Synthesis、Insecticidal And Fungicidal Activities Of 3-β Steroid Acylated Derivatives

Agricultural fungi and insects are important factors on plant growth and food production.Without controling,or inopportune controlling methods,crops yield,will be decrease by 30-100%.Chemicals pesticides are still the most widespread methods of control in the world in present.Though they relieve the threat of fungi and insects to a certain extent,also cause serious problems such as pesticide residue,environmental pollution,enemies death and so on.Therefore,people still search for new measures to replace chemical pesticide.As a safe,nonpollution and degradable new pesticide,botanical pesticides are widely concerned.Periplocosides are steroidal compounds isolated from Periploca sepium Bunge,which showed insecticidal and antifungicidal activity.In this study,a series of 3-βsteroid acylated derivatives were synthesized from dehydroepiandrosterone.The insecticidal activities against the 3rd instar larvae of Mythimna separata Walker and Trialeurodes vaporariorum Westwood were determined;the fungicidal activities were tested against Phyalospora piricola nose,Fusarium oxysporum f.sp.hiveum（E.F.Smith）wollen,Botrytis cinerea Pers,Phytophthora capsici Leonian and Valsa Mali Miyabe et Yamada,The main results are showed as follows:1.26 new 3-βsteroid acylated derivatives were synthesised,the structures of compounds were confirmed by ¹H NMR and ¹³C NMR,compared with the previous study,site 3 of DHEA was first derived,and optimized the synthesis method,which successfully improved the yield successfully and shortened the reaction time.2.The insecticidal activity of target compounds was tested against T.Westwood by foliar spray method at 1 mg/m L.The results showed that the compounds with substituents of 2-fluorobenzoyl,2-chlorobenzoyl,3-bromobenzoyl and 4-fluorobenzoyl had better activity.especially compound 5b(LC₅₀:0.27 mg/m L)with substituents of 2-chlorobenzoyl which was 5 times higher than that of P.sepium extract(LC₅₀:1.30 mg/m L).The results of field experiment showed that the control effect of compound 5b was 79.56%at 500μg/m L concentration,was similar to the concentration of Thiamethoxam at 125μg/m L.3.The insecticidal activity of target compounds against 3^rd instar larvae of M.separata was assessed by leaf dip method at 5 mg/m L.The results showed that compounds with substituents of 2-chlorobenzoyl,3-fluorobenzoyl,3,5-dimethylbenzoyl and2,4,6-trimethylbenzoyl had better activity,especially compound 5b(LC₅₀:0.94 mg/m L)with substituents of 2-chlorobenzoyl,which was 10 times higher than that of P.sepium extract(LC₅₀:9.16 mg/m L).4.The antifungicidal activity of target compounds against five fungi by plate method at100μg/m L was tested.The results showed that compounds with substituents of2-methylbenzoyl and 4-bromobenzoyl had better activity against P.Leonian,especially compound 5e(EC₅₀:0.051 mg/m L)with substituents of 2-methylbenzoyl,which was 10times higher than that of P.sepium extract(EC₅₀:0.52 mg/m L),and close to that of Coumoxystrobin(EC₅₀:0.049 mg/m L).5.Structure-activity relationship shows that 3-βacylated steroids derivatives have strong insecticidal activity with substituent of chlorobenzoyl or bromobenzoyl,and have dramatical fungicidal activity with substituent of methylbenzoyl or oxomethylbenzoyl.6.Symptom observation showed that synthetic steroids and periplocosides had similar toxic symptoms.Enzyme activity results showed that both of them had similar activation effect on Trypsin in midgut of M.separata.Therefore,it is inferred that they had the similar mechanism of action.Thus it is of substantial value to study application of 3-βsteroid acylated derivatives in agriculture,which will also offer evidences for further exploration.