The preparation and characterization of some Amadori compounds (1-amino-1-deoxy-D-fructose derivatives) derived from a series of aliphatic omega-amino acids.

Amadori compounds (1-amino-1-deoxy-D-fructose derivatives) were prepared by reacting D-glucose with a series of aliphatic amino acids. These include Amadori compounds derived from glycine (1), beta-alanine (2), gamma-amino butyric acid (3), delta-aminovaleric acid (4), epsilon-amino-caproic acid (5) and N alpha-formyl-L-lysine (6). In the FAB mass spectra, molecular-ion clusters as well as fragment ions corresponding to loss of water or CO2 molecules were observed. The 13C NMR spectra indicate that all the compounds are conformationally unstable, but that the predominant form present in solution (D2O) is the beta-pyranose form. The 1H NMR spectra of 1 and 2 indicate a slow rotation around the C-1-C-2 bond, possibly as a result of an intramolecular hydrogen bond involving the carboxyl group. The pK alpha's of all compounds were measured by pH-potentiometric titration in 0.2 M KNO3 solution at 25 degrees C. All compounds showed a decrease in the basicity of their amino groups (in the order of approximately 1.5 of the K alpha value), and 1 and 2 showed a decrease in the basicity of their carboxyl groups (in the order of approximately 0.2) in comparison with that of parent amino acids.