Detlef Wendisch

Microbial alteration of 17α(H)-hopanes in Madagascar asphalts: removal of C-10 methyl group and ring opening

Abstract The detailed investigation of the saturated hydrocarbon fractions of two biodegraded asphalts from the Morondava Basin, Madagascar, and the comparison with a related non-biodegraded asphaltic oil revealed new information on the compositional alteration of reservoired hydrocarbons due to biodegradation. A nuclear-demethylated 17α(H)-hopane was isolated from one of the asphalts and the preferred structure is suggested to be 25-nor-17α(H)-hopane. In addition to a homologous series of 25-nor-17α(H)-hopanes and 25-normoretanes a series of tetracyclic triterpanes was detected. These are thought to be derived from 17α(H)-hopanes by ring C opening. Steranes in the biodegraded asphalts were found to be altered but not completely removed.

Novel 23,28-bisnorlupanes in Tertiary sediments. Widespread occurrence of nuclear demethylated triterpanes

Abstract A pair of isomeric C 28 -bisnorlupanes was detected in high abundance in the saturated hydrocarbon fractions of Tertiary sediments from West Greenland and the Gulf of Suez. The compounds were isolated by preparative gas chromatography and the isomers separated by liquid chromatography. On the basis of mass spectrometric and nuclear magnetic resonance data the structures were assigned to be 17α(H)- and 17s(H)-23,28-bisnorlupane, respectively. The significance of nuclear demethylated triterpanes is discussed in terms of their generally high abundance, their uneven distribution within a given facies, and their worldwide occurrence.

Protonenresonanz-spektroskopie ungesättigter ringsysteme—IX : Die partielle analyse einiger bullvalen-spektren—ein beitrag zum problem der inneren rotation bei vinylcyclopropanen☆

Zusammenfassung Die Protonenresonanz-Spektren einiger Bullvalene wurden analysiert. Die erhaltenen Kopplungskonstanten werden mit denen im Cycloheptatrien[1,3,5] verglichen. Konsequenzen bezuglich des Potentialverlaufs fur die Drehung der Vinylgruppe im Vinylcyclopropan werden abgeleitet. Die Ergebnisse sind mit einem trans/gauche-Gleichgewicht vereinbar. Andere Befunde, die diese Annahme stutzen, werden diskutiert.Zusammenfassung Die Protonenresonanz-Spektren einiger Bullvalene wurden analysiert. Die erhaltenen Kopplungskonstanten werden mit denen im Cycloheptatrien[1,3,5] verglichen. Konsequenzen bezuglich des Potentialverlaufs fur die Drehung der Vinylgruppe im Vinylcyclopropan werden abgeleitet. Die Ergebnisse sind mit einem trans/gauche -Gleichgewicht vereinbar. Andere Befunde, die diese Annahme stutzen, werden diskutiert.

Sesquiterpene lactones from Neurolaena lobata

Abstract Eleven sesquiterpene lactones were isolated from above ground organs of Neurolaena lobata , obtained from Guatemala. Their structures were established by NMR spectroscopic methods, including 2D-NMR, as well as GC-MS analysis. Differences in the sesquiterpene lactone pattern and content in plants of different geographical origin in discussed.

Four annonins from Annona squamosa

Annonin IV, annonin VIII, annonin XIV and XVI, new linear acetogenins with hydroxylated bistetrahydrofuran moieties, and an α,β-unsaturated-γ-lactone were isolated from the seeds of Annona squamosa. Their constitutions and relative configurations have been established by 13C and 1H NMR and mass spectrometry.

Cripowellin A and B, a novel type of amaryllidaceae alkaloid from Crinum powellii

Abstract Two novel Amaryllidaceae alkaoids named cripowellin A (1) and B (3) were isolated from bulbs of Crinum powellii. Their structures were elucidated by spectroscopic investigations and confirmed by X-ray analysis.

Die stereoisomeren bicyclo[4.2.0]octan-cis-Diole-(7,8)

Zusammenfassung Die stereochemische Zuordnung der Bicyclo[4.2.0]octan- cis -diole-(7,8) wird uberpruft. Es wird gezeigt, das die auf verschiedenen Wegen dargestellten cis -Diole in der Tat Stereoisomere sind, von denen dem niedriger schmelzenden Diol exo -Konfiguration ( 1 ), dem hoher schmelzenden endo -Konfiguration ( 2 ) zukommt. Die Synthese des bislang unbekannten trans -verknupftenBicyclo[4.2.0]octan- cis -diols-(7,8) ( 3 ) durch photosensibilisierte Cycloaddition von Vinylencarbonat an Cyclohexen wird beschrieben.

Diterpenes from Arnica angustifolia

From flowerheads of Arnica angustifolia ssp. attenuata the labdane diterpenes labd-13(Z)-ene-8α,15-diol (main component) and (13R,14R)8,13-epoxylabdane-14,15-diol were isolated and their structures established by extensive NMR and MS measurements. Both compounds are reported as natural products for the first time. Oxidative degradation of the main component was observed and the oxidation products 8α-hydroxylabd-13(Z)-ene-15-al, 8α-hydroxylabd-13(E)-ene-15-al and 8,13-epoxylabdane-15-al were identified. Additionally, the tetranorlabdanolide norambreinolide, most probably also derived from the labdanes, was detected in minor amounts. A search for diterpenes in flowers of A. montana revealed the presence of small amounts of labd-13(Z)-ene-8α,15-diol.

Sesquiterpene lactones of Arnica cordifolia, subgenus Austromontana

Abstract From A. cordifolia , in addition to two known compounds, a sesquiterpene lactone, new as a natural compound, was identified. The structures were elucidated by spectroscopic methods.

Zwei neue pseudoguaianolide aus den blüten von arnica chamissonis less. Subsp. Genuina maguire

Zusammenfassung Aus den arzneilich verwendeten Blutenkopfchen von Arnica chamissonis Less subsp. genuina Maguire wurden die zwei dominierenden Sesquiterpenlactone isoliert. Es handelt sich um neue Pseudoguaianolide, die als Chamissonolid ( 1 ) und 6-Desoxychamissonolid ( 2 ) bezeichnet werden. Ihre Strukrtur wurde durch UV-, IR-, MS-, 1 H-NMR- und 13 C-NMR-Spektren-aufgeklart.