نتایج جستجو برای: racemization

تعداد نتایج: 821  

Journal: :Bulletin of the Chemical Society of Japan 1982

2016
Michael G. Friedrich Sarah E. Hancock Mark J. Raftery Roger J. W. Truscott

Multiple sclerosis (MS) is associated with breakdown of the myelin sheath that coats neurons in the central nervous system. The cause of MS is not known, although the pathogenesis involves destruction of myelin by the immune system. It was the aim of this study to examine the abundant myelin protein, myelin basic protein (MBP), to determine if there are sites of modification that may be charact...

Journal: :Dalton transactions 2013
Luis Lemus Juan Guerrero Juan Costamagna Romina Lorca Danilo H Jara Guillermo Ferraudi Allen Oliver A Graham Lappin

Complexation of copper(I) with the binucleating ligand, 1,3-bis(9-methyl-1,10-phenanthrolin-2-yl)propane, mphenpr, result in formation of helical dimers, [Cu2(mphenpr)2](2+). The resolution of the enantiomeric forms of the dimers has been carried out with Δ-[As(cat)3](-) as resolving agent and X-ray structures for two compounds, P-[Cu2(mphenpr)2](Δ-[As(cat)3])2 and P-[Cu2(mphenpr)2](Δ-[As(cat)3...

2003
P. A. LEVENE M. H. PFALTZ

In a previous communication I we reported on the action of weak and of stronger alkali on dextro-alanyl-dextro-alanine anhydride. I t was observed that the anhydride was partially racemized if it was allowed to remain in an aqueous solution containing one equivalent of sodium hydroxide for 24 hours. When the concentration of the alkali was increased tenfold, the anhydride was rapidly converted ...

Journal: :Organic Letters 2021

An efficient triphenylphosphine oxide-catalyzed amidation and esterification for the rapid synthesis of a series dipeptides, amides, esters is described. This reaction applicable to challenging couplings hindered carboxylic acids with weakly nucleophilic amines or alcohols, giving products in good yields (67–90%) without racemization. system employs highly reactive intermediate Ph3PCl2 as activ...

Journal: :Dalton transactions 2016
Dennis Pingen Çiğdem Altıntaş Max Rudolf Schaller Dieter Vogt

A Ru-based half sandwich complex used in amine and alcohol racemization reactions was found to be active in the splitting of secondary amines to primary amines using NH3. Conversions up to 80% along with very high selectivities were achieved. However, after about 80% conversion the catalyst lost activity. Similar to Shvo's catalyst, the complex might deactivate under the influence of ammonia. I...

Journal: :Organic letters 2012
Qinghui Wang Yong Wang Michio Kurosu

An Oxyma derivative, (2,2-dimethyl-1,3-dioxolan-4-yl)methyl 2-cyano-2-(hydroxyimino)acetate (2), displayed remarkable physicochemical properties as a peptide-coupling additive for peptide-forming reactions in water. Short peptides to oligopeptides could be synthesized by using 2, EDCI, and NaHCO(3) in water without measurable racemization. Significantly, a simple basic and acidic aqueous workup...

Journal: :The Journal of organic chemistry 2006
Paolo Pengo G Dan Pantos Sijbren Otto Jeremy K M Sanders

Microwave dielectric heating proved to be an efficient method for the one-pot and stepwise syntheses of symmetrical and unsymmetrical naphthalenediimide derivatives of alpha-amino acids. Acid-labile side chain protecting groups are stable under the reaction conditions; protection of the alpha-carboxylic group is not required. The stepwise condensation of different amino acids resulted in high y...

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