Organotin(IV) based anti-HCV drugs: synthesis, characterization and biochemical activity

Three new organotin(iv) carboxylates () of 3,5-dimethylbenzoate, have been synthesized and characterized by elemental analysis, FT-IR, multinuclear NMR ((1)H, (13)C and (119)Sn), mass spectrometry and single crystal X-ray structural analysis. Crystallographic data show that in compounds and , the geometry at the central Sn atom is skew-trapezoidal bipyramidal while compound displays a distorted trigonal bipyramidal coordination geometry. In the case of compounds and , the asymmetric chelating mode of the carboxylate groups is reflected in the unequal C-O bond distances, those observed for the O1 and O3 oxygen atoms being significantly longer than those found in the O2 and O4 atoms. In the case of compound , the carboxylate groups bridge asymmetrically adjacent tin atoms in an anti-syn mode generating polymeric zigzag chains running parallel to the crystallographic c-axis. The compounds were screened for anti-HCV (hepatitis C virus) potency by the Gaussia luciferase assay using infected Huh 7.5 cells (human hepatocellular cell). Structure-activity relationship studies led to the identification of dibutyltin(iv)bis(3,5-dimethylbenzoic acid) (compound ) as a potent HCV inhibitor, with log IC50 values equal to 0.69 nM in the cell-based assay. Compound was further subjected to quantitative analysis using real-time PCR assays and viral RNA count vs. drug concentration confirmed the Gaussia luciferase assay results. The HCV RNA targeting mode of the compounds () was confirmed by a compound-DNA interaction study. The compounds ()-DNA interactions were investigated by UV-vis spectroscopy and viscometry. The hypochromic effect in spectroscopy evidenced an intercalative mode of interaction with the binding affinity in the order of > > .