Aldonic acids salts

Oxidation to Sugar Acids and Lactones. When the aldehyde group of an aldose is oxidized, the resulting compound is an aldonic acid (salt form = aldonate) (11)4. Some aldonic acids are products of carbohydrate metaboHsm. 

So far only a table of the 13C chemical shifts of aldonic acid salts and aldonolactones has been published in the literature (Table 5.20, [696]). The carbons of the carboxylate ion groups of all D-aldonic acid salts resonate at 180 + 0.7 ppm. Upon /-lactone formation an upfield shift for C-l and a downfield shift for the /-carbon is observed throughout. 

Table 5.20. 13C Chemical Shifts ( c in ppm) of n-Aldonic Acid Salts (pH 14) and Aldono-lactones [696].

Fully acetylated aldonic acids can be prepared by oxidation of aldehydo-sugar peracetates. Direct acetylation of certain aldonic acid salts is possible, and addition of cadmium salts, in particular, affords high yields of acetates. The synthesis can also be accomplished by deamination of the readily prepared, acetylated amides with nitrous acid or nitrosyl chloride. Examples of the various methods are given in Ref. 86. 

Aldonic acids exist m equilibrium with their five or six membered lactones They can be isolated as carboxylate salts of their open chain forms on treatment with base... 

The hydroxyl groups of aldonolactones react with a variety of aldehydes and ketones to give the corresponding acetal derivatives. Treatment of the salts of aldonic acids with benzaldehyde and hydrochloric acid or zinc chloride as catalysts give benzylidene derivatives of aldonic acids or aldonolactones (3). 

Aldonamides are readily prepared by reaction of lactones with liquid ammonia (86,99,100), with ammonium hydroxide (101,102), or by bubbling ammonia gas into alcoholic solutions of the sugar lactones (103-104). Aldonamides of the tetronic adds are stable in aqueous solution (105), but penton- or hexon-amides are hydrolyzed, as shown by the change of the optical rotation of the amide solutions (106). The hydrolysis is catalyzed by acids and bases, and the product was the ammonium salt of the aldonic acid. 

Simple syntheses of suitable monomers for nylon 5 and nylon 6 analogs, such as 5-amino-5-deoxyaldonic and 6-amino-6-deoxyaldonic acids (51, 54), has been achieved starting from unprotected o-pentono- and hexono-1,4-lactones [68, 69]. Saponification of 5- or 6-azido-D-aldonolactones ribo-, arabino-, xylo-, galacto-, manno-, compound types 49 and 52) provided the corresponding 5- or 6-azido-aldonic acid sodium salts (50, 53). A catalytic hydrogenation after or before treatment with acidic resin afforded compounds 51 and 54 in excellent overall yields (Scheme 16). 

The Ruff degradation,67 involving interaction of a salt of an aldonic acid, ferric acetate, and hydrogen peroxide, was employed in the synthesis of 5-deoxy-L-arabinose218 and 5-deoxy-L-Iyxose.219... 

Two useful preparations of lower sugars by degradation of aldonic acids are discussed in the following Chapter. These are the traditional oxidation of salts of aldonic acids with hydrogen peroxide in the presence of ferric acetate (Ruff degradation) and the related oxidation of aldonic acids by hypochlorite, which was developed by Whistler and Schweiger.79... 

The reducing group in uronic acids can be oxidized by nitric acid or bromine to yield aldaric acids. Uronic acids, as salts, can be quantitatively reduced to aldonic acids by borohydride.239 Lactones are readily reduced, as in the controlled conversion of D-glucurono-6,3-lactone into D-gluco-hexodialdose. The carboxyl group of glucuronic acids may be reduced to a primary alcoholic group. 

Aldaric acids may be prepared from aldoses or aldonic acids by oxidation in aqueous solution with oxygen over platinum-charcoal255 or platinum-on-alumina.256 The effect of such promoters as bismuth or gold has also been studied.257 Hydrogen peroxide in the presence of iron salts has been used for the oxidation of uronic acids to aldaric acids.258... 

The procedure of Moore and Link16 is now generally preferred for the preparation of benzimidazoles from aldonic acids, their lactones, or their salts. Their specific example starting with calcium D-gluconate is given below. 

D-ribonate. In critical cases, such as the study of a mixture in which the presence of small quantities of D-arabinose is being considered, oxidation with bromine and a barium benzoate buffer according to Hudson and Isbell27 may be substituted, even though the procedure becomes more complicated if one wishes to fractionate the aldonic acids through their potassium and barium salts. While other examples of epimerization under these alkaline conditions have not been reported, the possibility of such rearrangements must always be kept in mind. 

L-arabinose and D-xylose in hemi-cellulose of sugar Cane, V, 279 Banana starch. See under Starch. Barium acid heparinate, III, 146 Barium 2-desoxy-D-gIuconate, III, 144 Barium D-gluconate, III, 144 Barium hypobromite, III, 163 Barium salts, in preparation of aldonic acids with NaCN, I, 23 Bark, tree, pentosan content, V, 271 Barley, alpha amylase of malted, V, 255-265... 

Calcium D-galactonate, I, 70 Calcium D-gluconate, III, 141, 142, 149, 152, 155, 156, 161 IV, 331 Calcium hypochlorite, III, 165 Calcium 2-keto-D-gIuconate, III, 148, 155 Calcium 5-keto-D-gluconate, III, 156 Calcium lactobionate, calcium bromide double salt, III, 155 Calcium Ievulinate, IV, 311 Calcium maltobionate, III, 161 Calcium D-mannonate, III, 152 Calcium pectate, I, 334 Calcium D-rhamnonate, III, 144 Calcium salts, in preparation of aldonic acids with NaCN, I, 23 Calcium vicianobionate, III, 154 Calcium D-xylonate, III, 155 Camphor, optically active, formed from inactive (racemic) camphor carboxylic acid in the presence of quinine, quinidine or nicotine, V, 53 Camphor carboxylic acid. See Camphor. Camphor, 3-hydroxy-, IV, 89 Camphorquinone, phytochemical reduction of, IV, 89... 

Oxidation of the aldehyde group of an aldose to a carboxylic acid group gives a derivative known as an aldonic acid. This occurs as a salt, aldonate, at physiological pH. If an aldonic acid contains five or more carbon atoms, a 8-lactone is formed spontaneously by the condensation of the carboxylic acid group and the hydroxyl group on C-5. 

Starting from a salt of an aldonic acid, the Ruff oxidative degradation reaction1 leads to an aldose with loss of one carbon atom. Known since 1898, the original process used aqueous hydrogen peroxide as oxidant, in the presence of catalytic amounts of ferric salts. 

These compounds are very stable, but as derivatives of aldonic acids they undergo epimerization with hot sodium hydroxide. They are oxidized by hypobromite to salts of the labile 2-phenyl-1,3,4-thia-diazole-5-carboxylic acid (15). The corresponding products from fucose and hexuronic acids were described in later papers. 

Oxidation free carbonyl groups are able to reduce alkaline solutions of metal (mainly copper) salts to the free metal or to the oxide, to give aldonic acids. Thus glucose gives rise to gluconic acid (Fig. 7.6). When the hydroxyl group... 

The various types of carbohydrates considered in this chapter are shown in formulas I-XVIII. The two ring forms (II and III) of the aldoses are shown because careful oxidation can produce the lactones X and XI directly without breaking the oxygen bridge. In most cases, however, the products of oxidation have been isolated as salts of aldonic acids (IX) thus the nature of the initial oxidation product, either a lactone having the same ring structure as the sugar, or possibly the free... 

The aldonic acids of the pentose series were prepared similarly. L-Arabonic acid was isolated by Kiliani as the calcium salt, and Ruff prepared calcium n-arabonate. In the latter case almost quantitative yields were reported. n-Lyxonic acid was isolated as the basic lead salt and converted to the crystalline lactone by Wohl and List. n-Ribose was oxidized to the crystalline cadmium n-ribonate by Levene and Jacobs the yield was less than 50%. The well-known boat-shaped crystals of the double salt of cadmium n-xylonate-cadmium bromide were prepared by the oxidation of n-xylose with an excess of bromine by Ruff, followed by a subsequent treatment with cadmium carbonate. Ruff also prepared L-erythronic acid, isolating it as the brucine salt the starting material was a crude n-erythrose sirup prepared by degradation of calcium L-arabonate. 

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