- HYDROXIDE-CATALYZED ISOMERIZATION OF D-(1-13C)MANNOSE: EVIDENCE FOR THE INVOLVEMENT OF 3,4-ENEDIOLS
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The KOH-catalyzed isomerization of D-(1-13C)mannose under anaerobic conditions was studied by 13C-n.m.r. spectroscopy.D-(1-13C)Glucose and D-(1-13C)fructose are generated during the reaction, as expected.In addition, however, (6-13C)glucose, (6-13C)mannose, and (6-13C)fructose are produced in small proportions, possibly via symmetrical 3,4-enediol intermediates.The involvement of the latter structures in 13C-label shifting is inferred from the observation of (1-13C)sorbose and (6-13C)sorbose in the reaction mixture.
- King-Morris, Melinda J.,Serianni, Anthony S.
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- Paramolybdate anion-exchange resin, an improved catalyst for the C-1-C-2 rearrangement and 2-epimerization of aldoses.
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Aqueous solutions of molybdate at 90 degrees bring about the inversion of the C-1-C-2 fragment of aldoses having four or more carbon atoms, generating thermodynamically equilibrated mixtures of the starting aldose and its 2-epimer. In some cases, notably with the aldopentoses, substantial proportions of the 3-epimers are produced, as well as 2-epimers that have not undergone inversion of the C-1-C-2 fragment. These side-reactions can be controlled by using the paramolybdate form of an anion-exchange resin (AG MP-1) together with the formate form of the same resin. The latter acts to scavenge unbound molybdate and paramolybdate anions that appear to be responsible for the side reactions.
- Clark Jr.,Hayes,Barker
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p. 263 - 270
(2007/10/02)
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