Synthesis,Antifungal Activity And QSAR Studies Of α-methylene-γ-butyrolactones Derivatives

Natural products withα-methylene-γ-butyrolactone structure were widely distributed in nature,which ownedγ-butyrolactone and exocyclic methylene structure had the unique mechanism.At present,its main research focuses on medicine,and there is little research on the anti-fungal properties of pesticides.At the same time,due to the different action way this lead compound has the potential to becoming new agrochemicals.Therefore,in this study,a series of derivatives were synthesized withα-methylene-γ-butyrolactone as the lead compound,and their antifungal activity and cytotoxic activity were tested,which provided a theoretical foundation for the development of new pesticide.Meanwhile,the qualitative and quantitative structure-activity relationship of the synthesized compounds was analyzed,and the structure information which contributed most to the molecule activity was obtained by the 3D-QSAR model,which could provide the suggestion and theoretical guidance for the follow-up structural modification.The main results of this dissertation are as followed.1.With theα-methylene-γ-butyrolactone structure as the lead compound,136derivatives were synthesized by Barbier reaction,Heck reaction,Perkin condensation reaction,which modified inγ-position,conbined with benzofuranone structure,and modified toδ-lactone.All compounds were confirmed by ¹HNMR,¹³CNMR and HR-MS（ESI）,and 92 compounds have not been reported.The reaction conditions of all the compounds are relatively mild,and the yield is good.From the NMR spectra of the compounds,it was confirmed that theγ-monobasicα-methylene-γ-butyrolactone derivatives and theα-methylene-γ-butyrolactone/δ-valerolactone derivatives were both E type.Theα-methylene benzobutyrolactone derivatives were the E/Z isomer mixture with a lower proportion of the mixture（5:1）.2.The preliminary screening results of in vitro antifungal activity showed that all the compounds have good inhibitory activity against Botrytis cinerea,Colletrichum lagenarium and Gaeumannomyces gramini.Screening results showed that compounds6c-5,3-10,3-27 and 2-10 have the higher EC50 against all three fungi.The in vivo antifungal activity showed the compounds 6a-3,6c-3,6c-5,3-4,3-7,3-9,3-27,3-34,3-36,3-42,3-43 and 2-10 had good efficacy（>65%）against B.cinerea,and compounds 6c-5,3-4,3-9 and 3-27 had better efficacy（>60%）against C.lagenarium.Compounds 6a-3,6a-5,6c-3,6c-5,3-10,3-27 and 2-10 were more effective against P.infestans（>70%）.The antifungal activity against Blumeria graminis showed that the protective efficacy of compounds 6c-5,3-10,3-27 and 2-10 were equal to triadimefon（150 mg/L）.However,the protective effects of compound 6c-3,6c-5,3-10,3-42 and2-10 against G.gramini were lower than the fungicide triadimefon（150 mg/L）but equal to carabrone（500 mg/L）.In addition,the selected 80 representative compounds showed weaker cytotoxic activity.3.The results of qualitative structure-activity relationship（SARs）show that the electron-withdrawing/electron-donating properties and steric hindrance of the compounds substituent were the key factors affecting the antifungal activity.Taking antifungal activity against B.cinerea as an example,compounds containing electron-withdrawing substituents are more active than electron-donating;para-substituents are more active than ortho-and meta-substituents,and meta-substituted compounds are more active than ortho substituents;substituents containing fungicide property would have higher antifungal activity.In addition,the in vitro and in vivo antifungal activity showed the second kind derivatives were higher than the other two,meanwhile,the antifungal activity ofα-methylene-γ-butyrolactone derivatives was higher thanδ-valerolactone derivatives.4.Quantitative Structure-Activity Relationship（QSAR）shows that the maximum atomic orbital electron number,the occupied electron energy level or number of atoms,the minimum electrostatic charge of C atom,and the maximum electrostatic charge of O atom are the four important descriptors which affecting theα-methylene-γ-butyrolactone derivative antifungal activity.Among them,the first two quantitative descriptors are used to describe the nucleophilic ability of a molecule,the ability to attack by a nucleophilic group,the charge-dispensing ability and polarity of a valence charge,which is aligned with the mechanism action ofα-methylene-γ-butyrolactone.5.Based on the second kind ofα-methylene benzobutyrolactone structure and the three built QSAR model,electron-withdrawing halogen atoms were introduced to its benzo and C=C structure to designed and synthesized highly antifungal activity compound T1-6.The results showed that compounds T4 and T5 had higher in vitro and in vivo antifungal activity,which the protective efficacy against B.graminis and G.gramini were equal to triadimefon（150 mg/L）,meanwhile,the results of the field efficacy test showed that the control efficacy of T4（1000 mg/L）against B.cinerea on tomato friuts was 65.29%,which indicating that compound T4 had the value of further development and utilization.At the same time,the difference between the predicted values of these six compounds against B.cinerea was smaller than that of QSAR model established in chapter 3,which verified the best QSAR model obtained in chapter 3 has higher applicability.In conclusion,the derivatives synthesized withα-methylene-γ-butyrolactone structure have certain antifungal activity and low cytotoxic activity.Among them,α-methylene benzobutyrolactone structure would be used as an ultrahigh lead compound to guide the synthesis of highly active compounds in the next step.Meanwhile,the key substitution sites which affect the antifungal activity ofα-methylene-γ-butyrolactone compounds have been confirmed by the qualitative structure-activity relationship and the best QSAR model,which also provides theoretval guidance for the next synthesis of subsequent compounds.In addition,the design and synthesis of compound T4 has the potential to develop and utilize as a fungicide.