Monosaccharides numbering

Table 20.3 The General Names of Monosaccharides Number of Carbon Atoms Prefix General Name of Sugar...

The simple sugars or monosaccharides are polyhydroxy aldehydes or ketones, and belong to Solubility Group II. They are termed tetroses, pentoses, hexoses. etc. according to the number of carbon atoms in the long chain constituting the molecule, and aldoses or ketoses if they are aldehydes or ketones. Most of the monosaccharides that occur in nature are pentoses and hexoses. 

Over 200 different monosaccharides are known They can be grouped according to the number of carbon atoms they contain and whether they are polyhydroxy aide hydes or polyhydroxy ketones Monosaccharides that are polyhydroxy aldehydes are called aldoses, those that are polyhydroxy ketones are ketoses Aldoses and ketoses are further classified according to the number of carbon atoms m the mam chain Table 25 1 lists the terms applied to monosaccharides having four to eight carbon atoms... 

Monomer (Section 6 21) The simplest stable molecule from which a particular polymer may be prepared Monosaccharide (Section 25 1) A carbohydrate that cannot be hydrolyzed further to yield a simpler carbohydrate Monosubstituted alkene (Section 5 6) An alkene of the type RCH=CH2 in which there is only one carbon directly bonded to the carbons of the double bond Multiplicity (Section 13 7) The number of peaks into which a signal IS split in nuclear magnetic resonance spectroscopy Signals are described as singlets doublets triplets and so on according to the number of peaks into which they are split... 

Storage polysaccharides are an important carbohydrate form in plants and animals. It seems likely that organisms store carbohydrates in the form of polysaccharides rather than as monosaccharides to lower the osmotic pressure of the sugar reserves. Because osmotic pressures depend only on numbers of molecules, the osmotic pressure is greatly reduced by formation of a few polysaccharide molecules out of thousands (or even millions) of monosaccharide units. 

Reaction of hydrazine 165 with a number of monosaccharides give hydrazones 166 (92BCJ546). Their acetylations gave peracetyl derivatives 167. The same reactions were extended to the /V-methyl and the 7-methyl derivatives of 165 (93 JPROO). That compounds 166 exist as open-chain structures was based on a 2D NMR study (93MI1) (Scheme 35). 

The carbon atoms of a monosaccharide are numbered consecutively in such a way that ... 

In this representation of a monosaccharide, the carbon chain is written vertically, with the lowest numbered carbon atom at the top. To define the stereochemistry, each carbon atom is considered in turn and placed in the plane of the paper. Neighbouring carbon atoms are below, and the H and OH groups above the plane of the paper (see below). 

Numbering of monosaccharide units, if desired, should proceed from right to left. 

Shortly afterwards, Westphal, Liideritz, and their coworkers using the newly developed method of paper chromatography, found a new class of sugars in lipopolysaccharides (LPS) from Gram-negative bacteria, and identified them as 3,6-dideoxyhexoses. This work is summarized in Ref. 4. These discoveries initiated more-systematic investigations of hydrolyzates from bacterial polysaccharides, and a number of new monosaccharides were completely or partially identified. This development has been summarized by Ashwell and Hickman. ... 

Monosaccharides are those carbohydrates that cannot be hydrolyzed into simpler carbohydrates They may be classified as trioses, tetroses, pentoses, hex-oses, or heptoses, depending upon the number of carbon atoms and as aldoses or ketoses depending upon whether they have an aldehyde or ketone group. Examples are listed in Table 13-1. 

Carbohydrates are major constiments of animal food and animal tissues. They are characterized by the type and number of monosaccharide residues in their molecules. 

Ethylene dithioacetals and diethyl dithioacetals have been investigated for a number of monosaccharides. The c.d. spectra show one, or two, c.d. band(s) of low intensity between 235 and 250 nm, and a third band of low intensity that peaks below 220 nm. These workers found no overall relationship between the configurational pattern of the monosaccharide and the sign of these bands. However, there does appear to be a correlation between the configurations of C-2, C-3 and C-4 and the sign of the c.d. band that peaks below 220 nm. 

Monosaccharides have the formula (CH2 0) , where n is between 3 and 6. Of the 70 or so monosaccharides that are known, 20 occur in nature. The most important naturally occurring monosaccharides contain five carbons (pentoses) or six carbons (hexoses). Structures of ribose, an important pentose, and a-glucose, a hexose that is the most common monosaccharide, are shown in Figure 13-14. As shown in the figure, it is customary to number the carbon atoms in a monosaccharide, beginning with the HCOH group adjacent to the ether linkage. 

Ribose and a-glucose are monosaccharides that occur in nature. The carbon atoms are numbered for identification purposes. 

---