- Preparation and (E/Z)-Isomerization of the Diastereoisomers of Violaxanthin
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Violaxanthin A (=(all-E,3S,5S,6R,3′S,5′S,6′ R)-5,6:5′,6′-diepoxy-5,6,5′,6′-tetrahydro-β, β-carotene-3,3′-diol = syn,syn-violaxanthin; 5) and violaxanthin B (=(all-E,3S,5S,6R,3′S,5′R,6′S)-5,6:5′, 6′-diepoxy-5,6,5′,6′-tetrahydro-β,β-carotene-3, 3′-diol = syn,anti-violaxanthin; 6) were prepared by epoxidation of zeaxanthin diacetate (1) with monoperphthalic acid. Violaxanthins 5 and 6 were submitted to thermal isomerization and I2-catalyzed photoisomerization. The structure of the main products, i.e., (9Z)-5, (13Z)-5, (9Z)-6, (9′Z)-6, (13Z)-6, and (13′Z)-6, was determined by their UV/VIS, CD, 1H-NMR, 13C-NMR, and mass spectra.
- Molnar, Peter,Deli, Jozsef,Zsila, Ferenc,Steck, Andrea,Pfander, Hanspeter,Toth, Gyula
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- Syntheses of Enantiomerically Pure Violaxanthins and Related Compounds
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The epoxides 16 and ent-16, prepared by Sharpless-Katsuki oxidation of 15 in excellent yield and very high enantiomeric purity, were used as synthons for the preparation of (+)-(S)-didehydrovomifoliol (45), (+)-(6S,7E,9E)-abscisic ester 46, (+)-(6S,7E,9Z)-abscisic ester 47, (-)-(3S,7E,9E)-xanthoxin (49), (-)-(3R,7E,9E)-xanthoxin (50), (3S,5R,6S,3'S,5'R,6'S,all-E)-violaxanthin (1), (3R,5R,6S,3'R,5'R,6'S,all-E)-violaxanthin (55) and their (9Z) (see 53, 57), (13Z) (see 54, 58), and (15Z) (see 60) isomers.The novel violadione (61) was prepared from 1 by oxidation with DMSO/Ac2O.By base treatment, 61 was converted into violadienedione (62), a potential precursor of carotenoids with phenolic end groups.
- Acemoglu, Murat,Uebelhart, Peter,Rey, Max,Eugster, Conrad Hans
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p. 931 - 956
(2007/10/02)
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