Isoflavonoid and pterocarpinoid extractives of Lonchocarpus laxiflorus

Abstract

Two new members of the rare isoflavan series and two new pterocarpans have been isolated from Lonchocarpus laxiflorus. Physical methods involved in solving the structural problems associated with the penta-substituted ring B of three of these compounds include the study of methoxy-proton shifts and i.r. stretching frequencies. Some possible errors of the method of methoxy-proton shifts are pointed out. Steric factors result in one isoflavan (Ionchocarpan) and its derivatives taking up unusual conformations; this gives rise to misleading o.r.d. curves and is also reflected in the n.m.r. spectra.