Robert M King

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.

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.

New germacranolides from Isocarpha species

Abstract The investigation of two Isocarpha species has yielded eight new germacranolides most of them belonging to the heliangolides. In addition to known p -hydroxyacetophenone-derivatives, a new dihydroeuparine derivative was isolated. The chemotaxonomical aspects are discussed.

Eudesmanolides and diterpenes from Wedelia trilobata and an ent-kaurenic acid derivative from Aspilia parvifolia

Abstract The reinvestigation of the aerial parts of Wedelia trilobata afforded, in addition to known compounds, six new eudesmanolides, two ent-kaurenic acid derivatives as well as a degraded one. A corresponding hydroxy compound was present in Gnaphalium undulatum. From Aspilia parvifolia new ent-kaurenic acid epoxides were isolated. The structures were elucidated by spectroscopic methods. The chemotaxonomic situation is discussed briefly.

Types of sesquiterpenes from Artemisia douglasiana

Abstract Artemisia douglasiana afforded, in addition to known compounds, two new C14-acetylenes, five longipinene derivatives, three nerolidol derivatives, a lactone and a ketone with a new carbon skeleton and lavendulol-2-methylbutyrate. The structures were elucidated by spectroscopic methods and some chemical transformations. The configurations of several oxo longipinene-7, 9-di- and 7, 8, 9-triesters isolated previously were corrected. The biogenesis of the new lactones is discussed briefly.

Neue sesquiterpene aus Liabum-arten

Abstract The reinvestigation of the roots of Liabum eggersii afforded, in addition to compounds reported before, several sesquiterpene hydrocarbons with unusual carbon skeletons and the first derivative of the propellane modhephene which itself is also present. The roots of L. floribundum contain a tricyclic sesquiterpene with three five-membered rings. This ketone most probably is a derivative of the sesquiterpene silphiperfolene. The structures of the new compounds were elucidated by extensive NMR studies and by some chemical transformations. Two further species only afforded known compounds. The chemotaxonomic situation is discussed briefly.

Sesquiterpene and diterpene derivatives from Solidago species

Abstract The investigation of four Solidago species afforded, in addition to known compounds, four new caryophyllene derivatives, two eudesmanes, two abietanes, a clerodane, two labdanes, three kauranes and an anol angelate. The structures were elucidated by spectroscopic methods and by some chemical transformations. While the diterpenes isolated are widespread in the genus Solidago , the sesquiterpenes have not been obtained before from any species. The overall picture of the large genus, however, is relatively uniform.

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.

Sesquiterpene lactones from Eremanthus species

Abstract The investigation of three Eremanthus species afforded, in addition to known compounds, several new sesquiterpenelactones, a cumambrin B isobutyrate, four lactones related to the eremantholides, two to zexbrevin and one to goyazensolide. Furthermore, a new coniferyl alcohol derivative was isolated. The overall picture of the genus is very uniform. The occurrence of eremanthine and germacranolides with a furanone ring seems to be especially typical.

Neue diterpene aus der subtribus espeletiinae

The investigation of several species from the newly created subtribe Espeletiinae afforded in addition to known compounds seven new diterpenes and two norditerpenes. The structures were elucidated by intensive 1H-NMR studies. The chemotaxonomic situation is discussed briefly.