Synthesis and structure of N-ferrocenylglycosylamines; redox chemistry of O-ferrocenyl glycosides and N-ferrocenylglycosylamines

Abstract

The N-ferrocenylamine–carbohydrate conjugates N,N-bis(ferrocenylmethyl)-N-(2,3,4,6-tetra-O-acetyl-1-deoxy-β-D-glucopyranosyl)amine, N-(2,3,4,6-tetra-O-acetyl-1-deoxy-β-D-glucopyranosyl)aminometyhylferrocene and N,N-bis(ferrocenylmethyl)-N-[4-(2,3,4,6-tetra-O-acetyl-β-D-galactopyranosyl)-2,3,6-tri-O-acetyl-1-deoxy-β-D-glucopyranosyl]amine have been synthesized from FcCH₂NMe₃⁺I⁻ and the appropriate aminosugars. Deprotection using an ion exchange resin gave the analogous water soluble complexes. A short C–N bond at the anomeric carbon in the crystal structure of the first compound is attributed to an exo-anomeric n–σ* interaction between the exo C–N and endo C–O bonds. N-Ferrocenylmethylalkanolamines FcCH₂NH(CH₂)_nOH and (FcCH₂)₂N(CH₂)_nOH (n = 2 or 5) were synthesized in good yield using reductive amination reactions. Owing to the basicity of the N-ferrocenylamine component the electrochemistry is both solvent and pH dependent; protonation occurs in polar solvents and in all solvents with the first two compounds. Rapid oxidation to the non-protonated ferrocenium complexes occurs in aqueous solvents under physiological pH.