1492-11-1Relevant articles and documents
Engineering a polymeric chiral catalyst by using hydrogen bonding and coordination interactions
Shi, Lei,Wang, Xingwang,Sandoval, Christian A.,Li, Mingxing,Qi, Qiaoyan,Li, Zhanting,Ding, Kuiling
, p. 4108 - 4112 (2006)
(Chemical Equation Presented) Noncovalent interactions are used to generate a polymeric supramolecular chiral catalyst (see picture). This heterogeneous catalyst, which is based on Feringa's MonoPhos/RhI system, is formed by orthogonal self-ass
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.
Oxidative functionalization of aliphatic and aromatic amino acid derivatives with H2O2 catalyzed by a nonheme imine based iron complex
Ticconi, Barbara,Colcerasa, Arianna,Di Stefano, Stefano,Lanzalunga, Osvaldo,Lapi, Andrea,Mazzonna, Marco,Olivo, Giorgio
, p. 19144 - 19151 (2018/05/31)
The oxidation of a series of N-acetyl amino acid methyl esters with H2O2 catalyzed by a very simple iminopyridine iron(ii) complex 1 easily obtainable in situ by self-assembly of 2-picolylaldehyde, 2-picolylamine, and Fe(OTf)2 was investigated. Oxidation of protected aliphatic amino acids occurs at the α-C-H bond exclusively (N-AcAlaOMe) or in competition with the side-chain functionalization (N-AcValOMe and N-AcLeuOMe). N-AcProOMe is smoothly and cleanly oxidized with high regioselectivity affording exclusively C-5 oxidation products. Remarkably, complex 1 is also able to catalyze the oxidation of the aromatic N-AcPheOMe. A marked preference for the aromatic ring hydroxylation over Cα-H and benzylic C-H oxidation was observed, leading to the clean formation of tyrosine and its phenolic isomers.
Simple and efficient Fmoc removal in ionic liquid
Di Gioia,Costanzo,De Nino,Maiuolo,Nardi,Olivito,Procopio
, p. 36482 - 36491 (2017/08/02)
A mild method for an efficient removal of the fluorenylmethoxycarbonyl (Fmoc) group in ionic liquid was developed. The combination of a weak base such as triethylamine and [Bmim][BF4] makes the entire system more efficient for the cleavage at room temperature of various amines and amino acid methyl esters in short reaction times. The procedure works well even in the case of N-Fmoc amino acids bearing acid-sensitive protecting groups and of N-alkylated amino acid methyl esters. The solvent-free condition provides a complementary method for Fmoc deprotection in solution phase peptide synthesis and modern organic synthesis.
IMMUNOSTIMULATING AGENT
-
Paragraph 0181, (2017/05/21)
The present invention aims to provide an immunostimulating agent superior in an immunostimulatory effect, particularly a compound useful as a vaccine adjuvant, a pharmaceutical composition containing the compound, a vaccine containing the compound and an
A new method for peptide synthesis in the N→C direction: Amide assembly through silver-promoted reaction of thioamides
Pourvali, Aysa,Cochrane, James R.,Hutton, Craig A.
supporting information, p. 15963 - 15966 (2015/01/09)
The Ag(i)-promoted coupling of amino acids and peptides with amino ester thioamides generates peptide imides without epimerisation. The peptide imides undergo regioselective hydrolysis under mild conditions to generate native peptides. This method was employed to prepare the pentapeptide thymopentin in the N→C direction, in high yield and purity.
Deprotection/reprotection of the amino group in α-amino acids and peptides. A one-pot procedure in [Bmim][BF4] ionic liquid
Di Gioia,Barattucci,Bonaccorsi,Leggio,Minuti,Romio,Temperini,Siciliano
, p. 2678 - 2686 (2014/01/06)
This paper presents an efficient one-pot protocol for the sequential deprotection/reprotection of the α-amino group in α-amino acid and dipeptide methyl esters. [Bmim][BF4] is used as the solvent in the entire process. In particular, the use of the ionic liquid allows for rapid and clean removal of the 4-nitrobenzenesulfonyl (nosyl) group and for facile subsequent tert-butyloxycarbonylation of the free α-amino function under very mild conditions. N-Boc-α-amino acid as well as peptide derivatives are isolated in excellent yields, and do not require any further purification. Absolute configurations of the precursors are totally preserved during the process.
Deprotectlon of N-Nosyl-α-amlno acids by using solid-supported mercaptoacetic acid
De Marco, Rosaria,Gioia, Maria Luisa Di,Leggio, Antonella,Liguori, Angelo,Viscomi, Maria Caterina
experimental part, p. 3795 - 3800 (2009/12/05)
A simple and efficient synthesis of a solid-supported thiol has been developed. Mercaptoacetic acid was first protected by the dimethoxytrityl group and then anchored to Wang resin through an ester bond. Deprotection of the thiol function led to resin-supported mercaptoacetic acid, a useful supported thiol reagent that can be used in the polymer-assisted solution-phase removal of nosyl (Ns) groups from the amino function of a-amino acids in peptide synthesis.
Oxidation of peptides by methyl(trifluoromethyl)dioxirane: The protecting group matters
Rella, Maria Rosaria,Williard, Paul G.
, p. 525 - 531 (2007/10/03)
Representative Boc-protected and acetyl-protected peptide methyl esters bearing alkyl side chains undergo effective oxidation using methyl(trifluoromethyl)dioxirane (1b) under mild conditions. We observe a protecting group dependency in the chemoselectivity displayed by the dioxirane 1b. N-Hydroxylation occurs in the case of the Boc-protected peptides, and side chain hydroxylation takes place in the case of acetyl-protected peptides. Both are attractive transformations since they yield derivatized peptides that serve as valuable synthons.
Application of chiral mixed phosphorus/sulfur ligands to enantioselective rhodium-catalyzed dehydroamino acid hydrogenation and ketone hydrosilylation processes
Evans, David A.,Michael, Forrest E.,Tedrow, Jason S.,Campos, Kevin R.
, p. 3534 - 3543 (2007/10/03)
Chiral mixed phosphorus/sulfur ligands 1-3 have been shown to be effective in enantioselective Rh-catalyzed dehydroamino acid hydrogenation and ketone hydrosilylation reactions (eqs 1, 2). After assaying the influence of the substituents at sulfur, the substituents on the ligand backbone, the relative stereochemistry within the ligand backbone, and the substituents at phosphorus, ligands 2c (R = 3,5-dimethylphenyl) and 3 were found to be optimal in the Rh-catalyzed hydrogenation of a variety of α-acylaminoacrylates in high enantioselectivity (89-97% ee). A similar optimization of the catalyst for the Rh-catalyzed hydrosilylation of ketones showed that ligand 3 afforded the highest enantioselectivities for a wide variety of aryl alkyl and dialkyl ketones (up to 99% ee). A model for asymmetric induction in the hydrogenation reaction is discussed in the context of existing models, based on the absolute stereochemistry of the products and the X-ray crystal structures of catalyst precursors and intermediates.
