Organometallic complexes with biological molecules. X: Dialkytin(IV) and Trialkythin(IV) Orotates: Spectroscopic and in vivo investigation

Several novel diorgano- and triorgano-tin(IV) derivatives of orotic acid, (2,6-dihydroxypyrimidine-4-carboxylic acid; H3or) have been synthesized. In the diorganotin(IV) derivatives, the orotic acid behaved either as a monoanionic or as a dianionic ligand, yielding R2Sn(H2or)2 and R2SnHor (R = Me, Bu) species, respectively, while in the triorganotin(IV) orotates only monodeprotonation of the orotic acid occurred, giving R3SnH2or (R = Me, Bu) derivatives. Structural hypotheses are proposed and discussed for the solid state based on Mössbauer and IR spectroscopic data, and for solution on 1H and C NMR results. Finally, investigations have been carried out in vivo, showing the inhibitor properties of all of the newly synthesized derivatives towards Ciona intestinalis embryos. In particular, in order to test the cytotoxicity in vivo of Me2SnHor, Bu2SnHor, Me3SnH2or and Bu3SnH2or, exposure to these chemicals of C. intestinalis embryos at the 2-4-blastomere stage has been studied. The compound which exerts the highest cytotoxic effect is Bu3SnH2or at 10-5 M concentration because it blocks embryo development immediately. Me3SnH2or at 10-5 M concentration inhibits cell cleavage in the embryos at the 32-blastomere stage, while Bu2SnHor at the same concentration gives rise to abnormal embryos. Me2SnHor, is less toxic than the trimethyl, dibutyl and tributyl analogues, since 40% of the total number of treated embryos resulted in normal larvae. The ligand does not affect embryonic development significantly. The results seem to indicate that the chemical species under investigation, especially Bu3SnH2or, interfere with polymerization of tubulin during the process of cell division in early embryo development