Design and Synthesis of Novel Oxathiapiprolin Derivatives as Oxysterol Binding Protein Inhibitors and Their Application in Phytopathogenic Oomycetes

Oomycetes, particularly those fromthe genus Phytophthora, are significant threats toglobal food securityand natural ecosystems.Oxathiapiprolin (OXA) is an effective oomycete fungicide that targetsan oxysterol binding protein (OSBP), while the binding mechanism ofOXA is still unclear, which limits the pesticide design, induced bythe low sequence identity of Phytophthora and templatemodels. Herein, we generated the OSBP model of the well-reported Phytophthora capsici using AlphaFold 2 and studied the bindingmechanism of OXA. Based on it, a series of OXA analogues were designed.Then, compound 2l, the most potent candidate, was successfullydesigned and synthesized, showing a control efficiency comparableto that of OXA. Moreover, field trial experiments showed that 2l exhibited nearly the same activity (72.4%) as OXA againstcucumber downy mildew at 25 g/ha. The present work indicated that 2l could be used as a leading compound for the discovery ofnew OSBP fungicides.

Automated summary

Oomycetes, particularly Phytophthora species, pose significant threats to global food security and natural ecosystems. This study used AlphaFold 2 to generate the OSBP model of Phytophthora capsici and investigated the binding mechanism of the fungicide OXA. Based on this, a series of OXA analogues were designed, and compound 2l showed comparable control efficiency to OXA. The findings suggest that 2l could serve as a lead compound for the development of new OSBP fungicides.