bluuebunny/crossref_metadata_2025_split huggingface dataset:
Studies on Benzothiazolo‐asycyanino‐colorants Synthesis, Structural Correlation with UV Absorption Maxima and Bactericidal Potentiality
Authors: Ansari Abdus Samad , Kumar Arvind 
Published: May 2015

AbstractFifteen new chromophoric chain β‐aryl substituted butadienyl‐benzothiazole asy‐cyanine colorants are synthesized by condensing substituted 3‐isopropylbenzothiazolium iodides and 4‐dimethylaminostyrylphenyl ketones using alkaline ethanolic DMF solution. The colorants show bathochromic shifts in comparison with unsubstituted analogues and styryl analogues but hypsochromic shifts when compared to 3‐methylbenzothiazolium analogues. The highly purified samples are screened in vitro against gram positive and gram negative microbes using Disc diffusion technique and found to be mildly active against some of them.
Synthesis of Asymmetric Triarylbenzenes by Using SOCl2‐C2H5OH Reagent
Authors: Hu Zhiguo , Liu Jun , Li Gongan , Dong Zhibing , Li Wei 
Published: May 2015

AbstractA simple and efficient method for synthesis of asymmetric branched functionalized triarylbenzenes is presented. The dypnone reacting with different substituted acetophenones, corresponding asymmetric 1,3,5‐triarylbenzenes were obtained in the presence of catalytic amounts of sulfurous oxychloride in anhydrous ethanol.
Modulation of Substrate Specificity upon Modification of Cholesterol Oxidase from Brevibacterium Sterolicum by Hydrogen Peroxide: Evidence for a Peripheral Site
Authors: Tritsch Denis , Loubat‐Hugel Claire , Biellmann Jean‐François 
Published: May 2015

AbstractEvidence for a peripheral site that recognizes micelles where cholesterol is inserted, is presented for cholesterol oxidase from Brevibacterium sterolicum (CHOD). The Ω loop part of this site contains methionine residues. Their oxidation is reflected in a different selectivity to the micelles. When CHOD is oxidized with hydrogen peroxide, preferential introduction of two oxygen atoms by hydrogen peroxide to the enzyme is observed by the electrospray mass spectrometry. The modified enzyme does not oxidize cholesterol inserted in H‐Triton X‐100/sodium cholate mixed micelles. However, cholesterol solubilized in microemulsions, in biphasic media or inserted in hydroxypropyl‐β‐cyclodextrin is oxidized by the modified enzyme. This modified enzyme oxidizes pregn‐5‐en‐3β‐ol solubilized in mixed micelles, and soluble steroids, such as 3β‐hydroxyandrost‐5‐en‐17β‐carboxylic acid or 3β‐hydroxyandrost‐5‐en‐17‐one. So the modification does not occur at the active site, but at the peripheral site (methionine 81), abolishing the recognition of the micelles and thus inactivating the enzyme specifically towards cholesterol inserted in the micelles.
Direct Formylation of Enol Ethers Using Cyanuric Chloride and N,N‐Dimethylformamide
Authors: Hou Duen‐Ren , Sun Chong‐Si , Sie Wu‐Sian , Jian Jing‐Yu , Hsu Yun 
Published: May 2015

AbstractA new method to prepare α,β‐unsaturated enol aldehydes is described. 3‐Ethoxymethacrolein (1) and 5‐formyl‐3,4‐dihydro‐2H‐pyran (5) were effectively prepared from enol ethers and the Vilsmeier‐Haack type complex, derived from cyanuric chloride and DMF. One byproduct, amidine 4, was also characterized.
2‐Cyanoacetamide in the Synthesis of Heterocyclic Compounds: Synthesis of New Polysubstituted Pyrazole, Pyridine and Pyrimidine Derivatives
Authors: El‐Rady Eman A. , Khalil Mohamed A. 
Published: May 2015

AbstractPhenylmethylenecyanoacetamide (1) was successfully transferred into polysubstituted pyrazole, pyridine and pyrimidine derivatives in a one‐pot reaction step. Hydrazine hydrate (2a,b), cyanoacetamide (6a), cyanothioacetamide (6b), cyanoacetic acid hydrazide (6c), thiosemicarbazide (10), urea (14a), thiourea (14b) and 2‐phenylenediamine (24) were selected as amine nucleophile reagents.
Catalytic Para‐Xylene Maximization. V. Toluene Methylation with Methanol and Disproportionation of Toluene Using Pt/ZSM‐5 and Pt/Mordenite Catalysts
Authors: Aboul‐Gheit Ahmed K. , Aboul‐Fotouh Sameh M. , Emam Eman A. , Ahmed Sahar M. 
Published: May 2015

AbstractToluene was methylated with methanol and disproportionated using catalysts containing different Pt contents (0.2, 0.4 and 0.6%) supported on H‐ZSM‐5 or H‐mordenite (H‐M) zeolites in a fixed‐bed flow‐reactor operated atmospherically at temperatures of 300–500 °C in a flow of hydrogen. Platinum dispersion in the zeolite supports and acid sites strength distribution were evaluated using hydrogen chemisorption (1:1 stoichiometry) and ammonia temperature programmed desorption (TPD) in a differential scanning calorimeter (DSC). Toluene methylation was much faster on all catalysts than toluene disproportionation (DISP). Both reactions were more accelerated using H‐ZSM‐5 containing catalysts than H‐M containing catalysts. The yield of xylenes, and in particular para‐xylene, was significantly influenced by the yield of trimethylbenzenes (TMBs) in product. The selectivities for para‐, ortho‐ and meta‐xylenes production were found largely dependent on the Pt content in the catalysts, particularly when supported on H‐ZSM5‐zeolite. However, using Pt/H‐M catalysts, these selectivities were not strictly controlled by Pt content in the catalysts.
Homology Models and Molecular Dynamics Simulations of Main Proteinase from Coronavirus Associated with Severe Acute Respiratory Syndrome (SARS)
Authors: Liu Hsuan‐Liang , Lin Jin‐Chung , Ho Yih , Hsieh Wei‐Chan , Chen Chin‐Wen , Su Yuan‐Chen 
Published: May 2015

AbstractIn this study, two structural models (denoted as MproST and MproSH) of the main proteinase (Mpro) from the novel coronavirus associated with severe acute respiratory syndrome (SARS‐CoV) were constructed based on the crystallographic structures of Mpro from transmissible gastroenteritis coronavirus (TGEV) (MproT) and human coronavirus HcoV‐229E (MproH), respectively. Various 200 ps molecular dynamics simulations were subsequently performed to investigate the dynamics behaviors of several structural features. Both MproST and MproSH exhibit similar folds as their respective template proteins. These structural models reveal three distinct functional domains as well as an intervening loop connecting domains II and III as found in both template proteins. In addition, domain III of these structures exhibits the least secondary structural conservation. A catalytic cleft containing the substrate binding subsites S1 and the S2 between domains I and II are also observed in these structural models. Although these structures share many common features, the most significant difference occurs at the S2 subsite, where the amino acid residues lining up this subsite are least conserved. It may be a critical challenge for designing anti‐SARS drugs by simply screening the known database of proteinase inhibitors.
Preparation of Nanostructural ZrO2‐Coated SiO2 Particles by Layer‐by‐Layer Assembly Technique
Authors: Chen Rufen , Song Xiuqin 
Published: May 2015

AbstractWe describe a method for controlled preparation of nanostructural ZrO2‐coated SiO2 particles by layer‐by‐layer assembly technique. ZrO2 colloids were synthesized by the sol‐gel method. The samples were characterized by FIIR, DTA‐TG, SEM, EDS, XPS and XRD techniques. The experimental results show that ZrO2 nanopowders on the surface of SiO2 particles are well distributed and compact; the amount of ZrO2 is increased with adding coating layers; the structure of this coating is tetragonal phase.
Cyanoacetanilides Intermediates in Heterocyclic Synthesis. Part 1: A Facile Synthesis of Polysubstituted and Condensed Pyridones
Authors: Ammar Y. A. , El‐Sharief A. M. Sh. , Mohamed Y. A. , Salem M. A. , Al‐Sehemi A. G. , El‐Gaby M. S. A. 
Published: May 2015

AbstractPolysubstituted pyridone derivatives were obtained through interaction of cyanoacetanilides with different reagents such as chalcones, 1,1,3‐tricyano‐2‐aminopropene, and arylidenemalononitrile and acetyl‐acetone.
A Convenient Synthesis of Some Pyrazolinone and Pyrazole Derivatives
Authors: Aly El‐Saied A. , Abdo Mohamed A. , El‐Gharably Atif A. 
Published: May 2015

AbstractA convenient synthesis of some novel 6‐amino‐4‐aryl‐1‐phenyl‐3‐pyridin‐4‐yl‐1,4‐dihydropyrano[2,3‐c]pyrazole‐5‐carbonitriles (3a,b) and 5‐chloro‐1‐phenyl‐3‐pyridin‐4‐yl‐1H‐pyrazole‐4‐carbaldehyde (4) is described. Compound 4 was obtained by the reaction of 2‐phenyl‐5‐pyridin‐4‐yl‐2,4‐dihydropyrazol‐3‐one (1) with dimethylformamide and phosphorus oxychloride under Vilsmeier‐Haack reaction conditions. Compound 4 was subjected to react with different reagents such as hippuric acid, sodium azide and aromatic ketones to afford 4‐(5‐chloro‐1‐phenyl‐3‐pyridin‐4‐yl‐1H‐pyrazolo‐4‐ylmethylene)‐2‐phenyl‐4H‐oxazol‐5‐one (5), 5‐azido‐1‐phenyl‐3‐pyridin‐4‐yl‐1H‐pyrazol‐4‐carbaldehyde (8) and 1‐aryl‐3‐(5‐chloro‐1‐phenyl‐3‐pyridin‐4‐yl‐1H‐pyrazol‐4‐yl)propenones (12a,b), respectively. The latter compounds were also prepared via Michael reaction by treatment of compound 1 with some different chalcones.
A New and Efficient Solid State Synthesis of N‐Aryl‐2‐Phenyldiazenecarboxamides
Authors: Xue Wan‐Xin , Li Jian‐Ping , Wei‐Li  , Wang Yu‐Lu 
Published: May 2015

AbstractAn efficient and convenient solid state reaction using Fe(NO3)3·9H2O/NaHSO4·H2O to oxidize aryl‐substituted semicarbazides for preparing azo compounds has been reported. Eight N‐aryl‐2‐phenyldiazenecarboxamides have been synthesized in excellent yields at room temperature. The method is efficient and rapid.
Probing the Enzyme Catalytic Mechanism by Nuclear Magnetic Resonance ‐ A Case Study of a Serine Protease
Authors: Tyukhtenko Sergiy I. , Huang Yao‐Te , Lin Ta‐Hsin , Chen Chinpan , Chang Chi‐Fon , Lee Shin‐Jye , Litvinchuk Alexandra V. , Shaw Jei‐Fu , Liaw Yen‐Chywan , Huang Tai‐Huang 
Published: May 2015

AbstractSerine proteases are among the most studied enzymes for their role as model enzymes for studying the enzyme catalytic mechanism and medical interest in their inhibition. We have applied NMR methods to determine the structure, dynamics, and catalytic mechanism of a serine protease, E. coli thioesterase/protease I (TEP‐I). In this article we review the results of our efforts. We showed that TEP‐I is an / / type SNGH‐hydrolase with Ser10, Asp154 and His157 as the catalytic triad residues. In free TEP‐I, His157 was found to forma strong hydrogen bond to Asp154, but not to Ser10‐O H. Modelfree analysis of 15N‐T1, 15N‐T2 and 1H‐15N NOE data revealed that TEP‐I is a rigid protein with a flexible catalytic binding pocket. Slow motion involving segments around the catalytic site was detected. The formation of Michaelis complex (MC) between TEP‐I and a transition state analogue, diethyl p‐nitrophenyl phosphate (DENP), and its subsequent conversion to the tetrahedral complex (TC) follow a two‐step process, a fast formation of MC followed by a slow conversion to TC. In both steps residues perturbed were confined mainly to four conserved segments comprising the active site. Comparable magnitudes of chemical shift perturbations were detected in both steps. From the large chemical shift perturbation upon conversion from MC to TC we proposed that the amide protons of Ser10 and Gly44 serve as the oxyanion‐hole proton donors to stabilize the tetrahedral adduct. The pattern of residues perturbed in both steps suggests a sequential, stepwise structural change upon binding of DENP.
The Triple Layer Model: A Different Perspective on Lipid Bilayers
Authors: Lee Clarence C. , Petersen Nils O. 
Published: May 2015

AbstractIn this review a modified view of the Singer‐Nicholson model, termed the triple layer model, is presented. Structural and dynamic studies of lipid bilayers have demonstrated that the two interface regions of a membrane are more rigid and less dynamic than the inner hydrocarbon region. The results from these studies are gathered in this paper to support the notion of modifying the viewpoint of the fluid mosaic model. The idea of lipid bilayers consisting of three distinct and functional layers has interesting implications. We speculate on how the triple layer model pertains to both the mechanical properties of membranes and its biological relevance.
DNA Hydrolysis Catalyzed by Tris(diisopropyl‐1,4,7‐triazacyclononanes)ethane Metal Complexes
Authors: Cheng Chien‐Chung , Huang Yan‐Chen , Liu Ming‐Chan 
Published: May 2015

AbstractNovel trinuclear coordinated ligands were designed using three of 1,4,7‐triazacyclononane moieties with a tribromo linker. These ligands show greater capability and potency in association with various metal ions. Tris(diisopropyl‐1,4,7‐triazacyclononanes)ethane (2) associated with Cu2+ and Ce4+ ions shows better reactivity to achieve DNA hydrolysis at 37 °C at pH 8 for 5 hr. Using high resolution of polyacrylamide gel electrophoresis, DNA cleavage reaction in Tris‐HCl buffer causes a nicking site at the single‐stranded region. Alternatively, the reaction in HEPES buffer shows a random DNA cleavage included the double‐stranded region. Hydrolysis of phosphodiester bond mediated by trinuclear metal complex is capable of performing at the physiological temperature 37 °C, but it has a lower reactivity compared to mono‐ and di‐nuclear metal complexes. The result suggests that trinuclear metal complexes have a bulky environment to prevent from going toward the phosphodiester bond. The design of an efficient chemical hydrolyase will be a challenge in order to construct a coordinate ligand with the enhancement of hydrolytic activity and the reduction of the steric environment.
Hypervalent Iodine(III) Sulfonate Mediated Synthesis of Imidazo[1,2‐a]pyridines
Authors: Huang Hsin‐Yu , Hou Rei‐Sheu , Wang Huey‐Min , Chen Ling‐Ching 
Published: May 2015

AbstractA direct and efficient method for the conversion of alkyl aryl ketones to imidazo[1,2‐α]pyridines has been developed based on initial formation of α‐organosulfonyloxy ketones and their subsequent cyclocondensation by 2‐aminopyridines in one‐pot conditions.
Nucleosides XII.1 Synthesis of 5‐Modified Isoguanosines and Reinvestigation of 5′‐Deoxy‐N3,5′‐cycloisoguanosine
Authors: Chien Tun‐Cheng , Kuo Chia‐Chi , Chen Chien‐Shu , Chern Ji‐Wang 
Published: May 2015

AbstractIsoguanosine (3) underwent a coupling reaction with diaryl disulfides in the presence of tri‐n‐butylphosphine when its 6‐amino group was protected by N,N‐dimethylaminomethylidene. The synthesis of 5′‐deoxy‐N3,5′‐cycloisoguanosine (6) and its 2′,3′‐O‐isopropylidene derivative (11) were accomplished in excellent yields from isoguanosines (3 & 10) in the presence of triphenylphospine and carbon tetrachloride in pyridine. Chlorination at the 5′‐position of isoguanosine (3) with thionyl chloride followed by the aqueous base‐promoted cyclization afforded the same product 6. The structures were elucidated by spectroscopic analysis including IR, UV, 1‐D and 2‐D NMR.
Formation of Caged Compounds in the Photocycloaddition of Furan to 2‐, 2,3‐, and 2,6‐Substituted Naphthalenes via Dipole‐Dipole Interaction
Authors: Mizuno Kazuhiko , Tachibana Yuko , Konishi Gen‐Ichi , Chiyonobu Kazuhiko , Maeda Hajime 
Published: May 2015

AbstractPhotocycloaddition of furan to naphthalene derivatives having electron‐withdrawing groups at 2‐ or 2,3‐position via exciplex afforded caged‐products in high yields. The structure‐reactivity relationship can be reasonably explained by dipole‐dipole interaction between two chromophoric molecules.
Photoinduced Electron Transfer and Electron‐Mediating Systems of [60]Fullerene and Triphenylamine Derivatives in the Presence of Viologen Dication in Polar Solvent
Authors: Sasaki Yoshiko , Araki Yasuyuki , Ito Osamu , Alam Maksudul M. 
Published: May 2015

AbstractPhotoinduced electron‐transfer processes between fullerenes (C60) and three triphenylamines (TPA's) including bis(tolylaminophenyl)cyclohexane in the absence and presence of hexylviologen dication (HV2+) and 1‐benzyl‐1,4‐dihydronicotinamide (BNAH) have been studied by the transient absorption method in the visible and near‐IR regions. Electron‐transfer takes place initially from TPA's to the triplet states of fullerenes (3C60*), giving the radical anions of fullerenes (C60−) and the radical cations of TPA's (TPA+). The rate constants and efficiencies of electron transfer are quite high, because of the high electron‐donor abilities of TPA's as their low oxidation potentials indicate. On addition of HV2+to the C60and TPA systems, the electron‐mediating process from C60−to HV2+occurs, yielding the viologen radical cation (HV+). In the further addition of BNAH, which acts as a sacrificial donor, steady‐state concentration of HV+was accumulated during continuous photoirradiation and persisted for a long time.
Fourth Order Derivative Spectrophotometric Determination of Benzyl Alcohol in Piroxicam Injections
Authors: Rizk M. , Ibrahim F. , Hefnawy M. , Nasr J. J. 
Published: May 2015

AbstractPiroxicam is a drug with analgesic and anti‐inflammatory properties. It is present in numerous pharmaceutical preparations. Injectable forms usually contain benzyl alcohol as an excipient, which is used as a blocking anesthetic (4%) and an antiseptic (4–10%). In this work, spectrophotometric methodology was used in order to determine benzyl alcohol in piroxicam injectable formulations by applying the fourth derivative method adopting the zero‐crossing technique. The results obtained show that the method has significant advantages over other reported methods and is appropriate for routine pharmaceutical analysis. The method showed excellent linearity in the range of 2–100 μg mL−1 with limit of detection (S/N = 3) 0.07 μg mL−1 (6.47 × 10−7 M). The proposed method could be applied successfully for the determination of benzyl alcohol in injectable formulations with average % recovery of 100 ± 0.61.
Theoretical Study of Weakly Bound Dimers between Hydrogen Fluoride and Some Polar Molecules
Authors: Chen Shyh‐Jong , Chen Cheng , Hong Yaw‐Shun 
Published: May 2015

AbstractWeakly bound linear and bent dimers, FH—X (where X = CO, OC, CNH, NCH, N2O and ON2), are investigated using the DFT B3LYP and ab initio MP2 methods with the same basis sets (6–311++G(3df,2pd)). The strengths of the H—C or H—N H‐bonds in dimers FH—CO, FH—CNH, and FH—N2O are compared with those of the H—O or H—N H‐bonds in dimers FH—OC, FH—NCH, and FH—ON2. The results obtained for the H‐bond distances, the elongation effect of the HF bond, the red shift of the HF stretching frequency, and the energy difference between the dimer and the charge transfer reveal that the H‐bonds of the first group of dimers are stronger than those of the second. The Gibbs energies calculated for the six dimer formations indicate that the weakly bound dimers are unstable at room temperature (T = 298 K) (FH—X's → FH + X's, ΔG < 0).
ESR Studies on a Friedel‐Crafts Alkylation Reaction in [bmim]Cl‐AlCl3 Ionic Liquid
Authors: Zhai Cui‐Ping , Song Ai‐Xin , Liu Wei‐Min , Wanga Han‐Qing 
Published: May 2015

AbstractThe paramagnetic complexes formed in Friedel‐Crafts alkylation reaction systems are invistigated by electron spin resonance (ESR) spectroscopy, in room temperature ionic liquids system 1‐butyl‐3‐methyl‐limidazolium chloride‐aluminium chloride ([bmim]Cl‐AlCl3). The results indicate that ESR spectra observed are due to polycyclic aromatic radical cations formed from their parent hydrocarbons. ESR spectrum of spin adduct is obtained in an ionic liquid system composed of [bmim]Cl‐AlCl3. In acidic solution the 14N hyperfine coupling constant of 4‐oxo‐TEMPO, 2.15 mT, is appreciably larger due to an adduct formed with AlCl3.
Novel Synthesis of Dihydroquinoxalinylpyridazine Derivatives
Authors: Elassar Abdel‐Zaher Abdel‐Aziz 
Published: May 2015

AbstractMethylquinoxaline derivative 1 undergoes bromination to give bromomethyl quinoxaline 2, which could be transferred to cyanomethyl quinoxaline 3. The latter compound 3 readily coupled with arene diazonium salts to give hydrazone derivatives 5a‐c. Compounds 5a,b reacted with active methylene reagents to give the target ring system, quinoxalinylpyridazine derivatives 8a‐c. Compound 1 reacted with DMFDMA to give the enamine derivative 9, which coupled with arene diazonium salts to give the aldehydic hydrazone derivatives 10a‐c. Compound 10 reacted with active methylene compounds to give quinoxalinylpyridazine derivatives. UV characterization of some of the prepared compounds was reported.
Formal Synthesis of (±)‐Trachelanthamidine via Base‐Induced Formal [3+2] Annulation and Intramolecular Cyclization
Authors: Hsu Ru‐Ting , Chang Nein‐Chen , Chang Meng‐Yang 
Published: May 2015

AbstractBase‐induced coupling/cyclization stepwise [3+2] annulation of α‐sulfonylacetamide with (Z)‐2‐bromoacrylates yielded polysubstituted pyroglutamates with three contiguous chiral centers with trans‐trans orientation in a one‐pot synthesis. The pyrrolizidine skeleton was obtained via an intramolecular cyclization. This facile strategy was used to synthesize (±)‐trachelanthamidine.
In Situ Generated Palladium Nanoparticles for Catalytic Dehalogenation of Aryl Halides and Deboronation of Arylboronic acids
Authors: Lai Rung‐Yi , Chen Chuan‐Lin , Liu Shiuh‐Tzung 
Published: May 2015

AbstractPalladium nanoparticles in situ generated from palladacyclic complexes efficiently catalyzed the deboronation of arylboronic acids and the dehalogenation as well as homo‐coupling of aryl iodides in an alcohol medium under basic conditions. Isotope labeled studies indicated that the β‐elimination of alcohols provided the hydrogen source for the reaction.
Density Functional Theory Study on the Nitration of Halobenzene by Nitronium Ion
Authors: Chen Li‐Tao , Chen Guang‐Ju , Xiao He‐Ming 
Published: May 2015

AbstractThe rate determining steps of isomeric ortho, meta and para nitrations of fluorobenzene and chlorobenzene have been theoretically investigated at the B3LYP/6‐311G* level. Stationary points of the step involving reactant, transition state and intermediate complexes were successfully located and characterized without any restriction on the internal coordinates. Their molecular geometries, electronic structures, IR spectra, and the FMO symmetries of two initial aromatic compounds and the NO2+ suggest that the halogens are ortho‐para directive, and also activating substituents in the gas phase. The blue shift of the C‐N stretching vibration and the red shift of the tetrahedral C‐H stretching vibration from transition state to Wheland intermediate demonstrate that the formation of the C‐N and the cleavage of the C‐H are not concerted but stepwise at the rate determining step. This provides theoretical evidence for the experimental fact of the absence of primary kinetic isotopic effect in most aromatic nitration reactions. The fully optimized geometries of nitro‐chlorobenzene complexes show that the C‐Cl bond in nitro‐chlorobenzene complexes become much shorter than in chlorobenzene molecules and appears as a double bond. On the contrary, the C‐F bond in nitro‐fluorobenzene complexes is still a single bond, and even lengthens slightly as the NO2+ moves toward the fluorobenzene. This reveals that there is a special interaction, namely inductomeric effect, between the chlorine and nitro group in nitro‐chlorobenzene complexes. The inductomeric effect may cause a marked increase in the percentage of ortho product for the nitration of chlorobenzene.