A range of analogues of parabactin A 4 and agrobactin A 5 have been sy
nthesised. All these comounds were able to chelate iron, and to promot
e the growth of iron-starved Paracoccus denitrificans to varying degre
es. A degree of flexibilty in the siderophore receptor system is thus
demonstrated which may be exploitable for the transport of new siderop
hore - antibiotic conjugates.