Subject aldonic acids

The aldose (11.1 mmol) was dissolved in water to a final concentration of 0.5 m and subjected to oxidation by addition of glucose oxidase (200 mg, 400 U) and a large excess of catalase (1 mL, 25 kU). The mixture was vigorously stirred under air and the pH was kept constant at 7.5 by means of a pH-stat adding continuously 1 m NaOH. The conversion degree was directly calculated considering the volume of added 1 m NaOH, since 1 mol of NaOH neutralizes 1 mol of aldonic acid formed. 

Cyanide ions react with aldehydes and ketones to yield cyanohydrins (Kiliani) (Fig. 2-28). Hydrolysis of the cyanohydrins gives aldonic acids, which can be reduced to aldoses. Kiliani reaction thus opens the possibility for chain lengthening of aldoses. Because of the formation, of a hydroxyl group in place of the aldehyde group a new asymmetric center is generated. It is to be observed, however, that the reaction is subject to so-called asymmetric induction, which means that the diastereoisomers are formed in unequal proportions. 

There are three known metabolic pathways to 3-deoxyulosonic acids. In the first, aldonic acids, formed by oxidation of aldopyranoses to the corresponding lactones, are dehydrated to the ulosonic acids (see Fig. 6). Thus, D-arabinose is converted by way of D-arabinonic acid to 3-deoxy-o-ffZj/cero-pentulosonic acid. The latter is then subjected to oxidative cleavage, yielding pyruvic and glycolic acids. L-Arabinose is oxidized and dehydrated to the 3-deoxy-L-g Z2/cero-pentulosonic acid, which is further oxidized to... 

Sowden s initial work with Hurd concerned the preparation of tritylated glycerols, and this became the subject of their first publication. Typical of the work in Hurd s laboratory was the problem on acetylated aldonic acids which was featured in Sowden s doctoral dissertation. This study was begun in October, 1935, and characteristically excellent laboratory results developed very rapidly. Hurd and Sowden were interested in the application of F. Arndt s diazomethyl ketone synthesis to ascension of the sugar series, and sought (as it turned out later, with several other investigators) a new route to the acetylated aldonic acids. Sowden presented the sequence ... 

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. 

Although this article deals with complexes of neutral carbohydrates, brief mention should be made of the aldonate and alduronate anions (the undissociated acids do not form complexes), which show complexing behavior similar to those of the neutral polyols. Interest in these acids, and particularly in the poly(hexuronates), is due to the industrially important gel-formation of alginic acid and pectin with calcium ions, caused by complex-formation. There is an extensive literature on this subject,which is not fully discussed here. 

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