Structures of complexes of cobalt(III) and glucosamine. Applications of molecular mechanics and NMR spectroscopy

Abstract

The 1H NMR signals of the hydrochlorides of 2-amino-2-deoxy-α and β -D-Glucose (α-and β-D-glucosamine) have been assigned and chemical shifts and coupling constants determined from their phase-sensitive COSY spectra in D2O. Based on the Karplus relation the observed coupling constants fit H-H dihedral angles calculated with MM2 parameters. The COSY spectrum of the Λ isomer of [Co(en)2'D-glucosamine]2+ shows that it is formed from the α anomer. The coupling constants, except for J3,4, agree qualitatively with dihedral angles predicted by MM2 parameters. The structure of triammine-Co(III)-L-malate simulated by using MM2 parameters agrees reasonably well with that from X-ray crystallography.