Search results for "epoxide"
showing 10 items of 251 documents
Ferrocenyl Glycidyl Ether: A Versatile Ferrocene Monomer for Copolymerization with Ethylene Oxide to Water-Soluble, Thermoresponsive Copolymers
2013
The first ferrocene-containing epoxide monomer, ferrocenyl glycidyl ether (fcGE), is introduced. The monomer has been copolymerized with ethylene oxide (EO). This leads to electroactive, water-soluble, and thermoresponsive poly(ethylene glycol) (PEG) derived copolyethers. Anionic homo- and copolymerization of fcGE with EO was possible. Molecular weights could be varied from 2000 to 10 000 g mol–1, resulting in polymers with narrow molecular weight distribution (Mw/Mn = 1.07–1.20). The ferrocene (fc) content was varied from 3 to 30 mol %, obtaining water-soluble materials up to 10 mol % incorporation of the apolar ferrocenyl comonomer. Despite the steric bulk of fcGE, random copolymers were …
Poly(ethylene glycol) with Multiple Aldehyde Functionalities Opens up a Rich and Versatile Post-Polymerization Chemistry
2019
Two novel epoxide monomers 3,3-dimethoxy-propanyl glycidyl ether (DMPGE) and 3,3-dimethoxy-2,2-dimethylpropanyl glycidyl ether (DDPGE) were developed for the introduction of multiple aldehyde functionalities into the poly(ethylene glycol) (PEG) backbone. The acetal protecting group for the aldehyde functionality is stable against the harsh, basic conditions of the anionic ring-opening polymerization. Both monomers could be homopolymerized as well as copolymerized randomly with ethylene oxide (EO) in a controlled fashion. Copolymers with molecular weights (Mn) in the range of 4500–20100 g/mol and low dispersity (Mw/Mn) between 1.06 and 1.14 were obtained. The polymers were characterized by s…
Hyperbranched Polyglycerols with Elevated Molecular Weights: A Facile Two-Step Synthesis Protocol Based on Polyglycerol Macroinitiators
2009
Hyperbranched polyglycerol (PG) is established as one of the few hyperbranched polymers that offer the possibility to control molecular weight up to Mn = 6000 g/mol. This work introduces a facile 2-step strategy that relies on the use of a low molecular weight PG (Mn = 500 and 1000 g/mol) as a macroinitiator for the slow addition of glycidol, permitting to overcome previous limitations concerning molecular weights and molecular weight control. A systematic investigation of the effect of the degree of deprotonation on the control of the polymerization reaction has been carried out. A series of hyperbranched PGs with molecular weights up to Mn = 24000 g/mol has been obtained under fully contr…
Functional PEG-based polymers with reactive groups via anionic ROP of tailor-made epoxides
2012
In this review article functional epoxide monomers that are suitable for controlled ring-opening polymerization (ROP) are discussed. Functional epoxides possess reactive groups, which either are directly accessible or carry suitable protective groups that can be removed in a facile one-step reaction after polymerization. The methods used to obtain linear, functional aliphatic polyethers rely on living polymerization techniques for the synthesis of well-defined structures. Materials properties, such as thermo-responsive behavior in combination with different functional groups that can be addressed selectively, render these novel materials interesting for a variety of applications.
A road less traveled to functional polymers: epoxide termination in living carbanionic polymer synthesis.
2010
Functional polymers possess tremendous potential both in academia and in industry. In particular, oxiranes offer manifold possibilities for the introduction of single hydroxyl or multiple orthogonal functionalities in carbanionic polymerization. Here, we present a brief overview of the fascinating possibilities arising from the employment of common as well as individually designed epoxide derivatives for the synthesis of end-functional polymers. Continuous flow techniques can be utilized for the rapid generation and screening of precisely defined hydroxyl-modified polymers. The utilization of functionalized polymers as precursors for the formation of complex macromolecular architectures (e.…
Multihydroxyl-Functional Polystyrenes in Continuous Flow
2010
We describe the synthesis of end-functionalized polystyrenes by living anionic polymerization in a microstructured reactor via termination by acetal-protected functional epoxides. Initiation of styrene polymerization by alkyllithium takes place in a micromixing device with efficient heat and mass transfer properties. A newly developed continuous polymerization−termination sequence enabled quantitative functionalization of the living carbanions by nucleophilic displacement with different, specifically designed glycidyl ethers (ethoxy ethyl glycidyl ether (EEGE), 1,2-isopropylidene glyceryl glycidyl ether (IGG), and trans-2-phenyl-1,3-dioxane glycidyl ether (PDGE)). Upon acidic hydrolysis the…
Catalytic triad of microsomal epoxide hydrolase: replacement of Glu404 with Asp leads to a strongly increased turnover rate
1998
Microsomal epoxide hydrolase (mEH) belongs to the superfamily of α/β-hydrolase fold enzymes. A catalytic triad in the active centre of the enzyme hydrolyses the substrate molecules in a two-step reaction via the intermediate formation of an enzyme-substrate ester. Here we show that the mEH catalytic triad is composed of Asp226, Glu404 and His431. Replacing either of these residues with non-functional amino acids results in a complete loss of activity of the enzyme recombinantly expressed in Saccharomyces cerevisiae. For Glu404 and His431 mutants, their structural integrity was demonstrated by their retained ability to form the substrate ester intermediate, indicating that the lack of enzymi…
Transformation of artemisin into artapshin and 8α-hydroxy-11β,13-dihydrobalchanin
1987
Abstract Partial syntheses of the sesquiterpene lactones artapshin ( 1 ) and 8α-hydroxy-11β, 13-dihydrobalchanin ( 2 ) from artemisin ( 3 ) are described.
Enzymic Control of Reactive Metabolites from Aromatic Carcinogens
1980
Mutation and transformation in C3H 10T 1/2 mouse fibroblasts were coordinately induced by 4-nitroquinoline N-oxide and identically modulated by caffeine strongly suggesting mutation as one necessary step in the sequence of events ultimately leading to transformation. The enzymic control of reactive metabolites derived from aromatic carcinogens was then investigated using bacterial mutagenicity as an analytical tool. It was shown that the correlation of bacterial mutagenicity with carcinogenicity of BP and four major metabolites was substantially better when these compounds were activated by intact hepatocytes as compared to commonly used broken cell preparations which suggests that the rela…
Polar [3 + 2] cycloaddition of ketones with electrophilically activated carbonyl ylides. Synthesis of spirocyclic dioxolane indolinones
2008
International audience; The [3 + 2] cycloaddition reaction between carbonyl ylides generated from epoxides and ketones (ethyl pyruvate, ethyl phenylglyoxylate, isatin, N-methylisatin and 5-chloroisatin) to give substituted dioxolanes and spirocyclic dioxolane indolinones was investigated. The effect of microwave irradiation on the outcome of the reaction was studied. The thermal reaction between 2,2-dicyano-3-phenyloxirane and N-methylisatin was theoretically studied using DFT methods. This reaction is a domino process that comprises two steps. The first is the thermal ring opening of the epoxide to yield a carbonyl ylide intermediate, whereas the second step is a polar [3 + 2] cycloadditio…