Chrysanthemic and pyrethric

Pyrethrum refers to the oleoresin extracted from the dried flowers of Tanacetum cinerariaefolium (Asteraceae) and is the source of the pyrethrins, chrysanthemates and pyrethrates. Among the natural pyrethrins, those incorporating the alcohol pyrethrolone, namely pyrethrins 1 and II (Fig. 9), are the most abundant and account for most of the insecticidal activity. The pyrethrins are recommended for control of a wide range of insects and mites on fruit, vegetables, field crops, ornamentals, glasshouse crops and house plants, as well as in public health, stored products, animal houses and on domestic and farm animals. Pyrethrins are sold in a wide variety of formulations, under many different trade names by a large number of different manufacturers. 

The Chrysanthemum Extract comprise of a mixture oiester e.g., chrysanthemic and pyrethric acids alcohols e.g., cinerolone and pyrethrolone. As the esters are usually more prone to get hydrolyzed and oxidized, hence it must be stored in sealed light-proof containers in a cool place. 

Chrysanthemol from the leaves of Artemisia ludiviciana (Asteraceae) belongs to the cyclopropane monoterpenes Cinerins, jasmolins and pyrethrins (all including derivatives 1 and 11) are esters of /rara-chrysanthemic and pyrethric acid with terpenoid hydroxypentenones such as cinerolone, jasmolone and pyrethrolone. These are the active insecticidal constituents of pyrethrum recovered from dried flowers of several Chrysanthemum species (e.g. Chrysanthemum cinerariaefolium, Asteraceae). Some synthetic esters of chrysanthemic acid are also applied as insecticides. 

Figure 3.15 Proposed mechanism for the biosynthesis of chrysanthemic and pyrethric acids.

METHYL CHRYSANTHEMATE DIMETHYL PYRETHRATE mixture contribute to the total monocarboxylic and dicarboxylic acids found. 

Besides classical monoterpenes that are formed via a head-to-tail addition of IPP to DMAPP (and the analogous addition of IPP to advanced intermediates toward higher terpenes), there are also monoterpenes known where the CIO skeleton cannot be rationalized by this standard coupling of the two activated isoprene units. Two important examples are chrysanthemic acid (60) and pyrethric acid (61), which are the main (ester bound) building blocks for the well-known family of the pyrethrins [1, 13]. In this case, an enzyme-catalyzed... 

SCHEME 6.12 Tail-to-middle combination of two molecules of DMAPP in the biosynthesis of irregular monoterpenes like chrysanthemic acid (60) and pyrethric acid (61). 

Many semi-synthetic esters, e.g. bioresmethrin, permethrin, and phenothrin, have been produced and these have increased toxicity towards insects and also extended lifetimes. All such esters retain a high proportion of the natural chrysanthemic acid or pyrethric acid structure. 

Ueda, K., and Matsui, M., Studies on chrysanthemic acid. Part 20. Synthesis of four geometrical isomers of ( )-pyrethric acid, Agr. Biol. Chem.. 34. 1119. 1970. 

Researches on chrysanthemic acid and its derivatives are usually oriented to synthesising esters of trans-chrysanthemic acid, many of which are naturally occurring (and are, therefore, presumably biodegradable) insecticides. The synthesis of pyrethric acid or its mono-ester (65) from chrysanthemic acid has been carried out in two laboratories. Ueda and Matsui prepared all four... 

Pyrethric acid (18) and from this, by optical resolution, the pure (-l-)-isomer, forming the acid component of pyrethrin II (10), cinerin II (12) and jasmolin II (14), was prepared by Matsui and Yamada (1963) by the oxidation of ( )-chrysanthemic acid. 

Car-4-ene derivatives (79) are readily available from car-3-ene, and their ozonolysis leads to (+ )-cis-homocaronic acid dimethyl ester (80), easily convertible into (-l-)-trans-chrysanthemic acid. Purification of mixtures of cis- and trans-chrysanthemic acid by lactonization of the cis-acid with a Lewis acid is reported, as is an improved method for resolving the (+ )-trans-acid using L-lysine. A reinvestigation of the synthesis of pyrethric acid isomers has been carried out. Two studies of the metabolism of the insecticidal esters of... 

Chemically pyrethrin I consists of an ester formed from the alcohol 6.50) with chrysanthemic acid (. 57), whereas pyrethrin II has the same alcohol esterified with pyrethric acid 6.52). The extra ester group in pyrethrin II gives it a more limited distribution and half-life in the insect. 

Pyrethrum flower consists of the dried flowerhead of Chrysanthemum cinerar ice folium Vis. and it owes its insecticidal properties to two types of ketoesters. One group consists of pyrethrin I and cinerin I, both of which have chrysanthemum monocarboxylic acid (chrysanthemic acid) as their acid component. The assay given below for pyrethrin I, which is based on the determination of total chrysanthemic acid, will therefore include cinerin I. The second group of esters consists of pyrethrin II and cinerin II, both of which have the monomethyl ester of chrysanthemum dicarboxylic acid (pyrethric acid) as their acid component since the assay given below for pyrethrin II is based on the determination of total pyrethric acid it will therefore include cinerin II. The keto-alcohol component of the pyrethrins is pyrethrolone and that of the cinerins is cinerolone. 

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