Search results for "solution"
showing 10 items of 5638 documents
ChemInform Abstract: Convenient High Yielding Gram Scale Solution Synthesis of Methionine-Enkephalin.
2010
A simple, large-scale synthesis of a cytokine, methionine-enkephalin, Tyr-Gly-Gly-Phe-Met, has been elaborated. Classical solution peptide chemistry methods without protection of amino acid side-chain functions and 1+(2+2) segment condensation were used. A nine-step synthesis from commercial amino acid derivatives was developed with yields ranging from 86% to 99%, averaging 92%. The purity of all intermediates was found to be 99.0-100% by HPLC. The process has been used to prepare greater than 150 g quantities of the pentapeptide as a monohydrate of 100% purity. Hydantoin formation was observed during saponification of Boc-Tyr-Gly-Gly-Phe-Met-OMe and minimised.
1986
Equilibrium solution coordination chemistry
2018
Welcome to this themed issue of New Journal of Chemistry entitled “Equilibrium Solution Coordination Chemistry”.
A comparative study of the multicomponent Ugi reactions of an oxabicycloheptene-based β-amino acid in water and in methanol
2006
Di-exo-3-amino-7-oxabicyclo[2.2.1]hept-5-ene-2-carboxylic acid 1, five aldehydes and two isocyanides were reacted both in methanol and in water to prepare a 10-membered β-lactam library via a Ugi-4-centre-3-component reaction. The yields were found to be similar in water and methanol. The diastereoselectivities of the aqueous reactions were similar, though in a few cases higher than those in methanol. The benefits of water are the facile isolation of the precipitated product and the shorter reaction time.
A Photoredox-Catalyzed Four Component Reaction for the Atom-Efficient Synthesis of Complex Secondary Amines
2020
The one-pot sulfonylation/aminoalkylation of styrene derivatives furnishing highly substituted gamma-sulfonylamines was accomplished through a photoredox-catalyzed four-component reaction. Apart from one molecule of water and the sodium counterion of the sulfinate, all atoms of the starting materials are transferred to the final product, rendering this process highly atom-efficient. The operationally simple protocol allows for the simultaneous formation of three new single bonds (C–S, C–N, and C–C) and therefore grants rapid access to structurally diverse products. The reaction proceeds under mild conditions in aqueous acetonitrile and shows a broad scope, including natural products and dru…
Microwave synthesis of core-shell structured biocompatible magnetic nanohybrids in aqueous medium
2011
In the past decade, biocompatible magnetic nanohybrids, i.e. materials consisting of an inorganic core encapsulated by a biocompatible polymeric corona, went throw various developments in biomedical applications especially in the fields of diagnosis and therapy. Numerous descriptions of their syntheses can be found in the literature (Zhang et al., 2002; Flesch et al., 2004; Fan et al., 2007; etc). These two-steps protocols often describe the use of organic or aqueous solvents, classical thermal heating, long time reaction as well as fastidious exchange and drying steps. In recent years, microwave heating has been proven to be a very original technology for nanoparticles synthesis due to its…
Umwandlung von 2-Bromäthoxycarbonyl-Schutzgruppen in 2-Phosphonioäthoxycarbonyl-Schutzgruppen für Aminosäuren1)
1976
Die Bromide 2 von 2-Phosphonioathoxycarbonylaminosauren (Peoc-Aminosauren) werden durch Umsetzung von 2-Bromathoxycarbonylaminosauren (Beoc-Aminosauren) mit tertiaren Phosphinen erhalten. Hierbei entstehen durch Reaktion mit Methyl(diphenyl)phosphin die mit der modifizierten Peoc-Gruppe geschutzten Verbindungen 2e - h in besonders guten Ausbeuten. Diese eignen sich zur Peptidsynthese nach dem Carbodiimid-Verfahren und sind besser in Wasser loslich als die entsprechenden Triphenylphosphonium-Derivate. Die Abspaltung der Me(Ph2)Peoc-Gruppe gelingt mit 0.01 N NaOH in Methanol/Wasser. Modification of 2-Brornoethoxycarbonyl Protective Groups to 2-Phosphonioethoxycarbonyl Protective Functions of …
Die polymerisation und pfropf-mischpolymerisation des acroleins unter dem einfluß von Co - 60 - gamma - strahlen. Polymere acroleine. 14. Mitteilung
1959
Die Polymerisation des Acroleins im reinen Zustand und in Losung unter dem Einflus von γ-Strahlen wird beschrieden und mit anderen Polymerisations-Methoden verglichen. Bei der Block-Polymerisation entsteht ein stark vernetztes, glasartiges Polymerisat, das in wasriger schwefliger Saure unloslich ist. In Losung polymerisiert das Acrolein viel rascher; die relative Geschwindigkeit der Polymerisation ist am grosten in wasriger Losung. Das hier erhaltene Polymere enthalt reaktionsfahige Aldehyd-Gruppen und ist loslich in schwefliger Saure. Acrolein last sich auf Polymethacrylester aufpfropfen. Sowohl oberflachliche als auch durchgehende Pfropfung vorgeformter Proben des Polymethacrylesters ist …
Structural characterization in solution of multifunctional nucleotide coordination systems
2000
The interaction in aqueous solution of the cyclophane receptors 2,6,10,13,17,21-hexaaza[22]orthocyclophane (L11) and 2,6,10,13,17,21-hexaaza[22]paracyclophane (L22) with the nucleotides ATP, ADP and AMP has been studied by pH titration and NMR. The obtained results are compared with those previously reported for the analogous meta-substituted receptor 2,6,10,13,17,21-hexaaza[22]metacyclophane (L). All the experimental data support the actuation of these cyclophane molecules as multi-point binders of nucleotides through electrostatic, hydrogen bonding and π-stacking interactions. The combined use of NMR and molecular dynamics permits us to get a rather reliable picture of the way in which th…
X-Ray Scattering Studies of Organic Monolayers on Electrolytic Solutions: Arachidic Acid on CdCl2
1992
The interaction between a charged monolayer of fatty acid molecules on the surface of a CdCl2 aqueous solution and the ions below has been investigated by means of X-ray Reflection and Grazing-Incidence Diffraction. A stoichiometric, localised layer of Cd++ ions forms an epitaxial 2×3 superstructure below the 2D-crystalline fatty acid monolayer.