The stereochemistry of 1,2,3-triols revealed by 1H NMR spectroscopy: principles and applications.
The conformational compositions of the tris(alpha-methoxy-alpha-phenylacetic acid) ester derivatives of 1,2,3-prim,sec,sec-triols are presented. These conformations have been determined by theoretical and experimental data (i.e., energy- and chemical-shift calculations, circular dichroism (CD) experiments, coupling-constant analysis, enantioselective deuteration experiments, and low-temperature NMR spectroscopic studies). A detailed analysis of the anisotropic effects due to the most significant conformers in the (1)H NMR spectra supported the correlation between the (1)H NMR spectra (Delta delta(RS) value of H(3') and |Delta(Delta delta(RS))| parameters) and the absolute configuration of the substrate. The study also allows the identification of the pro-R and pro-S methylene protons from their vicinal coupling constants and relative chemical shifts.
Department of Chemistry, University of Santiago de Compostela, Avd. Ciencias s/n. E-15782, Spain.
Félix
F
Freire
Enrique
E
Lallana
Emilio
E
Quiñoá
Ricardo
R
Riguera