Aldoses common names

As indicated previously, primary and secondary amines can also react with carbonyl compounds to form a mixture of compounds containing small molecules and polymers. The small molecule compounds obtained from an aldose and an amine have the common name Amadori products because the Amadori rearrangement is involved in their formation. The compounds generated from ketoses and amines are known as Heyns products (although the differentiation Amadori/Heyns is not always considered). The mechanism for the reaction of primary amines with a reducing sugar can be formulated as follows ... 

The nomenclature of carbohydrates usually includes the suffix -ose. Monosaccharides may also be identified according to the nature of the carbonyl functional group (aldose or ketose), the number of carbons in the molecule (tri-, tetr-, pent- ose) or a combination of these two. Monosaccharides also have common names such as ribose, glucose, galactose, and fructose (four of the most common monosaccharides found in nature). 

Aldopentoses are five-carbon aldoses. These carbohydrates contain three stereogenic carbons, and so there must be a total of eight stereoisomers (2 = 8). Figure 22.7 shows the four members of the D series of aldopentoses and their common names. 

Figure 24-1 o-Aldoses (up to the aldohexoses), their signs of rotation, and their common names. 

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

An intramolecular ether (commonly called an intramolecular anhydride), formally arising by elimination of water from two hydroxy groups of a single molecule of a monosaccharide (aldose or ketose) or monosaccharide derivative, is named by attaching the (detachable) prefix anhydro- preceded by a pair of locants identifying the two hydroxy groups involved. 

In clinical chemistry however, these systems have not been differentiated as yet. Since the oxidation of an alcohol corresponds to the reduction of a ketose or an aldose, the designations ketose reductase and aldose reductase, respectively, were suggested (H4, W14). In this paper however, the enzyme or enzyme system will be named polyol or sorbitol dehydrogenase (SDH), although the latter expression does not characterize exacdy the enzyme s function in a general biochemical sense. But sorbitol or fructose have been commonly used as substrates in clinical chemical investigations. 

Trivial names are common in carbohydrate nomenclature. Fifteen of them form the basis of the systematic nomenclature. They are assigned to the simple aldoses (polyhydroxyaldehydes), from triose to hexoses. 

Notice that glucose is an aldehyde and fructose is a ketone. Polyhydroxy aldehydes like glucose are called aldoses. Polyhydroxyke-tanes like fructose are called ketoses. Carbohydrates are also named for the number of carbons they possess triose, tetrose, pentose, hexose, heptose, and so on. The names are commonly combined making glucose an aldohevose... 

As the name implies, carbohydrates are characterized by a nominal (CH20) composition. Next to proteins, carbohydrates combined into polysaccharides are generally the most abundant (Table 8.6) and widely distributed biopol5miers in living organisms. (However, there are some plankton in which the lipid concentration exceeds that of carbohydrates (Wakeham et al, 1997).) The fundamental monomeric rmits of most carbohydrates are five- (pentose) and six-(hexose) carbon sugars, of which there are roughly ten common forms (Fig. 8.9). These structural units usually occur as either aldoses or ketoses, in which either the first (aldose) or second (ketose) carbon... 

The ketoses are classified as 2-ketoses, 3-ketoses, etc., following the carbonyl position on the chain. The 2 of 2-ketoses, a common natural structure, can be removed. The suffix ose is replaced by ulose in the parent name. Likewise, fructose is a 2-hexulose, or more simply, a hexulose. For the complete name, it is preceded by the configuration descriptor. The systematic name of fructose 4.37 would be D-araZ>Z o-2-hexulose. In the case of 2-ketoses, there is no possible ambiguity for the configuration of pyranoses and furanoses. The nomenclature is copied from that of aldoses as, for example, /3-D-fructopyranose 4.38. Methyl glycoside 4.39 of sialic acid is called methyl 5-acetamido-3,5-dideoxy-D-gZycera-a -D-gaZacfo-2-nonulopyranosidonic acid. 

Fructose was named long before its stracture was known, because it is commonly found in fmit. The same is trae for naming most aldoses. Names such as glucose, mannose, ribose, saA fructose are called trivial names, i.e., they are nonsystematic. 

The trivial names of the common sugars, including aldoses with up to six carbon atoms and ketohexoses, are still used (Fig. 15.1). These include the d- and L-forms of glycer-aldehyde, erythrose, threose, ribose, arabinose, xylose, lyx-ose, allose, altrose, glucose, mannose, gulose, idose, galactose, and talose (El Khadem, 1988). The prefixes derived... 

Of common occurrence in biochemistry are the D forms of the aldoses, namely glucose (the most important), mannose and galactose, and the ketose called fructose. 

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