Pyrethric acid

Recently a new constituent of pyrethrum extract was described by Godin et al. (9) jasmolin II, the cir-pent-2-enylrethronyl ester of pyrethric acid. Jasmolin II differs from pyrethrin II in that the terminal double bond of the alcoholic side chain is saturated. This constituent forms about 3% of the total pyrethrins. Jasmolin II is less toxic to the insects tested than a similar concentration of pyrethrins. The pyrethrum extract was 16 to 17 times as toxic as jasmolin II to Aedes aegypti and Fhaedon cochlearia adults, less than 17 times... 

Chrysanthemum dicarboxylic acid or pyrethric acid may exist in eight stereoisomers, owing to the trans or cis configuration on the side chain of the double bond as well as that of the cyclopropane. The natural acid has been shown to be the trans-trans acid. As in the case of the chrysanthemum monocarboxylic acid, the naturally occurring configuration is more insecticidally active than the racemic form or any of the three isomers synthesized. 

Figure 4. Infrared spectrum of methyl-transrpyrethrate Prepared from pyrethric acid isolated from hydrolysis mixture of pyrethrum concentrate. Pure ester isolated by gas chromatography...

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. 

Pyrethroids consist of pyrethrum and its synthetic pyrethrum analogs called synthetic pyrethroids. Pyrethrum is a solvent extract of dried flowers of Chrysanthemum cinerariaefo-lium. The active ingredients of pyrethrum are called pyrethrins. Pyrethrins consist of four esters, namely, pyrethrins I and II and cinerins I and II, which comprise the combination of two different alcohols (pyrethrolone and cinerolone) and two different acids (chrysan-themic acid and pyrethric acid), as follows ... 

D1 (+)-fra/7s-Chrysanthemic acid D2 (+)-frans-Pyrethric acid D3 (1S,2S)-Fragranol D4Junionone... 

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

Fitzsimmons and Fraser-Ried have converted the protected glycoside 289 into ( + )-(290) and (- )-pyrethric acid. The route is long, and the introduction of the cyclopropane in 289, using methyl diethylphosphonopropionate [(EtO)2POCHMeCOOMe] occurred in only 50% yield, but both optical isomers were made from the same intermediate. 

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. 

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. 

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. 

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. 

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