Nomenclature disaccharides

Using this disaccharide nomenclature system, 61 is named 0-a-d-altropyranosyl-(1 4)-a-d-mannopyranose. It is also possible to couple a furanose unit to another furanose or a furanose to a pyranose. When a-d-ribofuranose (62) is coupled 1 1 to a-d-xylofuranose (63), the disaccharide is 64 (O-a-d-ribofuranosyl-(l l)-a-d-xylofuranose). There are several possibilities for coupling, including ketofuranose and ketopyranose derivatives. 

Haworth representation, cyclic monosaccharides, 61-63 Hemiacetal groups disaccharides with, 149-150 without, 148-149 nomenclature, 122-123 oligosaccharides with, 153-154 without, 151-153... 

The mass-spectrometric behavior of permethylated disaccharides having (l- 2)-, (l->4)-, and (l->6)-linked hexose residues has been investigated by Kochetkov and coworkers. It was found that the fragmentation of both moieties of the disaccharide follows principles similar to those for permethylated glycosides. The nomenclature used by Chizhov and Kochetkov for the different fragmentation series of permethylated... 

The term carbohydrate includes a wide range of molecules which in many cases are quite complex structures. In chemical terms a carbohydrate is either a polyhydroxy aldehyde, a polyhydroxy ketone or, alternatively, it is a compound that can be hydrolysed to such a structure. The smallest unit that cannot be hydrolysed any further is called a monosaccharide. Glucose (Fig. 11.4.1) is the most abundant monosaccharide known and is by far the most important. Other examples include fructose and mannose. A carbohydrate which has been hydrolysed to two monosaccharide units is cabled a disaccharide and the best known example is sucrose, which is composed of a unit of glucose covalently linked to a unit of fructose. The nomenclature system continues in a logical fashion until one can refer to an ohgosaccharide as being a chain composed of several monosaccharide units. Depending upon whether a monosaccharide is an aldehyde or a... 

Fig. 5. Molecular representation of the chain structure of cellulose. Labeling of the cellobiose repeat unit is given in accordance with lUPAC nomenclature n indicates the number of repeating disaccharide units in a given cellulose chain. The reducing end of the chain is indicated a schematic representation of the chemical polarity of the chain is shown underneath this representation is used throughout this chapter. (See Color Plate 3.)...

Between 1884 and 1902 Emil Fischer determined the structures of all monosaccharides from trioses through nonoses and those of the most important disaccharides, among them sucrose, maltose, isomaltose, and lactose. Fischer also explained the structural basis of their optical activity, and he established the modern nomenclature of sugars, for example, by substituting glucose and fructose for dextrose and levulose ... 

In the nomenclature of oligosaccharides, trivial names are still used for a number of substances (e.g. maltose, cellobiose or trehalose. Figure 4.5). In the case of reducing disaccharides, systematic nomenclature takes as its basis the name of the monosaccharide with a free hemiacetal hydroxyl group, which is preceded by the name of the substituted monosaccharide and the respective anomeric configuration is indicated (a- or P-). Disaccharide maltose (Figure 4.5), formed by condensation of... 

Table 1.3 highlights the salient features of macromolecule construction. Polymeric carbohydrates are composed of monosaccharides linked by glyco-sidic bonds to form multiple units which, if relatively small, are called oligosaccharides, and, if larger, are called polysaccharides. Oligosaccharides may be described as disaccharide, trisaccharide, tetrasaccharide etc. according to their number of monomeric units. Similar nomenclature is employed for proteins and nucleic acids. The numbers of different monomeric units found in their respective macromolecules is low and variable. For example, there are over 300 amino acids known to man but only 20 plus a few of their derivatives are found in proteins. Also, many proteins exist which lack some of the 20 amino acids. 

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