Simple Monosaccharides

The monomeric units of all polysaccharides are derived from mono-oxopolyhydroxy compounds, C H2 0 , which formally result from the 

Sugars with four carbon atoms are called tetroses, those with five are pentoses, those with six are hexoses, and so on. According to the above rule, there have to be two keto pentoses, each with one d and one l form, or four altogether (cf. Table 31-1). In addition, there are four keto hexoses, four aldopentoses, and eight aldohexoses, each occurring once in the d form and once in the l form. These sugars are given trivial names (Table 31-1). 

In solution, the sugars are found predominantly in the cyclic form, more specifically, the hexoses in the pyranose form and the pentoses in the furanose form. The formation of rings creates a new asymmetric center. The two new isomers are distinguished from one another as a and p anomers, because they are epimeric with respect to C-1. In the a anomers, the anomeric hydroxyl group is axially oriented (while the anomeric hydrogen atom is equatorial), whereas in the P anomers it is equatorial. In D-glucose (d-glucopyranose) it follows that 

Derivatives of simple monosaccharides occur as building blocks in polysaccharides. 

Anhydro sugars are derivatives in which two hydroxyl groups within the same unit are intramerally etherated. An example of this is 3,6-anhydro-a-L-galactopyranose (Table 31-3). 

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Thomson JOV Click Organic Interactive to learn to draw and interpret Fischer projections of simple monosaccharides. 

Thomson -IOW Click Organic interactive to learn to draw cyclic forms of simple monosaccharides. 

Thomson I Click Organic Interactive to predict products from reactions of simple monosaccharides. 

The reversal of the well-known transformation of sugars into pyrans has been detailed as a method for assembling simple monosaccharides from simple furans (71T1973). A compound of the 2-furylcarbinol type was converted by the Br2/MeOH procedure into a mixture of the cis and trans isomers of the corresponding 2,5-dimethoxy-2,5-dihydrofuran derivative (129). Mild acid hydrolysis of (129) resulted in cleavage of the acetal bonds with formation of the dicarbonyl compound (130) which underwent immediate cyclization to 2,3-dideoxy-DL-alk-2-enopyranos-4-ulose (131 Scheme 29). 

S. Jarosz and B. Fraser-Reid, Synthesis of higher sugars via allytltin derivatives of simple monosaccharides, J. Org. Chem. 54 4011 (1989). 

Although we now have powerful spectroscopic methods available to determine the sizes of the oxide rings formed by the simple monosaccharides, the way in which this was done chemically for glucose highlights the difference in reactivity between ether and alcohol functions. 

The basic carbohydrate molecules are simple sugars, or monosaccharides, which are polyhydroxy aldehyde, polyhydroxy ketone, and their derivatives. All simple monosaccharides have the general empirical formula, (CH20)n, where n is the whole number ranging 3 to 8. 

Employing glycosyl donors of the above type and a simple monosaccharide acceptor such as methyl 2-0-benzyl-4,6-0-benzylidene-a-D-mannopyranoside or the... 

Draw the Fischer projection formula for a simple monosaccharide. 

T12. Thornalley, P., Wolff, S., Crabbe, J., and Stern, A., The autoxidation of glyceraldehyde and other simple monosaccharides under physiological conditions catalysed by buffer ions. Biochim. Biophys. Acta 797, 276-287 (1984). 

For a review, see Jarosz, S, Synthesis of higher carbon sugars via coupling of simple monosaccharides — Wittig, Homer-Emmons, and related methods, J. Carbohydr. Chem., 20, 93-107, 2001. 

Because poiysaccharides are natural macromolecules occurring in all living organisms, the structure of some polysaccharides can be much more complex, as they are not made only from simple monosaccharides. In the composition of natural polymeric carbohydrates, a wide variety of sugars are found. Among these, the most common are pentoses and hexoses. The structural formulas of three common pentoses are shown below. They frequently form cyclic structures with five-member rings (furanoses). 

Besides simple monosaccharides, a large number of associated compounds are found in the structure of natural polysaccharides. Among these are the deoxysugars. The structural formulas of two common deoxyhexoses are shown below ... 

In a recent work,138 we have attempted to parameterize the Karplus dependence of 3 7c,oi i couplings taking advantage of the redundant set of J couplings measured for the two anomeric forms of a simple monosaccharide, 4,6-O-benzylidene-l-metoxy-D-glucose (Figure 1). 

Simple monosaccharides with four, five, six, and seven carbon atoms are called tetroses, pentoses, hexoses, and heptoses, respectively. These molecules have multiple asymmetric carbon atoms and, for these monosaccharides, ih symbols D and L designate the absolute configuration of the asymmetric carbon... 

Figure 11.17 General form of a glycosyltransferase reaction. The sugar to be added comes from a sugar nucleotide-in this case. UiDP-glucose. The acceptor, designated X in the figure, can be a simple monosaccharide, a complex polysaccharide, or a serine or threonine residue belonging to a protein.

The Tables list oligosaccharide polymers of simple monosaccharides and of the following naturally occurring derivatives amino sugars, 2-acetamido sugars, uronic acids, and mono-O-methyluronic acids. Although it was considered desirable to include only compounds whose structures had been established beyond doubt, such a rule would have excluded many important compounds. Exceptions to this rule were, therefore, made for compounds of incompletely established structure, provided that there was sufficient evidence to show that they were unlikely to be compounds already known. 

Table III. Oligosaccharides Containing Simple Monosaccharides Only...

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