Interactions of the Aminoglycoside Neamine and 2-Deoxystreptamine with Copper(II) and Zinc(II)

Abstract Acid dissociation constants for the aminoglycosides neomycin and neamine and of 2-deoxystreptamine are reported. Solution NMR studies indicate that complexation with copper(II) and zinc(II) involves principally the primary amine donors, and formation constants with both neamine and 2-deoxystreptamine (2-DOS) and these metal ions are reported (at 25°C, I = 0.5 mol dm-3). Complexation studies probed by electrospray mass spectrometry identify both 1:1 and 1:2 species for Cu(II) and Zn(II) with 2-DOS, but only 1:1 species with neamine, consistent with behaviour in bulk solution. Preliminary formation kinetics of Cu(II) with neamine indicate rapid complexation at high pH but slower two-step processes near pH 7, consistent with complications in the thermodynamic determinations in the intermediate pH regime. Reaction of 2-DOS and neamine with Cu(II) in methanol appears as a single process, with the former occurring ~103-fold faster