Effects of alkyl groups attached to the carbamoyl nitrogen atom of an N-arylcarbamoylpyrazoline on insecticidal activity

N-Alkylated analogs (C₁–C₃) of an N-arylcarbamoylpyrazoline were prepared. The introduction of these alkyl groups completely changed the crystal structure in respect of the torsion angle of the amide C–N bond of the non-alkyl compound. The introduction of methyl and ethyl groups slightly, and that of an isopropyl group markedly, decreased insecticidal activity against American cockroaches and house flies. Conformational analyses of the compounds suggested that the insecticidally active conformer of this class of compounds is in the anti-position regarding the N′–C(=O) and N-aryl bonds in which the non-alkyl compound is energetically the most stable. The most stable conformers of the alkylated compounds are in the syn-position, and these compounds would interact with target sites in the less stable anti-form. © 1999 Society of Chemical Industry     

Effect of substituents at the 5-position of the pyridine ring of imidacloprid on insecticidal activity against Periplaneta americana

The insecticidal activities of imidacloprid derivatives with a wide range of substituents at the 5-position on the pyridine ring against American cockroaches, Periplaneta americana (L.), were measured by injection with and without synergists propyl 2-propynyl phenylphosphonate and piperonyl butoxide. The log(1/MLD) value (MLD = minimal lethal dose in mol) without synergists was 7.96 for the methyl derivative, and the values were lower for other derivatives. Synergists enhanced the potencies of all the compounds tested. Considering these compounds and those with other substituents at this position, the region for maximum activity was predicted to be in the conjunction of the pyridyl 6-chlorine atom with a lipophilic small group in the 5-position.     

Insecticidal activity of the enantiomers of fipronil

The two enantiomers of the insecticide fipronil were made by preparative HPLC. The insecticidal activities of the racemic mixture and the two enantiomers against selected agricultural or household pests (cotton stainer, Dysdercus cingulatus F; grain weevil, Sitophilus granarius L and house fly, Musca domestica L) were determined. There was no significant difference in acute or residual activity between the racemic mixture and the enantiomers of fipronil, indicating that there is no preferred chiral form of the compound in these key species of important insects. This observation clearly suggests that there is no major scope for marketing the insecticide in a one-enantiomer form.     

Synthesis and insecticidal activity of new amide derivatives of piperine

The natural lipophilic amides piperine and piperiline were isolated from Piper nigrum L (Piperaceae). Piperine was hydrolysed into piperic acid (85% yield) which was converted into 16 amides (28–89% yield). The contact toxicity of all synthetic amides, and also that of piperine and piperiline, at the dose 10 µg per insect, was evaluated for the Brazilian economically important insects Ascia monuste orseis Latr, Acanthoscelides obtectus Say, Brevicoryne brassicae L, Protopolybia exigua DeSaus and Cornitermes cumulans Kollar. The results demontrated that the insects have different sensivities to the various amides, with mortality ranging from 0 to 97.5% according to the compound and insect species. © 2000 Society of Chemical Industry     

Synthesis and insecticidal activity of new pyrethroids

BACKGROUND: Pyrethroids are among the most potent pesticides known, with great potential for structural variation with retention or enhancement of potency. The simple methyl ester is easier to prepare (at least one step shorter) than the more complex pyrethroids modified on the alcohol moiety. The objective was to synthesise methyl esters of pyrethroid acids containing an aromatic ring on the acid moiety and evaluate their biological activity against Ascia monuste orseis Latr., Tuta absoluta Meyrick, Periplaneta americana (L.), Musca domestica L. and Sitophilus zeamais (Motsch.). RESULTS: The synthetic sequence required seven steps: protection of the hydroxyl groups of D ‐mannitol, diol oxidative cleavage with sodium metaperiodate, alkene formation by Wittig reaction with methoxycarbonylmethylidene(triphenyl)phosphorane, cyclopropanation, acetal hydrolysis with perchloric acid and oxidative cleavage with sodium metaperiodate gave methyl (1S, 3S)‐3‐formyl‐2,2‐dimethylcyclopropane‐1‐carboxylate. The final step comprised reaction of the aldehyde with five different aromatic phosphorus ylides to give the pyrethroids. CONCLUSION: An efficient and versatile synthesis of ten new pyrethroid methyl esters has been accomplished from the readily available D ‐mannitol in seven steps. All compounds showed insecticidal activity, and methyl (1S, 3S)‐3‐[(Z)‐2‐(4‐chlorophenyl)vinyl]‐2,2‐dimethylcyclopropane‐1‐carboxylate was the most active, killing 90% of A. monuste orseis and 100% of T. absoluta and P. americana. Copyright © 2009 Society of Chemical Industry     

Comparison of anti-feedant and insecticidal activity of nimbin and salannin photo-oxidation products with neem (Azadirachta indica) limonoids

Photo-oxidation of the neem limonoids nimbin and salannin with UV light in the presence of oxygen gives two isomeric lactone products per limonoid, nimbinolide and isonimbinolide, and salanninolide and isosalanninolide, respectively. When compared in insect tests with the important limonoids of neem seeds, azadirachtin, nimbin and salannin, isonimbinolide and isosalanninolide show activity greater than that of nimbin or salannin and in some respects show activity approaching that of azadirachtin. The photo-oxidation products were tested for anti-feedant activity and toxicity against larvae of three species of Lepidoptera, Spodoptera littoralis (Boisd), Spodoptera frugiperda (FE Smith) and Helicoverpa armigera (Hübner) and nymphs of the locusts Schistocerca gregaria (Forsk?l) and Locusta migratoria (L).     

Efficacy and residues of phloxine B and uranine for the suppression of Mediterranean fruit fly in coffee fields

The field efficacy of a bait containing phloxine B, uranine and Provesta 621 protein was tested against Mediterranean fruit fly (Ceratitis capitata; Medfly) by aerial and ground spraying in about 84 ha of coffee fields in Kauai, Hawaii, USA. Concurrently, soil and crop samples were collected from the aerially sprayed field and its unsprayed control field for residue studies. Efficacy of the sprays was assessed through trapping with both protein-baited and trimedlure-baited traps and through the infestation level of coffee cherries collected at least three-quarters ripe. The C capitata population was low at the start of the aerial and ground spray studies, but dramatically increased in the control fields. This increase coincided with initial ripening of coffee cherries. During times of peak population levels, C capitata populations were reduced by more than 91% in the ground-sprayed field and 99% in the aerial-sprayed field, relative to the populations in their respective control fields and based on protein-baited trap catches. Results of residue analyses indicated that uranine dissipated quickly compared with phloxine B on coffee and soil. Coffee samples collected at pre-spray periods had phloxine B residues of 7.2-25.5 ng g-1 on berries. Phloxine B concentrations were much higher on coffee leaves (163-1120 ng g-1). Lower concentrations of the dye were found from coffee samples collected during rainy days. Average phloxine B concentrations immediately after spraying were 56 and 2840 ng g-1 in coffee berries and leaves, respectively. Dissipation of phloxine B on berries was fast, with a half-life (t1/2) of 3 days. Dissipation of phloxine B on leaves was fitted to two linear phases: the initial (0-4 days) with a shorter t1/2 of 3 days and the later phase (4-28 days) with a longer t1/2 of 15 days. Average concentrations of phloxine B in the top soil ranged from 50 to 590 ng g-1 at pre-spray. Phloxine B initial concentration (770 ng g-1) reached a plateau immediately after the last spraying, but showed a steady decline over time with t1/2 of 16 days. Fast dissipation of the dyes in the field indicates that these chemicals may be environmentally compatible and therefore a promising alternative for fruit fly control.     

山蒟中脂肪链酰胺类化合物的分离及杀虫活性

采用提取、萃取及柱层析等方法,从山蒟Piper hancei Maxim甲醇提取物的石油醚和氯仿萃取相中分离到6个脂肪链酰胺类化合物,通过核磁共振、质谱并结合相关文献比对,其结构被分别鉴定为已知化合物chingchengenamide A( C1 )、N-异丁基-反-2-反-4-癸二烯酰胺( C2 )、假荜拨酰胺A( C3 )、荜茇宁( C4 )、N-p-香豆酰酪胺( C5 )和N-反式-阿魏酰酪胺( C6 ),其中 C1 为首次从山蒟中获得。利用幼虫浸液法测试了各化合物对白纹伊蚊Aedes albopictus和致倦库蚊Culex pipiens quinquefasciatus幼虫的12 h杀虫活性。结果表明:在20 mg/L下,化合物 C1 对白纹伊蚊的杀虫活性较高,其校正死亡率为100%,LC₅₀值为5.37 mg/L;化合物 C1 、 C2 、 C3 和 C4 对致倦库蚊的杀虫活性较高,20 mg/L下的校正死亡率分别为100%、88.5%、100%和100%,LC₅₀值分别为1.03、9.68、3.08和2.87 mg/L。     

Correlations of the electrophysiological activity of neonicotinoids with their binding and insecticidal activities

The electrophysiological actions of various neonicotinoids, including substituted benzyl derivatives, against recombinant Drosophila SAD/chicken beta2 hybrid nicotinic acetylcholine receptor (nAChR) were measured to analyze the relationships between the in vivo (insecticidal) and in vitro (binding and agonist) activities. Most of the neonicotinoids tested were capable of inducing inward currents by activating the hybrid nAChRs expressed in Xenopus laevis oocytes, whereas some compounds had no agonist activity and only blocked the acetylcholine-induced currents. Variations in the agonist activity were well correlated with those in the binding potency evaluated using [3H]imidacloprid as well as insecticidal activities.     

Insecticidal activity of the pyrethrins and related compounds IV.—Essential features for insecticidal activity in chrysanthemates and related cyclopropane esters

A range of 5-benzyl-3-furylmethyl cyclopropane carboxylates and other esters are evaluated against house-flies, mustard beetles and two mosquito species. The results show the importance for activity of a gem-dimethyl group on the cyclopropane ring and that substitutions at C₃ give wide variations in insecticidal activity and marked species specificity. Some of the compounds had considerable knockdown activity against houseflies, but the structural requirements for this type of action differ markedly from those for kill.     

Sulfoxaflor and the sulfoximine insecticides: Chemistry,mode of action and basis for efficacy on resistant insects

The sulfoximines, as exemplified by sulfoxaflor ([N-[methyloxido[1-[6-(trifluoromethyl)-3-pyridinyl]ethyl]-λ⁴-sulfanylidene] cyanamide] represent a new class of insecticides. Sulfoxaflor exhibits a high degree of efficacy against a wide range of sap-feeding insects, including those resistant to neonicotinoids and other insecticides. Sulfoxaflor is an agonist at insect nicotinic acetylcholine receptors (nAChRs) and functions in a manner distinct from other insecticides acting at nAChRs. The sulfoximines also exhibit structure activity relationships (SAR) that are different from other nAChR agonists such as the neonicotinoids. This review summarizes the sulfoximine SAR, mode of action and the biochemistry underlying the observed efficacy on resistant insect pests, with a particular focus on sulfoxaflor.