Metal Complexes of D-Glucosamine and Its Derivatives. VIII. Metal Complexes of N-Methyl-D-glucosamine and Its Related Amino Sugars

N-Methyl-D-glucosamine (I), D-glucosamine (II), D-galactosamine (III), D-man-nosamine (IV) and D-talosamine (V) were investigated by pH titration method on their complex formations with metal ions. The pKa of these amino sugars were found to be I 7.86, II 7.38, III 7.61, IV 7.50, and V 7.98 respectively. Stability constants, log K1 of seven I-metal complexes were in the order ; Cu 4.5>Pb 3.7>Zn 3.2>Ni 3.1>Cd 2.9»Ca, Mg. Hydrolysis study on I-Cu complex revealed that I-Cu complex was more hydrolyzable to form monohydroxo complex I-Cu (OH), but less dimerized than II-Cu complex. Stability constants, log K1 of the amino sugar-Cu complexes were measured ; II-Cu 4.8, III-Cu 4.6, IV-Cu 5.0 and V-Cu 5.7 respectively. Discussions are given on the complex formation of amino sugar with Cu2+ with conformational considerations.