Germacranolides from Inula cappa

Authentic Inula cappa DC afforded a known and four unknown germacranolides related to the ineupatorolides as well as a new 2,3-dihydroxy-9-angeloxygermacra-4-en-6,12-olide. A collection previously described as Inula cappa which yielded only flavones was identified as Blumea balsamifera DC.     

Germacranolides from Eupatoriastrum nelsonii

The aerial parts of Eupatoriastrum nelsonii afforded, in addition to known sesquiterpene lactones, four new lactones all closely related to the germacranolides isolated previously from other genera of the tribe Eupatorieae. The structures were elucidated by spectroscopic methods. Chemotaxonomic aspects are discussed briefly.     

Germacranolides from Melampodium americanum and Melampodium pilosum

Chemical analysis of Melampodium americanum yielded, besides the known melampodinin A, four new melampolides, melampodinin B, melampodinin C, 9-des     

Germacranolides from Gochnatia vernonioides

The aerial parts of Gochnatia vernonioides afforded, in addition to dehydrocostus lactone, zaluzanin C and desacetyllaurenobiolide angelate, 14 further sesquiterpene lactones, ten 8, 12-and three 6,12-germacranolides as well as one eudesmanolide and three bisabolene derivatives. The structures were elucidated by spectroscopic methods and by comparing the data with those of closely related compounds. 8α-Angeloyloxytaraxic acid underwent an unusual autocatalysed cyclisation while the usual Cope rearrangement was not observed.     

Germacranolides from Perymenium klattianum and Perymeniopsis ovalifolia

The aerial parts of Perymenium klattianum afforded, in addition to kaurane and beyerane derivatives, three germacranolides, two of them isolated for the first time. The structures were elucidated by spectroscopic methods and by some chemical transformations, which in part gave unusual products. Perymeniopsis ovalifolia gave known compounds only.     

Pseudoguaianolides related to confertin from Stevia isomeca

The aerial parts of Stevia isomeca afforded, in addition to known compounds, four new sesquiterpene lactones, three pseudoguaianolides related to stevin and a xanthanolide. The structures were elucidated by spectroscopic methods and a few chemical transformations.     

Guaianolides related to arborescin from Artemisia adamsii

The aerial parts of Artemisia adamsii afforded, among several known compounds, arborescin as the main constituent. Furthermore, 11 new guaianolides, all related to arborescin, were present in minute quantities. The structures were elucidated by spectroscopic methods and the biogenetic relationships are discussed briefly.     

Germacranolides from Stilpnopappus species

The investigation of four Stilpnopappus species afforded in addition to known compounds seven new germacranolides, all related to glaucolides. The structures were elucidated by spectroscopic methods. The chemotaxonomy of the genus is discussed briefly.     

Germacranolides in Helianthus mollis

Desacetyleupaserrin, eupaserrin and two new germacranolides, mollisorin-A and mollisorin-B, were isolated from H. mollis. ¹H NMR and ¹³C NMR data and chemical interconversions of the four germacranolides are described.     

Germacranolides from Proteopsis Argentea

Proteopsis argentea (tribe Vernonieae) afforded in addition to known compounds three new sesquiterpene lactones, closely related to those isolated from Eremanthus species, indicating a close relationship between these genera.     

Stereochemistry of chapliatrin and its congeners from Liatris gracilis

Re-examination of Liatris gracilis afforded the known sesquiterpene lactones chapliatrin, isochapliatrin, acetlisochapliatrin, five new closely related 5,10-epoxygermacranolides and a new eudesmanolide. The stereochemistry of the 5,10-epoxygermacranolides has been settled by an X-ray analysis of isochapliatrin.     

Germacranolides from Piptolepis leptospermoides

Piptolepis leptospermoides afforded, in addition to known compounds, a new eremanthanolide and a germacranolide closely related to piptolepolide.     

Germacranolides from Dicoma tomentosa

An investigation of the aerial parts of Dicoma tomentosa afforded four new germacranolides and four melampolides together with urospermal A and its 11β,13-dihydroderivative. The structures were elucidated by spectroscopic methods. The chemotaxonomic situation is discussed briefly.     

Germacranolides from Piptolepis Ericoides and Vanillosmopsis species

The aerial parts of Piptolepis ericoides afforded in addition to known compounds two new germacranolides, a zexbrevanolide and piptolepolide, tentatively characterized as a germacranolide with a trans-disubstituted double bond. From the aerial parts of two Vanillosmopis species in addition to goyazensolide, a new isomer with an exocyclic double bond was isolated.     

Germacranolides from Mikania grazielae

Mikania grazielae afforded two new germacranolides which were identified as 2α-acetoxyeupatolide and 2α-acetoxylaurenobiolide.     

Germacranolides from Helianthus californicus

Five germacranolide sesquiterpene lactones and a trachylobane diterpene were isolated from the hexaploid species Helianthus californicus. Four of the sesquiterpene lactones are new, including a 1-oxo-3,10-diol without any carbon-carbon double bonds in the main ring whose structure was confirmed by X-ray crystallography. These results require revision of the structures of several previously published compounds. Two of the germacranolides have alkyl ether functions at a position β to a ketone and are believed to be artifacts of the isolation process. Based on terpenoid chemistry, there are no obvious progenitors of H. californicus among the diploid species of Helianthus examined to date.     

Terpenoids and a flavan-3-ol from viguiera quinqueradiata

The isolation is reported of the new natural products from Viguiera quinqueradiata, acetylleptocarpin and (2R,3S-4′-hydroxy-3′,5,7-tri-O-methyl-flavan-3-ol. The diterpenes 15α-angeloyloxy-ent-kaur-16-en-19-oic acid, 15α-tigloyloxy-ent-kaur-16-en-19-oic acid and the sesquiterpene lactones leptocarpin and budlein A were also found.     

Elemanolides from Zinnia peruviana

Zinnia peruviana from Honduras afforded two new acetal-type elemanolides as well as a mixture consisting primarily of zinaflorin III.