Amino acids p-nitrophenyl esters

Several crown ethers that possess side chains with terminal mercapto groups enhance the rate of transesterification of amino-acid p-nitrophenyl esters. Matsui and Koga (1978) reported the reactions of a number of amino-acid p-nitrophenyl ester hydrobromides dissolved in mixtures of ethanol and dichloromethane (1 4) and buffered with acetic acid and pyridine (pH 4.60 in... 

Y. Kurono, T. Furukawa, T. Tsuji, K. Ikeda, Esterase-Like Activity of Human Serum Albumin. VI. Reaction with p-Nitrophenyl Glycinate , Chem. Pharm. Bull. 1988, 36, 4068-4074 Y. Kurono, I. Kushida, H. Tanaka, K. Ikeda, Esterase-Like Activity of Human Serum Albumin. VIII. Reaction with Amino Acid p-Nitrophenyl Esters , Chem. Pharm. Bull. 1992, 40, 2169-2172. 

Y. Kurono, I. Kushida, H. Tanaka, K. Ikeda, Esterase-Like Activity of Human Serum Albumin. VIII. Reaction with Amino Acid p-Nitrophenyl Esters , Chem. Pharm. Bull. 1992, 40, 2169-2172. 

Pseudo-first-order rate constants (10 k/sec) for >-nitrophenol release [72] from amino acid p-nitrophenyl ester hydrobromides, RC02C6H4-/ -N02-Br ... 

Chiral differentiation between enantiomeric amino acid p-nitrophenyl ester hydrobromines was observed [9,73] in transacylations catalysed by the chiral 3,3-... 

It was already reported that thiol-bearing chiral crown ethers of type 1 showed rate enhancements in the thiolysis of a-amino acid p-nitrophenyl ester salts, due to the intra-complex nature of the reaction, forming the corresponding thioester as shown in Scheme 1 [5]. Evaluating the thioester as the reactive intermediate for nucleophile... 

The hosts are used to study the hydrolysis of l- and D-amino acid p-nitrophenyl esters. The reaction is carried out in 20% EtOH-CH2Cl2... 

Sequence 9-13 was synthesized in a stepwise fashion starting with the methyl ester of leucine (Figure 7). tert.-Butyloxycarbonyl amino acids p-nitrophenyl esters... 

Sequence I was synthesized stepwise, starting with phenylalanine amide using tert.-butyloxycarbonyl amino acid p-nitrophenyl esters or 2,4,5-trichlorophenyl esters (Figure 13). In the first stages of this synthesis we were, of course, treading along the path followed by Kenner, Sheppard and coworkers in their synthesis of gastrin. ... 

W Williams, GT Young. Amino acids and peptides. XXXV. Effect of solvent on the rates of racemization and coupling of acylamino acid p-nitrophenyl esters. Base strengths of amines in organic solvents, and related investigations. J Chem Soc Perkin Trans 1 1194, 1972. 

Fig. 16. Binding pocket of the lipase from P. aeruginosa for the acid part of 2-methyldecanoic acid p-nitrophenyl ester showing the geometric position of amino acids 160-163 which were randomized in cassette mutagenesis (49).

In the second major method of peptide synthesis the carboxyl group is activated by converting it to an active ester, usually a p-nitrophenyl ester. Recall from Section 20.12 that esters react with ammonia and amines to give fflnides. p-Nitrophenyl esters are much more reactive than methyl and ethyl esters in these reactions because p-nitrophenoxide is a better (less basic) leaving group than methoxide and ethoxide. Simply allowing the active ester and a C-protected amino acid to stand in a suitable solvent is sufficient to bring about peptide bond formation by nucleophilic acyl substitution. 

For the elongation of the chain starting from 11 toward the N-terminal group, direct condensation of the activated p-nitrophenyl esters of such amino acids as N-protected L-cysteine, L-glutamic acid, glycine, L-leu-cine, L-proline, L-serine, L-tyrosine, andL-valine with 2-acetamido-3,4,6-... 

The amino acid attached to a polymer is treated with an vV-protected, carboxyl-activated amino acid to give the supported peptide. In the following reaction the triazolide was formed in situ from the p-nitrophenyl ester and 1,2,4-triazole 1341... 

Poly(HASCL) depolymerases are able to bind to poly(3HB)-granules. This ability is specific because poly(3HB) depolymerases do not bind to chitin or to (crystalline) cellulose [56,57]. The poly(3HB)-binding ability is lost in truncated proteins which lack the C-terminal domain of about 60 amino acids, and these modified enzymes do not hydrolyze poly(3HB). However, the catalytic domain is unaffected since the activity with water-soluble oligomers of 3-hy-droxybutyrate or with artificial water-soluble substrates such as p-nitrophenyl-esters is unaffected [55, 56, 58, 59]. Obviously, the C-terminal domain of poly(3HB) depolymerases is responsible and sufficient for poly(3HB)-binding [poly(3HB)-binding domain]. These results are in agreement ... 

Deacylation of p-nitrophenyl esters of amino acids Histidine-functionalized micelles and synthetic vesicles. Rate enhancements and enantioselectivity observed Murakami et al., 1981 b... 

Deacylation of p-nitrophenyl esters of amino acids Synthetic vesicles + histidine-functionalized surfactant. Cholesterol increased rates and enantioselectivity Ueoka and Matsumoto, 1984... 

The rates of reaction of both enantiomers of amino-acid esters in the presence of (S)-[324] are the same, but with (S)-[323] they are in most cases different. The reactions of L-amino acid esters in the presence of (S)-[323] are faster than those in the presence of (R)-[323] by factors of 9.2 (R = i-Pr), 8.2 (R = C6H5CH2) and 6.0 (R = i-Bu). No difference in rates is observed for L-alanine p-nitrophenyl ester. The results were explained in terms of the formation of diastereomeric tetrahedral intermediates [325] and [326]. The bulk of the group R will determine how much the complex stability of the (D)-complex decreases relative to that of the (L)-complex, which difference is reflected in the activation energy of the rate-determining step. 

This O-acylisourea is attacked by p-nitrophenol to give the p-nitrophenyl ester of the Z-protected amino acid. 

Synthesis of these dendrimers is performed by condensation of the amino acid lysine, whose amino functions have previously been protected with tert-bu-tyloxycarbonyl groups (Boc), onto an (activated) L-lysine p-nitrophenyl ester. The resulting coupling product (Fig. 4.11) is then deprotected with trifluoroacetic acid and thus activated for renewed reaction. Iteration of the assembly and activation step ultimately led to a polylysine dendrimer with 1024 terminal butyloxycarbonyl groups [21]. 

Fig. 3 Hypothetical free energy diagram proposed to account for NCA reactivity. Free energy levels of NCAs and of the transition state of their aminolysis reactions compared to those of reactions of other amino acid derivatives (AA-X). A Comparison with linear anhydrides (X = OAc) B Alkyl ester (X = OR), thioesters (X = SR) and p-nitrophenyl esters (X = ONp). The free energy regions corresponding to the possibility of pathways involving NCAs are shown hashed...

The dipeptide is now coupled—but is still protected. Deprotection (HBr/AcOH) gave the HC1 salt of LeuGly ethyl ester for further reaction. The rest of the peptide was built up in much the same way—each amino acid being introduced as the Cbz-protected p-nitrophenyl ester before being deprotected ready for the next coupling, until all nine of oxytocin s amino acids had been introduced. 

The reaction of 42 with 43 was attempted with dicyciohexylcarbodiimide (DCC) or water-soluble carbodiimide in solvent systems. All these reactions seemed to be unsuccessful because of the low solubility and low reactivity of 43. Among the methods of activation of a carboxy group, only the activated ester method of p-nitrophenyl ester was successful. In the acid chloride method a side reaction with the amino group of adenine was reported56. ... 

Conversion of a Boc-protected amino acid to a p-nitrophenyl ester. 

Reaction of the p-nitrophenyl ester with an amino acid ester. 

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