Synthesis characterization and X-ray crystal structures of cis-1,4-diaminocyclohexane-platinum(II) nucleobase adducts

Platinum complexes of the type [Pt(cis-1,4-DACH)(L)2]X, where cis-1,4-DACH = cis-1,4-diaminocyclohexane; L = adenine (ade) (1), hypoxanthine (hyp) (2), 9-methylguanine (9-megua) (3), cytosine (cyt) (4), or 1-methylcytosine (1-mecyt) (5); and X = SO4 or Cl2 groups, were synthesized and characterized by elemental analysis and by 1H, 13C, and 195Pt nuclear magnetic resonance spectroscopy. The crystals of [Pt(cis-1,4-DACH)(9-megua)2]SO4[9-megua-H]2SO4 (3) and [Pt(cis-1,4-DACH)(1-mecyt)2]Cl2 · 6H2O (5) were also subjected to single-crystal X-ray diffraction. The base/PtN4 coordination plane dihedral angles were 74.55° and 85.61° in complex 3 and 78.12° and 81.80° in complex 5. The platinum had distorted square planar geometry in both complexes; the two adjacent corners were occupied by the two nitrogen atoms of cis-1,4-DACH, and the other two corners were occupied by the two N7 atoms of 9-megua in complex 3 and the two N3 atoms of 1-mecyt in complex 5. The cis-1,4-DACH, which has a unique twist-boat configuration, formed a seven-member chelating ring with platinum, which led to considerable strain during bidentate cis-1,4-DACH binding. Cations of both complexes 3 and 5 adopted C2 molecular symmetry. These adducts were the models for the intrastand cross-links that were relevant to the binding of the Pt(II) antitumor drugs to DNA.

Synthesis, and characterization of nucleobase complexes with cis-1,4-DACH-Pt have been synthesized and characterized by 1H, 13C, 195Pt NMR. The X-ray crystal structures of [Pt(cis-1,4-DACH)(9-methylguanine)2]SO4[9-methylguanine-H]2SO4 and [Pt(cis-1,4-DACH)(1-methylcytosine)2]Cl2 · 6H2O adducts are also reported here.Figure optionsDownload as PowerPoint slide