Discovery of WQ-3810: Design, synthesis, and evaluation of 7-(3-alkylaminoazetidin-1-yl)fluoro-quinolones as orally active antibacterial agents

Abstract

Novel 7-(3-alkylaminoazetidin-1-yl)fluoroquinolones were designed, synthesized, and evaluated for their antibacterial activities and oral absorption rates. Against Gram-negative bacteria, 10a–e, which have various alkyl groups containing different numbers of carbon atoms (C0–C3) at the C-7 alkylaminoazetidine position, showed potent and similar antibacterial activities, whereas the activity of 10f (C4, t-Bu) was significantly lower than those of 10a–e. Conversely, the oral absorption rates of 10a–e in rats increased depending on the number of carbon atoms in the alkyl groups; 10d (C3, n-Pr) and 10e (C3, i-Pr) had high oral absorption rates (>90% at 10 mg/kg). These results demonstrated that the introduction of alkyl groups onto C-7 aminoazetidine is useful for the improvement of the oral absorption rates of these drugs while maintaining their antibacterial activities. As a conclusion, from this series of fluoroquinolones, WQ-3810 (10e), having 3-isopropylaminoazetidine as the C-7 substituent, was identified as an orally active antibacterial agent with a potent in vitro activity.