Synthesis, structure and redox properties of ferrocenylmethylnucleobases

Abstract

Ferrocenyl derivatives of thymine 1, cytosine 2, and uracil and of N2-acetylguanine and 2-amino-6-chloropurine have been prepared from reactions of [Fe(η⁵-C₅H₅)(η⁵-C₅H₄CH₂N(CH₃)₃)] I with the corresponding pyrimidine or purine base. The predominant site of alkylation for thymine and cytosine was N1 while for uracil N3 was preferred. Alkylation of the guanine precursor 2-amino-6-chloropurine yielded two products, the N2-monosubstituted, and the N2,N9-disubstituted, derivatives. Acetyl protection/deprotection of the N2 amino group allowed selective N9-alkylation to yield 2-amino-6-chloro-9-ferrocenylmethylpurine. With N2-acetylguanine alkylation occurred at either the N7 or N9 positions in a ≈3∶1 ratio. The structures of eight compounds were determined by single crystal X-ray analysis. Electrochemical investigations by cyclic voltammetry revealed reversible redox processes for the compounds.