Aldonic acids aldoses

Derivatives of aldoses in which the terminal aldehyde function is oxidized to a car boxylic acid are called aldonic acids Aldonic acids are named by replacing the ose ending of the aldose by omc acid Oxidation of aldoses with bromine is the most com monly used method for the preparation of aldonic acids and involves the furanose or pyranose form of the carbohydrate... 

Aldonic acid (Section 25 19) Carboxylic acid obtained by oxi dation of the aldehyde function of an aldose Aldose (Section 25 1) Carbohydrate that contains an aldehyde carbonyl group in its open chain form Alicyclic (Section 2 15) Term describing an a/iphatic cyclic structural unit... 

Other multifunctional hydroxycarboxylic acids are mevalonic and aldonic acids which can be prepared for specialized uses as aldol reaction products (mevalonic acid [150-97-0] (13)) and mild oxidation of aldoses (aldonic acids). 

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. 

Aldonic acid (Section 25.19) Carboxylic acid obtained by oxidation of the aldehyde function of an aldose. 

Although the Tollens reaction is a useful test for reducing sugars, it doesn t give good yields of aldonic acid products because the alkaline conditions cause decomposition of the carbohydrate. For preparative purposes, a buffered solution of aqueous Br2 is a better oxidant. The reaction is specific for aldoses ketoses are not oxidized by aqueous Br2. 

Aldonic acid (Section 25.6) The monocarboxylic acid resulting from mild oxidation of the -CHO group of an aldose. 

Monocarboxylic acids formally derived from aldoses by replacement of the aldehydic group by a carboxy group are termed aldonic acids (see 2-Carb-20). 

The parent that includes the functional group most preferred by general principles of organic nomenclature [13,14], If there is a choice, it is made on the basis of the greatest number of occurrences of the most preferred functional group. Thus aldaric acid > uronic acid/ketoaldonic acid/aldonic acid > dialdose > ketoal-dose/aldose > diketose > ketose. 

Aldonic acids are divided into aldotrionic acid, aldotetronic acids, aldopentonic acids, aldohexonic acids, etc., according to the number of carbon atoms in the chain. The names of individual compounds of this type are formed by replacing the ending -ose of the systematic or trivial name of the aldose by -onic acid . 

Aldol addition, 2 63-64 acetone, 1 164 Aldolases, 3 675 4 711 Aldol process, for higher alcohol manufacture, 2 27t, 41-43 Aldonic acid, 14 132 Aldoses, 4 696... 

There are three possible classes of sugar acids which may be produced by the oxidation of monosaccharides (Figure 9.11). The aldonic acids are produced from aldoses when the aldehyde group at carbon 1 is oxidised to a carboxylic acid. If, however, the aldehyde group remains intact and only a primary alcohol group (usually at carbon 6 in the case of hexoses) is oxidised then a uronic acid is formed. Both aldonic and uronic acids occur in nature as intermediates in... 

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. 

We have devised a very simple procedure for the preparative synthesis of various aldonic acids from the corresponding aldoses. This green chemistry process takes advantage of the availability of cheap, robust industrial enzymes. 

Reductions with sodium amalgam are fairly mild. Only easily reducible groups and conjugated double bonds are affected. With the availability of sodium borohydride the use of sodium amalgam is dwindling even in the field of saccharides, where sodium amalgam has been widely used for reduction of aldonic acids to aldoses. 

The oxidation of an aldose (not a ketose) with bromine and water results in an aldonic acid. An example of this reaction is shown in Figure 16-9. 

The fact that only Cr(V)-disaccharide species are formed in the Cr(VI)/disaccha-ride reaction at pH 3-7 indicates that the disaccharides are better chelating agents for Cr(V) than are aldoses. The latter are poorer complexation agents than the corresponding aldonic acids so that oxo-Cr(V)-aldose-aldonic acid and oxo-Cr(V)-(aldonic acid)2 bis-chelates are the major species observed in the EPR spectra of the Cr(VI)/aldose reaction mixtures. 

The first step in the degradation is the preparation, starting from an aldose, of the acylated nitrile of an aldonic acid. The nitrile and the acyl groups may be removed by various methods to yield a new aldose,... 

Wohl prepared the acylated nitriles of the aldonic acids by heating the aldose oximes with a mixture of sodium acetate and acetic anhydride. With careful control of the reaction, this method may be used for preparative work with fairly good results. 

---