Chemical study of four samples of Ligularia brassicoides collected in Sichuan Province of China afforded 18 compounds, five of which were new. LC-MS profiles were somehow similar to each other, although the compound ratio was slightly different. One of the new compound was a Diels-Alder adduct between franoeremophilan-10 beta-ol and methacrylic acid.
Twenty-six eremophilane-type sesquiterpenoids, including six new compounds, were isolated from the title species. One of the new compounds, kanaitzensol, suggested the presence of an enzyme for the conversion of eremophil-7(11)-en-8-one derivative to furanoeremophilanes. The plant was collected at 15 locations in Yunnan Province of China and found to be diverse with respect to its sesquiterpenoid composition. DNA sequencing also revealed a large intraspecific diversity of the plant. (c) 2008 Els...
The ether extract of the liverwort Chiloscyphus polyanthos afforded sesquiterpenoids which are enantiomeric to those found in another liverwort Lepidozia vitrea. The absolute configurations of the sesquiterpenoids found in the title species were determined by spectroscopic evidence, chemical derivatization and /or X-ray crystallographic analysis.
Abstract Six novel eremophilenolides were isolated from a methanol extract of the aerial parts of Hertia cheirifolia and their structures were established by a combination of 1D and 2D 1 H and 13 C NMR. The compounds identified are 10β-hydroxyeremophilenolide, 8β, 10β-dihydroxyeremophilenolide, 8β-methoxy-10β-hydroxyeremophilenolide, 6β, 10β-dihydroxy-8β-methoxyeremophilenolide, 3β-angeloyloxy-6β, 10β-dihydroxy-8β-methoxyeremophilenolide and 3β-angeloyloxy-10β-hydroxy-8β-methoxyeremophilenolide.
Abstract The aerial parts of Euryops arabicus afforded in addition to several known furoeremophilanes four new ones as well as four eremophilanolides, two seco derivatives and a rearranged spiro lactone. Furthermore two quercetin derivatives and an unusual diester of glucose were present. The structures were elucidated by high field NMR techniques and the biosynthesis of the unusual compounds is discussed.
Mass spectral fragmentations of furanoeremophilane derivatives bearing oxygen-function on B ring were investigated. It was found that mass spectra measured by direct inlet system gave characteristic retro-Diels-Alder fragmentations, while indirect introduction of the samples afforded intense peaks at m/e 159 and m/e 145 containing the furan moiety. Fragmentation patterns of other poly-functional derivatives were examined by measurements of accurate masses and metastable ions.
Abstract An Australian member of the tribe Senecioneae, Bedfordia salicina , contains besides known compounds new dimeric eremophilenolides, new kolevane derivatives, a kaurenic acid and several further sesquiterpenes, most of them related to xanthatine. The structures are elucidated mainly by spectroscopic methods and by some chemical transformations. The chemotaxonomic aspects of these findings are discussed briefly.
The photosensitized oxygenation of petasalbin I gave almost quantitatively a crystalline mixture of two isomeric hydroperoxides, V-a and V-b, both of which were then transformed to the corresponding lactones, VI-a and VI-b, respectively, in good yields. The stereochemistry of these hydroperoxides and lactones has been established by spectral and chemical methods. Furthermore, two natural lactones, III and IV, were prepared by the reduction of the hydroperoxides.
Abstract A group of a new type of sesquiterpene, named bakkenolide-A, B, C, D, and E was isolated from the buds of Petasites japonicus (Sieb. et Zucc.) Maxim. subsp. giganteus (Fr. Schm.) Kitam. (Japanese name, Akita-buki). They have a novel spiro-γ-lactone grouping. The structure and stereochemistry including absolute configuration was established for bakkenolide-A (B-A) ( 1 ) on the basis of chemical degradations (Chart 1, 2) and physical measurements. The C 11 -dicarboxylic acid ( 5 ), a main...
From the roots of Ligularia cymbulifera collected in Yunnan Province, China, two new eremophilane-type sesquiterpenoids (1 and 2) together with ten known compounds (3-12) were obtained through the precise chemical component elucidation. The structure determination was mainly carried out with 1D and 2D NMR data.