored due to their highly complex chemical structures. In this study, we utilized total synthesis to produce KBD/AMM analogs with various site modifications and evaluated their antimicrobial activities. Our findings establish the first comprehensive SAR for KBD/AMM, paving the way for the development of novel KBD/AMM-based antibiotics.