Inhibition of Tobacco Bacterial Wilt with Sulfone Derivatives Containing an 1,3,4-Oxadiazole Moiety

Abstract

A series of new sulfone compounds containing the 1,3,4-oxadiazole moiety were designed and synthesized. Their structures were identified by ¹H and ¹³C nuclear magnetic resonance and elemental analyses. Antibacterial bioassays indicated that most compounds exhibited promising in vitro antibacterial bioactivities against tobacco bacterial wilt at 200 μg/mL. The relationship between structure and antibacterial activity was also discussed. Among the title compounds, <b>5′c</b>, <b>5′h</b>, <b>5′i</b>, and <b>5′j</b> could inhibit mycelia growth of Ralstonia solanacearum in vitro by approximately 50% (EC₅₀) at 39.8, 60.3, 47.9, and 32.1 μg/mL, respectively. Among them, compound <b>5′j</b> was identified as the most promising candidate due to its stronger effect than that of Kocide 3000 [Cu­(OH)₂] within the same concentration range. Field trials demonstrated that the control effect of compound <b>5′j</b> against tobacco bacterial wilt was better than that of the commercial bactericide Saisentong. For the first time, the present work demonstrated that sulfone derivatives containing 1,3,4-oxadiazole can be used to develop potential bactericides for plants