Cajanusflavanols A–C, Three Pairs of Flavonostilbene Enantiomers from Cajanus cajan

Three pairs of new flavonostilbene enantiomers, cajanusflavanols A–C (1–3), along with their putative biogenetic precursors 4–6, were isolated from Cajanus cajan. Compound 1 possesses an unprecedented carbon skeleton featuring a unique highly functionalized cyclopenta[1,2,3-de]isobenzopyran-1-one tricyclic core. Compounds 2 and 3 are the first examples of methylene-unit-linked flavonostilbenes. Their structures with absolute configurations were elucidated by spectroscopic analyses, X-ray diffraction, and computational calculations. Compounds 1 and 2 exhibited significant in vitro anti-inflammatory activities.