Design, Synthesis, and Characterization of Novel Tetrahydropyran-Based Bacterial Topoisomerase Inhibitors with Potent Anti-Gram-Positive Activity

There is an urgent need for new antibacterial drugs that are effective against infections caused by multidrug-resistant pathogens. Novel nonfluoroquinolone inhibitors of bacterial type II topoisomerases (DNA gyrase and topoisomerase IV) have the potential to become such drugs because they display potent antibacterial activity and exhibit no target-mediated cross-resistance with fluoroquinolones. Bacterial topoisomerase inhibitors that are built on a tetrahydropyran ring linked to a bicyclic aromatic moiety through a <i>syn</i>-diol linker show potent anti-Gram-positive activity, covering isolates with clinically relevant resistance phenotypes. For instance, analog <b>49c</b> was found to be a dual DNA gyrase–topoisomerase IV inhibitor, with broad antibacterial activity and low propensity for spontaneous resistance development, but suffered from high hERG K⁺ channel block. On the other hand, analog <b>49e</b> displayed lower hERG K⁺ channel block while retaining potent in vitro antibacterial activity and acceptable frequency for resistance development. Furthermore, analog <b>49e</b> showed moderate clearance in rat and promising in vivo efficacy against Staphylococcus aureus in a murine infection model