Design, synthesis, and fungicidal activities of novel piperazine thiazole derivatives containing oxime ether or oxime ester moieties

Abstract BACKGROUND To study the effect of changing the piperidine ring of oxathiapiprolin on the fungicidal activity, we designed and synthesized novel piperazine thiazole derivatives containing oxime ether or oxime ester moieties, and studied their fungicidal activities against Phytophthora capsici in vitro . RESULTS These derivatives showed moderate to good fungicidal activities against Phytophthora capsici , two oxime ether derivatives showed higher fungicidal activity in vitro than dimethomorph (EC 50 = 0.1331 μg mL −1 ) and comparable to oxathiapiprolin (EC 50 = 0.0042 μg mL −1 ). Oxime ester derivatives showed significantly reduced activities compared with oxime ether derivatives. Most of these derivatives showed broad‐spectrum fungicidal activity against the other eight kinds of fungi. Moreover, four derivatives exhibited good antifungal activities in vivo against Phytophthora capsici , Pseudoperonospora cubensis , and Phytophthora infestans. The hyphae morphology study showed that compound 10d might cause mycelial abnormalities of Phytophthora capsici . CONCLUSION The activity of 10b against Phytophthora infestans was better than that of mandipropamid, and compound 10d exhibited higher fungicidal activities against Pseudoperonospora cubensis and Phytophthora infestans than mandipropamid. These two derivatives emerged as promising candidates for antifungal drugs. © 2023 Society of Chemical Industry.