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Benzo
Kinds of Benzo Selected AbstractsDETERMINATION OF BENZO(a)PYRENE IN VEGETABLE OILS BY HIGH PERFORMANCE LIQUID CHROMATOGRAPHYJOURNAL OF FOOD QUALITY, Issue 3 2007EKERO, LU GÜLTEN ABSTRACT Analysis of 40 oil samples showed that 38 of them were contaminated with benzo(a)pyrene (BaP). Thirty of the 38 BaP-contaminated edible oil samples did not have any label of a brand name. BaP content for the 38 contaminated edible oil samples were in the range of 1.22,74.89 ppb. Sixteen of the contaminated oil samples had BaP content of more than 10 ppb, which is the maximum tolerable limit for the Turkish Food Codex Regulation. BaP contents of samples for each type of oil were significantly different (P < 0.05) from each other. [source] DNA adduct kinetics in reproductive tissues of DNA repair proficient and deficient male mice after oral exposure to benzo(a)pyreneENVIRONMENTAL AND MOLECULAR MUTAGENESIS, Issue 2 2010Nicole Verhofstad Abstract Benzo(a)pyrene (B[a]P) can induce somatic mutations, whereas its potential to induce germ cell mutations is unclear. There is circumstantial evidence that paternal exposure to B[a]P can result in germ cell mutations. Since DNA adducts are thought to be a prerequisite for B[a]P induced mutations, we studied DNA adduct kinetics by 32P-postlabeling in sperm, testes and lung tissues of male mice after a single exposure to B[a]P (13 mg/kg bw, by gavage). To investigate DNA adduct formation at different stages of spermatogenesis, mice were sacrificed at Day 1, 4, 7, 10, 14, 21, 32, and 42 after exposure. In addition, DNA repair deficient (Xpc,/,) mice were used to study the contribution of nucleotide excision repair in DNA damage removal. DNA adducts were detectable with highest levels in lung followed by sperm and testis. Maximum adduct levels in the lung and testis were observed at Day 1 after exposure, while adduct levels in sperm reached maximum levels at ,1 week after exposure. Lung tissue and testis of Xpc,/, mice contained significantly higher DNA adduct levels compared to wild type (Wt) mice over the entire 42 day observation period (P < 0.05). Differences in adduct half-life between Xpc,/, and Wt mice were only observed in testis. In sperm, DNA adduct levels were significantly higher in Xpc,/, mice than in Wt mice only at Day 42 after exposure (P = 0.01). These results indicate that spermatogonia and testes are susceptible for the induction of DNA damage and rely on nucleotide excision repair for maintaining their genetic integrity. Environ. Mol. Mutagen. 2010. © 2009 Wiley-Liss, Inc. [source] Light-dependent mutagenesis by benzo[a]pyrene is mediated via oxidative DNA damageENVIRONMENTAL AND MOLECULAR MUTAGENESIS, Issue 3 2005Su-Ryang Kim Abstract Benzo[a]pyrene (B[a]P) is an environmental carcinogenic polycyclic aromatic hydrocarbon (PAH). Mammalian enzymes such as cytochrome P-450s and epoxide hydrase convert B[a]P to reactive metabolites that can covalently bind to DNA. However, some carcinogenic compounds that normally require metabolic activation can also be directly photoactivated to mutagens. To examine whether B[a]P is directly mutagenic in the presence of light, we exposed Salmonella typhimurium strains with different DNA repair capacities to B[a]P and white fluorescent light at wavelengths of 370,750 nm. B[a]P plus light significantly enhanced the number of His+ revertants. Mutagenesis was completely light-dependent and required no exogenous metabolic activation. The order of mutability of strains with different DNA repair capacities was strain YG3001 (uvrB, mutMST) , strain TA1535 (uvrB) > strain YG3002 (mutMST) > strain TA1975. The uvrB gene product is involved in the excision repair of bulky DNA adducts, and the mutMST gene encodes 8-oxoguanine (8-oxoG) DNA glycosylase, which removes 8-oxoG from DNA. Introduction of a plasmid carrying the mOgg1 gene that is the mouse counterpart of mutMST substantially reduced the light-mediated mutagenicity of B[a]P in strain YG3001. B[a]P plus light induced predominantly G:C , T:A and G:C , C:G transversions. We propose that B[a]P can directly induce bulky DNA adducts if light is present, and that the DNA adducts induce oxidative DNA damage, such as 8-oxoG, when exposed to light. These findings have implications for the photocarcinogenicity of PAHs. Environ. Mol. Mutagen., 2005. © 2005 Wiley-Liss, Inc. [source] Benzo[a]pyrene bioavailability from pristine soil and contaminated sediment assessed using two in vitro modelsENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 3 2007Luba Vasiluk Abstract A major route of exposure to hydrophobic organic contaminants (HOCs), such as benzo[a]pyrene (BaP), is ingestion. Matrix-bound HOCs may become bioavailable after mobilization by the gastrointestinal fluids followed by sorption to the intestinal epithelium. The purpose of this research was to measure the bioavailability of [14C]-BaP bound to pristine soils or field-contaminated sediment using an in vitro model of gastrointestinal digestion followed by sorption to human enterocytes (Caco-2 cells) or to a surrogate membrane, ethylene vinyl acetate (EVA) thin film. Although Caco-2 cells had a twofold higher lipid-normalized fugacity capacity than EVA, [14C]-BaP uptake by Caco-2 lipids and EVA thin film demonstrated a linear relationship within the range of BaP concentrations tested. These results suggest that EVA thin film is a good membrane surrogate for passive uptake of BaP. The in vitro system provided enough sensitivity to detect matrix effects on bioavailability; after 5 h, significantly lower concentrations of [14C]-BaP were sorbed into Caco-2 cells from soil containing a higher percentage of organic matter compared to soil with a lower percentage of organic matter. The [14C]-BaP desorption rate from Caco-2 lipids consistently was twofold higher than from EVA thin film for all matrices tested. The more rapid kinetics observed with Caco-2 cells probably were due to the greater surface area available for absorption/desorption in the cells. After 5 h, the uptake of BaP into Caco-2 lipid was similar in live and metabolically inert Caco-2 cells, suggesting that the primary route of BaP uptake is by passive diffusion. Moreover, the driving force for uptake is the fugacity gradient that exists between the gastrointestinal fluid and the membrane. [source] 2-Substituted Benzo[b]furans from (E)-1,2-Dichlorovinyl Ethers and Organoboron Reagents: Scope and Mechanistic Investigations into the One-Pot Suzuki Coupling/Direct Arylation,EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 29 2010Laina M. Geary Abstract 2-Substituted benzo[b]furans can easily be assembled from simple phenols, boronic acids or other organoboron reagents, and trichloroethylene. The overall process requires only two synthetic steps, with the key step being a one-pot sequential Suzuki cross-coupling/direct arylation reaction. The method tolerates many useful functional groups and does not require the installation of any other activating functionality. The modular nature of the process permits the rapid synthesis of many analogues using essentially the same chemistry, of particular value in drug development. Results of kinetic isotope effect studies and investigations into the regioselectivity of the process indicate that the direct arylation step most likely does not involve an electrophilic palladation. The most likely mechanism lies somewhere on the continuum between a C,H bond metathesis and an assisted palladation or concerted metallation-deprotonation pathway. [source] Highly Efficient Fluorine-Promoted Intramolecular Condensation of Benzo[c]phenanthrene: A New Prospective on Direct Fullerene SynthesisEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 36 2009Konstantin Yu. Abstract Various functional groups have been tested as alternative promoters of the intramolecular condensation of benzo[c]phenanthrene under flash vacuum pyrolysis conditions. Methyl and fluorine functionalization were found to be promising approaches. Unexpectedly high selectivity was observed in the cyclization of fluorinated benzo[c]phenanthrenes. The mechanism for the condensation reaction and the advantages of fluorine as a promoter for the rational synthesis of fullerenes are discussed.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] An Efficient Method for the Synthesis of Benzo[f]quinoline and Benzo[a]phenanthridine Derivatives Catalyzed by Iodine by a Three-Component Reaction of Arenecarbaldehyde, Naphthalen-2-amine, and Cyclic KetoneEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 20 2008Xiang-Shan Wang Abstract A mild, efficient, and general method for the synthesis of benzo[f]quinoline and benzo[a]phenanthridine derivatives by a three-component reaction of arenecarbaldehyde, naphthalen-2-amine, and cyclic ketone using iodine as catalyst is described. A possible reaction mechanism for the formation of the product is proposed based on further experimental results.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source] Selective Palladium-Catalysed ipso Arylation of ,,,-Disubstituted Benzo[b]thien-2-ylmethanols with Aryl Bromides using PCy3 as LigandEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 8 2007A. Beatrix Bíró Abstract ,,,-Diphenylbenzo[b]thien-2-ylmethanol was treated with a series of aryl bromides in the presence of palladium(II) acetate and tricyclohexylphosphane to give the appropriate 2-aryl-benzo[b]thiophenes in good to excellent yield with concomitant formation of benzophenone. The reaction wassuccessfully extended to ,,,-diphenylbenzo[b]thien-3-ylmethanol, although in certain cases the transformation was biased by concurrent ortho arylation. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] Palladium-Catalysed Amination of Electron-Deficient or Relatively Electron-Rich Benzo[b]thienyl Bromides , Preliminary Studies of Antimicrobial Activity and SARsEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 17 2004Maria-João R. P. Queiroz Abstract Several diarylamines in the benzo[b]thiophene series were prepared in good to high yields by palladium-catalysed amination of ethyl 3-bromobenzo[b]thiophene-2-carboxylate with anilines and 5-aminoindole in the presence of Pd(OAc)2, BINAP and Cs2CO3 in toluene. The presence of the ester group at the 2-position of the benzo[b]thiophene moiety increases the yields and lowers the heating times relative to the reactions performed with 3-bromobenzo[b]thiophene. When aminopyridines were used instead of anilines, the ligand and the solvent need to be changed to XANTHPHOS and dioxane in the amination reaction. With 2-aminopyridine a one-pot C,N coupling and intramolecular cyclization involving the nitrogen atom of the pyridine ring occurred, with loss of ethanol, giving an interesting fluorescent tetracyclic heteroaromatic compound. The antimicrobial activity, the minimal inhibitory concentrations (MICs) and the structure-activity relationships (SARs) were evaluated. A selectivity with low MICs was observed against Bacillus Cereus, and good results were also obtained against Candida albicans. The acids obtained by hydrolysis of the ester group, as non-proteinogenic ,,,-unsaturated ,-amino acids, can be incorporated into peptide chains to induce conformational constraints. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source] Synthesis of Novel Amino Acids and Dehydroamino Acids Containing the Benzo[b]thiophene MoietyEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 8 2003Ana S. Abreu Abstract Several novel amino acids and dehydroamino acids containing the benzo[b]thiophene moiety were prepared by Michael addition or sequential Michael addition and palladium-catalyzed C,C or C,N cross couplings. The substrates for Michael addition were the methyl esters of N,N -bis(tert -butyloxycarbonyl)dehydroalanine [Boc2,,Ala,OMe] and N -(4-toluenesulfonyl)- N -(tert -butyloxycarbonyl)dehydroalanine [Tos,,Ala(N -Boc),OMe], and the nucleophiles were aromatic thiols and 3-iodobenzylamine. The addition of mercaptobenzo[b]thiophenes directly to Tos,,Ala(N -Boc),OMe gave stereoselectively, in good yields, the E -isomer of the corresponding dehydrocysteine. When thiophenols and 3-iodobenzylamine were used as nucleophiles the presence of an additional function (halogen or amine) allowed a subsequent palladium-catalyzed cross-coupling reaction with functionalized benzo[b]thiophenes (boronic acids, a halogen or an amine). Using this strategy, several racemic amino acid and dehydroamino acid derivatives, which are linked to the benzo[b]thiophene moiety by an aromatic spacer, were obtained in good yields. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003) [source] Correction of a Reported Xanthone Synthesis: The Preparation of a Benzo[c]coumarinHELVETICA CHIMICA ACTA, Issue 3 2010Michael Abstract Reinvestigation of a reported synthesis of 5,8-dihydroxy-1,3-dimethoxyxanthone from the reaction of 3,5-dimethoxyphenol with 2-(methoxycarbonyl)-1,4-benzoquinone resulted in the identification of the product as the isomer of benzo[c]coumarin, i.e., 7,10-dihydroxy-1,3-dimethoxy-6H -dibenzo[b,d]pyran-6-one, established by X-ray crystallography. This requires the revision of the structures of the derivatives that were reported. [source] Benzo[a]heptalenes from Heptaleno[1,2- c]furans.HELVETICA CHIMICA ACTA, Issue 4 2007Abstract It is shown in this ,Part 2' that heptaleno[1,2- c]furans 1 react thermally in a Diels,Alder -type [4+2] cycloaddition at the furan ring with vinylene carbonate (VC), phenylsulfonylallene (PSA), , -(acetyloxy)acrylonitrile (AAN), and (1Z)-1,2-bis(phenylsulfonyl)ethene (ZSE) to yield the corresponding 1,4-epoxybenzo[d]heptalenes (cf. Schemes,1, 5, 6, and 8). The thermal reaction of 1a and 1b with VC at 130° and 150°, respectively, leads mainly to the 2,3- endo -cyclocarbonates 2,3- endo - 2a and - 2b and in minor amounts to the 2,3- exo -cyclocarbonates 2,3- exo - 2a and - 2b. In some cases, the (P*)- and (M*)-configured epimers were isolated and characterized (Scheme,1). Base-catalyzed cleavage of 2,3- endo - 2 gave the corresponding 2,3-diols 3, which were further transformed via reductive cleavage of their dimesylates 4 into the benzo[a]heptalenes 5a and 5b, respectively (Scheme,2). In another reaction sequence, the 2,3-diols 3 were converted into their cyclic carbonothioates 6, which on treatment with (EtO)3P gave the deoxygenated 1,4-dihydro-1,4-epoxybenzo[d]heptalenes 7. These were rearranged by acid catalysis into the benzo[a]heptalen-4-ols 8a and 8b, respectively (Scheme,2). Cyclocarbonate 2,3- endo - 2b reacted with lithium diisopropylamide (LDA) at ,70° under regioselective ring opening to the 3-hydroxy-substituted benzo[d]heptalen-2-yl carbamate 2,3- endo - 9b (Scheme,3). The latter was O -methylated to 2,3- endo -(P*)- 10b. The further way, to get finally the benzo[a]heptalene 13b with MeO groups in 1,2,3-position, could not be realized due to the fact that we found no way to cleave the carbamate group of 2,3- endo -(P*)- 10b without touching its 1,4-epoxy bridge (Scheme,3). The reaction of 1a with PSA in toluene at 120° was successful, in a way that we found regioisomeric as well as epimeric cycloadducts (Scheme,5). Unfortunately, the attempts to rearrange the products under strong-base catalysis as it had been shown successfully with other furan,PSA adducts were unsuccessful (Scheme,4). The thermal cycloaddition reaction of 1a and 1b with AAN yielded again regioisomeric and epimeric adducts, which could easily be transformed into the corresponding 2- and 3-oxo products (Scheme,6). Only the latter ones could be rearranged with Ac2O/H2SO4 into the corresponding benzo[a]heptalene-3,4-diol diacetates 20a and 20b, respectively, or with trimethylsilyl trifluoromethanesulfonate (TfOSiMe3/Et3N), followed by treatment with NH4Cl/H2O, into the corresponding benzo[a]heptalen-3,4-diols 21a and 21b (Scheme,7). The thermal cycloaddition reaction of 1 with ZSE in toluene gave the cycloadducts 2,3- exo - 22a and - 22b as well as 2- exo,3- endo - 22c in high yields (Scheme,8). All three adducts eliminated, by treatment with base, benzenesulfinic acid and yielded the corresponding 3-(phenylsulfonyl)-1,4-epoxybenzo[d]heptalenes 25. The latter turned out to be excellent Michael acceptors for H2O2 in basic media (Scheme,9). The Michael adducts lost H2O on treatment with Ac2O in pyridine and gave the 3-(phenylsulfonyl)benzo[d]heptalen-2-ones 28a and 3- exo - 28b, respectively. Rearrangement of these compounds in the presence of Ac2O/AcONa lead to the formation of the corresponding 3-(phenylsulfonyl)benzo[a]heptalene-1,2-diol diacetates 30a and 30b, which on treatment with MeONa/MeI gave the corresponding MeO-substituted compounds 31a and 31b. The reductive elimination of the PhSO2 group led finally to the 1,2-dimethoxybenzo[a]heptalenes 32a and 32b. Deprotonation experiments of 32a with t -BuLi/N,N,N,,N,-tetramethylethane-1,2-diamine (tmeda) and quenching with D2O showed that the most acid CH bond is HC(3) (Scheme,9). Some of the new structures were established by X-ray crystal-diffraction analyses (cf. Figs.,1, 3, 4, and 5). Moreover, nine of the new benzo[a]heptalenes were resolved on an anal. Chiralcel OD-H column, and their CD spectra were measured (cf. Figs.,8 and 9). As a result, the 1,2-dimethoxybenzo[a]heptalenes 32a and 32b showed unexpectedly new Cotton -effect bands just below 300,nm, which were assigned to chiral exciton coupling between the heptalene and benzo part of the structurally highly twisted compounds. The PhSO2 -substituted benzo[a]heptalenes 30b and 31b showed, in addition, a further pair of Cotton -effect bands in the range of 275,245,nm, due to chiral exciton coupling of the benzo[a]heptalene chromophore and the phenylsulfonyl chromophore (cf. Fig.,10). [source] Thiophenylhydrazonoacetates in heterocyclic synthesisHETEROATOM CHEMISTRY, Issue 1 2004Rafat M. Mohareb Benzo[b]thiophen-2-yl-hydrazonoesters 4 were synthesized by coupling of 2-diazo-4,5,6,7-tetrahydrobenzo[b]thiophene-3-carboxamide (1) with either ethyl cyanoacetate or ethyl acetoacetate. The reactivity of 4 toward a variety of nitrogen nucleophiles was investigated to yield pyrazole, isoxazole, pyrimidine, triazine, pyrazolopyridine, and pyrazolopyrimidine derivatives. © 2003 Wiley Periodicals, Inc. 15:15,20, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/.hc10205 [source] Iron and Copper Salts in the Synthesis of Benzo[b]furansADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 10 2010Julien Bonnamour Abstract Intramolecular CO bond forming reactions of aryl 2-bromobenzyl ketones lead to benzo[b]furans. The cyclizations can be catalyzed by 10,mol% of iron trichloride (of 98% or of 99.995% purity) or sub-mol% quantities of copper(II) chloride (of 99.995% purity). [source] Highly Efficient One-Pot Synthesis of 2-Substituted Quinazolines and 4H -Benzo[d][1,3]oxazines via Cross Dehydrogenative Coupling using Sodium HypochloriteADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 2-3 2010C. Uma Maheswari Abstract This communication describes a catalyst-free synthesis of 2-substituted quinazolines and 4H -benzo[d][1,3]oxazines using commericially available sodium hypochlorite as oxidant. Operational simplicity, mild reaction conditions and the ability to construct structurally diverse 2-quinazolines and 2-substituted 4H -benzo[d][1,3]oxazines by this method render it to be a practical alternative for the synthesis of these heterocycles. [source] Phase-Transfer-Catalyzed Intramolecular Cyclization of ortho -Alkynyl Phenyl Ether Derivatives for Synthesis of 2,3-Disubstituted Benzo[b]furansADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 2-3 2010Jie Hu Abstract A variety of substituted benzo[b]furans are readily prepared in good to excellent yields under the mild reaction conditions from o -(1-alkynylphenoxy)-1-phenylethanone under phase-transfer catalysis (PTC). This methodology accommodates simple experimental operations, inexpensive and environmentally benign catalysts, metal catalyst-free conditions, facile reagents and the possibility to conduct large-scale preparations. The development of carbon-carbon bond formation processes via an overall structural isomerization represents the most atom-economical approach. [source] Lewis Acid-Mediated Selective Cycloadditions of Vinylidenecyclopropanes with Aromatic Aldehydes: An Efficient Protocol for the Synthesis of Benzo[c]fluorene, Furan and Furo[2,3- b]furan DerivativesADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 1-2 2009Chenliang Su Abstract Three kinds of Lewis acid-mediated reactions of vinylidenecyclopropanes and aromatic aldehydes are disclosed in this paper, providing an efficient and selective synthesis of a variety of functionalized benzo[c]fluorene, furan and furo[2,3- b]furan derivatives. [source] Proton-Promoted Hydroamination of 3-Dialkylthiomethylene-1,4-pentadiynes with o -Phenylenediamines: A Facile Route to Benzo[b][1,4]diazepinesADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 10 2008Yu-Long Zhao Abstract The first proton-promoted intermolecular hydroamination reaction of the enynes, ,,,-dialkynylketene S,S -acetals 2, is described. A series of benzo[b][1,4]diazepines, with the structures of 3 and 5, were prepared chemo- and regioselectively in good to high yields by reacting the readily available 1,4-diynes 2 with both terminal and internal alkyne functions with o -phenylenediamines under very mild conditions. [source] 2,3-Disubstituted Benzo[b]thiophenes from Diarylalkynes via Electrophilic Addition-Cyclization and Palladium-Catalyzed Cross-CouplingADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 13 2007Giuseppe Lamanna Abstract Diarylalkynes are readily transformed in 3-chlorobenzo[b]thiophenes in a two-step electrophilic addition-cyclization procedure that runs highly efficiently in solution or in the solid phase. The heteroaromatic carbon-chlorine bond participates in palladium-catalyzed Suzuki,Miyaura or Buchwald,Hartwig cross-couplings to give, in a single step, 2,3-disubstituted derivatives of pharmacological relevance . [source] Benzo[1,2- c:3,4- c']bis[1,2,5]selenadiazole, [1,2,5]selenadiazolo-[3,4- e]-2,1,3-benzothiadiazole, furazanobenzo-2,1,3-thiadiazole, furazanobenzo-2,1,3-selenadiazole and related heterocyclic systemsJOURNAL OF HETEROCYCLIC CHEMISTRY, Issue 6 2004Catherine M. Cillo The first synthesis of benzo[1,2- c:3,4- c']bis[1,2,5]selenadiazole has been developed starting from commercially available 4-nitrobenzo-2,1,3-selenadiazole. Improved syntheses of the related heterocycles [1,2,5]selenadiazolo[3,4- e]-2,1,3-benzothiadiazole, furazanobenzo-2,1,3-thiadiazole and furazanobenzo-2,1,3-selenadiazole are also reported. [source] The reaction of acetic acid 2-selenoxo-2H -pyridin-1-yl esters with benzynes: A convenient route to Benzo[b]seleno[2,3- b]pyridinesJOURNAL OF HETEROCYCLIC CHEMISTRY, Issue 1 2004U. Narasimha Rao Benzyne and its 3,4,5,6-tetraphenyl, 3- and 4-methyl, 3-methoxy and 4,5-difluoro derivatives react with acetic acid 2-selenoxo-2H -pyridin-1-yl esters 4a-e to give benzo[b]seleno[2,3- b]pyridines 10,15 in modest yields. The benzynes were generated by one or more of the following methods: diazotization of anthranilic acids 5a-g with isoamyl nitrate; mild thermal decomposition of 2-diazoniobenzenecarboxylate hydrochlorides 6a-d treatment of (phenyl)[o -(trimethylsilyl)phenyl]iodonium triflate (7) with tetrabutylammonium fluoride; and treatment of 2-trimethylsilylphenyl triflates 8a-c with cesium fluoride. In all the reactions, the corresponding 2-(methylselenenyl)pyridines 16a-d were also obtained suggesting that these reactions may involve selenium addition to benzyne via a SET (single electron transfer). [source] Reactions of 6-aminopyrimidines with 2-dimethylaminomethylenetetralone.JOURNAL OF HETEROCYCLIC CHEMISTRY, Issue 2 20015- b] quinolines, 6-Dihydrobenzo [h]pyrimido [, Regiospecific Synthesis Of Benzo[h]pyrimido[4,5- b]quinolines (3) have been synthesized via a regiospecific cyclocondensation reaction between 6-aminopyrimidines (1) and 2-dimethylaminomethylentetralone hydrochloride (2). The linear structure of the final compounds were determined by nmr measurements, especially by 1H,1H, 1H,13C COSY and DEPT experiments. [source] The influence of cytosine methylation on the chemoselectivity of benzo[a]pyrene diol epoxide-oligonucleotide adducts determined using nanoLC/MS/MSJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 8 2009James Glick Abstract Benzo[a]pyrene is a major carcinogen implicated in human lung cancer. Almost 60% of human lung cancers have a mutation in the p53 tumor suppressor gene at several specific codons. An on-line nanoLC/MS/MS method using a monolithic nanocolumn was applied to investigate the chemoselectivity of the carcinogenic diol epoxide metabolite, ( ± )-(7R,8S,9S,10R)-benzo[a]pyrene 7,8-diol 9,10-epoxide [( ± )- anti -benzo[a]pyrene diol epoxide (BPDE)], which was reacted in vitro with a synthesized 14-mer double stranded oligonucleotide (5,-ACCCG5CG7TCCG11CG13C-3,/5,-GCGCGGGCGCGGGT-3,) derived from the p53 gene. This sequence contained codons 157 and 158, which are considered mutational ,hot spots' and have also been reported as chemical ,hot spots' for the formation of BPDE-DNA adducts. In evaluating the effect of cytosine methylation on BPDE-DNA adduct binding, it was found that codon 156, containing the nucleobase G5 instead of the mutational hot spot codons 157 (G7) and 158 (G11), was the preferential chemoselective binding site for BPDE. In all permethylated cases studied, the relative ratio for adduction was found to be G5, G11 > G13 > G7. Permethylation of CpG dinucleotide sites on either the nontranscribed or complementary strand did not change the order of sequence preference but did enhance the relative adduction level of the G11 CpG site (codon 158) approximately two-fold versus the unmethylated oligomer. Permethylation of all CpG dinucleotide sites on the duplex changed the order of relative adduction to G5, G7 > G11 > G13. The three- to four-fold increase in adduction at the mutational hot spot codon 157 (G7) relative to the unmethylated or single-stranded permethylated cases suggests a possible relationship between the state of methylation and adduct formation for a particular mutation site in the p53 gene. Using this method, only 125 ng (30 pmol) of adducted oligonucleotide was analyzed with minimal sample cleanup and high chromatographic resolution of positional isomers in a single chromatographic run. Copyright © 2009 John Wiley & Sons, Ltd. [source] Soil properties, but not plant nutrients (N, P, K) interact with chemically induced resistance against powdery mildew in barleyJOURNAL OF PLANT NUTRITION AND SOIL SCIENCE, Issue 3 2003Joachim Wiese Abstract Chemically induced resistance is a promising method of plant protection against diseases, which can be triggered by systemically acting chemical inducers such as BTH (benzo(1, 2, 3)thiadiazole-carbothioic-acid-S-methylester). BTH is commercially distributed as a 50,% formulation, called Bion®. The uncertain success of Bion® application in controlling infection by powdery mildew is a major obstacle in using induced resistance for plant protection in agriculture. This study aimed to investigate the effect of soil properties, selected macronutrients (N, P, and K), and addition of organic matter on induced resistance and to identify possible factors responsible for the high variability of BTH effect under field conditions. A pot experiment under open-air conditions was set up using the pathosystem Hordeum vulgare cv. Ingrid / Blumeria graminis f. sp. hordei race A6. The different soils strongly affected the resistance of barley plants against powdery mildew after BTH treatment. The infection of barley by powdery mildew was lower than on all other soils when grown on an acid forest soil which was limed up to pH 4.9, even after BTH treatment. A reproducible induction of pathogen resistance by BTH was shown only on a mineral soil (Kleinlinden) with a negligible C content. Application of N, P, and K did not consistently affect the induction of resistance by BTH. The addition of green manure and compost led to an enhanced variability of resistance induction on the soil "Kleinlinden". Possible effects of soil microflora on resistance induction are discussed. Bodeneigenschaften, aber nicht Pflanzennährstoffe (N, P, K) interagieren mit der chemisch induzierten Resistenz gegen Gerstenmehltau in Gerste Chemisch induzierte Resistenz ist eine viel versprechende Methode im Pflanzenschutz, welche durch systemisch wirkende Substanzen wie BTH (Benzo(1, 2, 3)-thiadiazolcarbothion-Säure- S -Methylester) induziert werden kann. BTH ist die wirksame Komponente des kommerziell erhältlichen Produkts Bion®. Allerdings ist die Wirksicherheit von Bion® im Feld gering, wodurch die Anwendung des Produkts im Pflanzenschutz eingeschränkt ist. Das Ziel der vorliegenden Arbeit war es, den Einfluss verschiedener Böden, ausgewählter Makronährstoffe (N, P und K) und des Zusatzes von organischem Material zum Boden auf die induzierte Resistenz zu untersuchen und Faktoren zu identifizieren, die für die unsichere BTH-Wirkung im Feld verantwortlich sind. Dafür wurden Gefäßexperimente unter freilandähnlichen Bedingungen durchgeführt. In diesen wurde das Pathosystem Hordeum vulgare cv. Ingrid / Blumeria graminis f. sp. hordei Stamm A6 verwendet. Es wurde ein starker Einfluss des Bodens auf die Resistenz der Gerste gegen Gerstenmehltau nach BTH-Behandlung ermittelt. Die Mehltauinfektion von Gerste, welche auf einem sauren Waldboden kultiviert wurde, der auf einen pH-Wert von 4, 9 aufgekalkt worden war, war niedriger als auf allen anderen Böden, selbst nach BTH-Behandlung. Eine reproduzierbare Induktion der Pathogenresistenz durch BTH konnte nur auf einem Mineralboden mit vernachlässigbarem C-Gehalt gezeigt werden. Die Ernährung mit N, P und K hatte keinen konsistenten Einfluss auf die Resistenzinduktion mittels BTH. Der Zusatz von Kompost und Gründünger zum Boden ,Kleinlinden" erhöhte die Variabilität der Resistenzinduktion. Der mögliche Einfluss der Bodenmikroflora auf die Resistenzinduktion wird diskutiert. [source] Polycyclic aromatic hydrocarbon residues in the sediments of a dune lake as a result of power boatingLAKES & RESERVOIRS: RESEARCH AND MANAGEMENT, Issue 1 2001Thorsten D. Mosisch Abstract The potential chemical effects of motorized recreational activities (power boating, water skiing, jet skiing) on Brown Lake, an Australian perched, acid dune lake, were investigated. The objective of this study was to identify and quantify polycyclic aromatic hydrocarbon compounds (PAHs) that may have accumulated in the water and/or the organic bottom sediments of the test lake as a result of the operation of powered recreational watercraft, and to evaluate any risk to aquatic biota. To achieve this, a detailed sampling and analysis programme of the lake water and sediments was implemented. Basic water quality, ionic and nutrient data gave no indication of any deterioration in the water quality of the lake, which was attributable to human usage in general or motorized recreational activities in particular. However, analysis of samples taken from the organic bottom sediments of the lake revealed the presence of 10 PAH, including benzo(a)pyrene, chrysene, fluoranthene, phenanthrene and pyrene, which are known to be indicative of fossil fuel combustion processes. Three PAH compounds were found at all survey sites: benzo(a)pyrene (in 46% of samples), fluoranthene (in 53% of samples) and pyrene (in 44% of samples). Results of the analyses were compared with values from published guidelines for residues in freshwaters and sediments, as well as with previous studies dealing with the effects of fossil fuel combustion products on lakes. The highest PAH concentrations in sediments were recorded for benzo(a)pyrene, with three values (830, 955 and 1070 ,g kg,1 dryweight) exceeding the upper threshold recommended in the draft Canadian freshwater sediment quality guidelines. Benzo(a)pyrene also exceeded the lower Canadian sediment threshold in 51 (40%) samples. These results indicate a significant level of chemical contamination of Brown Lake as a consequence of four decades of motorized recreational activities and present a significant risk to aquatic biota, particularly benthic and littoral invertebrates associated with the contaminated sediments. [source] The processing of a Benzo(a)pyrene adduct into a frameshift or a base substitution mutation requires a different set of genes in Escherichia coliMOLECULAR MICROBIOLOGY, Issue 2 2000Nathalie Lenne-Samuel Replication through a single DNA lesion may give rise to a panel of translesion synthesis (TLS) events, which comprise error-free TLS, base substitutions and frameshift mutations. In order to determine the genetic control of the various TLS events induced by a single lesion, we have chosen the major N2-dG adduct of (+)- anti -Benzo(a)pyrene diol epoxide [(+)- anti -BPDE] adduct located within a short run of guanines as a model lesion. Within this sequence context, in addition to the major event, i.e. error-free TLS, the adduct also induces base substitutions (mostly G , T transversions) and ,1 frameshift mutations. The pathway leading to G , T base substitution mutagenesis appears to be SOS independent, suggesting that TLS is most probably performed by the replicative Pol III holoenzyme itself. In contrast, both error-free and frameshift TLS pathways are dependent upon SOS-encoded functions that belong to the pool of inducible DNA polymerases specialized in TLS (translesional DNA polymerases), namely umuDC (Pol V) and dinB (Pol IV). It is likely that, given the diversity of conformations that can be adopted by lesion-containing replication intermediates, cells use one or several translesional DNA polymerases to achieve TLS. [source] Photodynamic Action of Benzo[a]pyrene in K562 CellsPHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 6 2007Daza De Moraes Vaz Batista Filgueira Benzo[a]pyrene (BaP) is ubiquitously distributed in the environment, being considered the most phototoxic element among polycyclic aromatic hydrocarbon (PAHs). In presence of oxygen, PAHs can act as a photosensitizer by means of promoting photo-oxidation of biological molecules (photodynamic action, PDA). Thus, the present study analyzed the photodynamic action of BaP under UVA irradiation (BaP + UVA) and its oxidative effects on K562 cells. The evaluation of BaP kinetics showed that the highest intracellular concentration occurred after 18 h of incubation. Cell viability, reactive oxygen species (ROS) generation, lipid peroxidation, DNA damage (breaks and DNA,protein cross-link [DNAPC]) were assessed after exposure to BaP, UVA and BaP plus UVA irradiation (BaP + UVA). Cell viability was decreased just after exposure to BaP + UVA. Lipid peroxidation and DNA breaks increased after BaP + UVA exposure, while the DNAPC increased after BaP, UVA and BaP + UVA exposure, suggesting that BaP + UVA effects were a consequence of both type II (producing mainly singlet oxygen) and type I (producing others ROS) mechanisms of PDA. [source] Induction of centrosome amplification and chromosome instability in p53 -deficient lung cancer cells exposed to benzo[a]pyrene diol epoxide (B[a]PDE),THE JOURNAL OF PATHOLOGY, Issue 3 2008K Shinmura Abstract Benzo[a]pyrene diol epoxide (B[a]PDE), the ultimate carcinogenic metabolite of benzo[a] pyrene, has been implicated in the mutagenesis of the p53 gene involved in smoking-associated lung cancer. To further understand the role of B[a]PDE in lung tumour progression, we investigated its effect on the numerical integrity of centrosomes and chromosome stability in lung cancer cells lacking p53. Exposure of p53 -deficient H1299 lung cancer cells to B[a]PDE resulted in S-phase arrest, leading to abnormal centrosome amplification. Analysis of H1299 cells stably expressing fluorescence-tagged centrin (a known centriolar marker) revealed that the centrosome amplification was primarily attributable to excessive centrosome duplication rather than to centriole splitting. Forced expression of POLK DNA polymerase, which has the ability to bypass B[a]PDE,guanine lesions in an error-free manner, suppressed the B[a]PDE-induced centrosome amplification. Fluorescence in situ hybridization analyses with probes specific for chromosomes 2, 3, and 16 revealed that B[a]PDE exposure also led to chromosome instability, which was likely to have resulted from centrosome amplification. We extended these findings to primary lung carcinomas containing non-functional p53, and found a strong association between centrosome amplification and a high level of B[a]PDE,DNA accumulation. Therefore B[a]PDE contributes to neoplasia by inducing centrosome amplification and consequent chromosome destabilization as well as its mutagenic activity. Copyright © 2008 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd. [source] Benzo- and Naphthoborepins: Blue-Emitting Boron Analogues of Higher Acenes,ANGEWANDTE CHEMIE, Issue 33 2009Lauren Blaues Wunder: Ausgedehnte aromatische Systeme mit einem Borepinkern (siehe Bild) lassen sich durch Zinn-Bor-Austausch synthetisieren. Zu den Eigenschaften dieser luft- und feuchtigkeitsunempfindlichen Materialien gehört eine starke blaue Fluoreszenz. [source] Benzo- cis -cyclohexano-14-crown-4 and its lithium thiocyanate complexACTA CRYSTALLOGRAPHICA SECTION C, Issue 9 2000Jeffrey C. Bryan The structures of a 14-crown-4 ether containing both benzo and cyclohexano substituents, 2,6,13,17-tetraoxatricyclo-[16.4.0.07,12]docosa-1(18),19,21-triene, C18H26O4, and its lithium complex, [2,6,13,17-tetraoxatricyclo[16.4.0.07,12]docosa-1(18),19,21-triene-,4O](thiocyanato- N)lithium(I), [Li(NCS)-(C18H26O4)], are presented. The conformation of the free crown, (I), is not preorganized for cation binding, as its donor dipoles are oriented towards opposite sides of the crown ring. The Li+ -crown complex, (II), exhibits two formula units in the asymmetric unit. The binding conformation observed in (II) does not completely reorient the dipoles to one point, resulting in a long Li,O bond length [2.068,(5) and 2.073,(5),Å]. [source] | ||||||||||||||||||||||||||||||||||||||||