New sesquiterpene lactones from Artemisia herba alba

The structures of herbolides A, B and C, new sesquiterpene lactones isolated from Artermisia herba alba, were determined by chemical and spectroscopic methods.     

Pseudoguaianolides and other sesquiterpene lactones from Gaillardia species

The aerial parts of two Gaillardia species afforded in addition to known sesquiterpene lactones 23 new pseudoguaianolides, two dugaldiolide derivatives and two seco-neopulchellin derivatives. The structures were elucidated by spectroscopic methods. Biogenetic relationships are discussed briefly.     

Ant-repellent sesquiterpene lactones from Eupatorium quadrangularae

The chloroform extract from the leaves of Eupatorium quadrangularae has been systematically fractionated by following biological activity in a bioassay which measures repellency to the leafcutter ant Atta cephalotes (Formicidae, Attini). Several sesquiterpene lactones were isolated, two of which showed significant ant-repellency.     

Two sesquiterpene lactones of Calea ternifolia var. Calyculata

Chemical analysis of Calea ternifolia var. calyculata yielded the known sesquiterpene lactone calein A, as well as two new modified heliangolid     

Seven sesquiterpene lactones from Ferreyanthus species

The investigation of two Ferreyanthus species afforded seven germacranolides which have not been isolated previously. Two derivatives of linalol were also present. The structures were elucidated by spectroscopic methods. Chemotaxonomic relationships are briefly discussed.     

Glaucolide-like sesquiterpene lactones from Cotula cinerea

The aerial parts of Cotula cinerea gave, in addition to widespread compounds, a characteristic diacetylenic spiroketal enolether and several sesquiterpene lactones, three of them being glaucolide-like lactones. The structures were elucidated by highfield ¹H NMR spectroscopy.     

Two sesquiterpene lactones from Trichogonia gardneri

The structures and stereochemistries of two sesquiterpene lactones from Trichogonia gardneri were established as (6R,7S,8S,9S,IOR)-4E-9,10-dihydroxy-8-tigloxygermacr-4-en-6,12-olide) and (5R*,6R*,7S*,8S*,9R*)-14-acetoxy-3-chloro-9-hydroxy-2-oxo-8-tigloxyguia-1(10),3-dien-6,12-of olide by a combination of NMR spectrometry and X-ray diffraction. The results show that the structures of several sesquiterpene lactones which were isolated previously from related species require revision.     

Further sesquiterpene lactones from Calea and Viguiera species

The aerial parts of Calea clematidea gave three new germacranolides, those of Viguiera procumbens two orizabin derivatives and those of V. linearis dihydrobudlein A. In addition to these lactones, several known ones were isolated.     

The stereochemistry of matricin and 4-epimatricin,proazulene sesquiterpene lactones from Artemisia arborescens

An investigation of Artemisia arborescens afforded, in addition to the known compounds matricin, artabsin and artemetin, the new guaianolide 4-epimatricin. The stereostructures of 4-epimatricin and matricin were assigned on the basis of spectroscopic evidence.     

Flavones,sesquiterpene lactones and glycosides isolated from Centaurea aspera var. Stenophylla

From the alcoholic extract of Centaurea aspera var. stenophylla benzoic acid, p-hydroxybenzoic acid, apigenin, 6-methoxyluteolin, 11,13-dehydromelitensin, melitensin, stenophyliolide, ethyl-7-O-apigenin-glucuronate and the glucosides of sitosterol and stigmasterol were isolated and characterized. Stenophyllolide was shown to be 9,15-dihydroxygermacra-1(10),4,11-trien-12,6-olide.     

Sesquiterpene lactones of sagebrush: The structure of artecanin

Artemisia cana Pursh ssp. cana collected in Montana contained desacetylmatricarin, canin, artecanin and artevasin. Artecanin has been shown to have the structure 3 on the basis of the physical and spectral properties. The structure of canin has been revised to 2.     

New types of sesquiterpene lactones and other constituents from Trichogonia species

The investigation of five Trichogonia species afforded seven new furanoheliangolides, three dilactones of a new type, four pairs of epimeric rearra     

Dimeric guaianolides from Artemisia sieversiana

The aerial parts of Artemisia sieversiana afforded in addition to known compounds five new guaianolides and four dimeric guaianolides, three of them closely related to absinthin and one derived from estafiatin as a monomer. The structures were elucidated by extensive NMR studies, which allowed the assignment of the 14 chiral centres. Artemisia frigida afforded several known compounds and one new guaianolide, 8-desoxy-cumambrin B, the most likely precursor of many guaianolides.     

Three bourbonenolides and other sesquiterpene lactones from two vernonia species

A re-investigation of V. arkansana afforded several new sesquiterpene lactones, three bourbonenolides, obviously closely related to those isolated from this plant previously, a glaucolide and a methoxy derivative most probably formed by fragmentation of the corresponding bourbonenolide. From V. profuga in addition to known lactones a new guaianolide was isolated. The biogenetic relationships of the Vernonia sesquiterpene lactones are discussed briefly.     

Sesquiterpene lactones and other constituents from Schistostephium species

From four Schistostephium species, in addition to known compounds, 43 new ones were isolated, three isocomene, two bisabolene, two eudesmane, two allo-himachalene and two nerolidol derivatives, two sesquiterpenes with a new carbon skeleton derived from isocomene, nine eudesmanolides, 20 6,12- and 8,12-germacranolides respectively, and a prostaglandin-like acid. The structures were elucidated by spectroscopic methods, especially high field ¹H NMR and some chemical transformations. The stereochemistry of some 8,12-germacranolides was established by partial synthesis which required revision of the previous assignments of the configuration of inunolide, its 4,5- and 1,10-epoxide, vernudifloride, simsiolide, 6-hydroxy-1,10-epoxyinunolide and perhaps also of tanachin. The chemotaxonomic situation is discussed briefly.     

Tetraludin A,B and C,three new melampolides from Tetragonotheca ludoviciana

The investigation of the roots of the four Tetragonotheca species, T. ludoviciana, T. repanda, T. texana and T. helianthoides, resulted in the isolation of the known heptadeca-2-(Z)-8,10-(E)-16-tetraene-4,6-diin-1-ol and its aldehyde derivative from all four species. Aerial parts of T. ludoviciana also contained the acetate of the latter compound as a minor constituent and provided three new melampolide-type sesquiterpene lactones, tetraludin A, B and C.     

Modified eudesmanolides and other sesquiterpene lactones from Wunderlichia mirabilis and Actinoseris polymorpha

Re-investigation of Wunderlichia mirabilis afforded three new modified eudesmanolides of the same type isolated previously from an Onoseris species, and minute amounts of a germacranolide for which a structure only could be proposed. Actinoseris polymorpha also contained a new germacranolide, the angetate of desacetyllaurenobiolide. Structures were elucidated by spectroscopic methods and by some chemical transformations. The significance of these findings is discussed briefly.     

Sesquiterpene lactones from Sonchus macrocarpus

Eight sesquiterpene lactones were isolated from the roots of Sonchus macrocarpus. The eudesmanolides 15-hydroxy-4β, 15-dihydroreynosin and 15-hydroxy-4β, 15, 11β, 13-tetrahydroreynosin were isolated for the first time.     

New germacranolides and other sesquiterpene lactones from Dicoma species

Two subspecies of Dicoma anomala afforded, in addition to known compounds, an eudesmanolide, a guaianolide and four germacranolides, the latter being closely related 8, 12-lactones. D. schinzii gave three new germacranolides and D. zeyheri a pair of isomeric acetylenic compounds. The structures were elucidated by highfield ¹H NMR spectroscopy. The chemotaxonomic situation of this genus is discussed briefly.     

Ludalbin,a new lactone from Artemisia ludoviciana

Artemisia ludoviciana Nutt. ssp. albula (Woot.) Keck, a member of the vulgaris complex, contains a sesquiterpene lactone, ludalbin, which is 8-α-acetoxydouglanine.