Gulonic 2-keto

A Chinese pubHcation (47) with 17 references reviews the use of genetically engineered microorganisms for the production of L-ascorbic acid and its precursor, 2-KGA (49). For example, a 2-keto-L-gulonic acid fermentation process from sorbose has been pubUshed with reported yields over 80% (50). 

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

Diacetone-L-sorbose (DAS) is oxidized at elevated temperatures in dilute sodium hydroxide in the presence of a catalyst (nickel chloride for bleach or palladium on carbon for air) or by electrolytic methods. After completion of the reaction, the mixture is worked up by acidification to 2,3 4,6-bis-0-isoptopyhdene-2-oxo-L-gulonic acid (2,3 4,6-diacetone-2-keto-L-gulonic acid) (DAG), which is isolated through filtration, washing, and drying. With sodium hypochlorite/nickel chloride, the reported DAG yields ate >90% (65). The oxidation with air has been reported, and a practical process was developed with palladium—carbon or platinum—carbon as catalyst (66,67). The electrolytic oxidation with nickel salts as the catalyst has also... 

Keto-L-gulonic acid [526-98-7] M 194.1, m 171 . Crystd from water and washed with acetone. 

DAG (-)-2,3 4,6-di-0-isopropylidene-2-keto-L-gulonic acid hydrate [L-a /Zo-2-hexulosonic acid, bis-O-(l-methylethylidine)-]... 

A. fi(-)-a-(l-Naphthyl)ethylamine. A mixture of 58.44 g. (0.20 mole) of (-)-2,3 4,6-di-0-isopropylidene-2-keto-L-gulonic acid hydrate [(-)-DAG] (Note 1) and 1.7 1. of acetone (Note 2) is placed in a 3-1. Erlenmeyer flask. A boiling chip is added, and the mixture is heated to a gentle boil. To the resulting hot solution is added cautiously but rapidly, over a 1 minute period, 34.24 g. (0.20 mole) of racemic y.- 1 -naphthyl)et hylamine (Note 3) in 100 ml. of acetone. The mixture is allowed to stand at room temperature for approximately 4 hours. The (-)-amine (-)-DAG salt is filtered with suction, washed with 100 ml. of acetone, and dried in a vacuum oven at 60° to constant weight. The yield of the crude (-)-amine (-)DAG salt is 73-76 g., m.p. 205-207° (decomp.) (Note 4), [a]p —14.2° (c 1.01%, methanol). For crystallization, the crude salt and 4.2 1. of ethanol (Note 5) are placed in a 5-1. round-bottomed flask fitted with a reflux condenser and a mechanical stirrer. The mixture is stirred and heated at reflux... 

The 2-keto acids such as 2-keto-D-galactonic acid (XXIV) can be derived from the corresponding osone (XXIII) by oxidation with bromine.10 Oxidation of L-gulosone by the same method has provided 2-keto-L-gulonic acid. The success of this oxidation depends to a large extent upon the purity of the osone subjected to oxidation and this, as previously stated, is controlled by the purity of the osazone. 

A similar series of reactions applied to L-sorbose (once a rare sugar but now easily obtained from sorbitol by bacterial oxidation16) gives rise to 2-keto-L-gulonic acid.4 The method is not confined to keto-hexoses and has been employed in the preparation from L-erythropentulose (XXXI) of the 2-keto-L-ribonic acid (XXXV) which undergoes immediate transformation to the corresponding L-erythroascorbic acid (XXXVI).16... 

Ascorbic acid, which is closely related to the sugars and is no doubt derived from them in the metabolism of the cells of plants, has been shown to be identical with vitamin- C (Szent-Gyorgyi). It has the constitution of a lactone of a-keto-i-gulonic acid (W. N. Haworth, T. Reichstein) ... 

Anderson S, Marks CM, Lazarus R, Miller J, Stafford K, Seymour J, Light D, Rastetter W, Estell D. Production of 2-keto-L-gulonate, an intermediate in L-... 

Di-0-isopropylidene-2-keto-L-gulonic acid monohydrate (- DAG) [18467-77-1 ] M 292.3, m 100-101", 103°, [oc] s -21.6° (c 2.3, MeOH). Dissolve in Et20, filter, dry (MgS04), filter, evaporate to give a yellow oil. Addition of one drop of H2O induces crystn to the monohydrate, which also forms rhombic crystals by recrystn from 95% EtOH-H20 at room tempereture. [Flatt et al. S 815 1979 Reichstein and Grussner HCA 17 311 1934 Takagi and Jeffrey Acta Cryst Sect B 34 2932 1978 cf Org Synth 55 80 1976. ... 

Diacetone 2-sorbose 2-keto-2-gulonic acid 2-Ascorbic acid ... 

In the synthesis of vitamin C, the oxidation of diacetone L-sorbose to diacetone 2-keto-L-gulonic acid proceeds at an Ni-anode in the presence of hydroxide. Under these conditions, the nickel hydroxide surface is anodically transformed to NiOOH, the nickel peroxide, which acts as chemical oxidant via hydrogen atom abstraction. Thus, a chemically modified redox-active electrode acts as a heterogeneous redox catalyst [13] ... 

Direct Oxidation of L-Sorbose to L-xylo-2-HexuIosonic Acid ( 2-Keto-L-gulonic Acid )... 

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