Editing Pyrethrin (section)

==Biosynthesis==
[[File:CCPaseRxn'.png|320px|thumb|Cyclopropanation reaction producing chrysanthemyl diphosphate, an intermediate in the biosynthesis of [[chrysanthemic acid]]. The reaction starts from dimethylallyl pyrophosphate ([[Dimethylallyl pyrophosphate|DMAPP]]). ]]
Well after their use as insecticides began, their chemical structures were determined by [[Hermann Staudinger]] and [[Lavoslav Ružička]] in 1924.<ref>{{cite journal |doi=10.1002/hlca.19240070124 |title=Insektentötende Stoffe I. Über Isolierung und Konstitution des wirksamen Teiles des dalmatinischen Insektenpulvers |trans-title=Insecticidal substances I. About the isolation and structure of the active part of the Dalmatian insect powder |language=de |journal=Helvetica Chimica Acta |volume=7 |issue=1 |pages=177–201 |year=1924 |last1=Staudinger |first1=H. |last2=Ruzicka |first2=L. }}</ref> [[Pyrethrin I]] (C<sub>n</sub>H<sub>28</sub>O<sub>3</sub>) and [[pyrethrin II]] (C<sub>n</sub>H<sub>28</sub>O<sub>5</sub>) are structurally related [[esters]] with a [[cyclopropane]] core. Pyrethrin I is a derivative of (+)-''trans''-[[chrysanthemic acid]].<ref>{{cite book |title=Merck Index |edition=11th |page=7978}}{{full citation needed|date=April 2015}}</ref><ref>{{cite book |title=McGraw-Hill Ryerson Chemistry 12 |page=99 |first=Michael |last=Townsend}}{{full citation needed|date=April 2015}}</ref> Pyrethrin II is closely related, but one methyl group is oxidized to a carboxymethyl group, the resulting core being called pyrethric acid. Knowledge of their structures opened the way for the production of synthetic analogues, which are called [[pyrethroids]]. Pyrethrins are classified as [[terpenoid]]s. The key step in the [[biosynthesis]] of the naturally occurring pyrethrins involves two molecules of [[dimethylallyl pyrophosphate]], which join to form a [[cyclopropane]] ring by the action of the enzyme [[chrysanthemyl diphosphate synthase]].<ref>{{cite journal |doi=10.1073/pnas.071543598 |jstor=3055437 |pmid=11287653 |pmc=31842 |title=Chrysanthemyl diphosphate synthase: Isolation of the gene and characterization of the recombinant non-head-to-tail monoterpene synthase from Chrysanthemum cinerariaefolium |journal=Proceedings of the National Academy of Sciences |volume=98 |issue=8 |pages=4373–8 |year=2001 |last1=Rivera |first1=S. B. |last2=Swedlund |first2=B. D. |last3=King |first3=G. J. |last4=Bell |first4=R. N. |last5=Hussey |first5=C. E. |last6=Shattuck-Eidens |first6=D. M. |last7=Wrobel |first7=W. M. |last8=Peiser |first8=G. D. |last9=Poulter |first9=C. D.  |bibcode=2001PNAS...98.4373R |doi-access=free }}</ref>