The biological activity of some siderochrome derivatives

Semisynthetic derivatives of natural trihydroxamic acid iron chelates, or siderochromes, have been prepared and tested for biological activity. The activity of these compounds as growth factors for $\text{Arthrobacter}$$\text{JG-9}$ or as antagonists to the siderochrome antibiotic, albomycin, is relatively unaffected by structural alteration. However, their ability to function as ferric ionophores for the fungus, $\text{Ustilago}$$\text{sphaerogena}$, is very sensitive to minor structural variations. Branching at the β-position of the hydroxamate acyl function leads to loss of all biological activity.