Harold Robinson

Allenic germacranolides, bourbonene derived lactones and other constituents from Vernonia species

Abstract An investigation of seven Vernonia species, mainly from northern Brazil, afforded in addition to known compounds three new unusual sesquiterpene lactones with an allenic group. Intensive NMR studies fully established the structures. Furthermore, two lactones derived from bourbonene, two new glaucolides, a new furansesquiterpene, a nerolidol derivative and two other sesquiterpenes derived from eudesmane were isolated. The biogenetic relationships of the sesquiterpene lactones present in Veronia species as well as the chemotaxonomic aspects are discussed.

Five diterpenes and other constituents from nine Baccharis species

Abstract The investigation of nine Baccharis species afforded, in addition to known compounds, three new clerodane derivatives related to bacchotricuneatin B, two ent -labdane derivatives, two 3-acetoxyflavanones, a benzofuran derivative and a chromene. The overall picture of the chemistry of this large genus is still not very clear.

Germacranolides and diterpenes from Viguiera species

Abstract The investigation of six Viguiera species afforded in addition to known compounds two new diterpenes, the 9,11-dehydro derivatives of trachylobanic and stachenic acid, two new heliangolides closely related to viguiestenin, and the acetate of falcarinol. The chemotaxonomic situation is discussed briefly.

Seven germacranolides and four eudesmanolides from Tithonia rotundifolia

Abstract The aerial parts of Tithionia rotundifolia afforded, in addition to two known sesquiterpene lactones, eleven new ones, seven germacranolides and four eudesmanolides. The structures were determined by 1 H NMR spectroscopy.

Ein neues germacren-derivat sowie ein diterpenmalonat aus Baccharis-arten☆

Abstract The investigation of the aerial part of B. scandens afforded a new ketone, a germacrene derivative. The aerial parts of B. tricuneata var. lineata yielded, in addition to known ent-clerodane derivatives, a malonate of a further diterpene of this type. The structures are elucidated by spectroscopic methods.

Neue acetylenverbindungen aus chrysothamnus parryl

Abstract The investigation of Chrysothamnus parryi afforded, in addition to known compounds, several new matricaria ester derivatives. The structures were elucidated by spectroscopic methods and some chemical transformations. Furthermore, a naphthol derivative was isolated. Chemotaxonomic aspects are discussed briefly.

Neue guaianolide aus Cacosmia rugosa

Abstract The roots of C. rugosa afforded, in addition to known compounds, a C 17 -acetylenic epoxide and five new guaianolides, four of them being hydroperoxides. The structures were elucidated by extensive NMR studies. The aerial parts only contain triterpene mixtures, as those of C. hieronymi . The compounds isolated confirm that Cacosmia is unrelated chemically to true members of the tribe Senecioneae.

Three germacranolides and other constituents from Eremanthus species

Abstract The re-investigation of Eremanthus glomerulatus afforded three new germacranolides and a guaianolide, while from E. mollis two known furanoheliangolides and a new phenylpropanol derivative were isolated. The germacranolides most probably are precursors of the widespread glaucolides. The structures were elucidated by spectroscopic methods. The chemotaxonomic situation is discussed briefly.

Five germacranolides from Gochnatia discoidea

Abstract 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.

Germacranolides from Proteopsis Argentea

Abstract 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.