Design,Synthesis And Antifungal Activity Of Dihydrocumic Acid Derivatives

Natural products are important source for the invention of new pesticides.Turpentine,an important terpene natural product,has attracted the attention of scholars all over the world.In this paper,dihydrocuminic acid derived fromβ-pinene was used as the leading compound to design and synthesize two series of terpene-based derivatives.The antifungal activity of the target compounds against 7common pathogenic fungi.The effect of highly active compounds on relevant physiological and biochemical response of fungi was evaluated.Two soluble concentrate（SL）were prepared,and their performance was investigated.This work provided the theoretical guidance and technical support for the practical application of terpene-based antifungal compounds.The conclusions obtained from the study were as following:（1）The dihydrocuminic acid derived fromβ-pinene was used as the leading compound to synthesize two series of derivatives including 19 amide and 28thiadiazole amide through the cyclization and amidation reactions.Among them,45compounds are completely new that have not been reported.Their structures were characterized by¹H NMR,¹³C NMR and HRMS.（2）The antifungal activity of target compounds against Rhizoctonia solani,Valsa mali,Sclerotinia sclerotiorum,Botrytis cinerea,Gaeumanomyces graminis,Fusarium oxysporum and Fusarium graminearum were determined by the mycelial growth rate method.It was showed that the N-methylamide compounds 5o and 5p and sulfonamide compound 6aa exhibited better antifungal activity than other compounds.The EC₅₀values of compounds 5o and 5p against Rhizoctonia solani were 1.139μg/m L and 1.811μg/m L,repectively,and the EC₅₀value of compound 6aa against Valsa mali was 3.785μg/m L.The control effect of compounds 5o and 5p on rice plants was tested.The protective effect at a concentration of 200μg/m L（5o:73.41%,5p:77.33%）was better than that of the positive control Jinggangmycin（66.14%）.Their therapeutic effect at a concentration of 200μg/m L were equivalent,both were82.35%.In additional,the antifungal activity in vitro of compound 6aa on apple braches was investigated.The therapeutic effeft of compound 6aa at 500μg/m L（58.78%）was comparable to that of the positive control carbendazim at 100μg/m L（53.80%）.The effects of compounds 5o and 5p on the hyphae morphology,cell membrane permeability,cell membrane integrity and cell wall chitin content of Rhizoctonia solani was studied.The results showed that compounds 5o and 5p increased the content of chitin in the cell wall.The same experimental method was used to study the effect of the componud 6aa on the hyphae morphology,extracellular pectinase activity,cell membrane permeability,cell membrane integrity and cell wall chitin content of Valsa mali.The results showed that compound 6aa disrupted cell membrane integrity,decreased cell wall chitin content and extracellular pectinase activity.（3）Two kinds of soluble concentrate that meet the national quality and technical standards for pesticide preparations were prepared.The formulas were as follows:Compound 5o,20%.Ethanol,12.5%.OP-10,20%.Water make-up to 100%.Compound 5p,20%.Ethanol,10%.OP-10,25%.Water make-up to 100%.The analytical method for active ingredient compounds 5o and 5p was established by HPLC.The results showed that the linear relationship coefficients between the peak area and the concentration of the agent were 0.9995 and 0.9993,the coefficients of variation were 1.97%and 1.47%,and the average recoveries were 99.97%and100.02%.The accuracy and precision of the method were good.Finally,the antifungal activity of the two soluble concentrate against Rhizoctonia solani was determined by the mycelial growth rate method.The EC₅₀values of 20%5o（SL）and 20%5p（SL）against Rhizoctonia solani were 0.786μg/m L and 0.946μg/m L,which were better than that of compounds 5o（1.296μg/m L）and 5p（1.944μg/m L）.The control effect of20%5o（SL）and 20%5p（SL）on rice plants was tested.The protective effect at a concentration of 100μg/m L（20%5o（SL）:76.96%,20%5p（SL）:77.89%）were equivalent that at a concentration of 200μg/m L of the compounds 5o and 5p（o:73.41%,5p:77.33%）.Their therapeutic effect of 20%5o（SL）（81.20%）and 20%5p（SL）（81.20%）at 100μg/m L were comparable to those of compounds 5o（78.03%）and 5p（81.53%）at 200μg/m L.In summary,47 terpene-based derivatives from the natural product turpentine were designed and synthesized,and their antifungal activity was determined.compounds 5o,5p and 6aa with better activity were screened out.Two soluble concentrate that meet the national quality and technical standards were prepared.It provided a theoretical basis for the design,synthesis and application of terpene-based compounds with high antifungal activity,and also offered technical support for the high-value-added utilization of the natural forestry resource turpentine.