Metal sequestering agents in bioinorganic

Iron transport into the cells of microbes is mediated by low— molecular—weight sequestering agents (siderophores) which are powerful and highly specific sequestering agents for Fe(III). The current status of iron uptake by E. coli as mediated by the tricatechol siderophore entero— bactin will be reviewed. Recently the synthesis of kinetically inert Rh(III) complexes of enterobactin analogs have allowed the recognition process of the ferric enterobactin protein receptor to be characterized. The "salicylate" mode of bonding which occurs when ferric enterobactin is protonated has now been structurally characterized in a model system. Biomimetic approaches to metal—ion—specific sequestering agents based on enterobactin have been applied to two problems. The first is the synthesis of specific sequestering agents for actinide(IV) ions, including plutonium. The second is the synthesis of ferric ion sequestering agents of possible therapeutic utility. The structural characterization of one of these has provided an unprecedented example of a trigonal—prismatic Fe(III) complex.