Arylhydroxamic acid

Recent studies have shown that A-arylhydroxamic acids, 239, have found extensive applications as reagents in spot tests, gravimetric and colorimetric analyses, and in separations involving solvent extraction (Chart 3). ... 

In 1972, Gnpta and coworkers reported the preparation of twelve A-arylhydroxamic acids by the condensation of A-l-naphthylhydroxylamine and acid chloride in diethyl ether medium . An aqneons snspension of sodium bicarbonate was added to neutralize the liberated hydrochloric acid. The formation of a diacylated derivative was practically prevented by carrying ont the reaction at low temperature, preferably below 0 °C. 

Despite the typical use of the 1,5-dienic system in the hetero-Cope rearrangement the participation of triple bonds, C=N and C=C, in the [3,3]-sigmatropic rearrangement was also reported. Synthesis of A-substituted benzimidazolinones 175 by a hetero-Cope rearrangement of the adduct 174 formed by reaction of A-arylhydroxamic acids 172 with cyanogen bromide 173 in the presence of triethylamine and at low temperatures was reported by Almeida, Lobo and Prabhakar (equation 51). 

Figure 7.1 Some of the possible routes of metabolic activation of AAF. Abbreviations-. AAF, acetylamino-fluorene N-OH-AF, /V-hydroxyaminofluorene N-OH-AAF, /V-hydroxyacetylaminofIuorene A/-acetoxy AF, N-acetoxyaminofluorene N-(dG-8yl)-AF, AAdeoxyguanosinyl-aminof I uo rene N-(dG-8yl)-AAF, A/-deoxyguanosinyl-acety-laminofluorene P-450, cytochrome(s) P-450 DA, deacetylase NAT, A/-acetyltransferase AHAT, N, O-arylhydroxamic acid acyltransferase.

Narula and Gupta76 have measured the thermodynamic stepwise stability constants for the formation of complexes of dialkyltin(TV) ions, R2Sn2+ (R = Me or Bu ), with hydroxamic acids, RCONHOH (R = Ph, Me2CH, Me) potentiometrically in 75% dioxane-water media. This has been followed by determination of formation constant of Af-arylhydroxamic acids-dialkyltin(IV) ions.77... 

N,0-Acyltransferase. The /V-acyl transferase enzyme is believed to be involved in the carcinogenicity of arylamines. These compounds are first V-oxidized, and then, in species capable of their A-acetylation, acetylated to arylhydroxamic acids. The effect of N, O-transacetylation is shown in Figure 7.22. The A/-acyl group of the hydroxamic acid is first removed and is then transferred, either to an amine to yield a stable amide or to the oxygen of the hydroxylamine to yield a reactive N-acyloxyarylaminc. These compounds are highly reactive in the formation of adducts with both proteins and nucleic acids, and N, O -acy I Iransfcrasc, added to the medium in the Ames test, increases the mutagenicity of compounds such as A-hydroxy-2-acetylaminofluorine. 

Figure 7.22 N-, O-Acyltransferase reactions of arylhydroxamic acid. Ar = aryl group.

Larsen, E. and Christensen, L. P. 2000. Simple method for large scale isolation of the cyclic arylhydroxamic acid DIMBOA from maize (Zea mays L ). J. Agric. Food Chem. 48, 2556-2558... 

Finally, arylhydroxamic acids react with the azirine (223) forming 1,3,4-dioxazolines... 

Aryl sulfotransferases catalyze the transfer of the sulfuryl moiety from 3 -phosphoadenosine 5 -phosphosulfate to phenols, catechols, benzylic alcohols, arylhydroxylamines, and arylhydroxamic acids. This assay measures adenosine 3, 5 -diphosphate and is thus suited to quantitate enzyme activity when the sulfate esters formed are chemically unstable. 

Thionyl chloride reacts with N-arylhydroxamic acids to form the corresponding amides via ortho-halogenation (equation 30). ... 

PE Hanna, RB Banks. Arylhydroxylamines and arylhydroxamic acids conjugation reactions. In Bioactivation of Foreign Compounds. London Academy Press, 1985, pp 375 -02. 

Gupta VK, Tandon SG. 1973. N-Arylhydroxamic acids as reagents for vanadium (V). Spectrophotometric determination of vanadium (V) with N-M-Tolyl-p-methoxybenzohydroxamic acid. Anal Chim Acta 66 39- 48. 

Tiwari, V. and Pande, R. (2006) Molecular descriptors of N-arylhydroxamic acids a tool in drug design. Chem. Biol Drug Des., 68, 225-228. 

A in Fig. 13.25). This is the reaction formally catalyzed by EC 2.3.1.118 with acetyl-CoA acting as the acetyl donor the JV-hydroxy metabolites of a number of arylamines are known substrates. The same conjugates can be formed by intramolecular AT,0-acetyl transfer, when an arylhydroxamic acid (an AT-aiyl-JV-hydro y-acetamide) is substrate of, e.g., EC 2.3.1.56 (reaction 3-B). In addition, such an arylhydroxamic acid can transfer its acetyl moiety to an acetyltransferase, which can then acetylate an... 

O-Sulphate and O-sulphonate esters of iV-arylhydroxamic acids, e.g. 43, undergo rearrangement of the sulphonyloxy group from the nitrogen atom to the ortho position of the AT-aryl ring (equation 31)81"90. Only small amounts of the para isomer are observed, o p ratios being > 685,87,88. 

Arylhydroxamic Acid Acyltransferase Activity by Various Cytosol Fractions... 

Fig. 3. Enzymatic isomerization in vitro of arylhydroxamic acids to o-amidophenols.

---