Synthesis of L-Ascorbic Acid

Abstract

The methods by which L-ascorbic acid has been synthesized are readily divided into three major categories. The first involves coupling a C 1 fragment and a C 5 fragment, and the second involves coupling a C 2 fragment and a C 4 fragment. The third involves the conversion of a C 6 chain into the correct oxidation state and stereochemical configuration. All of these approaches will be reviewed with special regard given to those syntheses that are suitable for the prepara tion of analogues of L-ascorbic acid, the preparation of radiolabeled derivatives of L-ascorbic acid, and the current commercial synthesis of L-ascorbic acid.Following the isolation of crystalline "hexuronic acid" from the adrenal cortex of the ox and from orange juice in 1928 (1) and the determina tion in 1933 (2) that the structure of this material was 1 (with other proton tautomers shown in Scheme 1), efforts were begun to synthesize this novel vitamin. In a very short time several syntheses were success fully accomplished that confirmed that the structure of L-ascorbic acid or vitamin C was indeed that proposed (2). Complete details of the crystal structure of 1 have since been obtained by both x-ray (3,4) and neutron diffraction (5) analysis and are approximated by structure 1a.Efforts directed toward the synthesis of L-ascorbic acid have been governed by the following factors:1. The need to synthesize material to confirm the structure and provide larger quantities of material for further study. 2. The desire to synthesize analogues of L-ascorbic acid. 3. The desire to prepare radiolabeled material for use in the study of L-ascorbic acid metabolism in plants, fish, animals, and humans. 4. The need to develop a commercially viable, low cost syn thesis. This is illustrated by the fact that in 1934 1 kg of L-ascorbic acid sold for $7000 (6).

Utility of Squaraine Dyes for Dye-Sensitized Photocatalysis on Water or Carbon Dioxide Reduction

“…The supernatant separated after centrifugation of the SQ - and/or Re­(I)-treated suspensions show negligible absorption of SQ and Re­(I), confirming the quantitative fixation of the components. In this study, ascorbic acid (AscH) and 1,3-dimethyl-2-phenyl-1,3-dihydrobenzimidazole (BIH) were used as the electron donors for hydrogen evolution in water and for CO 2 reduction in dimethylformamide (DMF), respectively.…”

Molecular modeling of substrate binding in wild-type and mutantCorynebacteria 2,5-diketo-D-gluconate reductases

“…11 The major structural form of 2,5-DKG in aqueous solution, as determined by 13 C NMR, is the gem-diol hydrate at the C5 of the pyranose tautomer with minimal keto component. 11,12 However, there is evidence that the enzyme recognizes and stabilizes the keto-instead of the gem-diol form of the substrate. 13 This is also supported by the crystal structures of substrate complexes of other enzymes belonging to this family, which reveal that these enzymes recognize the keto form of the substrate.…”

“…The 2,5-DKG substrate was modeled in the reaction-competent keto-form, although the gem-diol form is the predominant form in solution. 11,12 The interaction of the substrate C5-keto with the His108 N⑀H and Tyr50 O groups suggests that juxtaposition of one, or both, of these groups facilitates binding of the keto-form of the substrate in solution. In particular, the interaction of the keto group with His108 may position the substrate C5 carbon for effective hydride transfer from the NADPH cofactor.…”

Growth and Antioxidant-Related Effects of the Reestablished Ascorbic Acid Pathway in Zebrafish (Danio rerio) by Genomic Integration of L-Gulonolactone Oxidase From Cloudy Catshark (Scyliorhinus torazame)

“…L-gulonate participates in the pentose synthesis pathway. Therefore, the pathway up until the production of the L-gulonate is conserved in virtually all animal species (Crawford, 1982). Availability of gluconolactonase has been observed in several teleosts, including zebrafish (Cho et al, 2007).…”