Synthesis And Fungicidal Activity Of Tetronic Acid Derivatives Incorporating Substituted Phenylhydrazine And Ester Moiety

Tetronic acids have attracted the great attention of scientific researchers for its bactericidal,insecticidal,acaricidal,antioxidant and such many bioactivities and strong structural reactivity,and become one of the hot fields in today's new pesticide discovery research.In the 1990s,Bayer developed spirodiclofen,spiromesifen and spirotetramat,all of which contained Tetronic acid structure having outstanding characteristic of novel structure,efficient and low toxicity,good compatibility with the environment,no interactive resistance and so on.Leaded withthe natural compounds like tetronic acid as lead compound,researchers have synthetised a large number of tetronic acid derivatives through structural modification,derivative,and optimized many new compounds with excellent bioactivity have been screened.In this paper,two moities of substituted phenylhydrazine and carboxylate were introduced to the structure of tetronic acid to design and synthesize thirty one novel tetronic acid derivatives.Their fungicidal activity were also evaluated.3-(1-Hydroxyethylidene)-5-methylfuran-2,4(3H,5H)-dione was prepared by the reactions of O-acetoacetylation and cyclization starting from L-ethyl lactate.And two 3-(1-hydroxyalkylidene)furan-2,4(3H,5H)-diones were prepared by 4-oxyalkylation,cyclization and acylation from ethyl 4-chloroacetoacetate.These intermediates were reacted with substituted phenylhydrazine to give ten 3-(1-(2-(substituted phenyl)hydrazinyl)alkylidene)furan-2,4(3H,5H)-diones.Then,they were reacted with chloroformates to get 31 novel tetronic acid derivatives containing substituted phenylhydrazine and ester group.The structures of these target compounds were confirmed by FT-IR,1H NMR,EI-MS and elemental analysis.The fungicidal activities of the target compounds against Fusarium graminearum,Botrytis cinerea,Rhizoctonia solani and Colletotrichum capsici were evaluated in vitro with mycelial growth rate method at the concentration of 10 ?g/mL.The EC50 values of some selected compounds were determined.The results showed that the target compounds exhibited remarkable fungicidal activities against the tested fungi.The compound B2 showed the best activity against F.graminearum with EC50 value of 0.0648 ?g/mL,lower than 0.4947 ?g/mL of the control drug carbendazim.The compound D2 exhibited the best activity against B.cinerea,its EC50 value of 0.0308 ?g/mL was better than 0.3577?g/mL of procymidone.The compound A7 gave the best activity against R.solani,its EC50 value 0.0757 ?g/mL was lower to the value 0.5417 ?g/mL of carbendazim.The compound B1 showed the hightest activity against C.capsici,and its EC50 value was 0.0236 ?g/mL,better than 0.3325 ?g/mL of azoxystrobin.