ABSTRACT
The mechanism by which bacteria process catecholamide siderophore iron complexes, recent discoveries regarding parabactin, agrobactin, and vibriobactin inhibition of tumor cell growth, coupled with the ligand's potential in the treatment of iron overload, have compelled investigators to synthesize additional catecholamides. The synthesis of each of the polyamine catecholamide chelators weighs heavily on the availability of the appropriately protected polyamines norspermidine, spermidine, and homospermidine. The major functional difference between hydroxamate siderophores and the catecholamides is related to environmental iron concentration. The hydroxamates are generated by the microorganism in a high iron environment, while the catecholamide "backup" system is activated when iron concentrations are low. Since an N-hydroxydiamine containing three to five carbons is the basic unit of many hydroxamate chelators, a method of differentiating the two nitrogens and protecting the oxygen is desirable. The mycobactins incorporate both the hydroxamate funtionality of ferrichrome, ferrioxamine as well as the oxazoline of parabactin.
