Synthesis, Antifungal Activity, and In Silico Study of Novel Quinoline Thioether Derivatives Inspired by Natural Quinoline.

Inspired by natural quinoline, a series of novel quinoline derivatives containing thioether groups were designed and synthesized. All target compounds were characterized using 1H NMR, 13C NMR, and high-resolution mass spectrometry (HRMS). Their antifungal activities were evaluated in vitro against 10 phytopathogenic fungi. Among the synthesized compounds, 3l (4-(allylthio)-8-fluoro-2,3-dimethylquinoline) exhibited significant antifungal activity, with inhibition rates exceeding 80% against Sclerotinia sclerotiorum and Physalospora piricola at 50 µg/mL. The structure-activity relationship (SAR) analysis revealed that the presence of an alkene group in the thioether side chain enhanced antifungal activity. Molecular docking studies with Sclerotinia sclerotiorum dihydroorotate dehydrogenase (SsDHODH) indicated that 3l forms a hydrogen bond with His89, whereas density functional theory (DFT) calculations provided insights into the electronic properties of the compounds. Additionally, absorption, distribution, metabolism, excretion, and toxicity (ADMET) predictions suggested that 3l has favorable pharmacokinetic properties, similar to the commercial fungicide tebufloquin. These findings highlight the potential of 3l as a lead compound for further development of novel antifungal agents.