Design, Synthesis and Biological Activities of Novel meta-Diamide Compounds Containing 1,2,4-Oxadiazole Group

To discover new bisamide compounds with insecticidal and fungicidal activities, 19 novel cyproflanilide derivatives containing 1,2,4-oxadiazole group were designed and synthesized according to the principle of biologically active factor splicing. Preliminary biological assay data indicated that the majority of target compounds demonstrated significant insecticidal activity against Lepidopteran pests. Meanwhile, compounds 5p and 5q showed 97.22 and 100% lethality against Tetranychus cinnabarinus at 400 mg L^-1, which were better than cyproflanilide (41.11% at 400 mg L^-1). In addition, it is exciting that we have achieved our initial goals as some of the target compounds exhibited both insecticidal and fungicidal activities. For instance, compounds 5b and 5c showed 59.26 and 74.07% fungicidal activities against Cucumber downy mildew at 400 mg L^-1, as well as 100% insecticidal activity against Plutella xylostella and armyworm at 100 mg L^-1. Compound 5h showed 100% insecticidal activity against armyworm at 10 mg L^-1, and also displayed 66.67% fungicidal activity against Cucumber downy mildew at 400 mg L^-1. The inhibition rate of compounds 5l and 5s against Cucumber downy mildew reached 88.89 and 96.30% at 400 mg L^-1. This work showed the effectively fungicidal application of 1,2,4-oxadiazole group in bisamide compounds and provides insights for optimal structural design.

Keywords:
1,2,4-oxadiazole group; insecticidal activity; fungicidal activity; meta-diamide compounds; structure-activity relationship