Search results for "Diphenyl ether"
showing 10 items of 71 documents
Trimeric Hemibastadin Congener from the Marine Sponge Ianthella basta
2012
The first naturally occurring trimeric hemibastadin congener, sesquibastadin 1 (1), and the previously reported bastadins 3, 6, 7, 11, and 16 (2-6) were isolated from the marine sponge Ianthella basta, collected in Indonesia. The structure of 1 was elucidated on the basis of 1D and 2D NMR measurements and by HRMS. Among all the isolated compounds, the linear sesquibastadin 1 (1) and bastadin 3 (2) showed the strongest inhibition rates for at least 22 protein kinases (IC(50) = 0.1-6.5 μM), while the macrocyclic bastadins (3-6) demonstrated a strong cytotoxic potential against the murine lymphoma cell line L5178Y (IC(50) = 1.5-5.3 μM).
Substituent effects of1H NMR parameters of chlorinated diphenyl ethers. A statistical approach
1994
The 1H NMR spectra of 64 polychlorinated diphenyl ethers (PCDEs) were measured and assigned. Multiple linear regression analysis was used to estimate the effects of chlorine atoms on the 1H NMR chemical shifts and coupling constants. The ‘simple sum rules’ were found to be inadequate for the prediction of 1H NMR chemical shifts of PCDEs. Therefore, corrective terms of two chlorine atoms were taken into account. The most important effects on chemical shifts were shown to be the steric interactions of two adjacent chlorine atoms and the intramolecular ring current effect observed in the ortho-proton of tri-ortho-substituted PCDEs. The substituent effects on J(HH) coupling constants were found…
Substituent effects on13C NMR parameters of chlorinated diphenyl ethers. A multiple linear regression analysis
1995
13C NMR chemical shifts and nJ(C,H) coupling constants of polychlorinated diphenyl ethers (PCDEs) were measured and analysed. The chlorine substituent effects on the chemical shifts and the coupling constants were determined by a multiple linear regression analysis. The 13C NMR chemical shifts depend on the conformational preferences in PCDEs. In addition to single substituent effects, corrective terms reflecting the conformational state of the molecule and the mutual steric interactions of two chlorine atoms had to be taken into account for the reliable prediction of the 13C chemical shifts. In contrast to chemical shifts, conformational effects play a minor role in the substituent effects…
Molecular orbital studies on brominated diphenyl ethers. Part II—reactivity and quantitative structure–activity (property) relationships
2005
Polybrominated diphenyl ethers (PBDEs) are widely used as flame retardants and are increasingly turning up in the environment. Their structural similarities to polychlorinated biphenyls and thyroid hormones suggest they may be a risk to human health. The present study examines the reactivity of brominated diphenyl ethers (BDEs) on the basis of the electronic structures as calculated by semiempirical AM1 self-consistent field molecular orbital (SCF-MO) method. Frontier orbital energies were used to elucidate the reactivity of BDEs in electrophilic, nucleophilic and photolytic reactions. From an examination of the frontier electron densities, the regioselectivity, or orientation, of metabolic…
Macrocyclic hexaureas: synthesis, conformation, and anion binding.
2009
Varied flexibility: Cyclic oligoureas are formed by using anions as templates. Linking of six xanthene and/or diphenyl ether fragments by urea groups leads to the formation of five macrocyclic compounds with a 48-membered ring with variable flexibility (see picture). Their interaction with anions shows a strong influence of acetate and chloride ions on the cyclization from four precursor molecules. Five macrocylic compounds XXXXXX, XXDXXD, XDXDXD, XDDXDD, and DDDDDD with 48-membered rings, in which six xanthene and/or diphenyl ether fragments are linked through six urea (-NH-C(O)-NH-) groups, have been synthesized. In the cyclization step, a linear diamine was allowed to react with the appr…
Effect of cropping cycles and repeated herbicide applications on the degradation of diclofop-methyl, bentazone, diuron, isoproturon and pendimethalin…
2002
A greenhouse study was conducted to investigate the ability of four crops (wheat, corn, oilseed rape and soybean) to influence the degradation of bentazone, diclofop-methyl, diuron, isoproturon and pendimethalin in soil. The present study showed that microbial biomass-carbon was significantly higher in planted soils than in bulk soil, especially with wheat and corn, after several cropping cycles. The biomass in corn and soybean planted soils was adversely affected by bentazone but recovered after three cropping cycles. In wheat-planted soils, diclofop-methyl application resulted in persistent increase of the amount of microbial biomass. Bentazone did not show accelerated degradation even af…
13C NMR spectroscopic study of diphenyl ether and 28 of its polychlorinated derivatives
1993
The 13 C NMR chemical shifts and coupling constants for diphenyl ether and 28 environmentally interesting polychlorinated diphenyl ethers were measured and analysed
On the reactions between ethyl benzoylacetate and anisidines
1975
4-Hydroxy-7-methoxy-3-[(m-methoxyphenylimino)-phenylmethyl]-2-quinolone (6) was a by-product of the condensation of ethyl benzoylacetate and m-anisidine; no corresponding products were obtained from p- and o-anisidine. From o-anisidine, 2-phenyl-8-methoxy-4-quinolone (1c) was isolated and characterized; the same reaction also gave 2-phenyl-4-o-anisidyl-1-8-methoxy-quinoline (11) and the Schiff base (14) as by-products; the crotonamide (15) also isolated, is a possible intermediate of the cyclization. The direct condensation of anisidines with ethyl benzoylacetate in diphenyl ether and the transformations of some intermediates were studied.
Method optimization to measure polybrominated diphenyl ether (PBDE) concentrations in soils of Bratislava, Slovakia.
2010
We modified an analytical method to determine polybrominated diphenyl ethers (PBDEs) in urban soils of Bratislava (Slovakia). Gel permeation chromatography (GPC) introduced as a clean-up step for soil extracts substantially reduced matrix enhancements when PBDEs were measured with gas chromatography-negative chemical ionization-mass spectrometry (GC-NCI-MS). The resulting method proved to be accurate, precise, and showed low detection limits. The sum of 15 PBDE concentrations in surface horizons of Bratislava soils ranged from 87 to 627 pg g(-1). PBDE concentrations were mostly higher in surface than deeper horizons probably because of atmospheric deposition and lack of substantial vertical…
Induction of Hsp70 by the Herbicide Oxyfluorfen (Goal) in the Egyptian Nile Fish, Oreochromis niloticus
1999
This paper deals with the expression of the biomarker hsp70 in the liver and kidney of the freshwater fish Oreochromis niloticus following exposure to the herbicide oxyfluorfen (Goal). Fishes were exposed to three concentrations, the 96-h LC50 (3 mg/L), the 96-h (1/2)LC50 (1.5 mg/L), and the 96-h (1/4)LC50 (0.75 mg/L) of oxyfluorfen for 6, 15, and 24 days, respectively, and samples were taken at three different time periods for each concentration. The livers responded to the herbicide by an induction of the expression of both the constitutive (hsp75; Mr 75 kDa) and the inducible (hsp73; Mr 73 kDa) hsp70 proteins. In kidney, the herbicide induced a time-dependent increase in the expression o…