Hydroxamic acids 0-benzoyl

Hydroxylamine, O-acetyl-A -benzoyl-.V-phenyl-hydroxamic acids from, 2, 506... 

The unstable cycloadducts 207, obtained from the dihydropyridines 205 (R = Me or Bn) and the benzoyl nitroso compound 206, undergo a hetero-Cope rearrangement in the presence of silicic acid to yield fused dioxazines 208 (equation 114)106. Adding the racemic hydroxamic acid 209 (R = r-Bu, cyclohexyl or Ph) to a two-phase mixture of... 

What about the isomers of the hydroxamic acids, the 0-acyl derivatives of hydroxy-lamine Having mentioned early in this study that N-methylhydroxylamine is more stable than its O-isomer, we are thus intrigued by the finding that iV-benzoylhydroxylamine (benzohydroxamic acid), or at least its A -f-butyl derivative, is less stable than its corresponding O-benzoyl isomer as shown by the thermal isomerization of the former to the latter, equation 55. 

It may be mentioned that an alternative name for hydroxamic acids, treating them as derivatives of hydroxylamine, continues to be used. For example A-phenylbenzohydroxamic acid [PhCON(Ph)OH] has also been named alternatively as A-benzoyl-A-phenylhydroxylamine even in recent literature. 

Hydroxylamine, O-acetyl-N-benzoyl-N-phenyl-hydroxamic acids from, 506 Hydroxylamine ligands, 101 Hydrozirconation, 342 Hypoxanthines metal complexes, 93... 

In the reaction of O-benzoyl hydroxamic acid (56) with Bu3SnH, Bu3Sn adds to the carbonyl oxygen and subsequent p-elimination occurs to form an amidyl radical through the weak N-O bond cleavage, where finally, y-lactam (57) via 5-exo-trig manner is formed (eq. 3.18). 

Other methods, among which thermolysis or photolysis of tetrazene [59], photolysis of nitrosoamines in acidic solution [60], photolysis of nitrosoamides in neutral medium [61], anodic oxidation of lithium amides [62], tributylstannane-mediated homolysis of O-benzoyl hydroxamic derivatives [63, 64], and spontaneous homolysis of a transient hydroxamic acid sulfinate ester [65] could have specific advantages. The redox reaction of hydroxylamine with titanium trichloride in aqueous acidic solution results in the formation of the simplest protonated aminyl radical [66] similarly, oxaziridines react with various metals, notably iron and copper, to generate a nitrogen-centered radical/oxygen-centered anion pair [67, 68]. The development of thiocarbazone derivatives by Zard [5, 69] has provided complementary useful method able to sustain, under favorable conditions, a chain reaction where stannyl radicals act simply as initiators and allow transfer of a sulfur-containing... 

The phosphazene bases BTPP and Bu-P2 mediate the rearrangement of unactivated A -alkyl-(9-benzoyl hydroxamic acid derivatives to give 2-benzoyl amides. The rate of reaction was found to be dependent upon the steric nature of the A -alkyl substituent [39a]. Treatment of malonyl derived (9-acyUiydroxamic acid derivatives with the phosphazene superbase Bu-P2 gives 2,3-dihydro-4-isoxazole carboxylic ester derivatives. The rate and yield of the reaction depend upon the (9-acyl substituent [36b] (Scheme 5.21). 

Clark, A.J., Al-Faiyz, Y.S.S., Patel, D. and Broadhurst, M.J. (2001) Rearrangement of unactivated A-alkyl-O-benzoyl hydroxamic acid derivatives with phosphazene bases. Tetrahedron Letters, 42, 2007-2009 Clark, A.J., Patel, D. and Broadhurst, M.J. (2003) Base-mediated reaction of A-alkyl-O-acyl hydroxamic acids synthesis of 3-oxo-2,3-dihydro-4-isoxazole carboxylic ester derivatives. Tetrahedron Letters, 44, 7763-7765. 

The nomenclature of this class of compounds is not at all clear. For example, the following names can be found in the literature hydroxamic acid chlorides, hydroxamic chlorides, hydroximic chlorides (Beilstein lists them as Hydroximsaure chloride ), and acyl and aroylchloride oximes. The latter names are used by Chemical Abstracts, Although the name benzoyl chloride oxime for benzhydroxamoyl chloride is formally correct, it does not reflect the close relationship between hydroxamoyl chlorides and hydroxamic acids, their hydrolysis products. In order to be consistent with the nomenclature used in the earlier chapters, I prefer the term hydroxamoyl to hydroxamic chloride. The interrelationship of the halides with the corresponding acids is shown below, and R is representative of the alkyl, aryl, acyl, aroyl, and carbalkoxy group. 

Many investigators have studied the incorporation of labeled amino acids into proteins. The system involved in mammalian cells seems to be associated with microsomes, but requires factors from the soluble portion of the cell. Both ATP and GTP are required. The function of the ATP may be to form activated amino acids. Several systems have been found with relative specificity for various amino acids that catalyze the exchange of pyrophosphate with ATP in the presence of the amino acid, and presumably form adenyl-amino acid compounds. The activated amino acids react with hydroxylamine to form hydroxamic acids. Several reactions have been considered as models for peptide bond formation. These include the formation of hippuric acid, in which benzoyl CoA condenses with glycine in a reaction similar to the acetylation of... 

Another method of detection of oximes is based on the oxidation with benzoyl peroxide nitrous acid is liberated, which can be detected by reaction with sulfanilic acid and 1-naphthylamine. The reaction is also given by hydroxamic acids. 

On this basis the extent to which an enzyme-catalyzed transamidation will occur will depend on the relative concentration of water and the replacement reagent, and the relative affinity of the replacement agent for the ES-complex. Durell and Fruton (51) have studied papain-catalyzed hydroxamic acid formation from o-benzoyl-L-argininamide. Their calculations show that hydroxylamine is about 420 times more efficient in its reaction with the enzyme-substrate complex than is water. Preliminary observations suggest that when amino acid amides or peptides are the attacking molecule the efficiency is even greater. Moreover, papain is a much more effective catalyst for transamidation than trypsin. 

A number of types of compound can be considered as hydroxylamine derivatives. Hydroxamic acids have the general formula RC(OH)NOH and can be used to precipitate or extract a range of metal ions, including Zr, Th, Fe and Cr. Cupferron (ammonium iV-nitroso-Af-phenylhydroxylamine) and iV-substi-tuted phenylhydroxylamines such as iV-Benzoyl-IV-plienylliydroxylamine behave similarly to the hydroxamic acids, and are used for similar purposes. 

A soln. of 0-benzoyl benzohydroxamic acid in tetrahydrofuran added with stirring and cooling to a soln. of LiAlH4 in the same solvent, and refluxed 15 hrs. -y benzylamine (Y 80%) and benzyl alcohol (Y 90%).— Reduction of acyl hydroxamates is smoother and gives better yields than reduction of the free hydroxamic acids. F. e. s. F. Winternitz and G. Wlotzka, Bl. 1960, 509. 

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