Sugars conformational analysis

Aldonolactones are useful starting materials for the synthesis of modified sugars. They have also been used as chiral templates in synthesis of natural products. Some of them are inexpensive, commercially available products or they may be obtained readily from the respective monosaccharides. The purpose of this chapter is to survey the main reactions of aldonolactones. Previous reviews on the subject include articles on gulono-1,4-lactones (1) and D-ribonolactone (2). Methods of synthesis, conformational analysis, and biological properties are not discussed in this chapter. 

C. Altona and M. Sundaralingam, Conformational analysis of die sugar ring in nucleosides and nucleotides. New description using the concept of pseudorotation, J. Am. Chem. Soc., 94 (1972) 8205-8212. 

The chemistry of the 2,5-anhydrides of aldoses subsequently entered a prolonged lull, and Peat s review21 of 1946 in this Series does not report on any work later than 1925. The experimental basis of the deamination of amino sugars with nitrous acid was, nevertheless, established. The progress afterwards made in the conformational analysis of sugars made it possible for Shafizadeh22 to draw a parallel with the nitrous acid deamination of the aminocyclohexanols, and to rationalize the whole of these results. 

Theoretical conformational analysis provides a basis for understanding the unique features of double-stranded DNA In terms of its chemical architecture. The well-known stiffness of the chain as a whole derives from the sequence of heterocyclic bases, while the local mobility of the constituent nucleotides reflects the structural complexity of the sugar-phosphate backbone. 

Several reviews have already been published on the subject, for example, the acetala-tion of alditols [4], of aldoses and aldosides [5,6], and of ketoses [7]. Some aspects of the stereochemistry of cyclic acetals have been discussed in a review dealing with cyclic derivatives of carbohydrates [8], also in a general article [9] and, more recently, in a chapter of a monograph devoted to the stereochemistry and the conformational analysis of sugars [10], Aspects on predicting reactions patterns of alditol-aldehyde reactions are reviewed within a general series of books on carbohydrates [11]. The formation and migration of cyclic acetals of carbohydrates have also been reviewed [12,13],... 

Tnformation about the characteristics of keto-hexoses in solution has been - derived mainly from optical rotatory data (I, 2, 3, 4) and in recent years by application of the principles of conformational analysis (5, 6). In the current study an attempt is made to describe the conformation and composition of these sugars in solution by nuclear magnetic resonance (NMR) spectroscopy, a highly sensitive means for examining stereochemistry and for differentiating between isomeric species. 

There are several reasons for reservations about applying the computer extrapolation of crystal structure data for carbohydrates. One is that much of the crystal structure data refer to unsubstituted sugars which are only soluble in hydroxylic or polar solvents where the conformational analysis may be complicated by hydrolysis, isomerism (muta-rotation) (12), or stereospecific solvent interactions which require a more sophisticated model. However, assuming that such chemical changes do not occur or can be suppressed, there still remain questions to be answered before the conformation observed in the crystal can be accepted as a close enough approximation to that of one or more of the rotomers which may predominate in the solution state. (a-L-Sorbose gives an example of the coexistence of two primary alcohol rotameric... 

S. J. Angyal and K. Dawes, Conformational analysis in carbohydrate chemistry. Equilibrium between reducing sugars and their glycosidic anhydrides, Aust. J. Chem., 21 (1968) 2747-2760. 

CARBON-PROTON COUPLING CONSTANTS IN THE CONFORMATIONAL ANALYSIS OF SUGAR MOLECULES... 

The major objective of this article is threefold to introduce some fundamental qualitative and quantitative aspects in analyzing the dynamics of carbohydrate molecules, to demonstrate the advantages and limitations of this approach, and to critically review the results that have been obtained in the field. A complementary article in this volume by Tvaroska and Taravel17 surveys the use of carbon-proton coupling constants in the conformational analysis of sugar molecules. 

Durette, Philippe L., and Horton, D Conformational Analysis of Sugars and Their Derivatives, 26,49-125 Dutcher, James D., Chemistry of the Amino Sugars Derived from Antibiotic Substances, 18, 259-308... 

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