Siderophores with Two Hydroxamic Acid Units

In siderophores of this series, 1,3-diaminopropane, 1,5-diaminopentane, or lysine (by its a-amino group) is connected to the outer two carboxyl groups of citric acid. 

Chart 3. Cyclization of citrate siderophores to amidic structures 

These spacers, in turn, are acylated and derivatized by a A -hydroxy group thus forming hydroxamic acids. For a synthesis concept see 404). 

The schizokinen-mediated Fe transport in Bacillus megaterium was studied by double labelling with e and (8). At 37°C, uptake of Fe and of are parallel during the first 30 sec, then that of e continues until it levels off after 2 min, while that of [ H]-schizokinen drops to a low constant level. At 0°C, uptake of both labels reaches this low level which is obviously due to the binding of the ferri-siderophore to the cell surface. At 37°C, transport into the cell, release of iron, and re-export of the ligand follow. Apparently a shuttle mechanism takes place, cf. the experimental results obtained with parabactin (Sect. 3.2) indicative of a taxi mechanism. 

Arthrobactin (Fig. 15, 51) was obtained from Arthrobacter spp. and originally described as the growth factor of A. terregens, the terregens factor (57). Its structure was elucidated (207) and confirmed by synthesis (202). Also the structure 

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Fig. 15. Citrate siderophores with two hydroxamic acid units...

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