Diterpenes from Koanophyllon species

The investigation of two Koanophyllon species afforded, in addition to known compounds, several new diterpenes, two new geranylgeraniol derivatives and four diterpenes, most probably closely related to clerodanes; their structures, however, could not be deduced with certainty. The chemotaxonomic situation of this genus is discussed briefly.     

Diterpenes from Mikania species

The investigation of four further Mikania species afforded several diterpenes, four geranylgeraniol derivatives and three kaurane epoxides. The structures were elucidated by spectroscopic methods and a few chemical transformations.     

Diterpenes from Baccharis species

The aerial parts of Baccharis minutiflora afforded in addition to known compounds eight new ent-kaurane derivatives, one being a homo kaurane, while the aerial parts of B. alatemoides gave two pairs of epimeric clerodane derivatives, which, however, had to be modified chemically before they could be separated. The stereochemistry of these diterpenes could not be elucidated with certainty.     

Diterpenes derived from clerodanes from Pulicaria angustifolia

The investigation of Pulicaria angustifolia afforded, in addition to known triterpenes and caryophyllene epoxide, four methyl esters of diterpenes, all derived from clerodane. Three of them are derivatives of seco-nidoresedic acid. The structures were elucidated by spectroscopic methods.     

Diterpenes from Heteropappus altaicus

The aerial parts of Heteropappus altaicus afforded, in addition to more widespread compounds and known clerodane derivatives, three new ones and a seco-clerodane acid. Furthermore, a neryl geraniol derivative was present. The structures were elucidated by spectroscopic methods. The stereochemistry was solved by NOE difference spectroscopy and by the Horeau method.     

Diterpenes from Baccharis species

The investigation of ten Baccharis species afforded in addition to known compounds eight new diterpenes, four ent-labdanes, three kaurenes and a clerodane derivative. Furthermore, two new p-hydroxyacetophenones, a flavone, 3′-methoxyxanthomicrol and two matricaria ester derivatives were isolated. The structures were elucidated by spectroscopic methods and a few chemical transformations. The chemotaxonomic situation of the large genus is discussed briefly.     

Diterpenes and sesquiterpenes from Osteospermum species

The investigation of several Osteospermum species afforded in addition to known compounds three diterpenes from the rare cassane type, two further sandaracopimarene derivatives, two 6-desoxyglucosides of cubebol and 13-hydroxycaryophyllene, respectively, an isomer of 7-hydroxycalamenene, two p-hydroxyacetophenone derivatives derived from toxol, a thymol derivative and the palmitates of lupeol, taraxasterol and 3β,20-dihydroxydammarene. The structures were elucidated by spectroscopic methods. The chemotaxonomy of the genus is discussed briefly.     

Grindelane diterpenoids from Grindelia campórum and Chrysothamnus paniculatus

The structures of nine grindelic acid related diterpenes isolated as methyl esters from Grindelia camporum and Chrysothamnus paniculatus, were elucidated based on their spectral properties.     

Isolation and structure of stephalic acid,a new clerodane diterpene from Stevia polycephala

From the methanolic extract of Stevia polycephala a new clerodane-type diterpene, stephalic acid, was isolated. The structure and stereochemistry were determined by a combination of spectral data and single-crystal X-ray analysis.     

Diterpenes and tetranorditerpenes from Acritopappus species

The investigation of four Acritopappus species afforded twenty-three new diterpenes of the labdane or kolavane type and three tetranorditerpenes as well as two new benzofuran derivatives and a hydroxybicyclogermacrene. The structures were elucidated by spectroscopic methods and by some chemical transformations. Though the absolute configuration were not established in all cases, most probably all diterpenes were ent-labdanes or kolavanes (clerodanes). The chemotaxonomic importance of this investigation is discussed briefly.     

Diterpenes from Palafoxia texana

The investigation of Palafoxia texana afforded in addition to the known compound jesromotetrol two new rosene derivatives: 3β-acetoxy-jesromotetrol and 3β,19-diacetoxy-jesromotetrol. The structures were determined by spectroscopic methods and chemical transformations.     

A further geranylnerol derivative from Helianthopsis species

The investigation of three species of the new genus Helianthopsis gave in all cases furoheliangolides, as well as kaurenic, tricholobanic and beyerenic acids. Furthermore, a new geranylnerol derivative was isolated from H. bishopii. The chemotaxonomy is discussed briefly.     

Eremophilane derivatives and other constituents from Senecio species

The investigation and reinvestigation respectively of 23 Senecio species afforded 11 further cacalol derivatives, a furoeremophilone, 17 eremophilanes, 4 bisabolene derivatives, a shikimic acid derivative, a bis-prenylated p-hydroxybenzaldehyde, menth-2-en- 1,7-diol and a cumol derivative. The configuration of some eremophilanes have been revised. Structures were elucidated by spectroscopic methods. The results are summarized in a table. The chemotaxonomic aspects agree with those of previous investigations.     

New labdane derivatives and further constituents of Brickellia species

The investigation of several Brickellia species and two further related species afford besides known compounds four new labdane derivatives, a new acetylenic carbinol and a new dihydrobenzofuran derivative. The structures have been elucidated by spectroscopic methods. The chemotaxonomic aspects are discussed briefly.     

Diterpenes and sesquiterpene lactones from Mikania congesta

The chloroform extract of the aerial parts of Mikania congesta, afforded four new geranylnerol derivatives, new analogs of deoxyelephantopin, a new melampolide and several known compounds. Structures were elucidated by spectroscopic methods and chemical transformations.     

Thirteen kolavane derivatives from Symphyopappus species

The aerial parts of Symphyopappus compressus afrorded three new kolavane derivatives and those of S. reticulatus ten diterpenes of this type, two of them esterified with long chain fatty acids. Furthermore, a dihydroxyphenylpropanol, also esterified with long chain fatty acids, was present in both species. The roots of S. reticulatus afforded a new tremetone derivative. The structures were elucidated by spectroscopic methods and some chemical transformations.     

Heliangolides and other constituents from Bejaranoa semistriata

The investigation of Bejaranoa semistriata, a new genus in the tribe Eupatorieae, afforded in addition to known compounds a new furanoheliangolide, two epimeric 1-keto-heliangolides, two germacranolides, two nerolidol derivatives and a geranylnerol derivative. The structures were elucidated by spectroscopic methods and a few chemical transformations.     

Clerodane diterpenoids from Aster alpinus

The aerial parts of Aster alpinus afforded, in addition to dammadienyl acetate and dammadienone, two clerodane derivatives related to salviarin and bacchotricuneatin A. The structures were elucidated by spectroscopic methods, especially high-field NMR. The chemotaxonomic situation is discussed briefly.