Search results for "Electrophile"

ChemInform Abstract: Oligosaccharide Synthesis via Electrophile-Induced Activation of Glycosyl-N-allylcarbamates.

2010

Abstract Glycosyl-N-allyl carbamates, obtained by reaction of anomerically unprotected saccharides with allyl isocyanate, can be activated by an electrophile-induced cyclisation and reacted with glycosyl acceptors to form the corresponding oligosaccharides By this method the mucin core 2 trisaccharide2 has successfully been synthesized. Due to the mild glycosylation conditions even 1-O-acetyl protected glycosyl acceptors can be used. This was demonstrated in the synthesis of a 1,6-linked glucosyl trisaccharide whereby a reptitious glycosylation strategy could be applied. 1. Dedicated to the memory of Professor Akira Hasegawa.

Regulation of Human ALDH-2 Activity by Electrophiles – Implications for Organic Nitrate Induced Tolerance, Oxidative Stress and Reactive Fatty Acid M…

2010

Synthesis and properties of polymers with unusual structure

1985

This lecture summarize some recent results of our current research. The first part describes the homopolymerization and copolymerization of a monocyclic and two bicyclic unsaturated acetals. In this way polyacetals with 1,4-cis-butadiene units and cyclohexene units respectively are obtained. Secondly, the N-substitution of polyamides is described. By N-metalation and subsequent alkylation comb-like polyamides are available. Longer branches cause a side-chain crystallinity. The anionic “grafting-from” technique forms irregular branched polyamides. By termination reaction between living ends of poly(2-isopropenylnaphthalene) and suitable electrophiles new macromonomers are available. The last…

Enzymes as Regulators of Toxic Reactions by Electrophilic Metabolites

1979

Conversion of many compounds which are not electrophilically reactive as such to metabolites responsible for cytotoxic, mutagenic and/or carcinogenic effects is catalyzed by mammalian enzymes. Many reactive agents, whether metabolites or parent compounds, are also subject to inactivation by mammalian enzymes.

Role of the Well-Known Basic and Recently Discovered Acidic Glutathione S-Transferases in the Control of Genotoxic Metabolites

1991

Glutathione S-transferases (GSTs; E.C. 2. 5. 1. 18) are a family of enzymes which have increasingly attracted the interest of toxicologists, pharmacologists, biochemists and clinicians since their discovery in 1961 (1). Initially, GSTs were believed to serve as intracellular transport proteins for endogenous compounds with limited solubility in water, thus acting as an intracellular equivalent to albumin in blood plasma. In this assumed capacity of reversible binding and transport of various ligands, the corresponding protein was named ligandin (2). Following the discovery of abundant GST occurrence in most forms of aerobic life including plants, and the GST-catalysed conjugation of a wide …

Chemical Carcinogenesis by Polycyclic Aromatic Hydrocarbons

1982

The realization that for a vast number of toxic effects, not the given compound itself was responsible but rather a metabolite that was produced from the compound, brought about an enormous step forward in chemical carcinogenesis and in toxicology in general (1–15). In chemical mutagenesis and in chemical carcinogenesis very often coumpounds, which by themselves are chemically inert, will produce mutagenic and carcinogenic effects. A prime example of this is the polycyclic aromatic hydrocarbons, which consisting of condensed aromatic rings are chemically inert, yet do produce mutagenic and carcinogenic effects. During the last 10 to 20 years researchers have started to realize that this is …

Mo-Based Oxidizers as Powerful Tools for the Synthesis of Thia- and Selenaheterocycles.

2019

A highly efficient synthetic protocol for the synthesis of thia- and selenaheterocycles has been developed. By employing a MoCl5 -mediated intramolecular dehydrogenative coupling reaction, a broad variety of structural motifs was isolated in yields up to 94 %. The electrophilic key transformation is tolerated by several labile moieties like halides and tertiary alkyl groups. Due to the use of disulfide or diselenide precursors, a high atom efficiency was achieved.

Studies on the Stereoselective Selenolactonization, Hydroxy and Methoxy Selenenylation of α- and β-Hydroxy Acids and Esters. Synthesis of δ- and γ-La…

2003

Abstract The diastereoselective synthesis of hydroxy substituted γ- and δ-lactones was accomplished following two approaches. A 5- or 6-endo cyclization promoted by electrophilic selenium reagents of α- or β-hydroxy acids and a 5- or 6-exo cyclization of hydroxy esters obtained through a diastereoselective hydroxy selenenylation reaction of α- or β-hydroxy esters. Moreover, the diastereoselective methoxy selenenylation of the above compounds was investigated showing a case in which the compound that was unreactive in the hydroxy selenenylation conditions gave, in the methoxy selenenylation conditions, the deprotected diol. The usefulness of the methoxy selenenylation procedure was proven by…

ChemInform Abstract: Multi-Arm 1,2,3-Thiadiazole Systems.

2010

Benzene derivatives 2a–c with 6, 4, and 3 side chains bearing terminal 1,2,3-thiadiazole rings, respectively, have been prepared. Alkaline cleavage of 2a–c led to the corresponding alkynethiolates 6a–c, which were trapped by electrophiles such as benzyl bromide or iodomethane. The method provides an alternative to the thermal or photochemical cleavage of 1,2,3-thiadiazoles to thioketenes, which react further with nucleophiles.

Synthesis of 1,3-Oxazolidines and 1,3-Dioxolanes by Reaction of (2R,3R)-3-Methylamino-3-phenyl-1,2-propanediol with Electrophiles.

2004

Abstract The chemoselective reaction of (2R, 3R)-3-methylamino-3-phenyl-1,2-propanediol 1 with dimethoxypropane and dichloromethane under different conditions are reported as useful preparative procedures, for the synthesis 1,3-oxazolidines and 1,3-dioxolanes.