- SEPARATION OF CHIRAL ISOMERS BY SFC
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The present invention relates to the field of separating chiral isomers from each other. Particularly, it relates to the field of separating of chiral isomers of chromane or chromene compounds, particularly tocopherols, 3,4-dehydro-tocopherols and tocotrienols, as well as the protected forms thereof. It has been found that the use of supercritical carbon dioxide as mobile phase combined with the very specific chiral phase as stationary phase leads to a very efficient separation of the individual chiral isomers. As the method is very efficient and fast combined with advantageous in view of ecology it is of big industrial interest.
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Page/Page column 32; 33
(2016/12/22)
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- Total synthesis of (R, R, R)-γ-tocopherol through cu-catalyzed asymmetric 1,2-addition
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Based on the asymmetric copper-catalyzed 1,2-addition of Grignard reagents to ketones, (R, R, R)-γ-tocopherol has been synthesized in 36% yield over 12 steps (longest linear sequence). The chiral center in the chroman ring was constructed with 73% ee by the 1,2-addition of a phytol-derived Grignard reagent to an a-bromo enone prepared from 2,3-dimethylquinone.
- Wu, Zhongtao,Harutyunyan, Syuzanna R.,Minnaard, Adriaan J.
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p. 14250 - 14255
(2015/03/18)
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- Kinetics of the reaction by which natural vitamin E is regenerated by vitamin C
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The rate constant and activation energy of the regeneration reaction of natural vitamin E by vitamin C were determined with a double-mixing stopped-flow spectrophotometer. The formation of vitamin C radical was observed in the absorption spectrum. The kinetic effect of methyl substitution on the aromatic ring of vitamin E radical indicates that partial charge-transfer plays a role in the reaction. Since a substantial deuterium kinetic isotope effect was not found, the tunneling effect may not play an important role under the present experimental conditions.
- Nagaoka, Shin-ichi,Kakiuchi, Takuhiro,Ohara, Keishi,Mukai, Kazuo
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- Easy route to labeled and unlabeled R,R,R-γ-tocopherol by aryl demethylation of α-homologues
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The interest in vitamin E research is increasingly focusing on the peculiar properties of the less investigated tocopherols and their metabolites, such as γ-tocopherol, which have been revealed as very important for human health. Metabolic studies of γ-tocopherol have been constricted by its high cost and the poor availability of stable isotope-labeled forms. An efficient, inexpensive and simple route is described for the preparation of labeled and unlabeled R,R,R-γ-tocopherol, starting from R,R,R-α-tocopherol, through simple thermal decarboxylation of γ-tocopherol-5-carboxylic acid.
- Mazzini, Francesco,Netscher, Thomas,Salvadori, Piero
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p. 813 - 817
(2007/10/03)
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- The substrate specificity of tocopherol cyclase
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The substrate specificity of the enzyme tocopherol cyclase from the blue-green algae Anabaena variabilis (Cyanobacteria) was investigated with 11 substrate analogues revealing the significance of three major recognition sites: (i) the OH group at C(1) of the hydroquinone, (ii) the (E) configuration of the double bond, and (iii) the length of the lipophilic side chain. Experiments with two affinity matrices suggest that substrates approach the enzyme's active site with the hydrophobic tail.
- Stocker, Achim,Fretz, Heinz,Frick, Haroun,Ruettimann, August,Woggon, Wolf-Dietrich
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p. 1129 - 1134
(2007/10/03)
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- The reaction mechanism of chromanol-ring formation catalyzed by tocopherol cyclase from Anabaena variabilis Kutzing (Cyanobacteria)
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Incubation of the synthetic 18O-labelled phytyl-hydroquinone (O4-18O)-2 with the tocopherol cyclase from Anabaena variabilis Kutzing (Cyanobacteria) in D2O furnished the doubly labelled γ-tocopherol, (2R,3S,4'R,8'R)-(1-18O,3-2H)-1. The chirality at C(3) was determined by two independent routes providing interlocking evidence that the enzyme-catalyzed ring closure proceeds by si-protonation of the double bond of 2 and concomitant re-attack of the phenolic O-atom.
- Stocker,Netscher,Ruttimann,Muller,Schneider,Todaro,Derungs,Woggon
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p. 1721 - 1737
(2007/10/02)
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- Reaction of 8a-Hydroperoxy Tocopherones with Ascorbic Acid
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8a-Hydroperoxy tocopherones, prepared from the photooxidation of α-, γ- and δ-tocopherols, were allowed to react with ascorbic acid in ethanol.The hydroperoxy tocopherones were reduced to 8a-hydroxy and 8a-ethoxy tocopherones which in turn were reduced to tocopherols by ascorbic acid.The tendency of the hydroperoxy tocopherones to form tocopherols during the reaction correlated with vitamin E activities of tocopherols.The results is indicate that α-tocopherol and ascorbic acid can act synergistically on the quenching of 1O2.The inhibitory effects of α-tocopherol and ascorbic acid were examined on the chlorophyll-sensitized photooxidation of methyl linoleate and soybean oil.At initial stage of the oxidation, the inhibitory effect of α-tocopherol was lengthened in the presence of ascorbic acid.
- Yamauchi, Ryo,Kato, Koji,Ueno, Yoshimitsu
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p. 2855 - 2862
(2007/10/02)
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- 2-METHYL-6-PHYTYLQUINOL AND 2,3-DIMETHYL-5-PHYTYLQUINOL AS PRECURSORS OF TOCOPHEROL SYNTHESIS IN SPINACH CHLOROPLASTS
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The incorporation of from SAM- into precursors indicates the following sequence of tocopherol synthesis in spinach: 2-methyl-6-phytylquinol (6-phytyltoluquinol) (1a) -> 2,3-dimethyl-5-phytylquinol (phytylplastoquinol) (2a) -> γ-tocopherol (5a) -> α-tocopherol (6). 1a is a particularly preferred to 2-methyl-5-phytylquinol (1b) and 2-methyl-3-phytylquinol (1c). 1a only forms 2a. 2a is converted to 6 via 5a and, to a lesser extent, 2,5-dimethyl-6-phytylquinol (2b) to 6 via β-tocopherol (5b).Trimethylphytylquinol (3) is not an intermediate in the formation of 6.All reactions are independent of light. - Key Word Index - Spinacia oleracea; Chenopodiaceae; tocopherol biosynthesis; 2-methyl-6-phytylquinol; 2,3-dimethyl-phytylquinol; phytylquinol synthesis.
- Soll, Juergen,Shultz, Gernot
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p. 215 - 218
(2007/10/02)
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