Systemic Aquired Resistance Based Pesticide Lead Derivation And Its Biological Activity

Plant activators, a new type of agrochemicals, have attracted more and moreattentions because of their environment-friendly characteristics with lower applicationdosage, broad-spectrum and long-lasting highly systemic aquired resistance(SAR).Acibenzolar-S-methyl(BTH) and tiadinial(TDL) are typically successful plant elicitors.Both of them are1,2,3-thiadizole derivatives.1,2,3-thiadizole is the core scaffold ofthese compounds which induce the formation of SAR of plant.In search for new leading compounds with both SAR and insecticidal activity orfungicidal activity, four series of novel1,2,3-thiadiazole derivatives (total106newcompounds) were designed and synthesized according to the principles of electronisosteric and combination of bioactive sub-structures. All the structures of the targetcompounds were characterized by IR, NMR, and Elemental analysis or HRMS. Onetypical compound in each type was selected to crystal culturation and determination byX-ray crystal diffraction for structures confirmation. The biological activities of thesynthesized compounds including SAR, insecticidal activity and fungicidal activitywere also systematically evaluated. The results are summarized as bellow:In the first part, twenty-nine N-(substituted)(1,2,3-thiadiazol)alkyl sulfilimine orsulfoximine derivatives were designed and synthesized from1,2,3-thiadiazolesubstituted alkyl halide as starting material. The preliminary bioassay results indicatedthat, although this series of title compounds did not exibit good insecticidal activityagainst Lepidopteta pests such as Mythimna separate, but most compounds exhibitedgood insecticidal activity against sap-feeding pests such as Myzus persicae. CompoundIB-1exhibited good insecticidal against Myzus persicae with the mortality of77.81%at100μg/mL, which also have good induction against tobacco mosaic virus(TMV) with41.09%of inhibition at50μg/mL. This provided the basis for novel insecticidedevelopment with SAR.In the second part, eighteen new N-t-butyl-N’-acyl-5-methyl-1,2,3-thiadiazole-4-carbohydrazides were designed and synthesized using5-methyl-1,2,3-thiadiazole-4-carbonyl chloride as a raw material. The preliminary bioassay results indicated that,although, most of this series of compounds synthesized lost their insecticidal activity,some compounds kept good induction activity against TMV. Compound II-17presentedgood inhibition activity against TMV with both curative effect and induction effect. In the third part, thirty novel2-(4-methyl-1,2,3-thiadiazol-5-yl)-4-(trifluoromethyl)-4,5-dihydrothiazol-4-ol esters were designed and synthesized viasulfuration, cyclization, esterification using4-methyl-1,2,3-thiadiazole-5-carboxamideas a starting material. The preliminary bioassay results indicated that, the targetcompounds had good antivirus activity against TMV, most compounds also had goodfungicidal activity at50μg/mL against Botrytis cinerea. And some typical compoundhad certain extent of insecticidal activity against Mythimna separate.In the fourth part, twenty-nine novel2-(5-methyl-1,2,3-thiadiazol-4-yl)-4-(trifluoromethyl)-4,5-dihydrothiazol-4-ol esters were designed and synthesized from5-methyl-1,2,3-thiadiazole-4-carboxamide as a starting reactant by sulfuration,cyclization, esterification. The preliminary bioassay results indicated that, thesecompounds not only had good induction activity but also exhibited excellent fungicidalactivity with the EC50of2.0-29.0. μg/mL; especially, compound IV-23and IV-27possessed broad-spectrum fungcidal activities against nine fungi tested with theinhibition more than70%at50μg/mL. Most compounds had insecticidal activity in acertain degree; especially, compounds IV-5、IV-13、IV-22、IV-23exhibited excelletinsecticidal activity against Mythimna separate, with the mortality of100%at200μg/mL.The results of these studies showed that, the1,2,3-thiadiazole is a very good activiesubstructure with systemic acquired resistance, it’s derivatives had various biologicalactivities such as fungicide and insecticide too. These results were benefit to novelpesticide development with both systemic acquired resistance and insecticidal orfungicidal activity in theoretical and practical values.