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.
Organic Chemistry Laboratories, Faculty of Chemistry and Biology, Norwegian University of Science and Technology (NTNU), NO-7491 Trondheim, Norway.
B F
BF
Lutnaes
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OR
Gautun
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S
Liaaen-Jensen
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