Deuterium surrounded carbocations support branching point analyses of multi product terpenoid synthases.
氘包围的碳正离子支持多产物萜类合酶的分支点分析。
The Variability of Sesquiterpenes Emitted from Two <i>Zea mays</i> Cultivars Is Controlled by Allelic Variation of Two Terpene Synthase Genes Encoding Stereoselective Multiple Product Enzymes
作者:Tobias G. Köllner、Christiane Schnee、Jonathan Gershenzon、Jörg Degenhardt
DOI:10.1105/tpc.019877
日期:2004.5
The mature leaves and husks of Zea mays release a complex blend of terpene volatiles after anthesis consisting predominantly of bisabolane-, sesquithujane-, and bergamotane-type sesquiterpenes. The varieties B73 and Delprim release the same volatile constituents but in significantly different proportions. To study the molecular genetic and biochemical mechanisms controlling terpene diversity and distribution in these varieties, we isolated the closely related terpene synthase genes terpene synthase4 (tps4) and tps5 from both varieties. The encoded enzymes, TPS4 and TPS5, each formed the same complex mixture of sesquiterpenes from the precursor farnesyl diphosphate but with different proportions of products. These mixtures correspond to the sesquiterpene blends observed in the varieties B73 and Delprim, respectively. The differences in the stereoselectivity of TPS4 and TPS5 are determined by four amino acid substitutions with the most important being a Gly instead of an Ala residue at position 409 at the catalytic site of the enzyme. Although both varieties contain tps4 and tps5 alleles, their differences in terpene composition result from the fact that B73 has only a single functional allele of tps4 and no functional alleles of tps5, whereas Delprim has only a functional allele of tps5 and no functional alleles of tps4. Lack of functionality was shown to be attributable to frame-shift mutations or amino acid substitutions that greatly reduce the activity of their encoded proteins. Therefore, the diversity of sesquiterpenes in these two maize cultivars is strongly influenced by single nucleotide changes in the alleles of two terpene synthase genes.
Absolute Configuration of 7-<i>epi</i>-Sesquithujene
作者:Ashot Khrimian、Allard A. Cossé、Damon J. Crook
DOI:10.1021/np200098z
日期:2011.6.24
7-epi-Sesquithujene (1) is a bicyclic sesquiterpene isolated from phoebe oil, an essential oil of the Brazilian walnut tree, Phoebe porosa. It is also produced by stressed ash trees and has been shown to elicit strong electrophysiological responses on emerald ash borer, Agrilus planipennis, antennae. In the course of the development of a synthetic 7-epi-sesquithujene lure for field testing against the emerald ash borer, we found that the absolute configuration of this compound had not been determined. We isolated >95% pure 7-epi-sesquithujene from phoebe oil via successive fractionation and conventional and argentation (HPLC) chromatographies. The specific optical rotation of this compound matched that of a synthetic product of known configuration. We also synthesized two other stereoisomers of sesquithujene and developed a chiral GC method to separate all four. Based on the specific rotation, stereoselective syntheses, and chiral GC analyses, 7-epi-sesquithujene present in phoebe oil and white ash was found to have the 2S,6S,7R absolute configuration.
A Gold-Catalyzed Entry into the Sesquisabinene and Sesquithujene Families of Terpenoids and Formal Total Syntheses of Cedrene and Cedrol
作者:Alois Fürstner、Andreas Schlecker
DOI:10.1002/chem.200801382
日期:2008.10.20
into the bicyclic cyclopropyl ketone derivatives 5 and 6 by way of a gold-catalyzed Ohloff-Rautenstrauch-type enynecycloisomerization is described. The required substrates were prepared by an asymmetric addition of the branched allylzinc reagent 21 to the alkynyl aldehyde 17 mediated by the deprotonated bisoxazoline (BOX) ligand 22. Compounds 5 and 6 were then converted into a host of different members