Oligomeric flavanoids. Part 34: Doubly-linked proteracacinidin analogues from Acacia caffra and Acacia galpinii

The rare series of doubly-linked proteracacinidin-type oligoflavanoids is extended by identification of four new analogues, oritin-(4α→7, 5→6)-epioritin-4α-ol 3, oritin-(4β→7, 5→6)-epioritin-4α-ol 5, epioritin-(4β→7, 5→6)-epioritin-4α-ol 7 and epioritin-(4β→7, 5→6)-oritin-4α-ol 9. The same sources also afforded epioritin-(4β→5, 3→4)-oritin-4α-ol 11 possessing a rare (4β→5)- as well as a unique (3→4)- ether linkage. Their structures and absolute configurations were established via spectroscopic methods.