3304-61-8Relevant academic research and scientific papers
Oxidative Damage in Aliphatic Amino Acids and Di- and Tripeptides by the Environmental Free Radical Oxidant NO3?: the Role of the Amide Bond Revealed by Kinetic and Computational Studies
Nathanael, Joses G.,Wille, Uta
, p. 3405 - 3418 (2019/03/11)
Kinetic and computational data reveal a complex behavior of the important environmental free radical oxidant NO3? in its reactions with aliphatic amino acids and di- and tripeptides, suggesting that attack at the amide N-H bond in the peptide backbone is a highly viable pathway, which proceeds through a proton-coupled electron transfer (PCET) mechanism with a rate coefficient of about 1 × 106 M-1 s-1 in acetonitrile. Similar rate coefficients were determined for hydrogen abstraction from the α-carbon and from tertiary C-H bonds in the side chain. The obtained rate coefficients for the reaction of NO3? with aliphatic di- and tripeptides suggest that attack occurs at all of these sites in each individual amino acid residue, which makes aliphatic peptide sequences highly vulnerable to NO3?-induced oxidative damage. No evidence for amide neighboring group effects, which have previously been found to facilitate radical-induced side-chain damage in phenylalanine, was found for the reaction of NO3? with side chains in aliphatic peptides.
Preparation of N-acetyl, tert-butyl amide derivatives of the 20 natural amino acids
Ekkati,Campanali,Abouelatta,Shamoun,Kalapugama,Kelley,Kodanko, Jeremy J.
scheme or table, p. 747 - 751 (2010/08/05)
N-Acetyl-AA(amino acid)-NHtBu derivatives of all 20 naturally occurring amino acids have been synthesized. Syntheses were performed via solution-phase methodology with yields that allow for access to gram quantities of substrates, in most cases. Syntheses include the coupling of a hindered amine, tert-butylamine, with each amino acid, either directly or in two steps using an activated ester isolated as an intermediate. The introduction of protecting groups was necessary in some cases. The development of synthetic sequences to access challenging substrates, such as the one derived from asparagine, are discussed.
Targeting peptides with an iron-based oxidant: Cleavage of the amino acid backbone and oxidation of side chains
Ekkati, Anil R.,Kodanko, Jeremy J.
, p. 12390 - 12391 (2008/03/30)
The oxidation of protected amino acids using an iron-based oxidant is described. Substrates of the general formula Ac-X-NHtBu, where X = Gly (1), Ala (2), Val (3), Phe (4), Tyr (5), Trp (6), and Met (7) were constructed to model individual amino acid residues within a polypeptide chain. Oxidation of 1 by the iron catalyst [FeII(N4Py)(MeCN)](ClO4)2 (8) and KHSO5 leads to scission of the amino acid backbone and produces N-acetylformamide as the major product. Decomposition of the iron-based oxidant [FeIV(O)(N4Py)]2+, derived from 8, is slower in the presence of 2,2-d2-1 (96% D) than with 1, giving a kinetic isotope effect of 4.8, which is consistent with [FeIV(O)(N4Py)]2+ cleaving an α-CH bond of 1. Aliphatic amino acid substrates 2 and 3 do not react with [FeIV(O)(N4Py)]2+ under the same conditions used with 1. With substrates 4-7 oxidation of the amino acid side chain is observed. Decomposition of [FeIV(O)(N4Py)]2+ upon treatment with 10 equiv of 1 and 4-7 revealed that 5 is the most reactive toward the FeIVO species. Pseudo-first-order rate constants of 17.0(5) × 10-3, 3.15(8) × 10-3 and 5.8(2) × 10-5 s-1 were obtained for decomposition of [FeIV(O)(N4Py)]2+ ([Fe] = 1 mM, 1:1 H2O/MeCN) by 6, 7, and 1, respectively. Copyright
Acylaminoacetyl Derivatives of Active Methylene Compounds. 2. The Cyclization of the Acetylaminoacetyl Derivatives to α-Substituted Tetramic Acids and the Formation of N-Acetyl-α-substituted Tetramic Acids
Igglessi-Markopoulou, Olga,Sandris, Constantine
, p. 1599 - 1606 (2007/10/02)
The reaction of aceturic acid p-nitrophenyl ester with active methylene compounds Y-CH2-CO2R has been found to give either the normally expected C-acylation compounds 2 (Y = -CN, -CO2R, -COCH3) or N-acetyl-α-Y-substituted tetramic acids 3 (Y = -CO2R, -COC
Carboxamidomethyl esters as reactive substrates for alpha-chymotrypsin. Orientational effects of hydrogen-bonding interactions.
Cohen,Torem,Vaidya,Ehret
, p. 4722 - 4728,4723, 4725 (2007/10/12)
Effects of hydrogen-bonding interactions of amide groups on reactivity of esters to alpha-chymotrypsin were studied. Of the methyl esters studied, only that from acetyl-L-phenylalanine has k3 rate-limiting. In methyl beta-phenylpropionates an alpha-acetamido substituent increased k2 greater than 550 times, k3 approximately 5 times; an alpha-acetylclycyloxy substituent increased k2 approximately 2 times, k3 approximately 6 times, both in comparison with the alpha-acetoxy esters. Essentially all carboxamidomethyl esters studied have k3 rate-limiting; reactivity to hydroxide is only 4 times that of methyl esters. In alpha-substituted beta-phenylpropionates, carboxamido-methyl esters show k2 values greater than 110 times greater than 280 times, greater than 26 times, and 7 times the k2 values of the methyl esters for the alpha substituents, acetoxy, acetylglycyloxy, hydroxy, and hydrogen, respectively. In esters of alpha-acetamido acids, carboxamidomethyl esters show k2 values 44 times, greater than 110 times, greater than 12 times, and approximately 33 times the k2 values of the methyl esters of glycine, alanine, leucine, and phenylalanine, respectively. Cyanomethyl esters also had k3 rate-limiting. Hydrogen-bonding to the enzyme of either an alpha-acetamido group or a carboxamidomethyl group combined with bonding of the beta-aryl group, orients the hydrolyzing groups properly, increasing k2. Hydrogen-bonding of both alpha-acetamido and carboxamido-methyl groups is effective to a lesser degree. The amide group appears to have small effects on Ks as hydrogen bonding is balanced by desolvation. It is proposed that desolvation during bonding increases k2 and Ks.
