2-Keto-L-gluconate

Synthesis of vitamin C (ascorbic acid) is conventionally performed via the Reichstein-Griissner procedure, which involves the fermentation of glucose followed by five chemical steps. Cerestar/ BASF recently developed a new process that consists of one fermentation step and two simple chemical steps (via 2-keto-L-gluconic acid). It is predicted that soon a fermentation process will be developed to convert glucose into vitamin C in a single step, eliminating several recovery steps and reducing extraction solvents. 

Diketo-gluconic acid (24) 2-Keto-L-gulonic acid (2-KGA)... 

The 2-keto-3-deoxy-aldonic acid (phosphate) aldolases from Pseudomonas strains - 3-deoxy-2-keto-L-arabonate (F.C 4.1.2.18), 3-deoxy-2-keto-D-xylonate (EC 4.1.2.28), 3-deoxy-2-keto-6-phospho-D-gluconate (EC 4.1.2.14) and 3-deoxy-2-keto-6-phospho-D-galactonate aldolase (EC 4.1.2.21) - appear to be specific even for the acceptor components, but allow stereoselective syntheses of the respective natural substrates29. 

The process of lactonization and enolization of 2-keto esters under the influence of alkaline reagents has also been applied to the production of analogs of L-ascorbic acid containing a six-membered ring structure.22 For example, methyl 3,4,6-trimethyl-2-keto-D-gluconate (XLI) is treated... 

There is good evidence for the presence of a five-membered ring in D-araboascorbic acid (XXXIX). This analog of L-ascorbic acid, prepared by method 2 (page 87) from methyl 2-keto-D-gluconate shows the same chemical properties and the same absorption characteristics as L-ascorbic acid. Titration of XXXIX with diazomethane affords, as in the case of L-ascorbic acid, a 3-methyl derivative LXXXII which upon further action with diazomethane gives rise to the 2,3-dimethyl-D-arabo-ascorbic acid (LXXXIII)3 ... 

Moreover, the compound (LV) obtained from the reaction of 2-keto-D-gluconic acid with o-phenylenediamine28 has been dehydrated to give a compound which Maurer erroneously described as LYI. In this case, also, the process of dehydration has been shown to be equivalent to that just described for compound L. The product obtained by interaction of 2-furyl-... 

J. Geigert, S. L. Neidleman, D. S. Hirano, B. Wolf, and B. Panchar, Enzymic oxidation of D-araWrco-hexos-2-ulose (D-glucosone) to D-arabino-2-hexulosonic acid ( 2-keto-D-gluconic acid ), Carbohydr. Res., 113 (1983) 163-165. 

Fig. 8.30 Microbial routes to 2-keto-L-gulonate (a) via L-sorbose (b) via 2,5-diketo-L-gulonate unwanted side reaction non-microbial steps are indicated by hatched arrows. Compounds 2,5DKG, 2,5-diketo-D-gluconate d-GcI, D-glucitol IDA, L-idonate 2KDG, 2-keto-D-gluconate L-Srb, L-sorbose L-Srn, L-sorbosone. Enzymatic activities ...

The principal organic acids in grape are L(+)-tartaric, L(—)-malic, shikimic and citric acid. Gluconic, 2-keto-D-gluconic and mucic acids are present in rot grapes as metabolites of Botrytis Cinerea. The structures of these compounds are reported in Figure 1.2. 

By careful regulation of conditions, the ketose sugars D-fructose and L-sorbose can be transformed by the agency of nitric acid into the corresponding 2-keto-D-gluconic acid (XXII) and 2-keto-L-gulonic acid (XXVI), respectively. 

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