Carbohydrates naturally occurring

Pentoses aldoses containing five carbon atoms. P. are an important group of monosaccharides (see Carbohydrates). Naturally occurring P. include d- and l-arabinose, L-lyxose, D-xylose, D-ribose and 2-deoxy-D-ribose, and the ketopentoses (pentuloses) o-xylu-lose and D-ribulose. P. occur chiefly in the furanose form. They are not fermented by the usual yeasts. By distillation with dilute acids, P. are converted into furfural, a reaction which serves for the detection of P. and their differentation from hexoses. 

Biopolymers are the naturally occurring macromolecular materials that are the components of all living systems. There are three principal categories of biopolymers, each of which is the topic of a separate article in the Eniyclopedia proteins (qv) nucleic acids (qv) and polysaccharides (see Carbohydrates Microbial polysaccharides). Biopolymers are formed through condensation of monomeric units ie, the corresponding monomers are amino acids (qv), nucleotides, and monosaccharides, for proteins, nucleic acids, and polysaccharides, respectively. The term biopolymers is also used to describe synthetic polymers prepared from the same or similar monomer units as are the natural molecules. 

Chemicals are ubiquitous as air, carbohydrates, enzymes, lipids, minerals, proteins, vitamins, water, and wood. Naturally occurring chemicals are supplemented by man-made substances. There are about 70000 chemicals in use with another 500-1000 added each year. Their properties have been harnessed to enhance the quality of life, e.g. cosmetics, detergents, energy fuels, explosives, fertilizers, foods and drinks, glass, metals, paints, paper, pesticides, pharmaceuticals, plastics, rubber, solvents, textiles thus chemicals are found in virtually all workplaces. Besides the benefits, chemicals also pose dangers to man and the environment. For example ... 

Some six hundred structures of naturally occurring carbogenic molecules appe on the pages which follow, together with the name of each compound and references to the original literature of successful chemical synthesis. Thus, Part Three of this book is effectively a key to the literature of chemical synthesis as applied to the complex molecules of nature. The survey does not include oligomeric or polymeric structures, such as peptides, proteins, carbohydrates and polynucleotides, which fall outside the scope of this book because they can be assembled by repetitive procedures. 

By far the majority of carbohydrate material in nature occurs in the form of polysaccharides. By our definition, polysaccharides include not only those substances composed only of glycosidically linked sugar residues but also molecules that contain polymeric saccharide structures linked via covalent bonds to amino acids, peptides, proteins, lipids, and other structures. 

Lipids are naturally occurring organic molecules that have limited solubility in water and can be isolated from organisms by extraction with nonpolar organic solvents. Fats, oils, waxes, many vitamins and hormones, and most nonprotein cell-meznbrane components are examples. Note that this definition differs from the sort used for carbohydrates and proteins in that lipids are defined by a physical property (solubility) rather than by structure. Of the many kinds of lipids, we ll be concerned in this chapter only with a few triacvlglycerols, eicosanoids, terpenoids, and steroids. 

Particularly in naturally occurring glycosides, the compound ROH from which the carbohydrate residue has been removed is often termed the aglycone, and the carbohydrate residue itself is sometimes referred to as the glycone . 

A list of most of the known natural compounds (e.g., terpenes, alkaloids, carbohydrates) to which structures have been assigned, along with structural formulas, melting points, optical rotations, and references, is provided in Devon and Scott, Handbook of Naturally Occurring Compounds , 3 vols.. Academic Press, New York, 1972. 

Development of biodegradable laminate films derived from naturally occurring carbohydrate polymers. Carbohydrate polymers, 60, 39-42. 

D-Fructose is the sweetest sugar known in naturally occurring carbohydrates, and its intense sweetness is produced only by ) -D-fructopyranose. "... 

Some of the potential uses of the fats and oils found in plants have been reviewed and some uses of carbohydrate-based polymers briefly discussed. Plants contain a whole variety of other chemicals including amino acids, terpenes, flavonoids, alkaloids, etc. When the potential for these naturally occurring materials are combined with the secondary products that can be obtained by fermentation or other microbial processes or by traditional chemical transformations, the array of chemicals that can readily be created from renewable resources is huge. In this section a few of the more interesting examples are considered. 

The carbohydrate nomenclature jointly established by the American and British Committees4 does not specifically refer to the branched-chain sugars nevertheless, the application and extension of its Rules can provide definitive names to augment or to replace the trivial or unsystematic terms which have been conferred on naturally occurring, branched-chain sugars and related synthetic products, including the branched-chain saccharinic acids.6 9... 

Naturally occurring chiral compounds provide an enormous range and diversity of possible starting materials. To be useful in asymmetric synthesis, they should be readily available in high enantiomeric purity. For many applications, the availability of both enantiomers is desirable. Many chiral molecules can be synthesized from natural carbohydrates or amino acids. The syntheses of (+)-exo-brevicomin (66) and negamycin (67) illustrate the application of such naturally occurring materials. 

Antibodies against sugars (carbohydrate residues) can be difficult to obtain and lectins are a solution to these problems. Lectins are naturally occurring plant and animal proteins or glycoproteins that selectively bind noncovalently to carbohydrate residues. Lectins can be labeled directly or secondary antibodies against lectins enables the use of other immuno techniques (30) including electron microscopy (31). 

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