Search results for "epoxide"

Water-intake and conflict-behaviour after acute and chronic treatment with rolipram, a phosphodiesterase inhibitor; interaction with chlordiazepoxide

1988

Neoclerodane Diterpenoids from Scutellaria pontica

1997

Seven novel neoclerodane diterpenoids, scupontins A-G, have been isolated from the Me2CO extract of the aerial parts of Scutellaria pontica (1-7), together with the known neoclerodanes scutalbin A and scutalpin M. Structures 1-7 were established by exhaustive NMR spectroscopic studies and chemical transformations. Scupontins A-D(1-4, respectively) and scupontins E (5)andF(6) possess unusual [(3¢S,3¢¢S)-3¢-[(3¢¢-acetoxybutyryl)oxy]butyryloxy and [(3¢S,3¢¢S,3¢¢¢S)- 3¢-[[3¢¢-[(3¢¢¢-hydroxybutyryl)oxy]butyryl]oxy]butyryl]oxy substituents, respectively, attached to the C-19 position of the neoclerodane framework. In the case of the 6R,7â-dibenzoate derivative 7 (scupontin G) its absolute config…

Chapter 2: METABOLISM OF CARCINOGENS, POSSIBILITIES FOR MODULATION

2009

: One of the structural elements which are widely occurring in very many chemical mutagens and carcinogens are aromatic and olefinic moieties. These can be transformed into epoxides by microsomal monooxygenases. Such epoxides may spontaneously react with nucleophilic centers in the cell and thereby covalently bind to DNA, RNA and protein. Such a reaction may lead to cytotoxicity, allergy, mutagenicity and/or carcinogenicity, depending on the properties of the epoxide in question. An important contributing factor is the presence of enzymes controlling the concentration of such epoxides. There are several microsomal monooxygenases which differ in activity and substrate specificity. With large…

Neoclerodane Diterpenoids from Scutellaria polyodon

1997

Nine new neoclerodane diterpenoids, scupolins A−I, have been isolated from an Me2CO extract of the aerial parts of Scutellaria polyodon (3−11), together with the known neoclerodanes jodrellin B (1) and scutecolumnin A (2). Structures 3−11 were established by spectroscopic means and by comparison with closely related compounds.

Flavonoids of honey and propolis : characterization and effects on hepatic drug-metabolizing enzymes and benzo(a)pyrene-DNA binding in rats

1996

The influence of dietary sunflower honey, propolis, and a flavonoid extract of propolis was examined on drug-metabolizing enzyme activities in rat liver and on microsome-mediated binding of benzo[a]pyrene to DNA. Characterization of flavonoids present in sunflower honey and propolis was achieved in order to assess the relative effects of different components of honey and propolis. Honey and propolis contained the same major flavonoids, pinocembrin, chrysin, galangin, and pinobanksin. The concentration of flavonoids was higher in propolis. Sunflower honey produced no significant changes on phase I and phase II enzyme activities and no modification of in vitro binding of benzo[a]pyrene to DNA…

Biodegradable hyperbranched polyether-lipids with in-chain pH-sensitive linkages

2016

Hyperbranched polyether-based lipids with cleavable acetal units were obtained via copolymerization of the epoxide inimer 1-(glycidyloxy)ethyl ethylene glycol ether (GEGE) and glycidol, using anionic ring-opening polymerization. Cholesterol-linear polyglycerol (Ch-linPG) was used as a macroinitiator, resulting in branched polyethers with an adjustable amount of acid-cleavable units. Random copolymerization led to Ch-P(GEGEx-co-Gy) copolymers, whereas sequential copolymerization provided access to Ch-P(GEGEx-b-Gy) amphiphiles. The amount of GEGE was varied between 8–49 mol% of the total amount of monomer units. In addition, hyperbranched polyethers with a single acetal unit were prepared usi…

PEG-based Multifunctional Polyethers with Highly Reactive Vinyl-Ether Side Chains for Click-Type Functionalization

2011

Introduction of highly reactive vinyl ether moieties along a poly(ethylene-glycol) (PEG) backbone has been realized by copolymerization of the novel epoxide monomer ethoxy vinyl glycidyl ether (EVGE) with ethylene oxide (EO). A series of copolymers with varying structure (block and random) as well as EVGE comonomer content (5-100%) with molecular weights in the range of 3,900-13,200 g/mol and narrow molecular weight distributions (M-w/M-n = 1.06-1.20) has been synthesized and characterized with respect to their microstructure and thermal properties. The facile transformation of the vinyl ether side chains in click type reactions was verified by two different post polymerization modification…

Aminal Protection of Epoxide Monomer Permits the Introduction of Multiple Secondary Amine Moieties at Poly(ethylene glycol).

2019

In contrast to acetal groups, aminal moieties are almost unknown in polymer chemistry. The aminal-protected isopropyl-hexahydro-pyrimidine glycidyl amine (PyGA) for the anionic ring-opening polymerization (AROP) is introduced. The monomer is prepared in a two-step synthesis and can be polymerized in a well-controlled manner under AROP conditions. Several poly(ethylene glycol) block and triblock copolymers are synthesized in a molecular weight range from 2 700 to 11 400 g mol-1 with up to 11 mol% PyGA. The molecular weight distributions are monomodal with low dispersity (Đ = Mw /Mn ) below 1.2. After the polymerization, the acid-labile hexahydro-pyrimidine rings can be conveniently cleaved i…

Vinyl ferrocenyl glycidyl ether: an unprotected orthogonal ferrocene monomer for anionic and radical polymerization

2015

The first orthogonal ferrocene monomer, vinyl ferrocenyl glycidyl ether (VfcGE), for both anionic and radical polymerization – without the need of a protection group – is presented. Anionic ring-opening copolymerization of VfcGE and ethylene oxide (EO) generates stimuli-responsive, multifunctional poly[(vinyl ferrocenyl glycidyl ether)-co-(ethylene oxide)] (P[VfcGE-co-EO]) copolymers (molecular weights of ca. 7500 g mol−1 and low molecular weight dispersities (Đ ≤ 1.14)). The amount of the equimolar ferrocenyl and vinyl groups are controlled by the comonomer ratio up to 15.4 mol% VfcGE. The pendant vinyl groups of P[VfcGE-co-EO] were post-modified with 3-mercaptopropionic acid via thiol–ene…

Multiarm Polycarbonate Star Polymers with a Hyperbranched Polyether Core from CO2 and Common Epoxides

2017

Multiarm star copolymers, consisting of hyperbranched poly(ethylene oxide) (hbPEO) or poly(butylene oxide) (hbPBO) polyether copolymers with glycerol branching points as a core, and linear aliphatic polycarbonate arms generated from carbon dioxide (CO2) and epoxide monomers, were synthesized via a “core-first” approach in two steps. First, hyperbranched polyether polyols were prepared by anionic copolymerization of ethylene oxide or 1,2-butylene oxide with 8–35% glycidol with molecular weights between 800 and 389,000 g·mol–1. Second, multiple arms were grown via immortal copolymerization of CO2 with propylene oxide or 1,2-butylene oxide using the polyether polyols as macroinitiators and (R,…