Important Monosaccharides

The major mechanistic and structural aspect of the acetalation process is its orientation toward derivatives obtained either under thermodynamically controlled conditions or under kinetically controlled conditions. We will not discuss here all structural factors concerning the relative stabilities of acyclic and cyclic acetals of polyols and monosaccharides, because such a discussion has been extensively reviewed and adequately commented on [8,10,12 -14]. However, it is important to focus here on the main consequences of these relative stabilities in relation to the various experimental conditions to orientate the choice of specific conditions, particularly for the most important monosaccharides (D-glucose, D-mannose, and D-galactose). 

The transformation of pentoses and hexoses into 2-furaldehyde and 5-(hydroxymethyl)-2-furaldehyde, respectively, by the action of acids is a well-known reaction. Professor Bognar was long interested in ascertaining whether this reaction is reversible. With both a theoretical and a practical goal, the Bogn r group then synthesized the dl forms of several important monosaccharides (xylose, ribose, and arabinose) from the aforementioned furan derivatives. 

Biologically Important Monosaccharides. Avery large number of monosaccharides have been found in biological systems, but a relatively smaller number of monosaccharides is found very frequently in virtually all kinds of cells. Most biochemists find it convenient to memorize the structures of this smaller group. Consult a standard biochemistry textbook for the structures of the following monosaccharides. The hexoses, D-glucose and D-ffuctose... 

In the structures, introduced so far, an O4 rhomb or O5 patterns turned out to be ideal building blocks for carbohydrate-metal complexes. The most important monosaccharide, D-glucose, in any of its hemiacetal forms does not exceed the simple 02 diol pattern ( a consequence is the epimerization reaction of glucose to 8-mannofuranose in the presence of trivalent metal ions). 

Most important monosaccharide units of piant heteropoiysaccharides associated with ceiiuiose (exci. jS-D-giu-copyranose)... 

Because it is the unit of which starch, cellulose, and glycogen are made up, and because of its special role in biological processes, (+) glucose is by far the most abundant monosaccharide—there are probably more ( + )-gIucose units in nature than any other organic group—and by far the most important monosaccharide. 

Sugars are structurally the simplest carbohydrates. They are the structural unit which makes up the other types of carbohydrates. Monosaccharides are single (mono=one) sugars. Important monosaccharides include ribose (C5H10O5), glucose (C6H12O6), and fructose (same formula but different structure than glucose). 

The most important monosaccharides are glucose, fructose, mannose and galactose. Their molecular formulae are identical (C6H1206) and as such they are all structural isomers of each other. 

It is the most important monosaccharide, it is the most abundant sugar found in nature and in animals. 

Monosaccharide Stereoisomers Cyclic Structure of Monosaccharides Reactions of Monosaccharides Important Monosaccharides... 

Among the most important monosaccharides that occur in living organisms are glucose, fructose, and galactose. The principal functional roles of these molecules are briefly described. 

Glucose, fructose, and galactose are among the most important monosaccharides in living organisms. 

Fig. 2.6 (a) Geochemically important monosaccharides (carbon numbering convention shown for D-glucose and D-fructose) and (b) their biological precursors. 

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