Harold Robinson

Pseudoguaianolides and other sesquiterpene lactones from Gaillardia species

Abstract 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.

Diterpene glycosides and other constituents from argentinian baccharis species

Abstract The investigation of the aerial parts of nine Baccharis species from Argentina gave 37 new compounds, seven ent -clerodanes, 13 ent -labdanes, two friedolabdanes, a nor-labdane ketone, seven coumaric acid derivatives, two umbelliferone derivatives, a flavanone, three sesquiterpenes including a nor-furanocadinene and a propiophenone derivative. Ten of the diterpenes were glycosides. The structures and the configurations were determined by highfield NMR spectroscopy and some chemical transformations. The absolute configurations of the diterpenes were proposed following observed Cotton-effects and in one case by using the Horeau-method together with 1 H NMR determination of the configuration of the main phenylbutyrate obtained. The chemotaxonomy is discussed.

A dimeric germacranolide and other sesquiterpene lactones from Mikania species

Abstract The investigation of two Mikania species, both previously placed in the genus Kanimia , afforded in addition to known compounds several new germ

Eudesmane derivatives from Verbesina species

Abstract 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.

Fourteen heliangolides from Calea species

Abstract 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.

Eriolanolides, eudesmanolides and a rearranged sesquiterpene from Eriophyllum species☆

The investigation of two Eriophyllum species afforded, in addition to numerous known compounds, eight new sesquiterpene lactones related to eriolanin, two eudesmanolides and a new type of sesquiterpene alcohol. The structures were elucidated by spectroscopic methods and a few chemical transformations. The chemotaxonomic situation of this genus, the placement of which is still in doubt, is discussed briefly.

ent-clerodanes and other constituents from bolivian Baccharis species

Abstract Investigation of seven Bolivian Baccharis species afforded in addition to known compounds 17 ent -clerodane, 10 ent -labdane, two bisabolene, a germacrane, a cadinane, a guaiane and a p -coumaric acid derivative. In one case the ent -labdane was linked with a bisabolene derivative via a malonate group. The structures were elucidated mainly by high field NMR techniques.

Further 5-methyl coumarins and other constituents from the subtribe mutisiinae

Abstract The investigation of four species from the subtribe Mutisiinae afforded eight new monoterpenes, seven 5-methyl coumarins, two closely related 5-methyl chromones, two coumarane derivatives, a p-hydroxy acetophenone derivative and a new C14-acetylene. The structures were elucidated by spectroscopic methods and a few chemical transformations. The chemotaxonomy of the Mutisiinae is discussed.

Further pyrrolizidine alkaloids and furoeremophilanes from Senecio species

Abstract The investigation of 17 Senecio species afforded in addition to 14 known pyrrolizidine alkaloids 20 new ones, including some compounds of a novel type with an additional lactone moiety. Furthermore seven known and 11 new furoeremophilanes, two known and a new eremophilone, a further shikimic acid derivative and an acetylenic compound, most likely formed by intramolecular Diels-Alder reaction were isolated. The structures were elucidated by spectroscopic methods, especially high field 1H and 13C NMR and NOE difference spectroscopy. The configuration of the seneremophilondiol esters has been corrected.

Caryophyllene derivatives and a heliangolide from Lychnophora species

Abstract The investigation of three Lychnophora species afforded three new caryophyllenic acids and a new heliangolide closely related to 15-desoxygoyazensiolide. All three species contain lupeol, lupeyl acetate and eremanthine. The chemotaxonomic situation is discussed briefly.