Isotope-Labeled Sugars

The preparation of sugars containing isotopic carbon, either uniformly distributed or in specific positions of the carbon chain, is a comparatively recent development in carbohydrate synthesis. Certain of the known synthetic methods have been applied for isotopic labeling and, in addition, certain new synthetic methods have been developed solely for the introduction of the isotope. 

Uniformly labeled D-glucose, D-fructose, and sucrose are prepared by photosynthesis using an appropriate plant and isotopic carbon dioxide 248), Similarly, uniformly labeled D-galactose is obtained by photosynthesis with C 02 and the red alga Irideae laminarioides, where it occurs as a 2-glycerol D-galactopyranoside (65). 

D-Glucose labeled only at carbons 3 and 4 is isolated by the hydrolysis of the liver glycogen of animals after injection of isotopic bicarbonate (249), 

Any of the chain-lengthening synthetic methods are, of course, applicable for the introduction of isotopic carbon. Of these, the cyanohydrin (260) and nitromethane (261) syntheses have proved useful for the preparation of 1-labeled aldoses. The addition of hydrogen cyanide to an aldose is essentially quantitative even with only stoichiometric amounts, whereas the 

The incorporation of isotope into carbon 6 of D-glucose is accomplished by the reaction sequence (254)  

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In addition to the foregoing examples, periodate oxidation has been applied to isotopically labeled sugars (for the determination of label distribution), 226 -226 to certain branched-chain sugars,227-229 and to some nitrogenous derivatives of the simple sugars.230-236... 

The resolution of racemic mixtures by amino acid oxidases also forms an important step in the synthesis of isotope labeled sugars and amino acids [259]. 

Starch synthesis is closely related to sucrose synthesis (see Chapters IX and XII). Experiments with isotopically labeled sugars have shown that leaves can form starch from externally supplied glucose, fructose, and sucrose, as well as from several other compounds. Starch is also formed from carbon dioxide during photosynthesis. It was found (78) that when labeled carbon dioxide was fed to leaves, the starch became labeled before the free sugars. Labeled glucose and glucose 1-phosphate did not contribute an... 

Hydrogen, isotopes of, sugars specifically labeled with,... 

To broaden the scope of his interests, he spent another year as a postdoctoral fellow in the Physics Department of Pennsylvania State University, working on the X-ray analysis of biological compounds. Equipped with an exceptionally broad and multidisciplinary education and experience, he proceeded to The Ohio State University, Columbus, Ohio, to work with Professor M. L. Wolfrom. His initial job was to investigate the ignition of cellulose nitrate, a project left over from World War II. In Fred s hands, this project was turned into an isotopic investigation of the biosynthesis and degradation of cellulose. At this time, there was very little known about the preparation of specifically labeled sugars, let alone the biosynthesis of... 

The polarized-TT frontier molecular orbital (PPFMO) method has been employed to study protonation and sulphenylation of sugar-related dihydrofurans and tetrahydropy-rans. The predictions are consonant with the experimental observations62. Contrary to expectations, the proton-catalysed addition of alcohols to glycals, such as 30, has been shown by isotope labelling (2H) not to be anii-diaxial addition. This observation has been rationalized by the initial attack by deuteron from the bottom, giving ion 31, and by the anomeric effect favouring axial substituent at C-l (32)63. 

Many of the enzyme reactions previously discussed result in the incorporation of isotopes of hydrogen from the solvent or cofactor. Only those labeled compounds synthesized on a preparative scale are included in the Tables, but suitable modification of the other enzyme systems may make them suitable for use in the preparation of other labeled sugars. 

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