Novel components of Acacia mearnsii

Abstract

From Summary: From the complex mixture of flavonoid components present in the heartwood of the black wattle tree (Acacia mearnsii) four new compounds have been isolated. These include a novel dioxane-linked dimeric proanthocyanidin based on leucofisetinidin. This is the first proanthocyanidin of its type to be isolated from a natural source. I solation was achieved by standard counter current partition separation and preparative paper chromatographic techniques. The compound, which forms an anthocyanidin, was identified by micro-degradation, and n.m.r. and mass spectrometry. Comparison of the spin-spin coupling constants of the heterocylic rings' protons with those of authentic monomeric flavan-3, 4-diols showed that the heterocyclic rings of the two symmetrical flavan moeities have 2,3-trans-3,4-cis configurations. Dreiding models suggest that the central dioxane ring has a half-boat conformation while the heterocyclic rings of the two flavan units have five point coplanar conformations. Two possible absolute configurations have been proposed