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Ferenc Fulop - One of the best experts on this subject based on the ideXlab platform.
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functionalized dialdehydes as promising scaffolds for access to heterocycles and β amino acids synthesis of fluorinated piperidine and azepane derivatives
Synthesis, 2017Co-Authors: Renata Anita Abrahami, Ferenc Fulop, Lorand Kiss, Santos FusteroAbstract:Functionalized dialdehydes are considered important substrates that can be transformed into various substituted heterocyclic, alicyclic, and polysubstituted compounds. Here, we report a robust stereocontrolled procedure for the synthesis of novel functionalized trifluoromethyl-containing piperidine and azepane derivatives, based on oxidative ring cleavage of the C=C bond of diversely substituted cycloalkenes, followed by reductive ring closure of the diformyl intermediates in the presence of fluorine-containing amines.
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new endomorphin analogues containing alicyclic β amino acids influence on bioactive conformation and pharmacological profile
Journal of Medicinal Chemistry, 2008Co-Authors: Attila Keresztes, Ferenc Fulop, Maria Szucs, Attila Borics, Katalin E Kover, Eniko Forro, Csaba Tomboly, Antal Peter, Annamaria Pahi, Gabriella FabianAbstract:Endomorphins were subjected to a number of structural modifications in a search for their bioactive conformations. The alicyclic β-amino acids cis-(1S,2R)ACPC/ACHC, cis-(1R,2S)ACPC/ACHC, trans-(1S,2S)ACPC/ACHC, and trans-(1R,2R)ACPC/ACHC were introduced into endomorphins to examine the conformational effects on the bioactivity. Use of a combination of receptor binding techniques, 1H NMR, and molecular modeling allowed the conclusion that Pro2 substitution by these residues causes changes in structure, proteolytic stability, and pharmacological activity. It seems that the size of the alicyclic β-amino acids does not have marked influence on the receptor binding affinities and/or selectivities. Among the new analogues, the cis-(1S,2R)ACPC2 and cis-(1S,2R)ACHC2-containing derivatives displayed the highest binding potencies and efficacies in receptor binding and ligand-stimulated [35S]GTPγS functional experiments. Molecular dynamic simulations and 1H NMR studies of the cis-ACPC/ACHC-containing analogues revea...
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liquid phase combinatorial synthesis of alicyclic beta lactams via ugi four component reaction
Organic Letters, 2002Co-Authors: Szilvia Gedey, Johan Van Der Eycken, Ferenc FulopAbstract:Alicyclic β-lactams were successfully synthesized via a parallel liquid-phase Ugi four-center three-component reaction (U-4C-3CR), starting from alicyclic β-amino acids such as cis-2-aminocyclohexa...
Steven J Rowland - One of the best experts on this subject based on the ideXlab platform.
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acute toxicity of aromatic and non aromatic fractions of naphthenic acids extracted from oil sands process affected water to larval zebrafish
Chemosphere, 2013Co-Authors: Alan G Scarlett, Charles E West, Richard A Frank, Helena C Reinardy, Theodore B Henry, L M Hewitt, Steven J RowlandAbstract:The toxicity of oil sands process-affected water (OSPW) has regularly been attributed to naphthenic acids, which exist in complex mixtures. If on remediation treatment (e.g., ozonation) or on entering the environment, the mixtures of these acids all behave in the same way, then they can be studied as a whole. If, however, some acids are resistant to change, whilst others are not, or are less resistant, it is important to establish which sub-classes of acids are the most toxic. In the present study we therefore assayed the acute toxicity to larval fish, of a whole acidified OSPW extract and an esterifiable naphthenic acids fraction, de-esterified with alkali: both fractions were toxic (LC50 ∼5–8 mg L−1). We then fractionated the acids by argentation solid phase extraction of the esters and examined the acute toxicity of two fractions: a de-esterified alicyclic acids fraction, which contained, for example, adamantane and diamantane carboxylic acids, and an aromatic acids fraction. The alicyclic acids were toxic (LC50 13 mg L−1) but the higher molecular weight aromatic acids fraction was somewhat more toxic, at least on a weight per volume basis (LC50 8 mg L−1; P < 0.05) (for comparison, the monoaromatic dehydroabietic acid had a LC50 of ∼1 mg L−1). These results show how toxic naphthenic acids of OSPW are to these larval fish and that on a weight per volume basis, the aromatic acids are at least as toxic as the ‘classical’ alicyclic acids. The environmental fates and other toxic effects, if any, of the fractions remain to be established.
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isolation and estimation of the aromatic naphthenic acid content of an oil sands process affected water extract
Journal of Chromatography A, 2012Co-Authors: David Jones, Charles E West, Alan G Scarlett, Richard A Frank, Steven J RowlandAbstract:Abstract The naphthenic acids of oil sands process-affected water (OSPW) are said to be important toxicants. The major acids are stated to have alicyclic structures and recently, numerous of these have been identified, but some evidence suggests ‘aromatic’ acids are also present. The proportions of such acids have not been reported because they exist in so-called supercomplex mixtures with the alicyclic species. Their contribution to the toxicity of OSPW, if any, is therefore unknown. Here we report the use of multidimensional comprehensive gas chromatography–mass spectrometry (GC × GC–MS) with polar first dimension and non-polar second dimension GC columns and argentation solid phase extraction, to separate methyl esters of the acids of an OSPW supercomplex, into distinct fractions. A major fraction (ca 70%) was shown to contain acids (methyl esters) previously identified as alicyclic species. Authentic adamantane acid methyl esters were shown to chromatograph in this fraction. This fraction was isolated by argentation solid phase extraction (SPE) by elution with hexane. GC–MS and GC × GC–MS confirmed this to be the major fraction in the original supercomplex containing alicyclic acids (methyl esters). A second fraction shown to contain monoaromatic acids (methyl esters) by GC × GC–MS was unexpectedly abundant (ca 30% relative to the acyclic acids). The naphtheno-aromatic dehydroabietic acid was confirmed by co-injection with an authentic compound and several acids previously tentatively identified as naphtheno-monoaromatics were present. This fraction was isolated by argentation SPE by elution with more polar 5% diethyl ether in hexane. GC–MS and GC × GC–MS confirmed that the fraction represented a significant proportion of the original supercomplex. A further fraction, eluting from the argentation SPE column with more 5% diethyl ether in hexane in the same retention volume as authentic methyl naphthoate, contained, in addition to some of the second fraction, a third, much more minor complex. This had somewhat similar GC × GC retention characteristics to that of methyl naphthoate and the methyl ester of authentic fluorene-9-carboxylic acid. Spectra are reported. Non-alicyclic, mono- and possibly diaromatic acids are a much more quantitatively significant proportion of OSPW than previously realised. The individual acids need to be better identified and the toxicity of these and other SPE fractions studied in order to assess any possible environmental effects of OSPW.
Jose G Santos - One of the best experts on this subject based on the ideXlab platform.
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concerted mechanisms of the reactions of 2 4 6 trinitrophenyl methyl carbonate and 2 4 6 trinitrophenyl acetate with secondary alicyclic amines
Journal of Organic Chemistry, 2001Co-Authors: Enrique A Castro, Maria Cubillos, Jose G SantosAbstract:The reactions of secondary alicyclic amines with 2,4,6-trinitrophenyl methyl carbonate (TNPMC) and 2,4,6-trinitrophenyl acetate (TNPA) are subjected to a kinetic study in aqueous solution, 25.0 degrees C, ionic strength 0.2 (KCl). The reactions are studied by following spectrophotometrically (360 nm) the release of the 2,4,6-trinitrophenoxide anion. Under amine excess, pseudo-first-order rate coefficients (k(obsd)) are found. Plots of k(obsd) vs [amine] are linear, with the slope (kN) independent of pH. The Bronsted-type plots (log k(N) vs pK(a) of the conjugate acid of the amines) are linear, with slopes beta = 0.41 and beta = 0.36 for the reactions of TNPA and TNPMC, respectively. The predicted breaks of the Bronsted plots for stepwise mechanisms are pK(a)0 = 6.8 and 7.3, respectively. The lack of Bronsted breaks for these reactions and the values of the Bronsted slopes are consistent with concerted mechanisms. By comparison of the reactions under investigation among them and with similar aminolysis and pyridinolysis, the following conclusions can be drawn: (i) Secondary alicyclic amines react with TNPA and TNPMC by concerted mechanisms. (ii) TNPA is more reactive toward these amines than TNPMC due to the greater electron release of MeO from the latter substrate. (iii) The change of 2,4-dinitrophenoxy to 2,4,6-trinitrophenoxy in the zwitterionic tetrahedral intermediate (T+/-) formed in the reactions of the title amines with 2,4-dinitrophenyl acetate greatly destabilizes T+/-. (iv) Secondary alicyclic amines destabilize T+/- relative to pyridines. (v) The intermediate T+/- formed in the reactions of the title amines with S-(2,4,6-trinitrophenyl) acetate is greatly destabilized by substitution of S-(2,4,6-trinitrophenyl) by O-(2,4,6-trinitrophenyl) as the leaving group.
Joseph M Suflita - One of the best experts on this subject based on the ideXlab platform.
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anaerobic biodegradation of alicyclic constituents of gasoline and natural gas condensate by bacteria from an anoxic aquifer
FEMS Microbiology Ecology, 2004Co-Authors: Todd G Townsend, Roger C. Prince, Joseph M SuflitaAbstract:The biodegradation of alicyclic compounds was studied under methanogenic and sulfate-reducing conditions in samples from a gas condensate-contaminated aquifer amended with whole gasoline. Aquifer microorganisms exhibited previously unrecognized anaerobic alicyclic hydrocarbon metabolism of a broad range of substrates at relatively rapid rates. Simple unsubstituted, methyl-substituted, and ethyl-substituted cyclopentenes, cyclopentanes and cyclohexanes were consumed without a substantial lag in the presence of sulfate, but rather less effectively under methanogenic conditions. Dimethyl-substituted cyclopentanes and cyclohexanes were biodegraded only in the presence of sulfate and a limited isomer-specific biodegradative pattern was seen. These results extend the range of hydrocarbons known to be susceptible to anaerobic decay and help indicate the patterns of alicyclic hydrocarbon biodegradation that can be expected
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biodegradation of an alicyclic hydrocarbon by a sulfate reducing enrichment from a gas condensate contaminated aquifer
Applied and Environmental Microbiology, 2003Co-Authors: Luis Rioshernandez, Lisa M Gieg, Joseph M SuflitaAbstract:We used ethylcyclopentane (ECP) as a model alicyclic hydrocarbon and investigated its metabolism by a sulfate-reducing bacterial enrichment obtained from a gas condensate-contaminated aquifer. The enrichment coupled the consumption of ECP with the stoichiometrically expected amount of sulfate reduced. During ECP biodegradation, we observed the transient accumulation of metabolite peaks by gas chromatography-mass spectrometry, three of which had identical mass spectrometry profiles. Mass-spectral similarities to analogous authentic standards allowed us to identify these metabolites as ethylcyclopentylsuccinic acids, ethylcyclopentylpropionic acid, ethylcyclopentylcarboxylic acid, and ethylsuccinic acid. Based on these findings, we propose a pathway for the degradation of this alicyclic hydrocarbon. Furthermore, a putative metabolite similar to ethylcyclopentylsuccinic acid was also found in samples of contaminated groundwater from the aquifer. However, no such finding was evident for samples collected from wells located upgradient of the gas condensate spill. Microbial community analysis of the ECP-degrading enrichment by denaturing gradient gel electrophoresis revealed the presence of at least three different organisms using universal eubacterial primers targeting 550 bp of the 16S rRNA gene. Based on sequence analysis, these organisms are phylogenetically related to the genera Syntrophobacter and Desulfotomaculum as well as a member of the Cytophaga-Flexibacter-Bacteroides group. The evidence suggests that alicyclic hydrocarbons such as ECP can be anaerobically activated by the addition to the double bond of fumarate to form alkylsuccinate derivatives under sulfate-reducing conditions and that the reaction occurs in the laboratory and in hydrocarbon-impacted environments.
Ben Zhong Tang - One of the best experts on this subject based on the ideXlab platform.
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changing the behavior of chromophores from aggregation caused quenching to aggregation induced emission development of highly efficient light emitters in the solid state
Advanced Materials, 2010Co-Authors: Wang Zhang Yuan, Shuming Chen, Jacky Wing Yip Lam, Zhiming Wang, Yang Liu, Hoi Sing Kwok, Ben Zhong TangAbstract:The development of efficient luminescent materials in the solid state is of both scientific and technological interest. An obstacle to their development is the notorious aggregation-caused quenching (ACQ) effect: the emission of conventional luminophores is often weakened in the solid state in comparison to in solution, due to aggregate formation in the condensed phase. [1‐3] The ACQ problem must be properly tackled, because the luminophores are commonly used as solid films in their practical applications. Various chemical, physical, and engineering approaches have been taken to frustrate luminophore aggregation. [4,5] The attachment of bulky Alicyclics, encapsulation by amphiphilic surfactants, and blending with transparent polymers are widely used methods to impede aggregate formation. These processes, however, are often accompanied by severe side effects. The steric effects of bulky Alicyclics, for example, can twist the conformations of the chromophoric units and jeopardize the electronic conjugation in the luminophores, and the electronic effects of the saturated surfactants and nonconjugated polymers can dilute the luminophore density and obstruct the charge transport in electroluminescence (EL) devices. The current approaches to the problem are thus far from ideal, because the ACQ effect is alleviated at the expense of other useful properties of the luminophores. A win‐win strategy would be the elimination of the ACQ effect without sacrificing other functional properties of the luminophores. In the work reported here, we have developed such a new approach. Triphenylamine (TPA) and its derivatives are luminescent when dissolved in good solvents [6] for them but become less emissive when aggregated in the solid state, and are therefore typical ACQ luminophores. [7] For