Cis- and trans-isoshinanolone from Dioncophyllum thollonii: absolute configurations of two 'known', wide-spread natural products

From the rare West African liana, Dioncophyllum thollonii (Dioncophyllaceae), the known acetogenic tetralones, cis- and trans-isoshinanolone, were isolated. Exemplarily on this material, a new ruthenium-catalyzed oxidative degradation procedure, related to the well-established stereoanalysis of 1,3-dimethyltetrahydroisoquinolines, was elaborated. The method allows to unambiguously attribute the absolute configuration of these natural products, which likewise occur in several other plant species. For the rapid discrimination between the four possible stereoisomeric forms of isoshinanolone (i.e. the cis- and trans-diastereomers and their enantiomers), an HPLC-analytical procedure on a chiral stationary phase has been developed.