Chrysanthemic acid derivatives, pyrethroid insecticides

In the 1960s and 1970s, from ingredients of chrysanthemums, an important group of insecticides, the pyrethroids, was developed these are derived from chrysanthemic acid. The pyrethroids and the phosphate esters replaced the previously intensively applied chlorinated hydrocarbons such as, for example, DDT. 

Figure 7 shows the course of development of various synthetic pyrethroids developed by retaining chrysanthemic acid as the acid moiety and modifying the alcohol moiety. Numerous useful compounds with favorable characteristics have been derived from the structural modification of natural cinerin I (7). These underlined compounds have been put into practical use as active ingredients, mainly for household insecticides. 

When the carbinol substituents (R) were the bulky 5-ler -butyl-2-(n-octyloxy)phenyl group, optimum enantioselectivities were achieved with the catalytic use of the corresponding Cu(II) complex (2) in both enantiomeric forms. Specific applications of the Aratani catalysts have included the synthesis of chrysanthemic acid esters (Eq. 5.6) and a precursor to permethrinic acid, both potent units of pyrethroid insecticides, and for the commercial preparation of ethyl (S)-2,2-dimethylcyclopropanecarboxylate (Eq. 5.2), which is used for constructing cilastatin. Several other uses of these catalysts and their derivatives for cyclopropanation reactions have been reported albeit, in most cases, with only moderate enantioselectivities [26-29],... 

Cyclopropanes are occasionally found in Nature, and one class of naturally occurring cyclopropanes, the pyrethroids, are useful insecticides. These compounds are highly toxic to insects but not to mammals, and because they are rapidly biodegraded, cyclopropanes do not persist in the environment. The naturally occurring pyrethroids are found in members of the chrysanthemum family and are formally derived from chrysanthemic acid. Many modified pyrethrins not found in Nature have been made in the laboratory and several are widely used as pesticides. The molecule known as pyrethrin I has the systematic name 2,2-dimethyl-3-(2-methyl-l-propenyl)cyclopropanecarboxylic acid 2-methyl-4-oxo-3-(Z-2,4-dipentadienyl)-2-cyclopenten-1-yl ester. See why the shorthand is used ... 

Miyamoto J, Nishida T, Ueda K (1971) Metabolic fate of resmethrin, 5-benzyl-3-furylmethyl A -trans chrysanthemate in the rat. Pestic Biochem Physiol 1 293-306 Miyamoto J, Suzuki T, Nakae C (1974) Metabolism of phenothrin (3-phenoxybenzyl A-trans-chrysanthemumate) in mammals. Pestic Biochem Physiol 4 438-450 Moss GP, Derden JC, Patel H, Cronin MT (2002) Quantitative structure-permeability relationships (QSPRs) for percutaneous absorption. Toxicol In Vitro 16 299-317 Mugeng J, Soderlund DM (1982) Liquid chromatographic determination and resolution of the enantiomers of the acid moieties of pyrethroid insecticides as their (-)-l-(l-phenyl)ethylamide derivatives. J Chromatogr A 248(1) 143-149... 

The potentials of this and other similar chiral Schiff base complexes of copper were originally explored for the manufacture of synthetic pyre-throids, a class of highly active pesticides. Cyclopropane rings with asymmetric centers are an integral part of the molecular structures of synthetic pyrethroids. Synthetic pyrethroids were made because the natural product chrysanthemic acid, 7.69, and its derivatives have insecticidal properties. 

Pyrethroids are synthetic analogs of derivatives of chrysanthemic acid, 25.6, naturally occurring in plants of the Chrysanthemum genus. The naturally extracted materials, pyrethrin I and II (25.7, 25.8), have been modified for better activity in compounds such as permethrin, 25.9, and deltamethrin, 25.10. They are toxic to cats and to aquatic life but have otherwise generally low toxicity to mammals and are broken down rapidly in the environment. They are widely used as domestic insecticides. You should note that although a single stereoisomer... 

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