Is (9Z)-"meso"-Zeaxanthin optically active?

The question raised in the title was answered. (3R, 3'S)-meso-Zeaxanthin wa s submitted to iodine catalyzed photochemical stereoisomerisation. The enan tiomeric (9Z) and (9'Z) geometrical isomers were isolated by semipreparativ e 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 (92, 3R, 3'S)-"meso "-zeaxanthin, in spite of having no symmetry elements, is optically inactiv e. The result has been rationalised in line with the current hypothesis on the origin of carotenoid CD spectra. Chirality 13:224-229, 2001. (C) 2001 W iley-Liss, Inc.