Fructose saccharinic acids from

A. Ishizu, B. Lindberg, and O. Theander, Saccharinic acids from D-xylose and D-fructose, Acta Chem. Scand., 21 (1967) 424 132. 

Fiqure 4.48 Formation of saccharinic acids from glucose and fructose. 

Komoto detected lactic acid in the mixture from reaction of D-glucose with ammonia,4 and presumed that it was produced from pyruvaldehyde formed by decomposition of D-glucose. Lactic acid has, indeed, been found as a product of the action of alkali (lime-water) on substituted D-glucose and substituted D-fructose,81,83,96 and the mechanism of its formation involves the reversible aldol reaction, followed by formation of pyruvaldehyde, and the benzilic acid rearrangement already described for saccharinic acid this is illustrated83,96 in Scheme 11. 

Ishizu et al.29H found that D-xylose and D-fructose react with aqueous calcium hydroxide to produce 13 lactonizable saccharinic and other acids. These were identified after separation by cellulose column and gas-liquid chromatography, and the Cs-saccharinic acids, 2-C-methyl-D-threonic acid (117) and 2-C-methyl-D-erythronic acid (118), were among those isolated. These authors299 later reported that L-sorbose reacts similarly, to generate 14 lactones, including the 2-C-methyl-L-xr/o o-l,4-lactone and 2-C-methyl-L-lyxono-1,4-lactone, which were also prepared from 1-deoxy-L-threo-pentulose via the cyanohydrin reaction. 

It has been postulated (37) that lactulose is formed from lactose by the Lobry de Bruyn and Alberda van Ekenstein transformation, whereby glucose is isomerized to fructose via an enol intermediate. In turn, two mechanisms have been proposed for the degradation of this intermediate (38)- One involves the addition of a proton to the enediol resulting in epimeric aldoses and the original ketose, while the other involves 8-elimination to yield galactose and saccharinic acids. The authors experimental data would tend to better support the second pathway. 

A wide range of carbohydrates is degraded by acids to furan compounds. For example, pentoses give 2-furaldehyde, and hexoses, 5-(hydroxymethyl)-2-furaldehyde (58), which may react further to yield levulinic acid. In 1910, Nef suggested the first mechanism, (55) to (58), for the formation of 5-(hydroxymethyl)-2-furaldehyde. His proposal was made at the end of his classical paper on the saccharinic acids, and was overlooked by subsequent workers and reviewers. In 1944, Haworth and Jones advanced an identical mechanism for the formation of 5-(hydroxymethyl)-2-furaldehyde from D-fructose. 

Biamperometric titration of cyclamate was exploited by Fatibello-Fiho et al. [84,85]. These investigators developed an inexpensive laboratory-built selectable voltage source specially constructed for use in biamperometric titrations. It was made of very simple electronic components and its performance was tested and compared with a potentiostat/galvanostat equipment. The titrant-reagent system was sodium nitrite in 1.0 M phosphoric acid and there was no interference from glucose, fructose, sucrose, lactose, sorbitol, saccharin, benzoic acid, salicylic acid, fumaric acid. Sunset Yellow, and Bordeaux-S. 

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