Synthesis and Biological Evaluation of Novel Sulfone Derivatives Containing 1,3,4-Oxadiazole Moiety

A series of novel sulfone derivatives containing 1,3,4-oxadiazole moiety were synthesized. All the target com-pounds were characterized by H and C nuclear magnetic resonance, infrared spectroscopy and elemental analysis. Their antifungal activities were tested in vitro with six important phytopathogenic fungi, namely, Gibberella zeae, Fusarium oxysporum, Cytospora mandshurica, Phytophthora infestans, Paralepetopsis sasakii and Sclerotinia sclerotiorum using the mycelium growth inhibition method. Their antibacterial activities were tested in vitro with two important phytopathogenic bacteria, namely, Xanthomonas oryzae and Ralstonia solanacearum from tobacco bacterial by the turbid meter test. Remarkably, compounds 5h, 5j, 5u and 5v exhibited the most potent inhibition against R. solanacearum and X. oryzae with 50% inhibition concentration (EC50) from 1.97 to 7.75 μg/mL and 0.45 to 0.52 μg/mL, respectively. Their antifungal tests indicated that among target compounds exhibited good antifungal activities against six kinds of fungi, especially against S. sclerotiorum with EC50 from 3.71 to 17.44 μg/mL. In vivo antibacterial activities tests demonstrated that the controlling effect of compounds 5u (81.9%) against rice bacterial leaf blight were better than that of bismerthiazol (50.8%) and thiodiazole-copper (44.7%). Our results also demonstrated that com-pounds 5h, 5u and 5v have a better antifungal and antibacterial activity, with good characteristics of broad spectrum. The structure−activity relationship (SAR) was also discussed.