70849-29-5Relevant academic research and scientific papers
D-Talose Anomerization: NMR Methods To Evaluate the Reaction Kinetics
Snyder, Joseph R.,Johnston, Eric R.,Serianni, Anthony S.
, p. 2681 - 2687 (2007/10/02)
The kinetics of anomerization of the aldohexose, D-talose, have been studied by several NMR methods in order to evaluate their limitations, complementarity, and internal consistency and to futher explore the effect of monosaccharide structure on reactivity.By use of Dtalose and 13C NMR spectroscopy, six tautomeric forms were detected and quantitated in aqueous solution: α- and β-talofuranoses, α- and β-talopyranoses, hydrate (1,1-gem-diol), and aldehyde.The 13C (75-MHz) and 1H (620-MHz) NMR spectra of D-talose have been interpreted, yielding chemical shiftsand coupling constants (JHH, JCC, JCH) that have been evaluated in terms of ring configuration and conformation.By use of 13C saturation-transfer NMR (ST-NMR), ring-opening rate constants (kopen) of the four cyclic forms were measured, and ring-closing rate constants (kclose) were calculated from kopen and equilibrium constants.NMR-derived rates of tautomer equilibration obtained after dissolving α-D-talopyranose in aqueous solution were predicted accurately from a computer treatment of the unidirectional rate constants determined by ST-NMR under similar solution conditions.Two-dimensional 13C exchange spectroscopy was applied to obtain overall rate constants of tautomer interconversion; rate constants obtained in this fashion compared favorably with those calculated from the ST-derived unidirectional rate constants using the steady-state approximation.Kinetic results show that anomeric configuration and ring size significantly affect ring-opening and ring-closing rates of monosaccharides.
