New chromonocoumarin (=6 H , 7 H ‐[1]Benzopyrano[4,3‐ b ][1]benzopyran‐6,7‐dione) derivatives from Polygala fruticosa BERG

Three chromonocoumarins ( =6 H , 7 H ‐[1]benzopyrano[4,3‐ b ][1]benzopyran‐6,7‐diones) 1–3 have been isolated from the leaves and the root bark of polygala fruticosa B ERG . (syn. Polygala oppositifolia L .; Polygalaceae). The structure of frutinone A ( 1 ) was established by X‐ray diffraction analysis. The structures of the previously undescribed compounds frutinone B ( 2 ) and C ( 3 ) were deduced by spectroscopic methods (EI‐MS, UV, IR, 1 H‐and 13 C‐NMR, including NOE and COSY) in comparison with 1 . Chromonocoumarins 1–3 are the first representatives of a new type of naturally occurring compounds. Frutinone A shows strong fungicidal activity against Cladosporium cucumerinum .