Effects insecticidal activity

Carbamate Insecticides. These are stmcturaUy optimi2ed derivatives of the unique plant alkaloid physostigmine [57-47-6] a cholinergic dmg isolated in 1864 from Phjsostigma venenosum (see Alkaloids) (17,24,35—39). The carbamates maybe considered synthetic derivatives of the synaptic neurotransmitter acetylcholine, with very low turnover numbers. The A/,A/-dimethylcarbamates of heterocycHc enols (36) and the Ai-methylcarbamates of a variety of substituted phenols (35) with a wide range of insecticidal activity were described in 1954 (35). The latter are the most widely used carbamate insecticides, and the A/-methylcatbamates of oximes have subsequentiy been found to be effective systemic insecticides. 

The polyether antibiotics exhibit a broad range of biological, antibacterial, antifungal, antiviral, anticoccidial, antiparasitic, and insecticidal activities. They improve feed efficiency and growth performance in mminant and monogastric animals. Only the anticoccidial activity in poultry and catde, and the effect on feed efficiency in mminants such as catde and sheep are of commercial interest. 

Godin et al. (10), working on the effect of insecticidal activity of pyrethrum flowers from fresh and dried flowers, showed that extracts from fresh flowers had little or no greater effect on pyrethroid content and insecticidal activity than extracts from dried flowers with drying temperatures up to 80 °C. However, some of all the pyrethrin was lost at 120°C. The principal loss was in pyrethin I and not pyrethin II. 

Bates, Hewlett, and Lloyd (2) therefore studied the synergistic effects of some compounds related to 2-diethylaminoethyl 2,2-diphenyl-w-pentanoate on the insecticidal activity of pyrethrins. They found active compounds when a 2-diethylamino moiety was joined to the diphenylmethyl moiety through an ester, ketone, or ether linkage. However, none of the compounds investigated approached piperonyl butoxide in synergistic activity with pyrethrins. 

A high degree of insecticidal activity per unit weight, effectiveness against many species of insects, prolonged residual effect combined with rapid knockdown, compatibility with various vehicles, and availability under wartime conditions are among the most important military characteristics of insecticides. No present insecticide is entirely satisfactory. 

After mothproofing wool, the next logical step for Geigy was to invent an insecticide that killed more kinds of pests. Imported natural insecticides made from plants, including pyrethrum from tropical chrysanthemums, rotenone from a tropical vine, and nicotine from tobacco, could be quite expensive they were also not persistent and were easily destroyed by light and heat. American and European attempts to synthesize their active ingredients had failed. Arsenic compounds remained the only cheap and effective insecticides. 

A. aegypti colonies were found to have developed cross-resistance to even polyfluoro benzylalcohol ester pyrethroids with potent insecticidal activity. Mosquito coils of these compounds were effective against allethrin-susceptible A. aegypti colonies at ultra-low concentration, but needed several times higher concentrations for A. aegypti colonies in Group III in Table 8 (unpublished). 

Metofluthrin is a newly developed highly effective pyrethroid which has excellent insecticidal activity against mosquitoes. Due to its superior characteristics, Metofluthrin is suitable for use in various types of mosquito control formulation, including mosquito coils and liquid vaporizers. Metofluthrin also has excellent... 

Chlorination of benzene gives an addition product that is a mixture of stereoisomers known collectively as hexachlorocyclohexane (HCH). At one time, this was incorrectly termed benzene hexachloride. The mixtnre has insecticidal activity, though activity was found to reside in only one isomer, the so-called gamma isomer, y-HCH. y-HCH, sometimes under its generic name lindane, has been a mainstay insecticide for many years, and is about the only example of the chlorinated hydrocarbons that has not been banned and is still available for general use. Although chlorinated hydrocarbons have proved very effective insecticides, they are not readily degraded in the environment, they accumulate and persist in animal tissues, and have proved toxic to many bird and animal species. 

Rodriguez-Saona CR, Maynard DF, Phillips S, Trumble JT, AlkyRurans Effects of alkyl side-chain length on insecticidal activity, J Nat Prod 62 191—193,... 

Animals often use toxins to immobilise their prey, often insects. Wasps, bees, spiders, mites, scorpions, snakes and other reptiles are all capable of producing potent toxins many of which are insect specific. There is much work in progress around the world examining the opportunities that exist to exploit these toxins to produce new insecticides. This is usually undertaken in two different ways. The first is to determine the mode of action of the natural toxin and to use this novel effect to find synthetic compounds with insecticidal activity in biochemical screens. The second is to attempt to synthesise compounds with the same structural features of the natural toxin and hence with the same mode of action but with better stability following application. The types of compounds that are known are discussed by Blagbrough and Moya13 but none has been commercialised to date. 

Lindane, the y-isomer of HCH, is a potent insecticide. Its insecticidal action is due to a hyperexcitatory effect on the insect s central nervous system induced by accumulation of acetylcholine in the synaptic region 73). We prepared a number of analogs in which some of the chlorine atoms are replaced by other substituents while maintaining the -configuration and determined their insecticidal activity against mosquitos74,). 

Insecticidal activity of DDT and related compounds is due to their neuroexcitatory effect, the mechanism of which is very similar to that of pyrethroids 75). Using a number of analogs of DDT (34), DDD (35), and prolan (36), p,p -substituents of which are modified variously as well as those of methoxychlor (37), the trichloro-... 

Oxygen heterocycles are less common amongst organophosphorus insecticides but two examples are dioxathion (79) (59JA139) and salithion (80) (62ABC452). The latter is the only phosphorus heterocycle that has achieved commercial use. The generally poor insecticidal activity of cyclic phosphorus esters has been ascribed to instability and steric effects (B-74MI10702). 

The presence of pesticidal activity among benzo[6 Jthiophene derivatives is well documented. The compound 4-Ar-methylcarbamoylbenzo[6 Jthiophene (372) has been marketed under the name Mobam as an effective insecticide. The anticholinesterase and insecticidal properties of the 3-, 5-, 6- and 7-isomers of (372) in the housefly have been reported. The 4- and 7-isomers were most active, the 5-isomer intermediate, and the 3- and 6-isomers least active. Broad pesticidal activity was claimed for a series of 2-amino-3,4-dihydro-2//-[ 1 Jbenzothieno[3,2-b Jpyrans (373). 

Aliphatic Hydrocarbons. After extensive research into the biological activity of the aliphatic hydrocarbons, relatively few of the pure Inonderivativel compounds have been found worthy of commercial attention. Popular for use in orchard spraying are the petroleum derivative oil spray s, which possess a good combination of acaricidal and insecticidal activity wiih low phytoioxicity. These sprays are effective against San Jose scale and mite. 

Carbamates such as Aldicarb undergo degradation under both aerobic and anaerobic conditions. Indeed the oxidation of the sulfur moiety to the sulfoxide and sulfone is part of the activation of the compound to its most potent form. Subsequent aerobic metabolism can completely mineralize the compound, although this process is usually relatively slow so that it is an effective insecticide, acaricide and nematocide. Anaerobically these compounds are hydrolyzed, and then mineralized by methanogens (61). 

Although a great deal of the work currendy being done in chiral separations is related to pharmaceuticals, the agricultural and the food and beverage industries are affected as well. For instance, several chiral pesticides are used commercially. It is possible that the enantiomers may differ in their persistence in the environment and their effectiveness against specific pests. For example, the neurotoxic action of the pesticide, ethyl-4-nitrophenyl phenylphosphono thionate (EPN), resides almost entirely in the S enantiomer while the desired insecticidal activity resides entirely in the R enantiomer (5). This raises the question of whether the pesticide may be safer and more effective if applied as an enantiomerically pure formulation. In the food and beverage industry,... 

AUethrin [584-79-2] (d 1.005—1.015, vp 16 mPa at 30°C) is the aUyl homologue of pyrethrin I, ie, R = allyl, —CH2CH=CH2. The synthetic product contains 75—95% of eight enantiomers, 70% (d=)-trans and 30% (d=)-cis acids esterified with (A)-cyclopentenolone alcohol. The relative insecticidal activities of the enantiomers are shown in Table 2. The rat LD5Qs of aUethrin are 920 (oral) and 11,000 (dermal) mg/kg. BioaUethrin [584-79-2] is the (+)-/rchrysanthemate ester of the (zt)-alcohol (RS) (R) which has enhanced knockdown activity (vp 2 mPa at 25°C, water solubility 4.6 mg/L). AUethrin is as effective as the natural pyrethrins against flies and mosquitoes but has a narrow spectmm of activity against other insect pests. 

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