(+)- and (−)-Cajanusine, a Pair of New Enantiomeric Stilbene Dimers with a New Skeleton from the Leaves of Cajanus cajan

A pair of new enantiomeric stilbene dimers, (+)- and (−)-cajanusine [(+)-1 and (−)-1], with a unique coupling pattern were isolated from the leaves of Cajanus cajan. Their structures including absolute configurations were elucidated on the basis of comprehensive spectroscopic and single-crystal X-ray diffraction analyses, as well as CD calculations. The plausible biogenetic pathway of 1 was also proposed. Additionally, (±)-1, (+)-1, and (−)-1 exhibited inhibitory activities on the growth of human hepatocellular carcinoma cells.