| Abstract: | The absolute configurations of heteroxanthin ((3S,5S,6S,3′R)- 7′,8′-didehydro-5,6-dihydro-β,β-carotene-3,5,3′,6′-tetrol) ex Euglena gracilis and of diadinoxanthin ((3S,5R,6S,3′R)-5,6-epoxy-7′,8′-didehydro-5,6-dihydro-β,β-carotene-3,3′-diol) from the same source have been established by chemical reactions, hydrogen bonding studies, 1H NMR and CD. Two previously unknown carotenoids (artefacts?) from Trollius europaeus, assigned the structures (3S,5S,6S,3′S,5′R,6′R)-6,7-didehydro-5,6,5′,6′-tetrahydro-β,β -carotene-3,5,6,3′,5′-pentol and its 5R epimer, served as useful models. |
