Semisynthesis of Esters of Fraxinellone C4/10-Oxime and Their Pesticidal Activities

Abstract

A total of 20 esters of fraxinellone C4/10-oxime were synthesized and determined by melting points, optical rotation, infrared spectra, proton nuclear magnetic resonance spectra, and high-resolution mass spectrometry spectra. Two steric configurations of compounds 7i and 8i were unambiguously confirmed by X-ray crystallography. Additionally, their pesticidal activities were assessed on two typical lepidopteran pests, Mythimna separata Walker and Plutella xylostella Linnaeus. Generally, all compounds exhibited less potent oral toxicity than toosendanin against third-instar larvae of P. xylostella. However, all compounds showed the growth inhibitory property against early third-instar larvae of M. separata. Notably, compounds 7m, 8b, 8k, 9, and 11 displayed more potent pesticidal activity than toosendanin. This demonstrated that introducing the C-4 carbonyl or oxime group on fraxinellone resulted in more promising derivatives than those bearing a C-10 carbonyl or oxime substituent.

Semisynthesis of novel N‐acyl/sulfonyl derivatives of 5(3,5)‐(di)halogenocytisines/cytisine and their pesticidal activities against Mythimna separata Walker, Tetranychus cinnabarinus Boisduval, and Sitobion avenae Fabricius

“…. More than 45.5% (the largest portion) of FMRs for compounds 5f , 5h , 7c , 7f , and 7i occurred at the pupae stage; whereas the largest portion of FMRs for esters of fraxinellone C4/10‐oxime, matrine ethers, and toosendanin was at the larval stage. These results suggest that cytisine derivatives, when compared with toosendanin, fraxinellone C4/10‐oxime esters and matrine ethers, may exhibit a different mechanism of action against early third‐instar larvae of M. separata .…”

“…NaOH (3 mL), followed by extraction with EtOAc (15 mL × 4). The combined organic phase was dried over anhydrous Na 2…”

“…With the drive toward increasing food production and efficiency, steps should be taken to reduce increasing insect pest threats to crop production . Mythimna separata Walker (Oriental armyworm), Tetranychus cinnabarinus Boisduval (spider mite) and Sitobion avenae Fabricius are three threatening and typical insect pests of a wide range of crops, and their infestations are usually very serious and hard to control . In China, intermittent outbreaks of M. separata occurred widely in 2012, and approximately four million hectares of crops were completely lost .…”

“…1 Mythimna separata Walker (Oriental armyworm), Tetranychus cinnabarinus Boisduval (spider mite) and Sitobion avenae Fabricius are three threatening and typical insect pests of a wide range of crops, and their infestations are usually very serious and hard to control. [2][3][4] In China, intermittent outbreaks of M. separata occurred widely in 2012, and approximately four million hectares of crops were completely lost. 5 Meanwhile, due to the extensive and unreasonable application of synthetic pesticides to control pests, resistance in pest populations and negative impacts on human health and environmental safety have simultaneously emerged.…”

Synthesis and insecticidal activities of 5-deoxyavermectin B2a oxime ester derivatives

“…[1][2][3] Considering that the use of natural pesticides may decelerate resistance development and reduce environmental pollution, greater attention has been placed on the development of nature-product-based agrochemicals. [4][5][6][7][8] Avermectins, one of the most important classes of natural insecticides, anthelmintics, and acaricides, are a family of 16membered ring macrocyclic lactones isolated from the culture broth of Streptomyces avermitilis. [9][10][11] Compared with traditional pesticides, avermectins can interact stereoselectively and with a high affinity with the glutamate-gated chloride channel, leading to a chloride ion ux into neurons, causing paralysis and death.…”