Hydroxamic acids oxidation hydroxamate moiety

NO-donors. In contrast, the effect of aceto-HX on B. subtilis subjected to oxidative stress is similar to that of HNO. SAHA, but not valproic acid lacking the hydroxamate moiety, enhances the radiosensitization of hypoxic tumor cells in vitro. This effect might also involve its abihty to serve as a NO-donor. It is concluded that HXs, which are HNO-donors under oxidizing environment, might be considered as NO-donors if HNO conversion into NO competes with its reaction with potential biological targets such as thiols and metalloproteins. 

In one of our alternative approaches the lactol unit of the 2,4-dihydroxy-2i/-l,4-benzoxazin-3(4//)-one skeleton was developed by oxidation of the unsubstituted methylene function (Fig. (9)) [114]. The starting cyclic hydroxamic acids have been prepared by catalytic transfer hydrogenation of appropriate 2-nitrophenoxyacetate precursors with the sodium borohydride/Pt-C method. The oxidative transformation intended caused a need for protection of the hydroxamic acid moiety. From several... 

Generally, A-oxide metabolites show an antibiotic activity in microorganisms and a convulsive effect in animals. On the other hand, deoxy compounds do not. The hydroxamic acid moiety in these metabolites seems to be essential for exhibition of their biological activities. Usually, deoxy compounds have a fluorescent violet color, whereas A-oxides are not fluorescent (9b). It seems useful to distinguish mycotoxin-producing fungi in seed. 

A unique example of direct olefination of a cyclopropane was also disclosed by the Yu lab [21]. An electron-deficient arylamide was employed as directing group, as the previously employed oxazoline or hydroxamic acid was unreactive in the alkenylation. The proposed mechanism for the reaction involves an amide-directed C-H insertion of the Pd(II) catalyst into the cyclopropane methylene C-H bond of 9, followed by olefin carbopalladation and p-hydride elimination to provide intermediate 10 (Scheme 3a). Pd(0) is re-oxidized back to Pd(II) by Ag(I)/Cu(II), and a tandem 1,4-addition between the amide moiety of 10 and the acrylate provides the corresponding y-lactam 11 as the sole isolated product, fii the presence of an... 

Complete hydrolysis of h3 uronic acid with mineral adds produces D-ghicosamine, acetic add, and carbon dioxide, the last named indicating the presence of a uronic acid. The latter compound was identified as d-g ucuronic acid by oxidation with nitric add, which led to the formation of D-glucaricacid. D-Glucuronic add was subsequently isolated after enzymic degradation. The carboxyl group of the uronic moiety is free, as shown by salt formation, titration, and the positive hydroxamic test after ester formation. 

It has been generally demonstrated that pyrazine 1-oxides are biologically active but that the deoxy derivatives are not. The hydroxamic acid moiety of these compounds is probably a major structural requirement for the exhibition of their biological activity, because the compounds containing the hydroxamic acid moiety show an antibiotic effect on microorganisms and a convulsive effect on animals. The naturally occurring fungal pyrazine 1-oxides are shown in Table II. 

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