Amides from oxime esters

Other Applications. Hydroxylamine-O-sulfonic acid [2950-43-8] h.2is many applications in the area of organic synthesis. The use of this material for organic transformations has been thoroughly reviewed (125,126). The preparation of the acid involves the reaction of hydroxjlamine [5470-11-1] with oleum in the presence of ammonium sulfate [7783-20-2] (127). The acid has found appHcation in the preparation of hydra2ines from amines, aUphatic amines from activated methylene compounds, aromatic amines from activated aromatic compounds, amides from esters, and oximes. It is also an important reagent in reductive deamination and specialty nitrile production. 

Synthesis of heterocycles from amino amide oximes has been described. Recently we have reviewed the synthesis of oximes, oxime 0-ethers and esters, and also the synthesis of heterocycles from oximes covering the literature data published in 1990-1999 . 

Other Applications. Hydroxylainine-O-sulfonic acid has many applications in the area of organic synthesis. The acid has found application in the preparation of hydrazines from amines, aliphatic amines from activated methylene compounds, aromatic amines from activated aromatic compounds, amides from esters, and oximes. 

Infrared spectroscopy is used as a monitoring method when the resin is functionalized with linkers that have chemical groups that absorb in the IR spectral region, such as carbonyls, esters, amides, or oximes. IR spectroscopy has also been used to monitor quantitative loading of a resin by comparing the difference in absorbance between two peaks, one from the starting material and the other one from the final product [45]. 

A soln. of startg. oxime ester (prepared from biphenyl-4-carboxylic acid and benzophenone oxime) in carbon tetrachloride irradiated with a 400 W high-pressure Hg-lamp through a Pyrex filter under N2 at room temp, until reaction complete 4-chlorobiphenyl. Y 88%. This radical method is generally applicable to ar., hetar. (e.g. pyridyl, quinolyl, quinoxalyl), and aliphatic acids (prim., sec. and tert.). Ketone, amide, and hydroxyl groups remained unaffected. F.e.s. M. Hasebe, T. Tsuchiya, Tetrahedron Letters 29, 6287-90 (1988). 

An idenhcal approach was followed for the preparahon of combinatorial libraries from ursohc acid, betulinic add, and lupeol (Figure 11.50). In the case of betuhnic acid (105) and ursohc acid, the triterpene scaffold was immobilized onto a prederivatized amino acid on 2-chlorotrityl or Sieber amide resin, and treated with a variety of ahphahc, aromatic, and amino acids, to generate a library of C-3 and C-28 derivatives 106.In another series, C-3 oxime esters 107 were prepared from... 

Two approaches for solid-phase chemical ligation have been described. Canne et al. have developed an elegant system that utilizes an oxime forming ligation to attach the first peptide to the resin, a selectively cleavable ester link to remove the peptide from the resin as a C-terminal carboxylic acid, and the Acm group to protect the N-terminal cysteine residue)311 A complementary approach has been developed by Brik et al. that utilizes native chemical ligation to attach the first peptide to the solid support, a safety-catch acid labile linker to remove the final polypeptide from the support as a C-terminal amide and either Acm or Msc group for N-terminal cysteine protection)32 ... 

Trimethylsilyl polyphosphate (PPSE),1 The reagent is prepared from P205 and [(CHj),Si]20. It is a colorless, volatile liquid, soluble in the usual organic solvents. It is comparable to polyphosphate ester for the Beckmann rearrangement of oximes to amides (3, 230 231). but it is prepared more easily. 

The resistance of the furoxan ring to chemical attack allows derivatives to be prepared via the reactions of the substituents (Section 4.22.3.4). Carboxylic acids are available by permanganate oxidation of methyl derivatives or by hydrolysis of the corresponding esters reaction with ammonia affords carboxamides. Acylfuroxans provide a source of hydroxyalkyl compounds by reduction, and oximes, for example, via nucleophilic addition. Acylation and oxidation of aminofuroxans allows the amide and nitro derivatives to be prepared. Nucleophilic displacements of nitro substituents can take place, but can be somewhat hazardous on account of the explosive nature of these compounds. Alkoxy derivatives are formed with sodium alkoxide, while reaction with thiolate anions yields sulfides, from which sulfones can be synthesized by peracid oxidation. Nitrofuroxans have also been reduced to... 

The conversion of oximes into amides or lactams (reactions 6 or 7), in particular, e-caprolactam from cyclohexanone oxime (X = H), is catalyzed by [NBu4][Re04] andCFsSOsH in refluxing nitromethane, via a postulated perrhenic ester of oxime [RR C=N-0-Re03]. ... 

Protected peptides are cleaved from the resin with N-hydroxypiperidine (HOPip), followed by treatment with zinc in AcOH to afford the free acidJ Resin-bound peptides can be cleaved from the oxime resin using the tetrabutylammonium salts of side-chain protected amino acids to directly provide the a-amino-protected (Boc), side-chain-protected pep-tide.[ 3o- 32] Peptide esters can be obtained from peptidyl oxime resin by treating with amino acid estersJ Peptide hydrazides are derived from peptidyl oxime resins on treatment with anhydrous hydrazine.b Protected peptide amides can be also derived from peptidyl oxime resins on treatment with ammoniaJ l Cyclic peptide acids as carboxy components were successfully prepared by this procedure through the Pac ester. 

---