Monosaccharides absolute configuration

Another approach for determination of the absolute configuration of the monosaccharide components69 involves their interaction with radioactive potassium cyanide and conversion of the products into a mixture of heptonamides. Isotopic-dilution experiments showed the presence of D-gfi/cero-L-manno-heptonamide, thus establishing the D-galacto configuration of the starting hexose. 

We now know the absolute configurations of (+) - and (—) -glyceraldehyde. These structures serve as the configurational standards for all monosaccharides. 

A very useful source on various NMR techniques and chemical shifts of functionalized carbon atoms that contains tabulated data on monosaccharides is Reference [23]. Specifically correlating functional groups with chemical shifts of protons and the associated carbon is an important tool for elucidating the stmcture of the monosaccharide moiety of many complex oligosaccharides. Since monosaccharides contain one or more chiral centers, absolute configuration must be known in order to predict the conformational shape of the molecules. The outcome of many stereoselective functionalizations of free and partially functionalized monosaccharides depends on conformation. 

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... 

The absolute configuration of the monosaccharides can be determined by analyzing the sugars (obtained from hydrolysis experiments) on a chiral HPLC column (86, 87). The absolute stereochemistry of the monosaccharides may also be derived by chiral GC analysis (88, 89). Moreover, one can also compare the observed value of the molecular rotation with the value calculated on the basis of Klyne s rule (90). 

In most studies of the structure of cell wall polysaccharides the absolute configuration of the monosaccharides is assumed—rhamnose, fucose, and arabinose are L, whereas mannose, galactose, glucose, glucuronic, and galacturonic acid are D. However, for a complete characterization it is essential to determine the absolute configurations experimentally. 

The absolute configuration of caryose was determined applying the Exciton Chiral Coupling to 36 [Fig. (8)], which is the di-O-p-bromobenzoyl derivative, obtained as the main product of the isopropylidenation of the monosaccharide equilibrium mixture (34a, 34b and 35) followed by esterification with p-bromobenzoyl chloride. The results obtained have suggested for caryose the absolute configuration... 

Figure 1.40 Structural summary of all main monosaccharides found in natural carbohydrates. ALL monosaccharides are displayed as their Fischer Projections to shown differences in absolute configuration.

James, T.D., Harada, T., Shinkai, S. (1993). Determination of the absolute configuration of monosaccharides by a colour change in a chiral cholesteric liquid crystal system, J. Chem. Soc. Chem. Comm 857. 

Relate the absolute configuration of monosaccharide D or L stereoisomers to those of... 

Heinrich J, Konig WA, Bretting H, and Mischnick P (1997) Enantiomer separation of permethylated monosaccharides and 1,5-anhydoalditols and simultaneous determination of hnkage positions and absolute configuration in... 

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