Saccharinic acids lactone

Hydroxylatlon of the unsaturated esters (15) and (16) with osmium tetraoxlde led to routes to the saccharinic acid lactones (17) and... 

In the carbohydrate series, the acids encountered are aldonic, aldaric, uronic, or saccharinic acids. Often, these acids are readily transformed into their lactones or methyl esters, and it is as derivatives of these that they are commonly studied. Table VIII (see p. 136) records examples in which derivatives of such acids and lactones have been subjected to gas-liquid chromatography. 

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. 

Earlier investigators of the alkaline-degradation products of lactose found succinic acid, formic acid, and a crystalline lactone, later identified by Kiliani as a -D-isosaccharinic lactone. This lactone was obtained in about 20% yield from the action of lime-water on lactose also detected as products of this reaction were D-galactose, lactic acid, pyruvaldehyde, formaldehyde, and other saccharinic acids. The... 

Three structurally isomeric forms have been established for the six-carbon saccharinic acids. In the order of their discovery, these are the sac-charinic or 2-C -methylpentonic acids, the isosaccharinic or 3-deoxy-2-C -(hydroxymethyl)-pentonic acids, and the metasaccharinic or 3-deoxy-hexonic acids. Although none of these six-carbon, deoxyaldonic acids has been crystallized, six are known in the form of crystalline lactones (saccharins). All the possible metasaccharinic acids of less than six-carbon content have been obtained, in the form of crystalline derivatives, by the sugar-alkali reaction. Only one example of a branched-chain deoxyaldonic acid (the racemic, five-carbon isosaccharinic acid) of other than six-carbon content has been so obtained. The formation of saccharinic acids containing more than six carbon atoms remains to be explored. 

Shortly after the discovery of Peligot s a -D-glucosaccharin, Dubrun-faut reported that the calcium salt of a monobasic acid resulted from the action of lime-water on maltose. Cuisinier named the acid isosaccharinic acid, after he had prepared from it a crystalline lactone (CeHioOt) isomeric with Peligot s a -D-glucosaccharin. The name was expanded to a -D-iso-saccharinic acid after Nef obtained evidence of the concurrent formation of its epimer, /3 -D-isosaccharinic acid, in the hexose-alkali reaction. 

The best evidence for the formation of 8 -D-isosaccharinic acid in the sugar-alkali reaction is the recent observation" that treatment of lactose, maltose, or 4-0-methyl-D-glucose with lime-water at room temperature provides initially a mixture of saccharinic acids consisting almost exclusively of a -D-isosaccharinic acid plus an acid with the properties of Nef s /3 -D-isosaccharinic acid [brucine salt, m. p. 185 to 210 (dec.), [a]n - 20 to —22° lactone, [ajp -)-6 to - -8.5°]. An experimental proof that this substance possesses the isosaccharinic acid structure would provide the necessary evidence that it is, indeed, the epimer of a -D-isosaccharinic acid. 

Formose sugars once formed are decomposed at extreme conversions, owing to the alkalinity of the reaction mixture (see Table IV, p. 188). The rate of decomposition depends on the kind of base used, its concentration, the reaction temperature, and the reaction period. A variety of compounds, such as acetals, acids, aldehydes, ketones, lactones, and saccharinic acids, are formed by decomposition. Such decomposition can be decreased by neutralizing the alkalis, or even by slightly acidifying the solution when the formose reaction reaches its peak rate, that is, soon after the solution in a batch reactor begins to turn yellow ( yellowing point ). 

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