P-Nitrophenyl carbonates

Alkyl p-Nitrophenyl Carbonate ROCOOC6H4-/7-NO2 (Chart 2) Formation/Cleavage ... 

This Fmoc analog is prepared from the chloroformate, O-succinimide, or p-nitrophenyl carbonate and is cleaved with 10% piperidine in 1 1 6M guanidine/IPA. It was designed to interact strongly on a column of porous graphitized carbon so as to aid in the purification of peptides after cleavage from the resin. 

The Paloc group was developed as an amino acid protective group that is introduced with the p-nitrophenyl carbonate (H2O, dioxane, 68-89% yield). It is exceptionally stable to TFA and to rhodium-catalyzed allyl isomerization, but it is conveniently cleaved with Pd(Ph3P)4 (methylaniline, THF, 20°, 10 h, 74-89% yield). ... 

Brass and Bender (1973) have recently studied reaction of bis (p-nitrophenyl) carbonate with cyclohepta-amylose. Michaelis-Menten kinetics were observed, and two equivalents of p-nitrophenol released. Release of the first equivalent of p-nitrophenol is rate-determining, the second one being released in a fast step. The latter... 

Pyridyl)ethyl-p-nitrophenyl carbonate, The reagent is prepared by reaction of (2-pyridyl)ethanol and p-nitrophenyl chloroformate. 

Reaction of the bis-p-nitrophenylcarbonate of 1,4-benzenedimethanol with 2-cyclohexen-l,4-diol A mixture is prepared under argon atmosphere, consisting of 1.1348 g (9.954 mmoles) of the diol, 4.6623 g (9.954 mmoles) of the bis-p-nitrophenyl carbonate 0.630 g of 18-crown-6, 7.0 g of potassium carbonate and 15 mL of dry dichloromethane. The reaction mixture is stirred and refluxed for 90 hours, after which time it is worked-up by the usual method. Three precipitations into 1.5 liter of methanol are necessary to obtain 2.760 g (91% yield) of the pure white polymer. The cis trans ratio of the cyclohexenediol units in polymer III is shown to be 35 65 by H-NMR reflecting the mixture used initially. 

Coupling, active ester Bis-(2,4-dinitrophenyl)carbonate. Chloroacetonitrile. Di(p-nitrophenyl)carbonate. 2-Ethoxypyridine-l-oxide. p-Nitrobenzyl tosylate. p-Nitrophenol. p-Nitrophenyl trifluoroacetate. Pentachlorophenol. Phenyltrimethylammonium ethoxide. Phosgene. Pyrazole. Sulfur dioxide-Dimethylformamide. Tetraethyl pyrophosphite. N,N -Thionyldiimidazole. 2,4,S-Trichlorophenol. 

The N-Fmoc-protected p-nitrophenyl carbonate monomers are accessible from the corresponding (3-amino alcohols. Solid-phase synthesis of oligocarbamates is very efficient, with a reported coupling yield of 99% per step. 

The reagent is prepared by reaction of pentachlorophenyl chloroformate (m.p. 58°) with /-butanol in benzene in the presence of pyridine. Like /-butyl azidoformate and /-butyl p-nitrophenyl carbonate, it reacts with amino acids to give /-butyloxy-carbonylamino acids in yields of 60-85%. ... 

Peptide synthesis, N-protection Acetic-formic anhydride. Adamantyl chloroformate. Benzylthiocarbonyl chloride. /-Butoxycarbonyl-N-hydroxysuccinimide ester. /-Butyl azido-formate. /-Butylcarbonic diethylphosphoric anhydride. /-Butyl fluoroformate. /-Butyl oxycarbonyl fluoride. /-Butyl pentachlorophenyl carbonate. /-Butyl 2,4,5-trichlorophenyl carbonate. Carbobenzoxy chloride. 3,5-Dimethoxybenzyl p-nitrophenyl carbonate. [2-(Diphenyl)isopropyljphenyl carbonate. /-Pentyl chloroformate. 

R = C(NH)CCI3 Trichloroacetimidate Wang resin R = C(=0)0C6H4N02 p-Nitrophenyl carbonate Wang resin... 

The enzyme SC was modified with methoxy PEG (molecular weight 5,000) activated with p-nitrophenyl carbonate (Sigma, M-3903). The enzyme (240 mg) was dissolved in 100 mM potassium phosphate buffer pH 7.8 and stirred with 480 mg ( 10 x molar equivalent) PEG for a period of 2 h. The reaction was monitored by release of the p-nitrophenyl group (absorbance at 405 nm). The modified enzyme was purified from the solution by washing with phosphate buffer in an ultrafiltration cell (Amicon, Model 8050) using a 30,000-Da molecular weight cut-off membrane, over several hours. The modified enzyme was then lyophiUzed as described below. 

Scheme 24 Preparation of A-protected p-nitrophenyl carbonate monomers 89 [57,156].

AMINO GROUPS 9-Anthtylmethyl p-nitrophenyl carbonate. 2- (Chloro-formylloxy] -ethyltriphenylphos-phonium chloride. Diborane. 2-Nitro-benzenesulfenyl chloride. 2,2,2-Tri-chloro-/-butyloxycarbonyl chloride. Vinyl chloroformatc. 

Various rea9ents have been used for the introduction of the tert-butojvcarbonyl group. Including tert-butyl p-nitrophenyl carbonate, tert-... 

Tryptophan protection. The trytophan nucleus has been protected by acylation with benzyl p-nitrophenyl carbonate to form the CB derivative. The reaction is effected with KF solubilized in 18-crown-6 as base to abstract a proton from the indole ring (equation I). 

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