Fortschritte der Chemie organischer Naturstoffe / Progress in the Chemistry of Organic Natural Products
Springer Science & Business Media, Jun 17, 2010 - Science - 264 pages
Lignans, by convention, are a group of natural products that are formed by linking two phenylpropanoid units (C C units) by oxidative coupling. Most importantly, in 6 3 a lignan, two (C C units) are bound through the central carbon of their side chains, 6 3 0 i. e. the 8 and 8 positions (1, 2). The occurrence of C C -dimers, linked at sites other 6 3 0 than the 8–8 positions, is also known and these compounds have been termed neolignans (3, 4). As these two groups of compounds have close structural as well as biosynthetic relationships, they are often associated together and incorporated under the general term “lignan” (5). The diverse structural categorization of true lignans and of a few neolignans is presented in Fig. 1. Through the years, several review articles or books covering different facets of lignans, including their ch- istry (6, 7), biogenesis (8), synthesis (9), and biological activities (10) have been published. Enduring research for the investigation of secondary metabolites of plants has evidenced some compounds that are biogenetically related to true lignans or neolignans but bear some features not discerned in conventional lignans. These compounds or groups of compounds have been termed as “non-conventional lignans”, and include coumarinolignans, ?avonolignans, and stilbenolignans. The non-conventional lignans, like the conventional ones, have two C C units linked 6 3 together but have additional structural features to place them also under the category of coumarins, ?avonoids, or stilbenes.
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13C NMR 1H NMR absolute configuration acetate acid activity Æ)-Dendrobine alcohol aldehyde alkaloids allylic Antidesmanin aromatic baccatum CH3OH Chem Chem Pharm Bull Chem Soc chemical chloride chromatography cleomiscosin A 9 compounds coniferyl alcohol coriamyrtin Coriaria coumarin coumarinolignans cyclization dendrobine 82 Dendrobium derivatives dioxane double bond Dried EPC-synthesis epimeric epoxide ester ether extracted flavonoid flavonolignans g-lactone gene cluster globosa gnetifolin H-NMR hydrogen hydroxy hydroxy group intramolecular isolated isomer Jommi Jones reagent ketone key step lactone lignans methoxy methyl mixture moiety Nat Prod natural products nobile O O O OCH3 OH O OH OH OH Orchidaceae overall yield oxidation pathway phenylpropanoid phenylpropanoid unit Phytochemistry Picrodendraceae picrodendrin picrotin picrotox picrotoxanes picrotoxinin plants Polyketide protons racemic reaction receptors reduction regioisomers Scheme Sesquiterpene silybin silyl ether spectra spectroscopic data spectrum stereoselectivity stilbene stilbenolignans structure determination Total Synthesis toxic Tricin tricyclic Trost tutin 11 X-ray