Spectroscopic characterization and biological activity of L-methionyl-L histidinato complexes of R2Sn(IV) ions (R = Me, nBu, pH) and X-ray structure of Me(2)SnMetHis center dot 0.5MeOH

Complexes of L-methionyl-L-histidine (H(2)MetHis) with R2Sn(IV) ions (R = M e, nBu, Ph) have been synthesized, The crystal and molecular structures of il Me(2)SnMetHis . 0.5MeOH have been determined by X-ray diffraction, The t itle compound contains two crystallographically independent molecular units possessing the same trigonal-bipyramidal geometry at tin, each dimethyltin (IV) moiety being coordinated by the terminal amino nitrogen, deprotonated peptide nitrogen and terminal carboxylate group, neither the imidazole nor thioether groups being involved in bonding. IR spectroscopy was used to probe the structure of the complexes in the sol id state, and the structure in solution (CD3OD) was assessed by H-1 and C-1 3 NMR. Me2Sn(IV)dipepbide complexes appear to be undissociated and to retai n a pentacoordinated structure. Rotamer population of C-terminal histidine was determined by analysis of vicinal coupling constants and sidechain orie ntations have been interpreted with a view to potential applications of the compounds as recognition agents, Biological activity was tested on Ascidian embryos of Ciona intestinalis at different stages of development. Copyright (C) 2000 John Wiley & Sons, Ltd .