Elmar Flaskamp

Massenspektroskopiche Fragmentierungsreaktionen, 4. Mitt.: Der Zerfall von 2-Alkoxy-3-hydroxy-tetrahydropyranen

2-Alkoxy-3-hydroxy tetrahydropyrans undergo ring contraction as observed with 3-hydroxy tetrahydropyrans which, however, initiates a series of fragmentation sequences (e.g., ethylene elimination).

Zur Diastereoisomerie natürlicher und synthetischer α-Bisabolole/On the Diastereoisomerism of Natural and Synthetic α-Bisabolols

Abstract The stereochemistry of α-bisabolol is discussed. The chiralities of the different α-bisabolols from Myoporum crassifolium, Populus balsamifera and Vanillosmopsis erythropappa are deduced from the absolute configuration of natural bisabolol from chamomile, which has to be considered as being (1′S,2S)-configurated according to most recent investigations. Based on this assumption, (1′S, 2R)-configuration has to be ascribed to (-)-α-bisabolol from Myoporum crassifolium, whereas (1′R,2R)-resp. (1′S,2S)-structure is present in (+)-α-bisabolol from Populus balsamifera and (-)-α-bisabolol from Vanillosmopsis erythropappa being therefore enantiomeric to the latter. Consequently, the (-)-α-bisabolols from Matricaria chamomilla and Vanillosmopsis erythropappa turn out to be identical in all respects. Synthetic α-bisabolols, however, featuring approximately equal amounts of all the four possible stereoisomers, differ not only optically but also in their stereochemical uniformity from natural α-bisabolols. By means of NMR spectrometric methods the identity of the native active agent can be established in chamomile specialities; as a consequence possible admixtures of synthetic racemates of α-bisabolol thus can be identified and quantified.

Zur Stereochemie der Bisaboloide aus Matricaria chamomilla L/On the Stereochemistry of the Bisaboloids from Matricaria chamomilla L.

Abstract The stereochemistry of the bisaboloids in chamomile-with the exception of bisabolol-oxide C-has been elucidated. The in-vitro-examination of the mutual convertibilities of some bisaboloids gave evidence for the stereochemical accordance of the common chiral centres of all the bisaboloids. The absolute configurations of the remaining third asymmetric carbon atoms in bisabololoxide A and B have been determined by NMR spectrometric studies in comparison with their unnatural semisynthetic epimers. All the stereogenic centres of the bisabololoxides A and B, of (-)-α-bisabolol and of bisabolonoxide A turn out to be S-configurated.

Ring-A-Fragmentierung von 4,4-Dimethyl-Δ2-Steroiden

Abstract4,4-Dimethyl-Δ2-steroids show besidesRDA-decomposition degradation of ringA in a characteristic manner by elimination of alkyl and alkenyl fragments (C1−C6).

Untersuchungen zur Charakterisierung des Prochamazulens Matrizin aus Matricaria chamomilla L. / Studies on the Characterization of the Chamazulene Precursor Matricine from Matricaria chamomilla L.

The relative configuration of the thermolabile chamazulene precursor matricine has been established by NMR spectrometric studies. The NMR spectral data prove to be consistent with the well-known structure of the chamomile component. On the basis of our results the levorotatory natural substance moreover can be specified stereochemically as (−)-(3S*, 3aR*, 4S*, 9R*, 9aS*, 9bS*)-4-acetoxy-2,3,3a,4,5,9,9a,9b-octahydro-9-hydroxy-3,6,9-trimethylazuleno[4,5-b]furan-2-one.