NMR Spectra of Peracetylated Methyl D-Hexopyranosides and Their 2-Acetamido-2-deoxy Derivatives in the Presence of an Europium Shift Reagent

Abstract

Proton NMR spectra of peracetylated methyl D-gluco-, D-galacto-, and D-mannopyranosides and their 2-acetamido-2-deoxy derivatives were measured at 100 MHz in the presence of a shift reagent, tris (2, 2-dimethyl-6, 6, 7, 7, 8, 8, 8-heptafluoro-3, 5-octanedionato)-europium. Chemical shifts and bound chemical shifts to lower fields were determined by first-order analysis for all the ring, methyl, acetyl, and amido protons in these compounds. Comparison between the neutral and the amino sugars showed that the signals of H-2, H-3, H-4, and H-6 (H-6') in the former and H-1, H-2, H-3, N-acetyl, and amido protons in the latter were more markedly shifted than others by the addition of the reagent. Differences in the bound chemical shifts were also marked between the two anomers and the greatest shifting ability was displayed by H-2 and N-acetyl protons in α-anomers of the amino sugars. From these results, the most probable coordination structures for the complexes between the sugars and the reagent were inferred, and their application for analysis of amino sugars appeared possible.