Triumbellin, A tricoumarin rhamnopyranoside from Daphne mezereum

From Daphne mezereum bark, a new tricoumarin glycoside, triumbellin and the corresponding aglycone triumbelletin were isolated and structurally elucidated by one- and TD-HF-NMR spectroscopy including two dimensional phase sensitive NOE experiments as 7-O-(α-l-rhamnopyranosyl)-3-[(2-oxo-2H-1-benzopyran-7-yl)oxy]-8-(2-oxo-2H-1-benzopyran-8-yl)-2H-1-benzopyran-2-one. The possible molecule conformations in solution were examined by theoretical conformation energy calculations. Beside the known coumarins daphnetin, umbelliferone, daphnoretin and daphnorin as well as the known diterpene esters daphnetoxin and mezerein, the following compounds are reported for the first time from this plant: the coumarins 7-hydroxy-8-methoxycoumarin and daphnorin-6″-hydroxymethylglutarate (rutarensin), the coumarinolignan daphneticin, the lignans, lariciresinol, syringaresinol, pinoresinol and dihydrosesamin and the diterpene esters gniditrin and daphneolone.