Syntheses of the Enantiomeric Aleuriaxanthins. Detection of a Predominant (Z)-Aleuriaxanthins in Aleuria

Article abstract of DOI:10.1002/hlca.19830660110

The enantiomeric C₁₀-building blocks 9 ((+)-(2E,6R)-6,7-dihydroxy-3,7-dimethyl-2-octen-1-yl acetate) and ent-9, and 11 ((+)-(2E,6R)-3,7-dimethyl-2,7-octadien-1,6-diyl diacetate) and ent-11, prepared from the optically active epoxygeraniols 7 and ent-7, respectively, have been used for the syntheses of (2'R)-aleuriaxanthin (1) and (2'S)-aleuriaxanthin (ent-1).At room temperature aleuriaxanthin exhibits no significant CD. nor ORD.However, at -180 deg C a very distinct CD. was observed, which in the UV. range showed a surprising resemblance to that of (3R,3'R)-zeaxanthin.By direct comparison of 1 with aleurixanthin isolated from Aleuria aurantia <2>, the (2'R)-chirality assigned to the latter by Liaaen-Jensen et al. <5> is confirmed.HPLC. separation of the mixture of carotenoids from Aleuria shows the presence of a predominant (Z)-aleuriaxanthin of yet undetermined structure.