Hydroxamate donor group

Another study of a synthetic siderophore analog of mixed cathechol and hydroxamate donor groups exhibited similar spectral shifts with pH as observed for tris-catecholate side-rophores, consistent with a salicylate-binding mode shift (102). While this synthetic siderophore mimic supports the growth of many species of bacteria, it also exhibits a low iron-binding affinity relative to other hexadentate siderophores, with a pFe value of 18.3 (see L(cat2hydroxamate) Table HE). 

The siderophores fall into two main chemical types, with either catecholate-phenolate or hydroxamate donor groups. Several subdivisions of the hydroxamate siderophores are known, and additional examples continue to be identified. The siderophores, with a small number of... 

Fig. 6. Saccharide-platform siderophore mimics with catechol and hydroxamic acid donor groups, H6L 34(9), H6Lg34(10), H3L 34(11), and H3L236(12).

Donor groups 1 hydroxamate, 1 catecholate, and 1 a-hydroxycarboxylate. Donor groups 1 catecholate and 2 a-hydroxycarboxylate. 

Fig. 23. Rotation around the hydroxamic acid C-N bond allows two possible configurations of the donor group, Z and E.

In general, C-acyl nitroso compounds-9,10-dimethylanthracene cycloadducts derived from hydroxamic acids (-R = alkyl, aryl, ti/2 = 4.1 h for -R = -Ph at 60°C) decompose more slowly than those derived from N-hydroxycarbamates or N-hydroxyureas [11, 13, 14]. Further addition of alkyl groups to the N atom of N-hydroxyurea-derived cycloadducts produces a further increase in the rate of the retro-Diels-Alder reaction of these cycloadducts [36]. These general trends suggest the possibility of the development of acyl nitroso compound-9, 10-dimethylanthracene cycloadducts as a general class of HNO or NO donors with varied release profiles. 

As points of reference, we will take two well-established hydrogen-bond donor/ acceptors, H2O and NH3. Their computed gas-phase Vs,max and Vs,mm are in Table 5, along with the same data for all of the molecules that have been discussed hydroxylamine (5), dimethylhydroxylamine (6), acetoxime (7), acetohydroxamic acid (8), and the isomeric pairs of oximes examined in the last section. Finally, we included an additional hydroxamic acid, 11, to see the effects of the strongly electron-withdrawing cyano group. 

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