Guillermo Schmeda-Hirschmann

Hirsutinolides, glaucolides and sesquiterpene lactone from Vernonia species

Abstract The investigation of nine Vernonia species afforded in addition to known sesquiterpenes 28 new ones. The structures were elucidated by high field 1 H NMR spectroscopy and the configurations were determined by NOE difference spectroscopy and, in one case, by X-ray analysis. The results indicated that configurations of several previously reported sesquiterpene lactones have had to be revised. In addition to known types two new ones, the jalcaguaianolides and the vernojalcanolides, are described. Furthermore some unusual reaction products are presented which, in part, led to some natural occurring lactones.

Eremophilane derivatives and other constituents from Senecio species

Abstract The investigation and reinvestigation respectively of 23 Senecio species afforded 11 further cacalol derivatives, a furoeremophilone, 17 eremophilanes, 4 bisabolene derivatives, a shikimic acid derivative, a bis -prenylated p -hydroxybenzaldehyde, menth-2-en- 1,7-diol and a cumol derivative. The configuration of some eremophilanes have been revised. Structures were elucidated by spectroscopic methods. The results are summarized in a table. The chemotaxonomic aspects agree with those of previous investigations.

Dimeric guaianolides and other constituents from Gochnatia species

Abstract The roots of Gochnatia polymorpha afforded two new bisabolene derivatives and four dimeric guaianolides, two of them being isolated previously from G. paniculata . The aerial parts gave two further dimeric guaianolides. The aerial parts of G. hypoleuca afforded three new germacran-8,12-olides, a germacranolide acid and four additional dimeric guaianolides, which may be characteristic for this genus, while the presence of oxygenated germacranolides seems to be typical for the whole subtribe.

Germacranolides from Gochnatia vernonioides

Abstract 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.

Clerodane and labdane diterpenoids from Baccharis species

Abstract The investigation of eight Baccharis species afforded, in addition to known compounds, five new clerodanes, three labdane derivatives and a nor-diterpene as well as one hydroperoxide derived from 4α-hydroxygermacra-1(10), 5-diene. The structures were elucidated by spectroscopic methods. The structures of esters isolated previously from B. cassinaefolia have to be revised. Chemotaxonomic aspects are discussed briefly.

Rhamnofolane derivatives from Jatropha grossidentata

Abstract From the root bark of Jatropha grossidentata two pairs of epimeric rhamnofolane derivatives were isolated. The structures are elucidated by high field NMR spectroscopy.

Heliangolides and germacrolides from Disynaphia multicrenulata

Abstract Investigation of Disynaphia multicrenulata afforded, in addition to known ent -kaurene derivatives and some widespread sesquiterpenes, several s

Beyerene derivatives and other terpenoids from Stevia aristata

Abstract The aerial parts of Stevia aristata afforded in addition to known compounds two new germacranolides, a melampolide, a 4 Z -melampolide and two beyerene derivatives. From the roots a new dihydrolongipinene derivative was isolated while the aerial parts of Stevia andina gave the E/Z -isomers of austroinulin and 6-desoxyaustroinulin. The absolute configuration of these typical diterpenes is discussed.

Further sesquiterpene lactones from Calea and Viguiera species

Abstract 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.

Seco-isotetrandrine from Laurelia sempervirens

Seco-isotetrandrine was isolated from Laurelia sempervirens leaves and its structure elucidated by extensive use of NMR spectroscopy.