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Ascorbic acid analogue

Kaneko et al. (1993) have described a group of lipophilic ascorbic-acid analogues that have been studied in cultured human umbilical vein endothelial cells that were first incubated with test drug and then exposed to lipid hydroperoxides. Although ascorbate itself did not protect the endothelial cells, derivatives like CV3611 protected. Pretreatment was necessary. CV3611 was synergistic with vitamin E. The authors concluded that these lipophilic antioxidants incorporate into endothelial cell membranes where they are effective inhibitors of lipid peroxidation. In contrast, lipophobic antioxidants were not effective in their hands (Kaneko et al., 1993). [Pg.267]

Many amino- and hydroxy-substituted heterocycles have reasonably low oxidation potentials and, as such, can act as lipid-peroxidation inhibitors. We have already discussed triaminopyrimidine examples (tirilazad and U78517) and several ascorbic-acid analogues. This section discusses a few more examples. [Pg.271]

This chapter provides an overview of the various available syntheses of L-ascorbic acid. The key synthetic discoveries that have resulted in the preparation of L-ascorbic acid analogues, the preparation of radio-labeled derivatives of L-ascorbic acid, and the production of commercial quantities of L-ascorbic acid are highlighted. For a comprehensive review of all these approaches, see Reference 7. [Pg.3]

This Cl homologation of osones proved to be valuable in the preparation of L-ascorbic acid analogues (16) as well as in the preparation of radiolabeled L-ascorbic acid (17-20), This synthesis was greatly improved when aldoses were discovered to be directly oxidized to osones with cupric acetate (Equation 1) (21), Subsequently, the conditions were modified so that D-xylose could be oxidized to D-xylosone in 50-55% yield with cupric acetate in methanol. The intermediacy of the imino ether was proved by the isolation of 7 when D-glucosone was treated with potassium cyanide (16), The initial cyanohydrin adduct (3a) easily undergoes cyclization to the imino ether intermediate (aqueous solution for 10 min at room temperature. Scheme 5). This feature will be compared with the conditions required for the lactonization of other intermediates. [Pg.5]

In a related synthesis (Scheme 9) diethyl oxopropanedioate (15) is condensed with the protected cyanohydrin of L-threose (14), producing L-ascorbic acid (27). This condensation presumably proceeds via the addition of anion 16 to 15 followed by hydrolysis and decarboxylation. Both of these synthetic approaches could be used in the preparation of L-ascorbic acid analogues. [Pg.12]

This new strategy consists of the synthesis of molecules that possess hydroxyl groups in such positions that a radical species can be stabilized by mesomery. This feature is found in natural flavonol such as kaemferol that possesses undeniable antioxidant properties. The first published example is a lipophilic analogue of vitamin C, Fig (13) [40]. In this paper, we have proved that the synthesised substituted 2-hydroxyfuran-2-one is a true ascorbic acid analogue. A radical anion that gives very similar data has been generated under the same conditions as for ascorbic acid with a stability somewhat lower and a redox potential lower than those of ascorbyl radical. Its antioxidant properties are also similar to that of ascorbic acid but it inhibits LDL peroxidation induced by Cu2+ or AAPH more efficiently probably due to a higher lipophilicity. [Pg.224]

Okamura M. Distribution of ascorbic acid analogues and associated glycosides in mushrooms. Journal of Nutritional Science and Vitaminology, 40 81-94 (1994). [Pg.1077]

Toyoda-Ono Y., Maeda M., Nakao M., Yoshimura M., Sugiura-Tomimori N., Fukami H. 2-0-(fS-D-Glucopyranosyl)ascorbic acid, a novel ascorbic acid analogue isolated from Lycium fruit. Journal of Agricultural and Food Chemistry, 52 2092-2096 (2004). [Pg.1086]

Both 2- and 5-oxo-D-gluconic acid have been found as products of bacterial oxidation of glucose. The importance of the 2-oxo-aascorbic acid analogues (LXI). [Pg.81]

Ascorbic acid has a variety of reactive positions that can be used to synthesize derivatives (99). Various derivatives and analogues have been prepared in attempts to find substances with increased biological activity (100,101). [Pg.18]

After completing the synthesis, workers in many laboratories then commenced a search for physiologically active analogues several were made in the Birmingham laboratories. A decade later, this topic was still of interest to Stacey, and with Lilian Turton, he reported that tetra-acetylglucosone hydrate provided a convenient initial material for the syntheses of analogues of ascorbic acid. [Pg.6]

Tetra Acetyl Glucosone Hydrate. A Novel Route to the Syntheses of Analogues of Ascorbic Acid and a Possible Mechanism for the Transformation of Hexoses into Kojic Acid, M. Stacey and L. M. Turton, J. Chem. Soc., (1946) 661 -664. [Pg.22]

Most of the work reported with these complexes has been concerned with kinetic measurements and suggestions of possible mechanisms. The [Ru(HjO)(EDTA)] / aq. HjOj/ascorbate/dioxane system was used for the oxidation of cyclohexanol to cw-l,3-cyclohexanediol and regarded as a model for peroxidase systems kinetic data and rate laws were derived [773], Kinetic data were recorded for the following systems [Ru(Hj0)(EDTA)]702/aq. ascorbate/dioxane/30°C (an analogue of the Udenfriend system cyclohexanol oxidation) [731] [Ru(H20)(EDTA)]70j/water (alkanes and epoxidation of cyclic alkenes - [Ru (0)(EDTA)] may be involved) [774] [Ru(HjO)(EDTA)]702/water-dioxane (epoxidation of styrenes - a metallo-oxetane intermediate was postulated) [775] [Ru(HjO)(EDTA)]7aq. H O /dioxane (ascorbic acid to dehydroascorbic acid and of cyclohexanol to cyclohexanone)... [Pg.84]

Fluoral has been condensed with an equivalent of chiral glycinate anion. The chirality stems from a chiral nickel complex with a chiral Schiff base derived from proline as hgand (Figure 5.17). (25, 35)-Difluorothreonine has thus been obtained with an excellent selectivity (de > 95%). This method also allows preparation of numerous fluoroalkyl and fluoroaryl analogues of threonine. Enantiopure difluorothreonine could also be prepared from ascorbic acid. ... [Pg.158]

For a better insight into the mechanism of the primary stages of photosynthesis it is of interest to study electron transfer reactions with the participation of chlorophyll and its synthetic analogues. As far back as 1948, a reversible reaction was discovered of photoreducing chlorophyll, Chi, in solutions containing ascorbic acid, AH, (the Krasnovskii reaction) [51]... [Pg.293]

The 5,6-O-isopropylidene acetal (152) of L-ascorbic acid has been prepared,340 and von Schuching and Frye341 prepared the corresponding cyclohexylidene acetal. These compounds were found to be more resistant than L-ascorbic acid toward oxidation, and the parent acid can be readily regenerated by acid hydrolysis. The derivative was used in the synthesis of 14C-labeled vitamin C. The C-2 and C-3 enols of L-ascorbic acid or its acetone derivative (152) can be readily methylated with diazomethane, yielding the corresponding dimethoxy analogues. [Pg.249]

The Primary Product of the Synthesis of Ascorbic Acid and its Analogues, W. N. Haworth and E. L. Hirst, Helv. Chim. Acta, 17, 520 (1934). [Pg.20]

The antioxidants studied can be classified into two broad types phenolic antioxidants and non-phenolic antioxidants. Phenolic antioxidants have been found to be more promising as they are obtained from dietary sources.Vitamin E (a-tocopherol), the first known chainbreaking antioxidant, is also an o-methoxy phenol. Pulse radiolysis studies of vitamin E and its water-soluble analogue, trolox C, have been reported several years ago. a-tocopherol reacts with almost all the oxidizing free radicals, and the phenoxyl radicals produced during oxidation reactions absorb at -460 nm (Fig. 1). The regeneration reaction of a-tocopherol phenoxyl radicals back to a-tocopherol by water-soluble antioxidant ascorbic acid was also first reported by pulse radiolysis method. The one-electron reduction potential of vitamin E is -0.48 V vs. NHE. Both a-tocopherol and trolox C are used as standards for evaluating the antioxidant ability of new compounds. [Pg.578]

It is known that a cooperative effect between LA and other natural antioxidants, such as tocopherol (vitamin E) or ascorbic acid, affords the possibility to reduce the formation of reactive oxygen species (ROS), associated with various pathological disorders. Thus triamine spacer as backbone was used to attach Trolox , a water-soluble analogue of vitamin E, and LA, to obtain new analogues 356 which were tested as inhibitors of the microsomal lipid peroxidation. Attachment of LA to the chroman moiety, as in compound 357, is a useful extension of this study <2001JME4300, 2004BMC4835>. [Pg.941]


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See also in sourсe #XX -- [ Pg.30 , Pg.224 ]

See also in sourсe #XX -- [ Pg.224 ]




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