Synthesis, characterization and in vitro DNA binding studies of tin(IV) complexes of tert-butyl 1-(2-hydroxy-1-phenylethylamino)-3-methyl-1-oxobutan-2-yl carbamate

Tin(IV) complexes 1(a and b) and 2(a and b) of valine derived peptide derivatives were synthesized and characterized on the basis of elemental analysis, IR, 1H, 13C, 119Sn NMR, ESI-MS spectra and molar conductance measurements. The C–Sn–C angle was estimated from I3C and 1H NMR data 1J(119Sn, I3C) = 623 Hz; solution 2J(119Sn, 1H) = 93.04 Hz to be 149.9°. In vitro binding studies of complexes 1 and 2 under physiological conditions at room temperature with CT-DNA were carried out employing UV–visible, fluorescence, circular dichroism and viscometric studies. The binding affinity of the complexes was quantified by calculating the Kb values and it follows the order 2a > 1a > 2b > 1b. To further examine the specific mode of binding, the interaction of complexes 2(a and b) were carried out with 5′GMP and 5′TMP by using absorption and NMR (1H, 31P) spectroscopy. The supercoiled pBR322 plasmid DNA cleavage activity of the complexes was ascertained by gel electrophoresis assay. The complexes cleave supercoiled pBR322 plasmid DNA efficiently into its nicked form at micromolar concentrations.