Structure Modification And Bioactivity Evaluation Of Natural Product Daphneolone Analogues

As one of the most important means of production in agricultural development,agrochemicals play an irreplaceable role in food security.However,the use of traditional agrochemicals brings many problems such as environmental pollution,drug resistance,etc.Therefore,it is necessary to develop environmental friendly 'green' agrochemicals with high efficiency,low toxicity to upgrade agrochemical products.Optimizing the structure of the plant natural products to increase the bioactivities is one of the important means in new pesticide discovery for example,by this way,people found pyrethroid insecticides,carbmade insecticides,etc.Stellera chamaejasme L.,used in Chinese traditional medicine,attracted much research attention because of its' various types of biological activities.?E?-1,5-diphenyl-2-penten-l-one?A?was isolated from the root of Stellera chamaejasme L.This natural product is similar in structure to daphneolone.Laboratory bioassay showed that this compound had good aphicidal activity and fungicidal activity.In order to find plant natural products analogues with excellent pesticidal activity and to contine the exploration of the structure optimizing method of plant natural products.In present work,using?E?-1,5-diphenyl-2-penten-l-one?A?as lead compound,four series,one hundred and five new analogues were designed and synthesized by introducing heterocycles such as morpholine and piperazine moiety to replace benzene ring of lead compound,or changing the middle chain bridge.All structures of the synthesized compounds were confirmed by IR,¹H NMR(¹³C NMR),and HRMS?ESI?or elemental analysis.The discoveries and achievement of this work are discribed as follows:?1?Using?E?-1,5-diphenyl-2-penten-l-one?A?as lead compound,series I compounds?37 compounds?were designed by introducing morpholine moiety to replace 1-phenyl and replacing 5-phenyl with substituted phenyl or thiophene ring.The two isomers of I-B compounds were separated and identified by NOESY technique and chemical method.The bioassay results indicated that,in general,at the concentration of 50 mg/L,I-A compounds exhibited lower fungicidal activities against tested fungi than 1-B compounds.In particular,compound IB-9a displayed the best activity with the inhibition rate of 91%and EC₅₀ of 8.38 mg/L against Valsa mali,superior to lead compound A.IB-Ib displayed good aphicidal activity against soybean aphid with 100%fatality rate at the concentration of 500 mg/L.In addition,Preliminary structure activity relationship?SAR?analysis indicated that,between two isomers of target compounds,the antifungal activities of the isomer with cis-2,6-dimethylmorpholine were better than the trans-isomer.?2?Using?E?-1,5-diphenyl-2-penten-l-one?A?as lead compound,series ? compounds?21 novel compounds?were designed by introducing piperazine moiety to replace 1-phenyl and replacing 5-phenyl with substituted phenyl or thiophene ring.The bioassay results indicated that most of these analogues exhibited moderate fungicidal activities and moderate to good insecticidal activities.Amongst them,compound ?-10 showed good activity against P.aphanidermatum with EC₅₀ of 20.9 mg/L,superior to lead compound A.The most potent ?-03,?-08 and 11-09 keep a mortality of 100%against larva of mosquito at the concentration of 1 mg/L.What's more,II compounds also showed moderate to good insecticidal activities against cotton bollworm?Helicoverpa armigera?,corn borer?Ostrinia nubilalis?and armyworm?Mythimna separate?at the concentration of 600 mg/L.Initial SAR analysis showed that,a methyl group can influence the biological activities significantly,the compounds with N-unsubstituted piperazine showed much better antifungal activities and larvicidal activity against mosquito than the compounds with N'-methylated piperazine.In addition,the larvicidal activity against mosquito had sharply declined when the substituent on benzene ring was changed from 4-position to 2 or 3-position.?3?Using?E?-1,5-diphenyl-2-penten-l-one?A?as lead compound,series ? compounds?32 compounds?were designed by introducing piperazine moiety and other different heterocycles or shorten the middle bridged chain.The single crystal structure of compound ?B-05 was analysized.The bioassay results indicated that the inhibition rates of ?A-04,?A-05,?A-09,?A-12 against Sclerotinia sclerotiorum were 96.7%,94.7%,85.9%,88.3%,respectively,much higher than the lead A,the EC₅₀ of ?A-12 against is 5.31 mg/L,superior to lead compound A?21.33 mg/L?.Compound IIIA-05,IIIA-09 and IIIB-14 keep a mortality of 100%against larva of mosquito at the concentration of 2 mg/L.Compounds ?A-09,?A-10,?B-11,?B-14 had mortality of 100%at the concentration of 600 mg/L,which is worthy to be further studied.Initial SAR analysis showed that,the fungicidal activities of III-A compounds are preferably when the Y ring is thiophene,furan and 1-methyl-3-ethyl-4-nitro pyrazole.With same aromatic ring,as a whole,the fungicidal activity will decline when the middle chain bridge were shorten from C5 to C3.?4?Using?E?-1,5-diphenyl-2-penten-l-one?A?as initial lead compound,high fungicidal active compound PMDD-?-02 as secondary lead compound,series IV compounds?15 novel compounds?were designed by modifying the aromatic ring or fine tuning the middle chain bridge.The bioassay results indicated that ? compounds showed good fungicidal activities against tested fungi,especially against Rhizoctonia solani.Amongst them,the EC₅₀ of ?-06 against Rhizoctonia solani is 2.26 mg/L,superior to lead compound A and secondary lead compound PMDD-?-02.?-06 also showed wider fungicidal spectrum than PMDD-II-02.Preliminary structureactivity relationship analysis indicated that the carbanyl group on the middle chain bridge paly an important role on the fungicidal activities,the fungicidal activities had an obvious decline when carbonyl group was protected with ethylene glycol.In summary,with active natural product?E?-1,5-diphenyl-2-penten-l-one?A?as lead compounds,four series of 105 compounds?103 novel compounds?were designed by the method of linking of active moiety,analogue synthesis and bioisosteric replacement.Their structure were characterized by ¹H NMR,IR,HRMS,EA,NOESY and X-ray diffraction technique.Their bioactivity were evaluated.The results indicated that,IB-9a had good fungicidal acticity against Valsa mali,?A-12 had good fungicidal acticity against Sclerotinia sclerotiorum,?-06 had good fungicidal acticity against Rhizoctonia solani.Amongst them,?-06 showed higher fungicidal activity and wider fungicidal spectrum than secondary lead compound PMDD-?-02.What's more,some ?-B,? and ?compounds showed good insecticidal activity.Amongst them,IB-1b had good aphicidal activity,?-03,?-08 and ?-09 had good larvicidal activity against mosquito,?A-09,?B-14 had good activity against both larva of mosquito and armyworm,which is worthy to be further studied.By the optimization of plant natural product?E?-1,5-diphenyl-2-penten-l-one?A?,this thesis explored the ways of structure optimizing of A on the basis of our previous work.Not only some 1,5-diphenyl-2-penten-l-one analogues with higher bioactivity were found,but also the SAR was analysized,which is worthy for the futher optimizing of lead A.The above results proved the design idea and will be useful for the study on new pesticides discovery from plant natural products.