Synthesis, characterization, and cytotoxic activity of triphenyltin complexes of N-(5-bromosalicylidene)-α-amino acids

Five new triphenyltin complexes of N-(5-bromosalicylidene)-alpha- amino acids, 5-Br-2- HOC6H3C(H)= NCH(R) COOSnPh3 (where R=H, 1; Me, 2; i-Pr, 3; i-Bu, 4; s-Bu, 5), were synthesized by one-step reactions of triphenyltin hydroxide, 5-bromosalicylaldehyde, and alpha-amino acid in 1:1:1 molar ratios and characterized by elemental analysis, IR, and NMR (H-1, C-13, and Sn-119) spectra. The crystal structures of 5-Br-2- HOC6H3C(H) = NCH(i-Pr) COOSnPh3 (3) and 5-Br-2- HOC6H3C(H) = NCH(s-Bu) COOSnPh3 (5) were determined and showed that the tin atom is five-coordinated and adopts a polymeric trans-O2SnC3 trigonal bipyramidal configuration with the axial positions occupied by a carboxylate oxygen from the ligand and the phenolic oxygen of the ligand in an adjacent complex. Bioassay results indicated that these compounds have stronger cytotoxic activity against three human tumor cell lines, HeLa, CoLo205 and MCF-7, than that of cis-platin used clinically.