ISOFLAVONE ATROPISOMERS FROM PISCIDIA-ERYTHRINA

A further investigation of the isoflavonoid constituents in the root b ark of Jamaican dogwood (Piscidia erythrina) has revealed four new iso flavones, each of which possesses a fully (penta)-substituted B-ring. These compounds form two pairs of atropisomers (erythbigenones A and B , and erythbigenols A and B). The isoflavones comprising each pair are diastereoisomeric and can be separated by TLC. The relative stereo-st ructures of these atropdiastereoisomers have been established by a com bination of spectroscopic and chemical methods. As each atropdiastereo isomer was shown to be a mixture of two enantiomers, erythbigenone A w as separated into its optically active components so that the relation ship between absolute stereochemistry and the CD Cotton effects could be determined.