Organotin flufenamates: Synthesis, characterization and antiproliferative activity of organotin flufenamates

The organotin flufenamates [Me2(flu)SnOSn(flu)Me2]2 (1), [Bu2(flu)SnOSn(flu)Bu2]2 (2) and [Bu2Sn(flu)2] (3) have been prepared and structurally characterized by means of vibrational and NMR (1H, 13C and 119Sn) spectroscopy. The crystal structure of [Me2(flu)SnOSn(flu)Me2]2 (1) has been determined by X-ray crystallography. Three distannoxane rings are present to the dimeric tetraorganodistannoxane of planar ladder arrangement. The structure is centro-symmetric and features a central rhombus Sn2O2 unit with two additional tin atoms linked at the O atoms. Six-coordinated tin centers are present in the dimer distannoxane. This structure is self-assembled via π → π and C–H → π stacking interactions. Flufenamic acid and flufenamates were evaluated for antiproliferative activity in vitro. Among the compounds tested [Bu2(flu)SnOSn(flu)Bu2]2 (2) and [Bu2Sn(flu)2] (3) exhibited high cytotoxic activity against the cancer cell line A549 (non-small cell lung carcinoma).