Formulation of anomerization and protonation in D-glucosamine, based on 1H NMR

The major anomer of non-protonated neutral D-glucosamine GlcN(0) is the beta-form, while the alpha-anomer is dominant for protonated cationic glucosamine GlcNH(+). The present work confirmed correlation between the anomer-ization and the protonation by simultaneous determination of signal intensity and chemical shift in pD-variation H NMR, and formulated the equilibrium constants between subspecies alpha-GlcN(0), beta-GlcN(0), alpha-GlcND and beta-GlcND to interpret the correlation. The individual anomerization constants, K-an = [beta GlcN(0)/[alpha GlcN] and K-Da.K-anD = [beta GlcND(+)]/[alpha GlcND(+)], are linked to each other through the relation KD alpha.KanD = K-D beta.K-an with the deuteration constants K-D alpha and K-D beta of the anomers. The anomer populations are stimulated by OD and D ions in the dose - response form. The acidic deuteron in alpha-GlcND(+) is populated mostly at the nitrogen atom, whereas the population in beta-GlcND(+) is comparable at nitrogen and anomeric oxygen; this difference is consistent with the basicity of the nitrogen and the anomerization process of glucosamine.