Pyrethrolone, structure

The great advance in the field of instrumentation, coupled with the discovery of the heterogeneity of the pyrethrolone radical, has advanced the knowledge of pyrethrum chemistry considerably beyond that known in 1945. LaForge and Barthel (24,25) have shown the structure of the active ingredients of pyrethrum, known collectively as pyrethrins, to be esters as represented by the structure shown in Table I. 

LaForge FB, Barthel WF (1945) Constituents of pyrethrum flowers XVIII. The structure and isomerism of pyrethrolone and cinerolone. J Org Chem 10 114-120... 

The natural pyrethrin insecticides are esters derived from the alcohols cinerolone, jasmololone, and pyrethrolone (Fig. 6). Extracts of pyrethrum, the dried flowerheads of Chrysanthemum cinerariae-folium, contain a mixture of six of these ester (Fig. 6) and are commonly available with the addition of the pyrethrum synergist piperonyl butoxide. Variations on these basic structures have... 

Gillam and West18 established the structure of pyrethrolone, XVII, the hydrolysis product of pyrethrin, by comparing its absorption spectrum with that of tetrahydropyrethrolone, XVIIT. Pyrethrolone was known to contain a five-membered ring, three ethylenic double bonds and a keto group, but their relative positions were not known. The absorption maxima of both pyrethrolone and tetrahydropyrethrolone were, found to be about the same but the absorption intensity was much lower in the latter compound. The... 

This indicated that the two ethylenic linkages in the side chain of pyrethrolone were in conjugation. Similar results were obtained18 by the curve subtraction method with the absorption curves of the semicarbazones of pyrethrolone and tetrahydropyrethrolone. Woodward and Singh19 proposed the structure of patulin as XIX, with the C=C—C=C—C=0 unit, only because of the fact that it absorbs at 276 m/x (e 17,000). 

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