ABSTRACT
Basically, two different systematic approaches can be used for a classification of carbohydrates: as carbohydrates either contain hydroxy and aldehyde functions (see Fig. 1.1a, glucose) or, alternatively, hydroxy and ketone functions (Fig. 1.1b, fructose), this discrimination may form a basis for a classification. Another approach that is often being used in basic monographs is based on the systematic discrimination between monosaccharides, di-saccharides, oligosaccharides and polysaccharides. In the present chapter, both approaches will be combined by including the functional aspects in the sub-chapter mono-saccharides. As the terms suggest, mono-and di-saccharides consist of one and two sugar units, respectively, while oligosaccharides are assumed to contain 3 to 10 subunits linked together (according to the Greek word oligos, for “a few”). Polysaccharides contain more than 10 subunits. 1.2.1 MonosaccharidesThe early constitutional as well as stereochemical investigations are closely related to the names Emil Fischer, Kiliani, and Tollens (Lichtenthaler, 1992). It was inferred from these basic results that monosaccharides can be considered to be oxidation products of alcohols that contain several hydroxy groups, resulting in polyhydroxy aldehydes or polyhydroxy ketones. The former group of oxidation products is nominated aldoses, while the latter group is called ketoses.
