Heliangolides,and nerolidol and p-hydroxyacetophenone derivatives from Calea species

A new Calea species afforded a heliangolide, closely related to niveusin C, while from Calea teucrifolia two new nerolidol derivatives and eight p-hydroxyacetophenone derivatives were isolated. The structures were elucidated by spectroscopic methods and a few chemical transformations. The spectral data of 8β-angeloylatripliciolide, the main constituent of C. teucrifolia, are also included. The chemotaxonomic situation is discussed briefly.     

Neue ent-atisiren- und ent-kaurensäure-derivate aus Helianthus-arten

The investigation of four Helianthus species afforded, in addition to known compounds, four new atisirenic acid derivatives, a new ent-kaurenic acid derivative, three new labdane derivatives and an unknown C₁₅-acetylenic compound. The structures of the diterpenes were elucidated by intensive NMR studies and some chemical transformations. An unusual fragmentation in the mass spectra of the atisirenes is discussed briefly.     

8-Oxo-α-selinen und neue scopoletin-derivate aus Conyza-arten

The investigation of three South African and a North American Conyza species afforded, in addition to known compounds, a new eudesmane ketone and five new scopoletin derivatives. The structures are elucidated by spectroscopic methods and by some chemical transformations. Two of the scopoletin enol ethers have very unusual structures. While most of the Conyza species investigated so far contain typical C₁₀-acetylenes, also present in related genera, there are some with different chemistry. The relationship of the genus to Aster and Erigeron, however, is clearly indicated.     

Weitere hirsutinolide aus Vernonia-arten

The investigation of two Bolivian Vernonia species afforded, in addition to known compounds, five further enollactones of the hirsutinolide type and a new hydroxyzaluzanine. The structures were elucidated by intensive ¹H NMR studies and some chemical transformations. The results show again that the hirsutinolides are probably of chemotaxonomic importance in the large genus Vernonia.     

Neue sesquiterpene,triterpene, flavanone und andere aromatische verbindungen aus Flourensia heterolepis

The investigation of a further Flourensia species afforded in addition to already known compounds 12 new sesquiterpene acids isolated as their methyl esters, a new eudesmane diol, four lupane derivatives and two flavanones, two cinnamic acid derivatives, also isolated as methyl esters and a ketone. The structures are elucidated mainly by spectroscopic methods and by some chemical transformations. Several of the compounds isolated are more or less similar to those isolated from other Flourensia species; the considerable amounts of eudesmanes, however, are unusual. The overall picture of the genus is still relatively uniform. Close relationships to Helianthella are obvious, while to Helianthus, placed in the same subtribe, no clear relations are visible.     

Neue melampolide und cis,cis-germacranolide aus vertretern der subtribus melampodiinae

The investigation of four South American species of the tribe Heliantheae afforded in addition to known compounds 14 new sesquiterpene lactones, mostly belonging to the melampolides, but four being further examples of cis,cis-germacranolides. The stereochemistry is established by intensive ¹H-NMR studies and some chemical transformations. Some of the new lactones were only obtainable as inseparable mixtures of 2-methylbutyric and isovaleric esters. Furthermore a new acetylenic aldehyde was isolated. The chemotaxonomic situation is discussed especially with regard to the position of the genus Smallanthus.     

Neue labdan-derivate aus Carterothamnus anomalochaeta

The investigation of a Carterothamnus species afforded in addition to known euparine derivatives four new diterpenes, all being labdane derivatives. The structures are elucidated by ¹H-NMR-studies and by some chemical transformations. The chemotaxonomic situation is briefly discussed. The constituents of the Carterothamnus species show a distinct differentiation to those of the neighbouring groups; however, in addition they also indicate some relationships.     

β-Isocomen,ein neues sesquiterpen aus Berkheya-arten

The investigation of several Berkheya species afforded in addition to already known compounds three unusual sesquiterpene hydrocarbons. Together with modhephene and isocomene, a new one is present, its structure being elucidated by spectroscopic methods and by some chemical transformations. All 18 species investigated contain the typical thiophene derivatives, isolated earlier; the patterns of compounds present divide the species into two groups.     

Five germacranolides from Gochnatia discoidea

The investigation of two further Gochnatia species afforded five new germacranolides, all being 8,12-lactones. The structures were elucidated by intensive ¹H NMR studies and by some chemical transformations. The chemotaxonomic aspects are discussed briefly.     

Neue sesquiterpene aus Liabum-arten

The reinvestigation of the roots of Liabum eggersii afforded, in addition to compounds reported before, several sesquiterpene hydrocarbons with unusual carbon skeletons and the first derivative of the propellane modhephene which itself is also present. The roots of L. floribundum contain a tricyclic sesquiterpene with three five-membered rings. This ketone most probably is a derivative of the sesquiterpene silphiperfolene. The structures of the new compounds were elucidated by extensive NMR studies and by some chemical transformations. Two further species only afforded known compounds. The chemotaxonomic situation is discussed briefly.     

Neue eremophilene aus südafrikanischen Senecio-arten

The investigation of the South African Senecio species, S. gerardii, S. scaposus, S. cathcartensis and S. rhomboideus affords several new eremophilenes, the diesters of seneremophilondiol, senescaposone and isosenescaposone, both esterified with the previously unknown 4-methyl-5-acetoxy-pent-2c-en acid, and two further esters, one esterified with cis-hex-2-enoic acid. The side chains in three of these compounds have the unusual 7α- configuration. Furthermore the germacrene derivatives rhomboidol and the corresponding acetate have been isolated. The structures are elucidated by spectroscopic methods and some chemical transformations.     

Zwei neue germacranolide aus Artemisia argentea

The aerial parts of Artemisia argentea afforded, in addition to known compounds (arborescin, artemetin, sitosterol and lirioresinol-B-dimethyl ether), two new germacranolides, closely related to ketopelenolide, also isolated from an Artemisa species. The structures were elucidated by intensive ¹H NMR studies and by some chemical transformations.     

Fourteen heliangolides from Calea species

The investigation of two further Calea species afforded, in addition to known compounds, fourteen new heliangolides, most of them being 11,13-epoxides. One lactone is a new type, a heliangolide substituted with a monoterpene residue. Furthermore, a new chromene and a new dithienyl derivative were isolated. The structures were elucidated by spectroscopic methods. The chemotaxonomic situation is discussed briefly.     

Withaminimin,a withanolide from Physalis minima

The structure of withaminimin, a new ergostane-type steroid from Physalis minima, was established by spectral analysis (¹H and ¹³C NMR, MS) and chemical transformations, as (20S,22R)-15α-acetoxy-5α,6β,14α-trihydroxy-1-oxowitha-2,16,24-trienolide. An unusual MH₂O⁺ quasi-molecular ion was observed in the chemical ionization mass spectrum of the natural product.     

Neue chalkon-derivate aus südafrikanischen Helichrysum-arten

The investigation of two South African Helichrysum species afforded in addition to known compounds two new chalcone derivatives, four related dihydrochalcones,5,7,8-trimethoxyflavone and 5-methoxy-7,8-methylenedioxyflavone. The structures are elucidated by spectroscopic methods and some chemical transformations. The chemotaxonomic situation in the large genus Helichrysum is discussed, in the light of these results.     

Neue flavone und phloroglucin-derivate aus Helichrysum herbaceum und Helichrysum chrysargyrum

The investigation of two further South African Helichrysum species afforded five new flavones and six new phloroglucinol derivatives. The structures were elucidated by spectroscopic methods and some chemical transformations. The chemotaxonomic situation is discussed briefly.     

Neue furanoeremophilane und andere sesquiterpene aus vertretern der gattung Euryops

Investigation of a further 27 Euryops species affords, besides known compounds, 55 new furanoeremophilanes together with several other compounds. The configuration of six furanoeremophilanes earlier given as 10β-H has to be changed to 10α-H. Furthermore 9 new eremophilenes were isolated; the configurations of four compounds of this type isolated before have had to be changed. One of the eremophilenes is esterified with 3-methylpent-3(E)-enoic acid, not found before in nature. Two hemiacetals, which are probable precursors of the furanoerephilanes, and a corresponding lactone are also present. Furthermore two benzylic esters, cis-caryophyllene, a bicyclo-germacrene derivative, and a new oplopanone derivative have been found. The structures are elucidated mainly by spectroscopic methods together with some chemical transformations. From the chemotaxonomic viewpoint, the high concentration of very variable furanoeremophilanes may be important. The proposed differentiation into sections however can not be clearly correlated with the chemical constituents, though some taxonomic conclusions seem to be supported by the chemical evidence.     

Cannabigerol-ähnliche verbindungen aus Helichrysum umbraculigerum

The investigation of a further South African Helichrysum species afforded eleven resorcinol derivatives, most of them closely related to cannabigerol and the corresponding acid, both also being present in the aerial parts of H. umbraculigerum. Furthermore a new geranyl chalcone is present. The structures are elucidated by spectroscopic methods and some chemical transformations. The occurrence of the cannabigerol-like compounds in a composite is surprising. Probably, some of these compounds are formed by the combination of three different biogenetic pathways.     

Sesquiterpene and diterpene derivatives from Solidago species

The investigation of four Solidago species afforded, in addition to known compounds, four new caryophyllene derivatives, two eudesmanes, two abietanes, a clerodane, two labdanes, three kauranes and an anol angelate. The structures were elucidated by spectroscopic methods and by some chemical transformations. While the diterpenes isolated are widespread in the genus Solidago, the sesquiterpenes have not been obtained before from any species. The overall picture of the large genus, however, is relatively uniform.     

Eudesmane derivatives from Verbesina species

The investigation of seven Verbesina species afforded, in addition to known compounds, several new eudesmane and germacrane derivatives, all bearing a cinnamate or derivatives as residue. Furthermore, a new bisabolene aldehyde and two acetophenone derivatives were isolated. The structures were elucidated mainly by spectroscopic methods and some chemical transformations. The chemotaxonomic situation is discussed briefly.