Hydroxamic acids 1,4-dihydroxy

Benzoxazolin-2(3H)-one is a phytotoxic allelochemical resulting from a two step degradation and root exudation process based upon an acetal glucoside of the 2,4-dihydroxy-2H-1,4-benz-oxazin-3(4H)-one skeleton. Such benzoxazinoids or cyclic hydroxamic acids occur in Acanthaceae, Poaceae, Ranunculaceae, and Scrophulariaceae. Their aglucones and resulting benzoxazolinones act as a plant s... 

Atkinson, J., Morand, P., Arnason, J. T., Niemeyer, H. M. and Bravo, H. R. 1991. Analogues of the cyclic hydroxamic acid 2,4-dihydroxy-2H-1,4-benzoxazin-3-one decomposition to benzoxazolinones and reaction with -mercaptoethanol. J. Org. Chem. 56, 1788-1800... 

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... 

In addition to hydroxamic acids, the dihydroxybenzene (catechol) moiety is employed as the chelating unit of some sidero-phores. In all strains of enteric bacteria studied to date, the natural iron transport agent is the cyclic triester of 2,3-dihy-droxy-N-benzoylserine known as enterobactin (Figure 23) (54, 55, 56). In Bacillus subtillus 2,3-dihydroxy-N-benzoylglycine has been shown to stimulate iron transport (54, 57). In addition,... 

A series of hydroxamic acid derivatives with 4-hydroxy-l,4-benzoxazin-3-one structures occur in a number of cereal grain species (Poaceae or Gramineae) (Fig. 7.8) (Niemeyer, 1988). These compounds usually occur in plants as the 2-3-(9-D-glucosides enzymes that hydrolyze the compounds usually co-occur. DIBOA [2,4-dihydroxy-1,4(2H)-benzoxazin-3-one] (22) is the major compound in rye and DIMBOA [2,4-dihydroxy-7-methoxy-1,4(2H)-benzoaxa-... 

DIMBOA (2,4-dihydroxy-7-methoxy-1,4-benzoxazin-3-one) is a cyclic hydroxamic acid produced by members of the Gramineae as a defense against herbivores or microbial pathogens [60]. Maize CYP71C1 catalyzes the hydroxylation of indolin-2-one at the 3-position... 

APCI has become a popular ionization source for applications of coupled HPLC-MS. Figure 1.33 shows an example of an application of HPLC-APCI coupling [79]. It shows the analysis obtained from extracts of maize plants. Six compounds are identified by mass spectrometry. These compounds have been identified as glucoconjugated DIMBOA (2,4-dihydroxy-7-methoxy-l,4-benzoxazin-3-one) and similar molecules that differ by the number of methoxy groups in the benzene ring and/or by the N-O methylation of the hydroxamate function. This example clearly shows the influence of the analyte on the type of observed molecular species. Indeed, the presence of an acidic group in the compound from peak 1 allows mainly the detection of deprotonated molecular ions, whereas the compound from peak 4 does not contain an acid group and thus leads only to the formation of adduct ions. 

Cyclic sulfite 211 derived from a,/3-dihydroxy hydroxamate 210 underwent stereoselective ring opening at the a position to give azido alcohol 212, which further cyclized to )Q-lactam derivative 213 under Mitsunobu conditions (90TL4317) (Scheme 50). A similar Q-lactam synthesis by the ring opening of cyclic sulfate 214 derived from tartaric acid with azide nucleophile followed by reduction has been reported (90JOC5110) (Scheme 51). 

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