Configuration of sugars

The Mills-Nixon hypothesis that small ring annelation on benzene would induce bond fixation (bond alternation) by trapping out one Kekul6 tautomer is a casualty of early twentieth century structural chemistry. Due to a lack of direct methods for analyzing molecular structure, structural postulates of that time were often supported by an analysis of product distributions. An experimental observable such as product selectivity or isomer count was correlated to an unobservable structural feature derived on the basis of a chemical model. Classical successes of this method are van t Hoff s proof of the tetrahedral carbon atom and Fischer s proof for the configuration of sugars. In the case of Mills and Nixon, however, the paradigm broke down. 

By convention, one of these two forms is designated the d isomer, the other the l isomer. As for other biomolecules with chiral centers, the absolute configurations of sugars are known from x-ray crystallography. To represent three-dimensional sugar structures on paper, we often use Fischer projection formulas (Fig. 7 2). 

H. Kiliani, Uber das Cyanhydrin der Lavulosc, Ber. Dtsch. Chem. Ges. 18 3066 (1885) E. Fischer, Reduction von Sauren der Zuckergnippe, Ber. Dtsch. Chem. Ges. 22 2204 (1889). For recent historical review articles dealing with the work of Emil Fischer on the configuration of sugars, see ... 

F. W. Lichtenthaler, Emil Fischer s proof of the configuration of sugars A centennial tribute, Angew. Chem. Int. Ed. Engl. 37 1541 (1992). 

J. Hoffman, B. Lindberg, and S. Svensson, Determination of the anomeric configuration of sugar residues in acetylated oligo- and polysaccharides by oxidation with chromiun trioxide in acetic acid, Acta. Chem. Scand., 26 (1972) 661-666. 

Whether the enantiomeric preference, such as found in the L-configuration of amino acids or the D-configuration of sugars, comes from a deterministic or a random process... 

K. Leontein, B. Lindberg, and J. Lonngren, Assignment of absolute configuration of sugars by g.l.c. of their acetylated glycosides formed from chiral alcohols, Carbohydr. Res., 62 (1978) 359—362. 

Carbohydrate complexes. Bdeseken deduced configurations of sugar anomers by studying their effect on the electrical conductivity of boric acid solutions. 

Whatever the real time scale required for evolution, the process was a protracted and continuous progression from primitive, inefficient mechanisms to more complex, efficient ones. The reactions all occurred in the oceans, or along the shorelines, and metal ions must have played a critical role both in determining the compositions of the biopolymers we know today and in dictating whether the l- or D-configurations of sugars... 

The present day convention is to use capital letters D and l to indicate the absolute configurations of sugars and amino acids the absolute configurations of all other molecules are indicated by the symbols R and S. For the convention see Cahn et al. (1966). 

Fischer projection /fish-er/ A way of representing the three-dimensional structure of a molecule in two dimensions. The molecule is drawn using vertical and horizontal lines. Horizontal lines represent bonds that come out of the paper. Vertical lines represent bonds that go into the paper (or are in the plane of the paper). Named for Emil Fischer, the convention was formerly used for representing the absolute configuration of sugars. 

Lectins and other carbohydrate-binding proteins bind to specific configurations of sugar molecules can serve to identify cell types or cellular components, making them versatile primary detection reagents in histochemical applications and flow cytometry. 

A novel and very sensitive procedure for determining the absolute configuration of sugars involving an HPLC procedure operating on a picamole scale involved making the derivatives 1 by use of a resolved acid which was coupled with a peracetylated glycosyl chloride. ... 

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