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Synthese von optisch aktiven Carotinoiden mit 3,5,6-Trihydroxy-5-6-dihydro-β-Endgruppen

✍ Scribed by Richard Buchecker; Urs Marti; Conrad Hans Eugster

Publisher
John Wiley and Sons
Year
1984
Tongue
German
Weight
904 KB
Volume
67
Category
Article
ISSN
0018-019X

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✦ Synopsis

Abstract

Syntheses of Optically Active Carotenoids with 3,5,6‐Trihydroxy‐5,6‐dihydro β‐End Groups

For the specification of the relative and absolute configuration in carotenoids with 3,5,6‐trihydroxy‐5‐6‐dihydro β‐end groups, several ionone derivatives and carotenoids bearing this end group were synthesized. Acid‐catalyzed hydrolysis of (3__S__,5__S__,6__R__)– acetoxy‐5,6‐epoxy‐5,6‐dihydro‐β‐ionone (7) and of its (3__S__,5__R__,6__S__)‐isomer (13) gave the diols 8 and 15, respectively, with exclusive inversion at c(5) (Scheme 2). Compared to this, mild acid hydrolysis of caroten‐5‐6‐expoxides in the presence of H~2~O resulted in the formation of 5,6‐diols with either inversion or retention of the configuration at C(6) (Scheme 3). Spectroscopic data allowed us to distinguish the relative configurations (3__R__*,5__S__*,6__S__*) (see A), (3__R__*,5__R__*,6__R__*) (see B), (3__R__*,5__S__*,6__R__*) (see C), and (3__R__*,5__R__*,6__S__*) (see D), of the 3,5,6‐trihydroxy‐5‐6‐dihydro β‐end groups. Syntheses of the optically active carotene‐hexols 20 and 21 and comparison with published data led to a revision of the structure of mectrazanthin (now formulated as 20), heteroxanthin (now formulated as 28), and further carotenoids with 3,5,6‐trihydroxy end groups.

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