| Pests are one of the main reasons for the reduction of crop yield and quality,which have a bad impact on production efficiency and healthy development of agriculture.Insecticides are still the main method of treating pests.However,as insecticides have been used for a long time,problems such as insecticides resistance and environmental pollution have become more and more serious.Therefore,it is necessary to develop new low-toxicity,high-efficiency and environmentally friendly pesticides.Natural products play a key role in the research and development of insecticides,occupying more than 70%of the market share,and popular insecticides such as neonicotinoids,pyrethroids,and abamectins are all derived from natural products.Utilizing natural products as lead compounds for structural modification to improve their insecticidal activity is an important approach for the research and development of insecticides.The previous research of our research group showed that pyrrole-2-carboxylic acid ester compounds,the secondary metabolites of endophytic bacteria,have a high inhibitory effect on aphids.Its core structure,4-methyl-1H-pyrrole-2-carboxylic acid,shows more excellent aphidicidal activity.In this thesis,4-methyl-1H-pyrrole-2-carboxylic acid was used as the lead compound for structural modification and the structure-activity relationship was studied in order to find compounds with better insecticidal activity.The research content is mainly divided into the following two aspects:(1)Design and synthesis of derivatives:We used 4-methyl-1H-pyrrole-2-carboxylic acid as the lead compound to investigate the effects of changes in the substituents on the pyrrole ring,esterification and amination of the 2-position carboxylic acid on the insecticidal activity.Design and synthesis of a series of pyrrole-2-carboxylic acid derivatives,and the structures were identified using structural identification techniques such as 1H NMR,13C NMR,and mass spectrometry.(2)Test of insecticidal activity:Firstly,we used the lead compound 4-methyl-1H-pyrrole-2-carboxylic acid(A0)as a control to test the aphidicidal biological activity of A1-A44 at 100 mg/L.The inhibitory effect of 17 compounds among on aphids was better than that of the effect of A0.Among them,the activity of A30(93.52%)was the most prominent.Its inhibitory effect on aphids was more than 3 times that of the control group(27.69%),followed by A40(84.93%)and A43(73.68%),A4(59.08%).With the lead compound A0 as the control and imidacloprid as the positive control drug,the four compounds were tested for their aphidicidal virulence.The test results showed that these four compounds have significant lethal effects on aphids.The LC50 of A4,A30,A40 to aphids was 0.14,0.28,and 0.30 mg/L,respectively,better than the lead compound A0(LC50=0.8 mg/L),but there was still a certain gap compared to the positive control drug imidacloprid(LC50=0.05 mg/L).According to the results of insecticidal experiments,combined with the structure of the compound,we can initially obtain the following structure-activity relationships:① When the five-membered aromatic heterocycle is the pyrrole ring,the activity is optimal,and the activity of the furan ring or the thiophene ring is significantly reduced;②The carboxyl group is necessary for activity at the 2-position,and it is inactive at the 3-position;③ The activity is strongest when the other three positions on the pyrrole ring are unsubstituted;④ The carboxyl group of the pyrrole-2-carboxylic acid is esterified,activity improved. |
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