Struktur und Eigenschaften von 5-epi-Flavoxanthin und 5-epi-Chrysanthemaxanthin

Structure and properties of 5-epi-flavoxanthin and 5-epi-chrysanthemaxanthin The absolute configurations of 5-epi-flavoxanthin ( 6 ) and 5-epi-chrysanthemaxanthin ( 7 ) prepared by acid catalysed rearrangement of semi-synthetic lutein epoxide 5 are shown to be (3S, 5S, 8R, 3′R, 6′R) and (3S, 5S, 8S, 3′R, 6′R), respectively. Contrary to published data 5] the relationship of the polyene chain and H₃(18) on the dihydrofurane ring is cis for the pair of stereoisomers having a Δδ = δ (H? C(7)) ? δ (H? C(8)) = 0,22 ppm and ³J ≡ 0. These conclusions are in full accord with the chiroptical data.