Synthesis and Degradation of Monosaccharides

Exploring carbohydrates, from the simple to the complex Observing the reactions, synthesis, and degradation of monosaccharides Checking out lipids, specifically fats... 

From this survey (see Table II), it may be seen that the interconversion of monosaccharides and starch or glycogen is catalyzed by multi-component, enzyme systems in which the synthesis and degradation of (1—>4)-and (1—>6)-a-D-glucosidic linkages is carried out by distinct enzymes. Moreover, the properties, especially the detailed specificity, of the several enzymes in the plant, animal, and microbial kingdoms are different. 

This chapter will be concerned chiefly with the mechanisms involved in the synthesis and degradation of complex saccharides from monosaccharides. But it will begin with a brief outline of the present state of knowledge of the intermediate compounds that are formed in plants after... 

A. The Measurement of Isotopes. B. The Synthesis and Degradation of Labeled Compounds (Including. Application to Metabolic Studies) Monosaccharides and Polysaccharides Citric -Acid Cycle Intermediates Glycolic, Glyoxylic and Oxalic Acids Purines and Pyrimidines Porphyrins Amino. Acids and Proteins Steroids Methylated Compounds and Derivatives Sulfur Compounds Fatty. Acids Phospholipids Coenzymes lodinatftd Compounds Intermediates of Photosynthesis 0 -Labeled Phosphorus Compound. . 

In addition to the common pathways, glycolysis and the TCA cycle, the liver is involved with the pentose phosphate pathway regulation of blood glucose concentration via glycogen turnover and gluconeogenesis interconversion of monosaccharides lipid syntheses lipoprotein formation ketogenesis bile acid and bile salt formation phase I and phase II reactions for detoxification of waste compounds haem synthesis and degradation synthesis of non-essential amino acids and urea synthesis. 

Much of the chemistry of monosaccharides is the familiar chemistry of alcohols and aldehydes/ketones. Thus, the hydroxyl groups of carbohydrates form esters and ethers. The carbonyl group of a monosaccharide can be reduced with NaBH4 to form an alditol, oxidized with aqueous Br2 to form an aldonic acid, oxidized with HNO3 to form an aldaric acid, oxidized enzymatically to form a uronic acid, or treated with an alcohol in the presence of acid to form a glycoside. Monosaccharides can also be chain-lengthened by the multistep Kiliani-Fischer synthesis and can be chain-shortened by the Wohl degradation. 

The chiral synthesis,219-221 by the use of monosaccharides, of optically active natural products having mainly branches of the B-type has now become common in organic chemistry. The reduction of alkylidene derivatives was actually used for the synthesis of thromboxane B2,222 cana-densolide,223 and a degradation product from boromycin.224... 

Reduction of an aldose forms one alditol reduction of a ketose forms two alditols. Br2 oxidizes aldoses, but not ketoses ToUens reagent oxidizes both. Aldoses are oxidized to aldonic acids or aldaric acids. Aldoses and ketoses react with three equivalents of phenyUiydrazine, forming osazones. C-2 epimers form identical osazones. The Kiliani-Fischer synthesis increases the carbon chain of an aldose by one carbon— it forms C-2 epimers. The Ruff degradation decreases the carbon chain by one carbon. The OH groups of monosaccharides react with acetyl chloride to form esters and with methyl iodide/silver oxide to form ethers. 

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