Plant Virus Oriented Design,Synthesis And Bioactivity Of Novel 1,2,3-Thiadiazole Derivatives

Plant virus disease,which is widespread and cause serious damage in agricultural production for a long time,is the second major plant disease after fungus.There are nearly 1000 types of plant virus diseases caused by more than 700 kinds of viruses.It was reported that the loss caused by plant virus is up to U.S.$100 million worldwide.Therefore,to prevent and control plant virus disease has become urgent for plant protection workers.The transmission routes of plant virus mainly include mediators and non-mediators,and the insect mediator is the most serious way.There are 378 species of insect vectors in the world,which transmit 275 kinds of plant viruses.Among them,205 plant viruses were transmitted by 193 species of aphid vectors.Therefore,the aphids are thought to be the first vector insect.In view of this,the control strategy of plant virus disease is based on two points.On the one hand,the effective anti-virus agents for treating the infected host plants need to be studied;on the other hand,the strategy of "preventing disease via control insect vectors" is a good choice to stop the occurrence of plant virus disease.Anyway,to discover a compound with double functions of control insect vector and anti-virus will be an ideal way.In order to control the plant virus disease,two strategies,including controlling the vector aphids and discovering novel antiviral agents,were applied in present paper.Thus,the aphid alarm pheromone(E)-?-farnesene(EBF)and the commercial plant activator tiadinil containing 1,2,3-thiadiazole were chosen as the lead compounds for further modification with the aim to find new active compounds with multiple efficiency.The discoveries and results were mainly described as follows:(1)In order to discover novel compounds with high anti-virus and repellent activity,a total of 52 novel EBF analogues containing 1,2,3-thiadiazole were designed and synthesized with the lead of EBF.Their structures were confirmed by IR,1H NMR,13C NMR,and HRMS(ESI).The stability of representative compounds was studied by HPLC and NMR techniques.The results showed the stability of the title compounds is much better than that of the lead EBF.(2)In order to obtain compounds with high activities,the EBF analogues were evaluated for their repellent activity,aphicidal activity and anti-virus activity.The results showed that the compounds have both repellent and insecticidal activity against Myzus persicae,among which the compounds I-A containing ester group exhibited good repellent activity while compounds I-D containing amide with heterocyclic group showed good insecticidal activity.The anti-TMV activities of compounds I-A01,?-B01,?-B02 and ?-C10 were more prominent on four modes(inactivation,cyrative,protection and induced activity),which were comparable to the control ribavirin.Considering all aspects of activity,both compounds ?-A01 and ?-C10 could be candidate compounds for further study.(3)In order to study the mechanism of EBF analogues,the binding test between EBF analogues and ApisOBPs or TMV CP were carried out.The results showed as follows:? Target compounds?-A01??-A02??-A03??-C01??-C11??-D03??-D11??-D12,showed good affinity to ApisOBP3,ApisOBP7 and ApisOBP9,which has the similar binding characteristics and higher binding activity to the lead EBF.? The above compounds with high affinity to ApisOBPs exhibited outstanding repellent activity against Myzus persicae,the repellent rates were above 60%.While the compounds with low affinity to ApisOBPs showed bad repellent activity against Myzus persicae as usual.As a result,ApisOBPs may be the target of EBF analogues.? Molecular docking results showed that the interaction between EBF analogues and MvicOBP3 amino acid residues are mainly hydrophobic interaction.Target compounds with different hydrophobicity due to different substituents showed vary binding affinity to MvicOBP3.? Target compounds I-A01,I-B01,I-B02 and I-C10 with high anti-TMV activity are also have the strong affinity to TMV CP.Therefore,TMV CP may be their target.(4)In order to prepared target compounds,two series of intermediates P and H(totally 38 EBF analogs)were prepared,of which 32 compounds were first reported in this thesis.The optimum condition of synthetic intermediate P was explored as follows:leq K2CO3 as acid-binding agent,0.1 eq KI as catalyst,acetonitrile as solvent,adding 3eq DDAO,geranyl chloride reacted with aniline at 25?for 4h to obtain P.The preparation condition of intermediates H:using NaBH3CN as a mild reducing agent,and anhydrous ZnCl2 as a catalyst,citral with heterocyclic amine react in methanol for 0.5?2h to get H.Interestingly,repellent activity tests showed all the intermediates exhibited some extent repellent activity except P-15 at the dose of 5 ?g,and especially,compounds P-13,H-09 and H-12 exhibited good activity with repellent rate of 62.0%,62.5%and 64.6%,respectively.(5)In order to discovery compounds with high anti-virus activity,two series of ? and ? totally 51 novel compounds were designed based on tiadinil as the lead compound by replacing the amide bond in tiadinil with hydrazone bond,and optimizing the substituents on the benzene ring and 1,2,3-thiadiazole ring step by step.Their structures were confirmed by 1H NMR,IR,EA or HRMS,and the single crystal structures of the targets ?-17 and ?-08 was obtained by single crystal X-ray diffraction.The target compounds were evaluated for their anti-TMV activity in vivo and fungicidal activity in vitro.The target compounds showed a certain degree of curative activity against TMV at the concentration of 500 ?g/mL,especially the activities of compounds ?-01,?-02,?-21 and ?-24 were higher than those of the control agents ribavirin and tiadinil,and close to ningnanmycin.The target compounds generally showed good fungicidal activity,especially ?-04 and ?-24 for Valsa mali and Sclerotinia sclerotiorum which EC50 values were respective of 1.8?g/mL and 1.5?g/mL,3.9 ?g/mL and 3.1?g/mL.Furthermore,anti-TMV activities of those two compounds were all above 40%.Therefore,III-04 and III-24 could be candidate drug molecules for further study.Structure-activity relationship analysis indicates that:The position of the substituent R on the benzene ring played an important role in fungicidal activities,the compounds containing halogen at para position exhibit the best activity;The longer of carbon chain of the alkyl on the 4-position of 1,2,3-thiadiazole,the higher the fungicidal activity is.In conclusion,141 compounds(135 are novel)were designed and synthesized.Their structures were identified through 1H NMR,IR,HRMS or elemental analysis.Some target compounds showed favorable bioactivities,especially,four compounds ?-A01??-C10??-04 and ?-24 were found to be candidate with higher activity.The molecular mechanism of the compounds was preliminary studied by protein binding assay,and the rules of structure-activity relationship were systematically explored.The above results provide a good theoretical basis and guidance for the further development of new agent both with antiviral and repellent activity.