Beetles Do It Differently: Two Stereodivergent Cyclisation Modes in Iridoid‐Producing Leaf‐Beetle Larvae. Issue 3 (22nd January 2013)

• Record Type: Journal Article
• Authors: Kunert, Maritta; Rahfeld, Peter; Shaker, Kamel H.; Schneider, Bernd; David, Anja; Dettner, Konrad; Pasteels, Jacques M.; Boland, Wilhelm
• Is Part Of: Chembiochem. Volume 14:Issue 3(2013)
• Page Start: 353
• Page End: 360
• Publication Date: 2013-01-22
• Subjects: Biochemistry -- Periodicals; Molecular biology -- Periodicals; Pharmaceutical chemistry -- Periodicals; 572
• DOI: 10.1002/cbic.201200689
• Languages: English
• ISSNs: 1439-4227

Abstract

<abstract abstract-type="main" xml:lang="en"> <title>Abstract</title> <p>Larvae of the Chrysomelina species <italic>Phaedon cochleariae</italic>, <italic>Hydrothassa marginella</italic>, <italic>Phratora vulgatissima</italic>, <italic>Gastrophysa viridula</italic>, <italic>Gastrophysa atrocyanea</italic>, <italic>Gastrophysa cyanea</italic> and <italic>Gastrophysa polygoni</italic> produce the iridoid chrysomelidial (<bold>1</bold>) to defend themselves against predators. Feeding experiments with a deuterated precursor ([<sup>2</sup>H<sub>5</sub>]8‐hydroxygeraniol <bold>9</bold>) and in vitro isotope exchange experiments with defensive secretion in <sup>2</sup>H<sub>2</sub>O revealed differences in the cyclisation of the ultimate precursor 8‐oxogeranial (<bold>8</bold>) to <bold>1</bold>, between members of the genus <italic>Gastrophysa</italic> and all other species. In <italic>P. cochleariae</italic>, <italic>H. marginella</italic> and <italic>P. vulgatissima</italic><bold>1</bold> is most likely produced by a Rauhut–Currier‐type cyclisation via a "transoid dienamine", with loss of a single deuterium atom from C(4) of the precursor. In contrast, members of the genus <italic>Gastrophysa</italic> cyclise <bold>8</bold> via a "cisoid dienamine" intermediate, with exchange of all three deuterium atoms from the methyl group at C(3). To study whether the different cyclisation modes influence the stereochemistry of <bold>1</bold>, the absolute configuration of <bold>1</bold> of the larvae was determined by GC‐MS on a chiral column. In accordance with literature (J. Meinwald, T. H. Jones, <italic>J. Am. Chem. Soc.</italic><bold>1978</bold>, <italic>100</italic>, 1883 and N. Shimizu, R. Yakumaru, T. Sakata, S. Shimano, Y. Kuwahara, <italic>J. Chem. Ecol.</italic><bold>2012</bold>, <italic>38</italic>, 29), we found (5<italic>S</italic>, 8<italic>S</italic>)‐chrysomelidial (<bold>1</bold>) in <italic>H. marginella</italic> and <italic>P. vulgatissima</italic>, but <italic>P. cochleariae</italic> and all investigated members of the genus Gastrophysa synthesise (5<italic>R</italic>, 8<italic>R</italic>)‐chrysomelidial (<bold>1</bold>).</p> </abstract>