Biosynthese von Iridodialen in Wehrdrüsen von Blattkäferlarven (Chrysomelinae)

Abstract

Aus Geraniol über 8‐Oxocitral produzieren Larven von Blattkäfern Dialdehyde wie 1 analog zur pflanzlichen Biosynthese von Iridoiden. Die Dialdehyde können anschließend auf erstaunlich vielfältige Weise zu Iridodialen cyclisiert werden, wie Untersuchungen an drei Arten dieser Insektenlarven ergaben.

Beetles Do It Differently: Two Stereodivergent Cyclisation Modes in Iridoid‐Producing Leaf‐Beetle Larvae

“…[6] Consistent with the previously studied stereochemical course of iridoid biosynthesis, [7,12] loss of a single deuterium atom from C(4) of the precursor was observed in 1 produced by feeding larvae of P. cochleariae (Scheme 3), H. marginella and P. vulgatissima. The same observation was made for 2, generated from [ 2 H 5 ]-9 by the larvae of P. versicolora, P. laticollis, L. aenea, P. vulgatissima and P. phellandrii, as well as for plagiolactone produced by P. versicolora, L. aenea and H. marginella, and for 3 produced by G. cyanea.…”

“…[6,18,19,23] In juvenile leaf beetles they are synthesised de novo. [6,7,11] The early steps of terpenoid biosynthesis along the mevalonic acid pathway occur within the fat body. [4] This tissue produces 9, which is glucosylated to 7 and transported in the haemolymph to the defensive system.…”

“…Lorenz et al [6] already observed differences in the biosynthesis of 1 when using juvenile P. cochleariae or G. viridula leaf beetles. In the current study we used a deuterated probe ( [6,7] this precursor is cyclised in P. cochleariae and other leaf-beetle larvae with the loss of a single deuterium atom from C(4) of the acyclic precursor 8: C(4)-H S [7] in the case of P. cochleariae (Scheme 3), and C(4)-H R in the carnivorous Philonthus spp. [12] The results of the current and previous experiments with labelled precursors such as [ an intramolecular Rauhut-Currier reaction, which has been well studied and employed for the synthesis of iridoids.…”

“…Whether this cyclisation and isomerisation sequence requires two discrete enzymes (Scheme 2) or only a single cyclase (catalysing both steps) remains unknown. [6,7] Lorenz et al and Veith et al [6,7] studied the biosynthesis of 1 in P. versicolora, G. viridula and P. cochleariae, and used synthetic (2E,6E)- [5, H 5 ]2-methylocta-2,6-diene-1,8-diol as a precursor. They observed loss of a single deuterium atom from C(4) in nor-chrysomelidial of P. versicolora and P. cochleariae, but not in the product of G. viridula.…”

Insect-Plant Interactions − Metabolism of Plant Compounds to Pheromones and Allomones by Lepidoptera and Leaf Beetles

“…Feeding of deuterated 37 led to highly labelled 1,3-hexanediyl esters. The which is oxidized to 8-hydroxygeraniol (29), [56][57] the β-glucoside of which has also been identified in the defensive larvae obviously reduce the hydroxyketone 37 to the diol 35 and then form the hexanediyl esters.…”