Über die Carotinoide Flavoxanthin und Chrysanthemaxanthin: 1 H‐NMR.‐, 13 C‐NMR.‐ und Massen‐Spektren und absolute Konfiguration. (Kritische Überprüfung veröffentlichter chemischer und physikalischer Daten)

On the Carotenoids Flavoxanthin and Chrysanthemaxanthin: 1 H‐NMR., 13 C‐NMR. and Mass Spectra, Absolute Configuration, Survey of Published Data Very pure flavoxanthin ( 1 ) and chrysanthemaxanthin ( 2 ) have been reisolated from flower heads of Taraxacum officinale. Both compounds were characterized by chromatographic, chemical and chiroptical data and extensive NMR. measurements. Examination of many published data on 1 and 2 led to the conclusion that flavoxanthin has often been mistaken for chrysanthemaxanthin and vice versa. Chemical degradation of 1 and 2 to (−)‐loliolide ( 5 ) coupled with NMR. evidence (ASIS, spin‐decoupling, NOE) allowed the assignment of the absolute configurations of 1 and 2 . Thus (+)‐flavoxanthin is (3S,5R,8R, 3′R,6′R)‐5, 8‐epoxy‐5, 8‐dihydro‐β, ε‐carotene‐3, 3′‐diol and (+)‐chrysanthemaxanthin its C(8)‐epimer.