Study On Synthesis And Fungicidal Activity Of A Novel Cyclopropylpyrimidine Formamides

The biologically active pyrimidine group was introduced into the carboxylic acid part of succinate dehydrogenase inhibitor fungicide boscalid by active substructure splicing method,and the 2 or 6 position of pyrimidine ring was modified with the active pharmacophore cyclopropyl.The amine part draws on the benzene ring of highly active fungicides such as triadimefon and boscalid that have been marketed as the main skeleton,and partially replaces the hydrogen on the benzene ring with halogen,alkyl or alkoxy groups.A total of 42 novel pyrimidine formamide compounds were designed and synthesized,and the compounds were tested for antifungal activity.The main research contents are as follows:1.Ethyl 2-ethoxymethylene acetoacetate was synthesized from ethyl acetoacetate and triethyl orthoformate,and then ringed with cyclopropyl formamidine hydrochloride to obtain ethyl 2-cyclopropyl-4-methylpyrimidine-5-carboxylate,which was hydrolyzed to obtain 2-cyclopropyl-4-methylpyrimidine-5-carboxylic acid,and finally,14 kinds of 2-cyclopropyl-4-methylpyrimidine-5-carboxamide compounds（A series）were synthesized with substituted aniline/benzylamine in the presence of EDCI and DMAP.2.Ethyl（E）-4-methoxy-2-oxopent-3-enoate was synthesized from 2-methoxypropene and ethyl oxalyl chloride,and then reacted with cyclopropyl formamidine hydrochloride to obtain ethyl 2-cyclopropyl-6-methylpyrimidine-4-carboxylate,which was hydrolyzed to obtain 2-cyclopropyl-6-methylpyrimidine-4-carboxylic acid.Finally,14 kinds of 2-cyclopropyl-6-methylpyrimidine-4-carboxamide compounds（B series）were synthesized with substituted aniline/benzylamine in the presence of HATU and DMAP.3.Methyl（Z）-4-cyclopropyl-4-methoxy-2-oxo-3-butenoate was synthesized from ethyl 4-cyclopropyl-2,4-dioxobutanoate and methanol,and then reacted with acetamidine hydrochloride to obtain methyl 2-methyl-6-cyclopropylpyrimidine-4-carboxylate.The compound was hydrolyzed to obtain 2-methyl-6-cyclopropylpyrimidine-4-carboxylic acid.Finally,14 kinds of 2-methyl-6-cyclopropylpyrimidine-4-carboxamide compounds（C series）were synthesized with substituted aniline/benzylamine in the presence of HATU and DMAP.4.The synthesized compounds were confirmed by IR,¹H NMR,¹³C NMR and HRMS,and the test results were analyzed in detail.5.The fungicidal activity of the compounds was tested by mycelium growth rate method with Rhizoctonia solani,Sclerotinia sclerotiorum and Botrytis cinerea as test strains.The results showed that most of the compounds had certain fungicidal activity against the three fungi.In general,the antifungal efficacy of the synthesized compounds on Rhizoctonia solani and Botrytis cinerea was higher than that of Sclerotinia sclerotiorum.Compared with A series of compounds,the other two series of compounds also have moderate inhibitory activity,but generally do not have the high inhibitory activity of a series of compounds.Among them,compound A14（n=1,R=2-F-4-Br）has the best antifungal efficacy on Rhizoctonia solani.At the concentration of 50 mg/L,the inhibition rate of Rhizoctonia solani reached 82.9%,and the EC₅₀ reached 5.63 mg/L.It also has a good antifungal efficacy on Botrytis cinerea,with an EC₅₀ value of 19.63 mg/L.In addition,compounds A3（n=0,R=4-Cl）,A4（n=0,R=4-Br）also had good antifungal efficacys on Botrytis cinerea,and compound A7（n=0,R=3,4-Cl₂）also had good antifungal efficacys on Sclerotinia sclerotiorum,with EC₅₀ values between22.60–25.50 mg/L.In series B,compounds B₁₁（n=1,R=4-Cl）,B₁₂（n=1,R=OCH₃）and B13（n=1,R=2-CF₃）had good antifungal activity against Rhizoctonia solani,and the inhibition rates were 75.7%,77.1%and 70.8%at 100 mg/L,respectively.In the C series,compound C10（n=1,R=4-F）had better antifungal activity against Rhizoctonia solani,and the inhibition rate against Rhizoctonia solani reached 76.0%at 100 mg/L concentration.6.One highly active target compound for each series（A14:n=1,R=2-F-4-Br;B12:n=1,R=OCH₃;C10:n=1,R=4-F）was docked with succinate dehydrogenase.It was found that the amide oxygen atom and pyrimidine nitrogen atom of the target compound may form several strong hydrogen bond interactions with amino acid residues TRP-173 or TYR-58.The pyrimidine ring can also form cation-πinteractions with amino acids TYR-58 and ARG-43,revealing that succinate dehydrogenase may be the target enzyme of substituted pyrimidine formamide compounds.