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Ammonium Acetate (ammonium + acetate)
Kinds of Ammonium Acetate Terms modified by Ammonium Acetate Selected AbstractsChemInform Abstract: Synthesis of Pyrazolo[3,4-b]pyridines Using Ammonium Acetate as Green Reagent in Multi-Component Reactions.CHEMINFORM, Issue 47 2008Madhukar N. Jachak Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] Ytterbium Triflate as an Efficient Catalyst for One-Pot Synthesis of Substituted Imidazoles Through Three-Component Condensation of Benzil, Aldehydes and Ammonium Acetate.CHEMINFORM, Issue 13 2007Li-Min Wang Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source] Microwave-Assisted Solvent-Free Friedlaender Synthesis of 1,8-Naphthyridines Using Ammonium Acetate as Catalyst.CHEMINFORM, Issue 34 2006K. Mogilaiah Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source] An Eco-Friendly Regeneration of Aldehydes Exploiting Ammonium Acetate under Microwave Irradiation.CHEMINFORM, Issue 38 2004Alok Kumar Mitra Abstract For Abstract see ChemInform Abstract in Full Text. [source] Analysis of sesterterpenoids from Aspergillus terreus using ESI-QTOF and ESI-ITPHYTOCHEMICAL ANALYSIS, Issue 4 2010Zhi-Jun Wu Abstract Introduction , Biosynthesis of terretonin was studied due to the interesting skeleton of this series of sesterterpenoids. Very recently, López-Gresa reported two new sesterterpenoids (terretonins E and F) which are inhibitors of the mammalian mitochondrial respiratory chain. Mass spectrometry (MS), especially tandem mass spectrometry, has been one of the most important physicochemical methods for the identification of trace natural products due to it rapidity, sensitivity and low levels of sample consumption. The potential application prospect and unique skeleton prompted us to study structural characterisation using MS. Objective , To obtain sufficient information for rapid structural elucidation of this class of compounds using MS. Methodology , The elemental composition of the product ions was confirmed by low-energy ESI-CID-QTOF-MS/MS analyses. The fragmentation pathways were postulated on the basis of ESI-QTOF-MS/MS/MS and ESI-IT-MSn spectra. Common features and major differences between ESI-QTOF-MS/MS and IT-MSn spectra were compared. For ESI-QTOF-MS/MS/MS experiments, capillary exit voltage was raised to induce in-source dissociation. Ammonium acetate or acetic acid were added into solutions to improve the intensity of [M + H]+. The collision energy was optimised to achieve sufficient fragmentation. Some fragmentation pathways were unambiguously proposed by the variety of abundance of fragment ions at different collision energies even without MSn spectra. Results , Fragmentation pathways of five representative sesterterpenoids were elucidated using ESI-QTOF-MS/MS/MS and ESI-IT-MSn in both positive- and negative-ion mode. The key group of characterising fragmentation profiles was ring B, and these fragmentation patterns are helpful to identify different types of sestertepenoids. Conclusion , Complementary information obtained from fragmentation experiments of [M + H]+ (or [M + NH4]+) and [M , H], precursor ions is especially valuable for rapid identification of this kind of sesterterpenoid. [source] Enaminones in heterocyclic synthesis: A new regioselective synthesis of 2,3,6-trisubstituted pyridines, 6-substituted-3-aroylpyridines and 1,3,5-triaroylbenzenesJOURNAL OF HETEROCYCLIC CHEMISTRY, Issue 5 2002Balkis Al-Saleh 1-Substituted-3-dimethylaminopropenones 1a-d reacted with acetylacetone and with ethyl acetoacetate to yield regioselectively 2,3,6-trisubstituted pyridines. Refluxing 1a-d in acetic acid/ammonium acetate resulted in the formation of 6-substituted-3-aroylpyridines, whereas refluxing in acetic acid alone afforded 1,3,5-triaroylbenzene. [source] Determination of flurbiprofen enantiomers in plasma using a single-isomer amino cyclodextrin derivative in nonaqueous capillary electrophoresis,ELECTROPHORESIS, Issue 17 2008Anne Rousseau Abstract A nonaqueous capillary electrophoresis (NACE) assay was developed for the separation and determination of flurbiprofen enantiomers in plasma samples using 6-monodeoxy-6-mono(3-hydroxy)propylamino-,-cyclodextrin as chiral selector. The nonaqueous background electrolyte was made up of 40,mM ammonium acetate in methanol (MeOH), and flufenamic acid was employed as internal standard. Solid-phase extraction was used for sample cleanup prior to the NACE separation. The NACE method reproducibility was optimized by evaluating different capillary washing sequences between runs. After having tested various conditions, trifluoroacetic acid (1,M) in MeOH was finally selected. Concerning the solid-phase extraction procedure, good and reproducible analyte recoveries were obtained using MeOH for protein denaturation and a polymeric phase combining hydrophobic interactions with anion exchange properties (Oasis® MAX) was selected as extraction sorbent. The method selectivity was not only demonstrated toward a blank plasma sample but also toward other non-steroidal anti-inflammatory drugs. The method was then successfully validated with respect to response function, trueness, precision, accuracy, linearity and limit of quantification. [source] Analysis of major alkaloids in Rhizoma coptidis by capillary electrophoresis-electrospray-time of flight mass spectrometry with different background electrolytesELECTROPHORESIS, Issue 10 2008Junhui Chen Abstract CE-based techniques with DAD and detection ESI-TOF-MS have been developed for the analysis of seven protoberberine alkaloids and one aporphinoid alkaloid in Huanglian (Rhizoma coptidis), a well-known traditional Chinese herbal medicine. One aqueous BGE and one nonaqueous BGE were developed for CE-DAD and CE-MS analyses, and the CE-ESI-TOF-MS conditions including nebulizer gas pressure, the sheath-liquid composition, its flow rate, etc. were optimized. Eight main alkaloids in R. coptidis could be separated with baseline resolution by CE-DAD with these two different BGEs, and identified by TOF-MS analysis. Moreover, three major alkaloids (berberine, palmatine, and jatrorrhizine) could be quantified accurately by CE-DAD and CE-MS with the BGE system consisting of 50:50 v/v water and ACN containing 50,mM ammonium acetate at pH,6.8. Both techniques provided similar LODs and could be applied with confidence within similar linear dynamic range. However, reproducibility and speed of analysis were better using CE-DAD. When the CE technique was compared with the RP-HPLC method, the CE-DAD and CE-MS methods provided greater efficiency and faster analysis speed, i.e., achieving baseline resolution for all the eight main basic compounds in less than 14,min. The CE method, as a viable alternative to HPLC, is suitable for use as a routine procedure for the rapid identification and quantification of basic compounds in herbal or natural product applications. [source] Chiral CE of aromatic amino acids by ligand-exchange with zinc(II),L -lysine complexELECTROPHORESIS, Issue 15 2007Li Qi Abstract A novel method of chiral ligand-exchange CE was developed with either L - or D -lysine (Lys) as a chiral ligand and zinc(II) as a central ion. This type of chiral complexes was explored for the first time to efficiently separate either individual pairs of or mixed aromatic amino acid enantiomers. Using a running buffer of 5,mM ammonium acetate, 100,mM boric acid, 3,mM ZnSO4·7H2O and 6,mM L -Lys at pH,7.6, unlabeled D,L -tryptophan, D,L -phenylalanine, and D,L -tyrosine were well separated, giving a chiral resolution of up to 7.09. The best separation was obtained at a Lys-to-zinc ratio of 2:1, zinc concentration of 2,4,mM and running buffer pH,7.6. The buffer pH was determined to have a strong influence on resolution, while buffer composition and concentration impacted on both the resolution and peak shape. Boric acid with some ammonium acetate was an adoptable buffer system, and some additives like ethylene diamine tetraacetic acid capable of destroying the complex should be avoided. Fine-tuning of the chiral resolution and elution order was achieved by regulating the ratio of L -Lys to D -Lys; i.e. the resolution increased from zero to its highest value as the ratio ascended from 1:0 to 1:infinitive, and L -isomers eluted before or after D -isomers in excessive D - or L -Lys, respectively. [source] Determination of trace cationic impurities in butylmethylimidazolium-based ionic liquids: From transient to comprehensive single-capillary counterflow isotachophoresis-zone electrophoresisELECTROPHORESIS, Issue 23 2006Marek Urbánek Abstract Determination of impurities in ionic liquids (ILs) remains a difficult task. In this work, the hyphenation of isotachophoretic,(ITP) preconcentration to zone electrophoresis,(ZE) has been explored for the trace analysis of the cationic impurities Na+, Li+, and methylimidazolium (MI+) in butylmethylimidazolium (BMI+)-based ILs. Simultaneous detection of UV-transparent and UV-absorbing impurities was ensured by a BGE composed of creatinine-acetate buffer. To induce ITP, three different strategies were evaluated: (i),Sample self-stacking ensured by the addition of ammonium acetate (NH4Ac) to 25,50-fold diluted IL solution (transient ITP). (ii),Complete ITP-ZE separation performed in a single capillary: ITP was realized in discontinuous electrolytes comprising an 80,mM NH4Ac, 40,mM acetic acid, 30,mM ,-CD, pH,5.05, leading electrolyte,(LE) and a 10,mM creatinine, 10,mM acetic acid, pH,4.9, terminating electrolyte,(TE). To create the ZE stage, the ITP stack of analytes was moved back toward the capillary inlet by pressure and simultaneously the capillary was filled with the BGE. This protocol made it possible to accommodate a 2.5-times diluted IL sample. (iii),Complete counterflow ITP-ZE with continuous electrokinetic sample supply: the ITP stage was performed in a capillary filled with a 150,mM NH4Ac, 75,mM acetic acid, 30,mM ,-CD, pH,5.0 LE, with 40-times diluted IL at the capillary inlet. BMI+ from IL acts as the terminating ion. The LODs reached in this latter case were at the 10 and 1,ppb levels for MI+ and Li+ in diluted IL matrix, respectively. [source] A generic approach to the impurity profiling of drugs using standardised and independent capillary zone electrophoresis methods coupled to electrospray ionisation mass spectrometryELECTROPHORESIS, Issue 9 2005Aurélie Vassort Abstract Three standardised, capillary zone electrophoresis-electrospray ionisation mass spectrometry (CZE-ESI-MS) methods were developed for the analysis of six drug candidates and their respective process-related impurities comprising a total of 22 analytes with a range of functional groups and lipophilicities. The selected backround electrolyte conditions were found to be: 60/40 v/v 10 mM ammonium formate pH 3.5/organic, 60/40 v/v 10 mM ammonium acetate pH 7.0/organic and 10 mM piperidine, pH 10.5, where the organic solvent is 50/50 v/v methanol/acetonitrile. The coaxial sheath flow consisted of either 0.1% v/v formic acid in 50/50 v/v methanol/water, or 10 mM ammonium acetate in 50/50 v/v methanol/water, depending on the mixture being analysed. Factor analysis and informational theory were used to quantify the orthogonality of the methods and predict their complementarities. The three selected CZE-ESI-MS methods allowed the identification of 21 out of 22 of all the drug candidates and their process-related impurities and provided orthogonality with four established high-performance liquid chromatography-mass spectrometry (HPLC-MS) methods. These methodologies therefore form the basis of a generic approach to impurity profiling of pharmaceutical drug candidates and can be applied with little or no analytical method development, thereby offering significant resource and time savings. [source] Capillary electrophoresis analysis of glucooligosaccharide regioisomersELECTROPHORESIS, Issue 6 2004Gilles Joucla Abstract Complex gluco-oligosaccharide mixtures of two regioisomer series were successfully separated by CE. The gluco-oligosaccharide series were synthesized, employing a dextransucrase from Leuconostoc mesenteroides NRRL B-512F, by successive glucopyranosyl transfers from sucrose to the acceptor glucose or maltose. The glucosyl transfer to both acceptors, occurring through the formation of ,1,6 linkages, differed for the two series only in the glucosidic bond to the reducing end namely ,1,6 or ,1,4 bond for glucose or maltose acceptor, respectively. Thus, the combination of the two series results in mixed pairs of gluco-oligosaccharide regioisomers with different degrees of polymerization (DP). These regioisomer series were first derivatized by reductive amination with 9-aminopyrene-1,4,6-trisulfonate (APTS). Under acidic conditions using triethyl ammonium acetate as electrolyte, the APTS-gluco-oligosaccharides of each series were separated enabling unambiguous size determination by coupling CE to electrospray-mass spectrometry. However, neither these acidic conditions nor alkaline buffer systems could be adapted for the separation of the gluco-oligosaccharide regioisomers arising from the two combined series. By contrast, increased resolution was observed in an alkaline borate buffer, using differential complexation of the regioisomers with the borate anions. Such conditions were also successfully applied to the separation of glucodisaccharide regioisomers composed of ,1,2, ,1,3, ,1,4, and ,1,6 linkages commonly synthesized by glucansucrase enzymes. [source] Slow desorption behavior of one highly resistant aromatic amine in Lake Macatawa, Michigan, USA, sedimentENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 12 2005Shihua Chen Abstract The desorption behavior of benzidine from Lake Macatawa (Holland, MI, USA) sediment was investigated in this study using batch solvent extraction method. Seven solvents were tested as the extracting reagents: Deionized water (DI), calcium chloride in DI (CaCl2), sodium hydroxide in DI (NaOH), acetonitrile (ACN), a mixture of acetonitrile and ammonium acetate in DI (ACNNH4OAc), methanol (MeOH), and hydrochloric acid in DI (HCl). These solvents are proposed to react with sediment-associated benzidine by different mechanisms (e.g., cation exchange, hydrophobic partitioning, and covalent binding). Three sets of sorption isotherm experiments were conducted separately in these seven solvents with a 7-d, three-week, and two-month contact time. The results demonstrated nonlinear isotherms with Freundlich 1/n values varying from 0.25 to 0.52. The desorption behavior of benzidine in the solvents was evaluated after the sorption of benzidine onto the sediment with same contact times of 7 d, three weeks, and two months. A two-stage model subsequently was applied to simulate the experimental data. The rapidly desorbing rate constants were on the order of one to two per day for ACN, ACN-NH4OAc, and NaOH solvents, and the slowly desorbing rate constants were on the order of 10,5 to 10,4/d. Sequential desorption experiment demonstrated low total extraction efficiency of less than 40%. Both the observed sorption and desorption phenomena suggested that hysteresis and/or mass-transfer limited diffusion may result in the slow desorption behavior observed in this study. [source] Efficient Routes to Acenaphthylene-Fused Polycyclic Arenes/Heteroarenes and Heterocyclic Fluoranthene AnaloguesEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 10 2005Kausik Panda Abstract The acenaphthenone-derived , -oxoketene dithioacetal 2 has been subjected to various [3 + 3] aromatic and heteroaromatic annulation and other heterocyclization reactions previously developed in our laboratory, providing short and efficient routes to a diverse range of known and unknown acenaphtho-annulated linear and angular PAHs, heteroaromatics and five-membered heterocycles in good yields. Thus, benzo- and naphthoannulation of 2 with various allyl and benzyl Grignard reagents afforded substituted fluoranthenes 4a,c and benzo[k]fluoranthene 8, respectively, in good yields. Similarly, the parent benzo[j]fluoranthene 15a and its substituted derivative 16b have been synthesized by base-induced conjugate 1,4-addition of arylacetonitriles to 2, followed by acid-induced cyclization of the conjugate adducts 12a,b to give 13a,b and subsequent further transformations. The adducts obtained by 1,4-addition of anions derived from acetophenone and acenaphthenone were subjected toheterocyclization in the presence of ammonium acetate to give 8-arylacenaphtho[1,2- b]pyridines 18a,b and bis(acenaphtho)-annulated pyridine 20. Heterocyclization of 2 with bifunctional nucleophiles such as 2-picolyllithium and guanidinium nitrate afforded the corresponding acenaphtho[1,2- b]quinolizinium salt 23 and acenaphtho[1,2- d]pyrimidine 24, respectively, in high yields. Finally, acenaphtho[1,2- c]-fused five-membered heterocycles such as 7-(methylthio)acenaphtho[1,2- c]thiophene (25), 7-(methylthio)acenaphtho[1,2- c]furan (27) and 7-(methylthio)acenaphtho[1,2- c]pyrrole-2-carboxylic acid (30) were obtained in good yields by subjection of 2 to Simmons,Smith reaction conditions or by treatment with dimethylsulfonium methylide or glycinate dianion. Some of these newly synthesized PAHs or fused heterocycles were subjected to Raney Ni desulfurization to furnish sulfur-free compounds. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source] An ethnoarchaeological study of chemical residues in the floors and soils of Q'eqchi' Maya houses at Las Pozas, GuatemalaGEOARCHAEOLOGY: AN INTERNATIONAL JOURNAL, Issue 6 2002Fabián G. Fernández This ethnoarchaeological study at the Q'eqchi' Maya village of Las Pozas, Guatemala, aimed to refine the understanding of the relationship between soil chemical signatures and human activities for archaeological applications. The research involved phosphorus, exchangeable ion (calcium, potassium, magnesium, sodium), and trace element analysis of soils and earth floors extracted by Mehlich II, ammonium acetate, and DTPA chelate solutions, respectively. The results showed high levels of phosphorus, potassium, magnesium, and pH in food preparation areas, as well as high phosphorus concentrations and low pH in food consumption areas. The traffic areas exhibited low phosphorus and trace element contents, whereas refuse disposal areas were enriched. These results provide important information for the understanding of space use in ancient settlements. © 2002 Wiley Periodicals, Inc. [source] An efficient and green synthesis of 1,4-dihydropyridine derivatives through multi-component reaction in ionic liquidHETEROATOM CHEMISTRY, Issue 5 2006Xue Sen Fan Through multi-component condensation of aldehydes, 1,3-dione, Meldrum's acid, and ammonium acetate in an ionic liquid ([bmim][BF4]), a series of 1,4-dihydropyridine derivatives were prepared in excellent yields in the absence of any additional catalysts. In addition, [bmim][BF4] can be recovered and reused effectively for at least six times without obvious decrease of its efficiency. Advantages of this novel protocol include simple operational process, environmental benignancy, and high efficiency. © 2006 Wiley Periodicals, Inc. Heteroatom Chem 17:382,388, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20221 [source] Interference between male-targeted and female-targeted lures of the Mediterranean fruit fly Ceratitis capitata (Dipt., Tephritidae) in ItalyJOURNAL OF APPLIED ENTOMOLOGY, Issue 1 2004M. Tóth Abstract: The efficacy of male-targeted and female-targeted baits was compared when lures were presented together or singly in traps for capturing the Mediterranean fruit fly, Ceratitis capitata (Wiedemann). For male-targeted baits, either trimedlure or ceralure presented singly attracted large numbers of flies, supporting data from many previous reports. The present results are the first published data on the attractiveness of ceralure to a European population of C. capitata. The quaternary female bait consisting of ammonium carbonate, putrescine, trimethylamine and acetic acid was a potent attractant for female flies (and also showed some activity for males). Replacing acetic acid with ammonium acetate in the quaternary female bait did not influence activity. Traps with female-targeted and male-targeted baits together always showed a tendency of catching fewer flies than traps with only one type of bait. The decrease was significant in females, regardless of whether ceralure or trimedlure was the male-targeted bait. In males, the tendency was the same for traps with trimedlure or ceralure alone, catching higher numbers than those with both male and female baits. Our present results suggest that both types of baits mutually decrease the numbers of the non-target sex in the trap. In conclusion, it is advisable to use both male- and female-targeted baits in separate and distant traps and not jointly in the same trap, lest the efficacy of detection or monitoring trials be compromised. [source] Determination of glycyrrhetic acid in human plasma by HPLC-MS method and investigation of its pharmacokineticsJOURNAL OF CLINICAL PHARMACY & THERAPEUTICS, Issue 3 2008W.-J. Zhao PhD Summary Objective:, To develop a high performance liquid chromatography mass spectrometry (HPLC-MS) method for the determination of the glycyrrhetic acid (GA) in human plasma and for the investigation of its pharmacokinetics after the oral administration of 150 mg diammonium glycyrrhizinate test and reference capsule formulations. Methods:, The GA in plasma was extracted with ethyl acetate, separated on a C18 column with a mobile phase of methanol (5 mmol/L ammonium acetate),water (85 : 15, V/V) and analysed using a MS detector. Ursolic acid (UA) was used as internal standard. The target ions were m/z 469·5 for GA and m/z 455·6 for UA, the fragment voltages were 200 V and 100 V for GA and UA respectively. Results:, The calibration curve was linear over the range of 0·5,200 ng/mL (r = 0·9974). The limit of quantification for GA in plasma was 0·5 ng/mL, the recovery was 76·0,80·0%, and the inter- and intra-day relative standard deviations (RSD) were <12%. The pharmacokinetic parameters of GA after a single dose of 150 mg diammonium glycyrrhizinate test and reference were as follows: the half life (t1/2) 9·65 ± 3·54 h and 9·46 ± 2·85 h, the time to peak concentration (Tmax) 10·95 ± 1·32 h and 11·00 ± 1·30 h, the peak concentration (Cmax) 95·57 ± 43·06 ng/mL and 103·89 ± 49·24 ng/mL; the area under time-concentration curve (AUC0,48 and AUC0,,) 1281·84 ± 527·11 ng·h/mL and 1367·74 ± 563·27 ng·h/mL, 1314·32 ± 566·40 ng·h/mL and 1396·97 ± 630·06 ng·h/mL. The relative bioavailability of diammonium glycyrrhizinate capsule was 98·88 ± 12·98%. Conclusion:, The assay was sensitive, accurate and convenient, and can be used for the determination of GA in human plasma. Comparison of the bioavailability and pharmacokinetic profile of GA indicated that the test and reference capsules were bioequivalent. [source] One-pot synthesis of spiro[diindeno[1,2- b:2,,1,- e]pyridine-11,3,-indoline]-trionesJOURNAL OF HETEROCYCLIC CHEMISTRY, Issue 5 2010Ramin Ghahremanzadeh A one-pot and pseudo four-component synthesis of spiro[diindeno[1,2- b:2,,1,- e]pyridine-11,3,-indoline]-trione derivatives by cyclo-condensation reaction of isatins, 1,3-indandione, and ammonium acetate in refluxing acetic acid is reported. J. Heterocyclic Chem., (2010). [source] Facile and one pot synthetic routes for various novel, differently fused and promising heteropolycyclesJOURNAL OF HETEROCYCLIC CHEMISTRY, Issue 2 2010Shallu Gupta Four-component one pot cyclocondensation of aromatic aldehydes 1, ethyl cyanoacetate 2, barbituric acid 3 and ammonium acetate in methanol gave substituted and functionalised pyrido[2,3-d]pyrimidine derivatives 4 and 4, after initial Knoevenagel, subsequent Micheal and final heterocyclization reactions. Compounds 4 on reaction with different active methylene compounds resulted in the formation of again functionalized and diversly substituted pyrimidonaphthyridines 5-7, 9 and benzo[b] pyrimidonaphthyridines 8. The various compounds of systems 7 and 8 on further condensation with the reactive and mostly the bifunctional moieties like urea/thiourea, and 2-aminopyridine generated the novel and differently fused dipyrimidonaphthyridines 10/11 and pyrimidonaphthyridinoquinazolines 13/14, and pyridopyrimido- pyrimido[1,8]naphthyridines 15 and pyrimidonaphthyridino- pyridoquinazolines 16, respectively, hitherto unknown in literature. Compounds 7 on condensation with o -phenylenediamine produced novel pyrimidonaphthyridinobenzodiazepines 12. Other novel systems like pyrido[2,3-d;6,5-d,]dipyrimidines 17, dipyrimido[4,5-b:5,,4,-g][1,8]naphthyridines 18, 1,3,4,6,7,8,9,11-octazabenzo[de]naphthacenes 19, dipyrimido[4,5-b:5,,4,-g][1,8]naphthyridines 20, pyrimido[5,,4,:6,7][1,8]naphthyridino[4,3-b][1,5]benzodiazepines 21, dipyrimido[4,5-b:4,,5,-f][1,8]naphthyridines 22 and dipyrimido [4,5-b:5,,4,-g][1,8] naphthyridines 23 have also been generated in this study. J. Heterocyclic Chem., (2010). [source] Extension of a cascade reaction: Microwave-assisted synthesis of the GFP chromophore derivativesJOURNAL OF HETEROCYCLIC CHEMISTRY, Issue 2 2010Runhong Jia A facile microwave-assisted synthesis of imidazol-5(4H)-one derivatives is accomplished via reactions of 4-arylmethylene-2-phenyloxazol-5(4H)-ones with urea (or ammonium acetate) in ethylene glycol. The cascade reaction is simple to perform and occurs under mild conditions with broad scope of applicability. J. Heterocyclic Chem., (2010). [source] A green and efficient synthesis of 3,3,-arylidenebis[4-hydroxy-6-methyl-2(1H)-3-pyridinone]s in water under microwave irradiationJOURNAL OF HETEROCYCLIC CHEMISTRY, Issue 1 2010Feng Shi A series of 3,3,-arylidenebis[4-hydroxy-6-methyl-2(1H)-3-pyridinone]s were synthesized via three-component reactions of aromatic aldehydes, 4-hydroxy-6-methyl-2H -pyran-2-one, and ammonium acetate in water under microwave irradiation. This method has the advantages of environmental friendliness, short reaction time, high yields, and easy operation. This efficient synthesis not only offers an economical and green synthetic strategy to this class of significant compounds but also enriches the investigations on microwave-assisted synthesis in water. J. Heterocyclic Chem., (2010). [source] An efficient and green synthesis of 3,3,-benzylidenebis (4-hydroxy-6-methylpyridin-2(1H)-one) derivatives through multi-component reaction in ionic liquidJOURNAL OF HETEROCYCLIC CHEMISTRY, Issue 5 2008Daqing Shi A series of new 3,3,-benzylidenebis(4-hydroxy-6-methylpyridin-2(1H)-one) derivatives were synthesized via a three-component reaction of an aldehyde, an aniline or ammonium acetate and 6-methyl-4-hydroxypyran-2-one in ionic liquid. These heterocyclic compounds produced could be conveniently separated from the reaction mixture without any volatile organic solvents, and the ionic liquid could be readily reused without efficiency loss after simple treatment. [source] One-pot three-component synthesis of 2-substituted 4-aminoquinazolinesJOURNAL OF HETEROCYCLIC CHEMISTRY, Issue 4 2006Kurosh Rad-Moghadam A facile and rapid synthesis of the title compounds via one-pot reaction of 2-aminobenzonitrile, orthoesters and ammonium acetate under solvent-free and microwave condition is described. [source] Heterocyclic compounds from 4h -3,1-benzoxazin-4-one derivatives as anticancer agentJOURNAL OF HETEROCYCLIC CHEMISTRY, Issue 7 2005Taha M Abdel-Rahman Behaviour of 2-(4-oxo-4H -benzo[d][l,3]oxazin-2-yl)-benzoic acid (1) towards nitrogen nucleophiles namely, hydrazine hydrate, in different solvents, ammonium acetate, and o -phenylenediamine has been investigated to give aminoquinazolin-4-one, benzotriazepinone, spiro-type compound, and nitrogen bridgehead compounds 3-5, respectively. Also, reactivity of the aminoquinazolin-4-one 2 towards carbon elec-trophiles such as ethyl acetoacetate, ethyl phenylacetate, ethyl chloroacetate, and aromatic aldehydes has been discussed. Reaction of Schiff s base 8 with sulfur nucleophiles namely o -aminothiophenol and/or thio-glycolic acid afforded Michael type adducts. Structural assignments, of products 1-24 have been confirmed by elemental analysis and spectral data (1H- and 13C -NMR and MS fragmentation). The bioassay indicates that some of the target compounds obtained have good selective anticancer activity. [source] Studies with enaminones: synthesis of new coumarin-3-yl azoles, coumarin-3-yl azines, coumarin-3-yl azoloazines, coumarin-3-yl pyrone and coumarin-2-yl benzo[b]FuransJOURNAL OF HETEROCYCLIC CHEMISTRY, Issue 4 2001Fathy Mohamed Abel Aziz El-Taweel 3-Acetylcoumarine was condensed with dimethylformamide dimethylacetal (DMFDMA) to yield the enaminone, which reacts readily with hydroxylamine and with hydrazines to yield coumarin-3-ylisoxazoles and coumarin-3-ylpyrazoles respectively. Reaction of the enaminone with benzamidine hydrochloride and 3-amino-1,2,4-1H -triazole affords the pyrimidine and triazolo[3,4- b]pyrimidine. The enaminone reacts with hippuric acid and with the dithiocarboxylic acid to yield pyranones. The reaction of the enaminone with 3-amino-1H -1,2,4-triazole gives the triazolo[3,4- b]pyrimidine. The enaminone underwent self dimerization on reflux in acetic acid ammonium acetate to yield the coumarinyl pyridines and reacted with ketone under the same conditions to yield the pyridine. The reaction of the enaminone with 1,4-benzoquinone and 1,4-naphthoquinone gives benzofuryl coumarine derivatives. [source] Preparation of 2-phenyl-2-hydroxymethyl-4-oxo-1,2,3,4-tetrahydroquinazoline and 2-methyl-4-oxo-3,4-dihydroquinazoline derivatives formation,JOURNAL OF HETEROCYCLIC CHEMISTRY, Issue 4 2000Pavel Hradil The cyclization of phenacyl anthranilate has been studied with the aim to develop the synthesis of 2-(2,-aminophenyl)-4-phenyloxazole. However, a different course of the reaction than expected was observed. 2-Phenyl-2-hydroxymethyl-4-oxo-1,2,3,4-tetrahydroquinazoline (3a) was formed by the reaction of phenacyl anthranilate (2) with ammonium acetate under various conditions. 3-Hydroxy-2-phenyl-4(1H)-quinolinone (4) arose by heating compound 3a in acetic acid. The same compound was obtained by melting compound 3a, but the yield was lower. Different types of products resulted in the reaction of compound 3a with acetic anhydride. Under mild conditions acetylated products 2-acetoxymethyl-2-phenyl-4-oxo-1,2,3,4-tetrahydroquinazoline (7a) and 2-acetoxymethyl-3-acetyl-2-phenyl-4-oxo-1,2,3,4-tetrahydroquinazoline (8) were prepared. If the reaction was carried out under reflux of the reaction mixture, molecular rearrangement took place to give cis and trans 2-methyl-4-oxo-3-(1-phenyl-2-acetoxy)vinyl-3,4-dihydroquinazolines (9a and 9b). All prepared compounds have been characterised by their 1H, 13C and 15N NMR spectra, IR spectra and MS. [source] Quantitative analysis of EO9 (apaziquone) and its metabolite EO5a in human plasma by high-performance liquid chromatography under basic conditions coupled to electrospray tandem mass spectrometryJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 10 2006Liia D. Vainchtein A sensitive and specific LC-MS/MS assay for the quantitative determination of EO9 and its metabolite EO5a is presented. A 200-µl human plasma aliquot was spiked with a mixture of deuterated internal standards EO9- d3 and EO5a- d4 and extracted with 1.25 ml ethyl acetate. Dried extracts were reconstituted in 0.1 M ammonium acetate,methanol (7 : 3, v/v) and 25 µl-volumes were injected into the HPLC system. Separation was achieved on a 150 × 2.1 mm C18 column using an alkaline eluent (1 mM ammonium hydroxide,methanol (gradient system)). Detection was performed by positive ion electrospray followed by tandem mass spectrometry. The assay quantifies a range from 5 to 2500 ng/ml for EO9 and from 10 to 2500 ng/ml EO5a using 200 µl of human plasma samples. Validation results demonstrate that EO9 and EO5a concentrations can be accurately and precisely quantified in human plasma. This assay will be used to support clinical pharmacologic studies with EO9. Copyright © 2006 John Wiley & Sons, Ltd. [source] Effect of buffer cations and of H3O+ on the charge states of native proteins.JOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 6 2003Significance to determinations of stability constants of protein complexes Abstract The progressive reduction of charge in charge states of non-denatured proteins (lysozyme, ubiquitin, and cytochrome c), observed with nanospray in the positive ion mode, when the buffer salt ammonium acetate is replaced by ethylammonium acetates (EtNH3Ac, Et2NH2Ac and Et3NHAc) is rationalized on the basis of the charge residue model (CRM). The charge states of the multiply protonated protein are shown to be controlled by the increasing gas-phase basicities, GB(B), of the bases(B) NH3, EtNH2, Et2NH and Et3N. Charge states derived from evaluated apparent gas-phase basicities GBapp of the basic side-chains of the protein and the known GB(B) of the above bases are found to be in agreement with the experimentally observed charge states. This is a requirement of the CRM, because in this model the small positive ions (the buffer cations in the present case) at the surface of the electrospray droplets are the excess ions that provide the charge of the final small droplet that contains the protein molecule and on evaporation of the solvent transfer the charge to the protein. The observed charge states in the absence of buffer salts, i.e. pure water, are attributed to excess H3O+ ions produced by the electrolysis process that attends electrospray. A proposed extended mechanism provides predictions of factors that determine the sensitivity for detection of the multiply protonated proteins. Consideration of restraints imposed by the CRM lead to some simple predictions for conditions that should be present to obtain accurate determinations by electrospray and nanospray of stability constants for the protein,complex equilibrium in aqueous solution. Copyright © 2003 John Wiley & Sons, Ltd. [source] Effect of eluent on the ionization efficiency of flavonoids by ion spray, atmospheric pressure chemical ionization, and atmospheric pressure photoionization mass spectrometryJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 12 2001Jussi-Pekka Rauha Abstract The effect of nine different eluent compositions on the ionization efficiency of five flavonoids was studied using ion spray (IS), atmospheric pressure chemical ionization (APCI), and the novel atmospheric pressure photoionization (APPI), in positive and negative ion modes. The eluent composition had a great effect on the ionization efficiency, and the optimal ionization conditions were achieved in positive ion IS and APCI using 0.4% formic acid (pH 2.3) as a buffer, and in negative ion IS and APCI using ammonium acetate buffer adjusted to pH 4.0. For APPI work, the eluent of choice appeared to be a mixture of organic solvent and 5 mM aqueous ammonium acetate. The limits of detection (LODs) were determined in scan mode for the analytes by liquid chromatography/mass spectrometry using IS, APCI and APPI interfaces. The results show that negative ion IS with an eluent system consisting of acidic ammonium acetate buffer provides the best conditions for detection of flavonoids in mass spectrometry mode, their LODs being between 0.8 and 13 µM for an injection volume of 20 µl. Copyright © 2001 John Wiley & Sons, Ltd. [source] | ||||||||||||||||||||||||||||||||||