Characterisation of Metal Binding Sites for 8-Azaguanine and 8-Azahypoxanthine Derivatives Synthesis and X-Ray Structural Analysis of Methylmercury(II) and Zinc(II) Complexes

Abstract

<jats:title>Abstract</jats:title><jats:p> The complexes [(CH<jats:sub>3</jats:sub>Hg)AGuaH ] (1) and [(CH<jats:sub>3</jats:sub>Hg)<jats:sub>2</jats:sub>AGua] • H<jats:sub>2</jats:sub>O (2) have been isolated from aqueous 1:1 and 2:1 solutions of CH<jats:sub>3</jats:sub>HgOH and 8 -azaguanine (AGuaH<jats:sub>2</jats:sub>) at respective pH values of 5 and 9. Only one CH<jats:sub>3</jats:sub>Hg<jats:sup>+</jats:sup> complex of 8 -azahypoxanthine (AHxH<jats:sub>2</jats:sub>), namely [(CH<jats:sub>3</jats:sub>Hg)<jats:sub>2</jats:sub>AHx] (3), could be isolated under analogous conditions. X-ray structural analyses established N1 and N9 as metal binding sites in 3 and N9 as the coordination position in [Zn(H<jats:sub>2</jats:sub>O)<jats:sub>4</jats:sub>(AHxH)<jats:sub>2</jats:sub>] (4). With 8-aza-9-benzylhypoxanthine (9-BzAHxH) only one CH<jats:sub>3</jats:sub>Hg<jats:sup>+</jats:sup> complex [(CH<jats:sub>3</jats:sub>Hg)9-BzAHx] (5) could be isolated in the pH range 2-10. N1 was established by X-ray structural analysis as the binding site. The relevance o f these findings to an understanding of ligand behaviour of the antineoplastic agent 8 -azaguanine is discussed.</jats:p>