P-Nitrophenyl carbamates

Alternatively, two phosgene equivalents were studied, methyl chloroformate and p-nitrophenyl chloroformate. When methyl chloroformate was used for the end game, N-carbamate 54 was obtained smoothly but subsequent cyclization to ben-zoxazinone 1 was sluggish. Furthermore, removal of the unreacted intermediate methyl carbamate 54 from Efavirenz was not trivial, thus we did not pursue this method. On the other hand, reaction of 53 and p-nitrophenyl chloroformate initially provided the corresponding p-nitrophenyl carbamate 55 under mild basic conditions (KHC03). Carbamate 55 was smoothly cyclized to 1 upon increasing... 

Arenecarbonitrile oxides react with alkyl (p-nitrophenyl)carbamates at the nitro group, the nitrogen atom of the latter being the nucleophilic center. Tautomeric N-hydroxybenzimidazole N-oxides 382 and 383 form as the final products (430). 

A mechanistic analysis of antibody DF8-D5 showed it to cleave p-nitrophenyl carbamate [134] with kcat = 0.3 s l, Km = 120 p,M, and cat/ uncat = 300 at 14°C (Appendix entry 4.3) (Wentworth et al., 1997). This is some tenfold more active than a carbamatase antibody generated by Schultz... 

Preparation of Hydrogel p-Nitrophenyl Carbamates. A 20 mL solution of hydrogel (2-3.0 g) in pyridine was treated with 3 g... 

To activate the hydrogel adducts for enzyme immobilization, it was necessary to reduce the nitro function to the corresponding amine. From the many techniques available to effect this modification, we selected sodium dithionite as the mildest procedure with the least potential problems with residual reagent. Since the hydrogels were quite hydrophilic it was possible to use a two phase solvent system (THF/H2O) to effect the reduction. The arylsulfonyl carbamates were reduced selectively under these conditions no reduction of p-nitrophenyl carbamate was observed. 

Liskamp and coworkers [64] also reported the use of p-nitrophenyl carbamate derivatives obtained by reaction of Boc-protected iV-substituted ethylenediamines with p-nitrophenyl chloroformate for the synthesis of ureapeptoids. 

Supramolecular gels were also used as matrix to perform various chemical reactions in confined environments. Eor instance, macrocycUzation reactions were performed in acetonitrile gel of bis-p-nitrophenyl carbamate valine derivatives (Eigure 34). ... 

Figure 34 (a) Schematic representation of the gel-templated macrocyclization reaction (b) Conversion of bis-p-nitrophenyl carbamate... 

Scialdone MA, Shuey SW, Soper P, Hamuro Y, Bums DM. Phosgenated p-nitrophenyl(polystyrene)ketoxime or phoxime resin. A new resin for the solid-phase synthesis of ureas via thermolytic cleavage of oxime-carbamates. J Org Chem 1998 63 4802-4807. 

A recent study concerned the microwave-assisted parallel synthesis of di- and tri-substituted ureas utilizing dedicated 96-well plates in the CombiCHEM system [60], In a typical procedure, modification of the Marshall resin utilized was achieved by treatment with p-nitrophenyl chloroformate and N-methylmorpholine (NMM) in dichloromethane at low temperatures. The resulting resin was further modified by attaching various amines to obtain a set of polymer-bound carbamates (Scheme 7.48). 

Participation by neighbouring alkoxide ion is observed in the cyclization of p-nitrophenyl and ethyl esters of 2-hydroxymethyl-N-methylcarbanilic acid [30]-[33] (Hutchins and Fife, 1973b). As with the carbamates having a neighbouring phenolic hydroxyl, ring... 

As Table I illustrates, the chemical classes represented by the pesticides studied include thiophosphates [0,0-diethyl-o-p-nitrophenyl phos-phorothioate], carbamates [1-naphthyI-N-methylcarbamate], dinitrophe-nols [2,4-dinitro-o-sec-butylphenol and 2,4-dinitro-o-cyclohexylphenol], and chlorophenoxy acids [2,4-dichlorophenoxyacetic acid, 2,4,5-trichloro-phenoxyacetic acid, and 2-(2,4,5-trichlorophenoxy)propionic acid]. In addition, a number of molecularly related nitrophenols have been studied to establish the effects of molecular geometry and substituent groups on adsorption of pesticide-type materials. 

The 0,0-diethyl-o-p-nitrophenyl phosphorothioate (parathion) was obtained from the American Cyanamid Co., and the 1-naphthyl-N-methyl-carbamate (Sevin) was obtained from the R. A. Taft Sanitary Engineering Center, U. S. Public Health Service. The Dow Chemical Co. provided... 

Aldridge, W.N. (1953). Two types of esterase (A and B) hydrolysing p-nitrophenyl acetate, propionate and butyrate, and a method for their determination. Biochem. J. 53 110-17. Aldridge, W.N., Reiner, E. (1972). Enzyme Inhibitors as Substrates, Interaction of Esterases with Esters of Organo-phosphorus and Carbamic Acids. North-Holland, Amsterdam. Andersen, R.A., Mikalsen, A., Saetre, T. (1983). Cholinesterase levels in two stocks of Wistar rats, effect of hypophysectomy. Gen. Pharmacol. 14 285-6. 

In another example, p-nitrophenyl chloroformate was required to introduce a sophisticated carbamate function in a multi-steps synthesis of retroviral protease inhibiting compounds (Ref. 26). The structure of the intermediate carbonate is given in scheme 30. 

The toxicity of organophosphates or carbamates can be potentiated several-fold if the activity of CarbE is inhibited by pretreatment. Potentiation of malathion toxicity by EPN (O-ethyl-O-p-nitrophenyl phenyl-phosphonothionate) was reported about half a century... 

A second route (Method B in Scheme 36) involves the reaction of triphosgene with the deprotected terminal amine, providing chloroformamides that lose HCl to give isocyanates. A urea derivative is formed by adding an anthranilate or an an-thranilic acid derivative. Alternatively, an activated carbamate can be produced from p-nitrophenyl chloroformate as the reactive intermediate (Method C in Scheme 36). 

In order to obtain amines the Wang resin is transformed into the p-nitrophenyl or succinimi-dyl carbonate and treated with amines. The formed carbamate bond is cleaved with TFA. 

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