Specifically labeled with isotopes hydrogen

SUGARS SPECIFICALLY LABELED WITH ISOTOPES OF HYDROGEN ... 

IX. Tables of Known Sugars Specifically Labeled with Isotopes of Hydrogen.. 181... 

Most of the sugars specifically labeled with isotopes of hydrogen that have been synthesized were prepared for use in mechanistic studies of enzymes. 

Labelling with Isotopic Hydrogen.—Various oestrogenic steroids with high specific radioactivity were obtained by reduction of their 2,4-dibromo- or 2,4-iodo-derivatives with tritium gas over 5% Pd-A Oa, to give 2,4-ditritiated products." Betamethasone 17-benzoate (484) was labelled [1,2- H2] by selective reduction of... 

Barker, S. A., and Bourne, E. J., Acetals and Ketals of the Tetritols, Pentitols and Hexitols, 7, 137-207 Barnett, J. E. G., Halogenated Carbohydrates, 22, 177-227 Barnett, J. E. G., and Corina, D. L., Sugars Specifically Labeled with Isotopes of Hydrogen, 27, 127-190 Barrett, Elliott P., Trends in the Development of Granular Adsorbents for Sugar Refining, 6, 205-230 Barry, C. P., and Honeyman, John, Fructose and Its Derivatives, 7, 53-98... 

Sometimes the strongly basic properties of Gngnard reagents can be turned to synthetic advantage A chemist needed samples of butane specifically labeled with deuterium the mass 2 isotope of hydrogen as shown... 

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

When the hydrogen transferred as hydride to the cofactor is retransferred to the same carbon atom in the product, the movement is far more difficult to detect. The conversion of D-glucose 6-phosphate (58) into lL-mt/o-inositol 1-phosphate (61) occurs by cyclization of the carbon skeleton, with formation of a new bond between C-l and C-6. When each carbon atom in turn was specifically labeled with tritium, there was complete retention of tritium, even in the presence of added NADH, although there was an apparent, small isotope-effect with D-glucose-5-t 6-phosphate.19 The mechanism proposed for the cyclization19 was an initial oxidation at C-5 to give NADH and xylo-hexos-5-ulose 6-phosphate (59), followed by an aldol reaction causing cyclization to lL-myo-inosose-2 1-phosphate (60), which is then... 

Characterization of ion structures by bimolecular reactions, in which an ion is allowed to react with a neutral gas of known structure and the ionic products are analysed by mass spectrometry, depends on isomeric species having distinctive reactivities which reflect the functional group(s) that are present. This method is conceptually analogous to the use of structure-specific test reagents in classical solution chemistry. Sometimes a group may be transferred to a particular ion from the gas (methylene transfer is commonly encountered) on other occasions, hydrogen transfer is monitored. The latter is conveniently combined with isotopic labelling. 

For example, the ene reaction proceeds stereoselectively in a suprafacial manner specifically, oxygen attack and hydrogen removal take place on the same side of the double bond. As a result, neither racemization of optically active com-pounds nor cis-trans isomerization occurs. Diradical or dipolar intermediates are not consistent with these observations. The lack of a Markovnikov-type directing effect also rules out dipolar intermediates.360 399 Isotope effects observed in the reaction of different deuterium-labeled 2,3-dimethyl-2-butenes indicated that... 

An FIK study of n-pentylbenzenes specifically labelled at 3, 7, 5, and e positions showed that at times longer than lOOps, formation of (C7H8)f ions occurred through hydrogen transfers via 3-, 4-, 5- and 6-membered cyclic transition states with an average isotope effect of 1.12 [90]. 

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