Is (9Z)-"meso"-zeaxanthin optically active?
The question raised in the title was answered. (3R, 3'S)-meso-Zeaxanthin was submitted to iodine catalyzed photochemical stereoisomerisation. The enantiomeric (9Z) and (9'Z) geometrical isomers were isolated by semipreparative HPLC and separated as diastereomeric dicarbamates on a chiral column only. Cleavage of the carbamate could not be effected. CD-Spectra of (1"S, 1"S)- and (1"R, 1"R)-dicarbamates of geometrical isomers of (3R, 3'R)- and (3R, 3'S)-meso-zeaxanthin were systematically studied and the contribution from the carbamate moieties revealed. It was concluded that (9Z, 3R, 3'S)-"meso"-zeaxanthin, in spite of having no symmetry elements, is optically inactive. The result has been rationalised in line with the current hypothesis on the origin of carotenoid CD spectra.
Lutnaes
B F
BF
Organic Chemistry Laboratories, Faculty of Chemistry and Biology, Norwegian University of Science and Technology (NTNU), NO-7491 Trondheim, Norway.
Gautun
O R
OR
Liaaen-Jensen
S
S
D002851:Chromatography, High Pressure Liquid; D002942:Circular Dichroism; D013237:Stereoisomerism; D024341:Xanthophylls; D065146:Zeaxanthins; D019207:beta Carotene / Q000031:analogs & derivatives / Q000737:chemistry* / Q000302:isolation & purification
D024341:Xanthophylls; D065146:Zeaxanthins; D019207:beta Carotene; C584722:meso-zeaxanthin