Search results for "dipeptide"
showing 10 items of 99 documents
Diorganotin(IV) dipeptide complexes with potential antitumour activity
1993
A series of complexes of the dimethylltin(IV) moiety with dipeptides has been synthesized. The dipeptides are L-alanyl-L-histidine (H2AlaHis), L-methionyl-L-methionine (H2MetMet), L-glycyl-L-histidine (H2GlyHis) and L-histidyl-L-glycine (H2HisGly). The complexes have been characterized by IR and 119Sn Mossbauer spectroscopy in the solid state and by 1H NMR in CD3OD and D2O solutions. They consist of monomeric entities, with the tin atom arranged in a pentacoordinated trigonal bipyramidal structure. The dipeptides are coordinated via the amino group, deprotonated peptide nitrogen and carboxylate group. Neither imidazole in histidine-containing dipetides, nor the thioether group in MetMet, is…
Complexes of tryptophan dipeptides with the R2Sn(IV)2+ ion (R=Me, Ph): Spectroscopic studies, solution properties and structural implications
1995
Tryptophan dipeptides such as L-tryptophyl-L-alanine (H 2 TrpAla), L-tryptophyl-L-tyrosine (H 2 TrpTyr), L-tryptophyl-L-tryptophan (H 2 TrpTrp), along with L-histidyl-L-tyrosine (H 2 HisTyr), were reacted with R 2 SnO (R=Me, Ph) yielding the corresponding complexes. The complexes have been characterized by IR and 119 Sn Mossbauer spectroscopy in the solid state and by 1 H and 13 C NMR in CD 3 OD solutions. Monomeric species were detected, with the tin atom arranged in a pentacoordinated trigonal-bipyramidal structure. The dipeptides are coordinated via the terminal amino group, deprotonated peptide nitrogen and terminal carboxylate group. No side-chain appears to be involved in bonding. Det…
Peptide metal-organic frameworks under pressure: flexible linkers for cooperative compression
2018
We investigate the structural response of a dense peptide metal-organic framework using in situ powder and single-crystal X-ray diffraction under high-pressures. Crystals of Zn(GlyTyr)2 show a reversible compression by 13% in volume at 4 GPa that is facilitated by the ability of the peptidic linker to act as a flexible string for a cooperative response of the structure to strain. This structural transformation is controlled by changes to the conformation of the peptide, which enables a bond rearrangement in the coordination sphere of the metal and changes to the strength and directionality of the supramolecular interactions specific to the side chain groups in the dipeptide sequence. Compar…
Metal ion-promoted activation of amino acid esters of carbohydrates in the synthesis of peptides
1992
Abstract Carbohydrate esters 1 and 2 of N-protected amino acids are activated by coordination of metal ions and subjected to aminolysis by amino acid esters 3 to form peptides 4 .
Synthesis, crystal structure and molecular conformation of the tBuCO-D,L-Ala-Δz-Phe-NhiPr α,β-unsaturated dipeptide
2009
The crystal structure of the tBuCO-D,L-Ala-delta Z-Phe-NHiPr dipeptide has been solved by X-ray diffraction. The peptide crystallizes in monoclinic space group P2(1)/c with a = 13.445 (3) A, b = 35.088 (4) A, c = 14.755 (3) A, beta = 116.73 (1) degree, Z = 12 and dc = 1.151 g.cm-3. The three independent molecules per asymmetric unit accommodate a beta II-folded conformation, but only one of them contains the typical i + 3----i interaction characterizing a beta-turn. In the other two molecules, the N...O distance exceeds 3.2 A, a value generally considered the upper limit for hydrogen bonds in peptides. In solution, the beta II-turn conformation is largely predominant.
A three-component Mannich-type condensation leading to phosphinic dipeptides—extended transition state analogue inhibitors of aminopeptidases
2011
Abstract N-Protected α-aminoalkylphosphinic acids bearing a P–H function were found to be novel practical building blocks in three-component condensations with formaldehyde and secondary amines (amino acids). Such Mannich-type N -phosphonomethylation is a common approach for phosphorus acid derived substrates and leads to multifunctional (phosphonic/amino/carboxylic) compounds of diverse relevance. The utility of this reaction was examined for construction, in a single synthetic step, of advanced phosphinic pseudodipeptides designed to act as extended transition state analogue inhibitors of selected aminopeptidases. Phosphinomethylation of primary amino acids was less efficient and yielded …
Das System 2‐Halogenethylester/Cholinester als Zweistufen‐Schutzgruppe für die Carboxylfunktion von Aminosäuren und Peptiden
1979
Das System 2-Chlorethyl- und 2-Bromethylester/Cholinester wird als Carbonsaure-Schutzfunktion beschrieben. Die 2-Chlorethyl-(OEt(Cl))- und die 2-Bromethylester (OEt(Br)) der Aminosauren (4) lassen sich einfach herstellen und mit Z- und Boc-Aminosauren zu Z- und Boc-Dipeptidestern 5 und 6 verknupfen. Die Esterfunktionen sind gegen nicht zu stark saure und basische Einflusse bestandig. Sie konnen mit Natriumiodid in DMF in 2-Iodethylester 8 ubergefuhrt werden, welche mit Zink in einer Eintopfreaktion spaltbar sind. Durch Umsetzung mit Trimethylamin gehen die hydrophoben 2-Halogenethylester in die hydrophilen Cholinester 10 und 11 uber. Diese sind sehr stabil gegen Sauren. Sie konnen in wasrig…
Synthesis of cyclic dipeptide templates, their incorporation into peptides and studies on their conformational and biological properties.
2009
This study investigated the diastereoselective synthesis of three dipeptide templates 1, 2 and 3, which may be regarded as conformationally restricted analogs of H-Gly-Xaa-OH, in which Xaa constitutes an aromatic amino acid. Bond formation between α-C of Gly and the aromatic moiety was achieved by proton-catalyzed intramolecular electrophilic aromatic substitution. The absolute configuration of the dipeptide templates was determined by single-crystal X-ray crystallography or by nuclear Overhauser enhancement measurements. A protective group strategy was elaborated to allow their incorporation into peptide sequences by liquid phase as well as by solid-phase peptide synthesis. The templates w…
Selektive enzymatische Schutzgruppenabspaltungen: Der n-Heptylester als Carboxylschutzgruppe in der Peptidsynthese
1991
Selective Enzymatic Removal of Protecting Groups: n-Heptyl Esters as Carboxy Protecting Functions in Peptide Synthesis Amino acid heptyl (Hep) esters are accessible as generally crystalline hydro tosylates 3 from the amino acids by azeotropic esterification with 1-heptanol in high yields. They can be condensed with Z-, Boc-, and Aloc-protected amino acids to give the dipeptides 7–9 in the presence of 1-ethoxycarbonyl-2-ethoxy-1,2-dihydroquinoline (EEDQ). From the fully protected dipeptides the N-terminal protecting groups are cleaved by chemical methods without affecting the Hep esters. On the other hand, the heptyl esters can be hydrolyzed under mild conditions (pH = 7.0, 37°C) and with hi…
Glycoside synthesis via electrophile-induced activation of N-allyl carbamates
1993
Abstract O-Benzyl-, O-acyl-, N-acyl- and isopropylidene-protected glycosyl N-allylcarbamates, obtained from anomerically unprotected monosaccharides and allyl isocyanate, are activated by an electrophile-induced cyclisation and react with hydroxyl compounds to form the corresponding glycosides.