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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
291

Construções gráficas polinomiais fazendo uso de derivadas

Queiroz, Luiz Fernando Barbosa de 06 August 2016 (has links)
Submitted by Renata Lopes (renatasil82@gmail.com) on 2017-01-09T13:34:32Z No. of bitstreams: 1 luizfernandobarbosadequeiroz.pdf: 1375461 bytes, checksum: 4021226e02ca23e0d0e6b20cc9f9d415 (MD5) / Approved for entry into archive by Adriana Oliveira (adriana.oliveira@ufjf.edu.br) on 2017-02-07T13:22:13Z (GMT) No. of bitstreams: 1 luizfernandobarbosadequeiroz.pdf: 1375461 bytes, checksum: 4021226e02ca23e0d0e6b20cc9f9d415 (MD5) / Approved for entry into archive by Adriana Oliveira (adriana.oliveira@ufjf.edu.br) on 2017-02-07T14:08:29Z (GMT) No. of bitstreams: 1 luizfernandobarbosadequeiroz.pdf: 1375461 bytes, checksum: 4021226e02ca23e0d0e6b20cc9f9d415 (MD5) / Made available in DSpace on 2017-02-07T14:08:29Z (GMT). No. of bitstreams: 1 luizfernandobarbosadequeiroz.pdf: 1375461 bytes, checksum: 4021226e02ca23e0d0e6b20cc9f9d415 (MD5) Previous issue date: 2016-08-06 / Esse trabalho trata dos temas de funções, limites e derivadas. Tendo por objetivo final mostrar a aplicação dos conceitos de derivada nas construções gráficas de funções polinomiais, especificamente de funções polinomiais do segundo e terceiro grau por serem as mais adequadas ao Ensino Médio. Para isso, serão utilizados instrumentos matemáticos que fazem uso de derivadas, tais como: Teste da Derivada primeira e Teste da Derivada segunda. / This work deals with the issues of functions , limits and derivatives . With the ultimate goal to show the application of the concepts of derivatives in the graphic construction of polynomial functions, in particular polynomial functions of degree two and three since they are the most suitable for the high school. To this end, we will use mathematical tools that make use of derivatives, such as: Test of the first derivative and Test of the second derivative.
292

A política de hedge e o tratamento do risco nas empresas não-financeiras / The Hedge policy and the treatment of risk in the non-financial companies

Ricardo Humberto Rocha da Silva 10 May 2007 (has links)
O gerenciamento dos riscos e seus impactos na lucratividade das empresas não-financeiras têm sido objeto constante de estudos nos últimos anos. As crises globais ocorridas nos últimos dez anos, conjugadas com a liberalização dos fluxos de capitais, ampliação da base tecnológica e acirramento das disputas comerciais têm obrigado as empresas a conhecerem detalhadamente os fatores de risco associados aos processos de produção, comercialização e divulgação de seus produtos, bem como a influência desses fatores de risco no retorno do investimento e na lucratividade das operações. Elaborar um modelo que permita captar os possíveis efeitos do risco sobre a lucratividade das empresas e, dessa forma, quantificar monetariamente a implementação de estratégias de mitigação e o custo das políticas de hedge, passa a ser um fator de diferenciação, competitividade e sobrevivência. Desde 1994, ocorre grande desenvolvimento de metodologias e modelos que permitem a medição do risco como o modelo value at risk desenvolvido pelo Banco J.P.Morgan, cuja eficiência está relacionada à gestão de riscos em instituições financeiras. Para instituições não-financeiras, outras abordagens são discutidas, testadas e aprimoradas. Para as empresas não-financeiras este trabalho propõe uma modelagem via árvore binomial aditiva que permite a projeção do lucro operacional, a quantificação dos efeitos do risco sobre esse lucro e o custo financeiro das operações de hedge. O modelo desenvolvido será aplicado a um conjunto de empresas escolhidas por representarem setores importantes para a economia brasileira. / The management of risk and of its impact over corporate profitability have been widely studied and researched over the recent past. The global crises which occurred during the last ten years coupled with the liberalization of capital flow, the spread of the information technology infra-structure and the increase in commercial disputes have demanded more from companies and have obliged them to better understand the risks associated with their activities and production and sales processes, and also the impact of such risk factors over their investment return and operational profitability. The possibility of developing a successful model which can capture the eventual risk influence over corporate profitability and also quantify the impact of the hedge strategies and their respective costs might turn into a differentiation factor, if not into a survival and competitive advantage factors. Since 1994, new methodologies and models have been developed aimed at measuring risk, such as the value at risk model, developed by the J.P.Morgan Bank, whose efficiency is related to the risk management of financial institutions. For non-financial institutions, other approaches have been discussed, tested and improved over time. Following this reasoning, the goal of this research is to propose a model of binomial additive three which allows for the projection of operational profit, for the quantification of risk effects over such profit and for the determination of the financial cost of the hedge instruments to be used. In addition to present the model of binomial additive three, this paper will apply such model to a sample of companies, considered relevant in the Brazilian economy and in their respective sectors.
293

Synthesis of novel quinoline derivatives and their cytotoxicity in A549 lung cancer cells

Nkosi, S'busiso Mfan'vele January 2017 (has links)
Thesis submitted in fulfilment of the requirements for the Degree of Master's in Chemistry, Durban University of Technology, 2017. / Quinoline and its derivatives represent an important class of nitrogen-containing heterocylces as they are useful intermediates in organic synthesis and possess a broad spectrum of biological activities, such as anti-asthmatic, anti-inflammatory and anti-malarial activity. Hence, synthesis of novel compounds with potent biological activities is important in medicine. Significant research is directed into the development of new quinoline based structures and new methods for their preparations. In the past, synthesis of complex molecules was accomplished by step-wise reaction. This was time consuming and yield was generally low. Nowadays, multi-component reactions (MCRs) are being used since three or more substrates can be reacted in a one-pot reaction. Therefore yields are higher and the reaction is more efficient. In this research investigation novel quinoline derivatives, using the multi-component reaction protocol, were synthesized. After characterization of the product by several spectroscopic techniques, the biological potential of these compounds were assessed using lung cancer cell lines, bacteria and molecular modeling in an enzymatic system. In the synthetic part of this study, the first step was the preparation of the starting compound 2- chloro-3-formyl quinoline for which the Vilsmeier-Haack cyclisation protocol was used. The cyclisation was carried out by combining DMF and POCl3 at 5°C to form an electrophile which then reacted in situ with N-phenylacetamide at 100ºC to afford 2-chloro-3-formyl quinoline in high yield (95%). This was followed by the synthesis of a series of novel quinoline derivatives in a MCR system comprising 2- chloro-3-formyl quinoline, malononitrile, aromatic amines and dimethyl acetylenedicarboxylate in the presence of a catalytic amount of triethylamine. Valuable features of this routine included high yields, extensive substrate range and straight forward procedures. Eight novel poly-functionalised dihydropyridine quinoline derivatives were synthesized, purified and characterized. The outline for the synthesis of poly-functionalised dihydropyridine quinoline derivatives is presented graphically in Scheme 1. Scheme 2 shows the eight compounds synthesized and used subsequently for further studies. . Step 1 CH3 a N O H CHO N Cl Step 2 CHO CN N Cl CN NH2 R O OCH3 b OCH3 O MeO2C MeO2C N Cl CN N NH2 R = m-CH3, o-OCH3, p-Cl, m,p-Cl, o-F, m-F, p-F R Reaction Conditions: a. DMF, POCl3 b. Et3N, EtOH Scheme 1: Graphical representation for the synthesis of poly-functionalised dihydropyridine quinoline derivatives The novel eight compounds were screened for their potential activity in lung cancer cell lines. A549 cells were incubated for 24 hours with a range of concentrations of each compound, in triplicate, in a micro-titre plate together with an untreated control. Each experiment was conducted twice on separate occasions; the results from the first set matched the repeated experiment. The cells were then incubated (37ºC, 5% CO2) with the MTT substrate for 4 hours. Thereafter all supernatants were aspirated and DMSO was added to the wells. Finally the optical density was measured at 570 nm at a reference wavelength of 690 nm with an ELISA plate reader. The net MTT dependant absorbance (optical density) of each sample was calculated by subtracting the average absorbance of the blank from the average absorbance of each sample. Data were represented as mean optical density plus or minus the standard deviation. Four of the synthesized compounds (A1-A8) were evaluated for their cytotoxicity activities. The anti-cancer assay indicated that poly-functionalised dihydropyridine quinoline compounds, A2, A3 and A4 have good potential as anti-cancer drugs. Among them, A2 and A4 proved to be dose dependent with A4 having the highest toxicity at 250 µM and A8 having the highest toxicity at 125, 250 and 500 µM, whereas A1, A5, A6 and A7 were not cytotoxic. O H3CO H3CO O N Cl CN NH2 O H3CO H3CO O N Cl CN N NH2 OCH3 O H3CO H3CO O N Cl CN N NH2 O H3CO H3CO O N Cl CN NH2 CH3 Cl A1 A2 A3 A4 O H3CO H3CO O N Cl CN N NH2 F O H3CO H3CO O N Cl CN N NH2 O H3CO H3CO O N Cl CN NH2 O H3CO H3CO O N Cl CN N NH2 F Cl F Cl A5 A6 A7 A8 Scheme 2: Structures of novel poly-functionalised dihydropyridine quinoline derivatives by MCRs Since molecular docking is a key tool in structural molecular biology and computer-assisted drug design, these compounds were subjected to molecular docking and the binding mode for the compounds, within the active site of the protein, was analyzed. Docking of A1 to Human mdm2 protein provided insights into the binding regions. Three hydrogen bonds were formed between GLU 25 (2.7 Å distance), LEU 27 (3.2 Å distance) and LEU 54 (3.2 Å distance) atoms with binding energy of -8.91 kcal/mol. Docking of A1 with Human mdm2 indicated the lowest binding energy thereby showing strong affinity of the ligand molecule with the receptor which has been stabilized by strong hydrogen bond interactions in the binding pocket. This confirms that A1 is a better inhibitor for E3 ubiquitin-protein ligase mdm2 than all the other compounds tested (A2-A8). Further, the eight novel poly-functionalised dihydropyridine quinoline derivatives were evaluated for their antibacterial activity. This was performed using the MABA method against three strains i.e. Gram negative; Pseudomonas aeruginosa (ATCC 27853), Escherichia coli (ATCC 25922) and Gram positive; Staphylococcus aureus (ATCC 29213) using the broth micro dilution method. Standard antibiotics (ciprofloxacin and nalidixic acid) were used as positive controls and DMSO was used as a negative control. The results obtained from the anti-bacterial assay showed that compounds A4, A7 and A8 have high activity, whereas A2 and A3 showed poor activity against all the tested bacterial strains. Compound A6 showed no activity against S. aureus and E. coli. / M
294

Synthèse, Caractérisation et Activité biologique des complexes à base de thiosemicarbazone / Synthesis, structural characterization and biological activity of complexes based on thiosemicarbazone

Jaafar, Amani 17 July 2017 (has links)
Le thiosemicarbazide et le 4-méthylthiosemicarbazide réagissent par condensation avec des dérivés benzaldéhyde pour donner des produits de type thiosemicarbazone pouvant jouer le rôle de ligands.Ces derniers peuvent conduire en milieu éthanolique à la formation de divers complexes en réagissant avec des sels métalliques comme les chlorures et/ou bromures de cuivre(II), de nickel(II), de zinc(II), de cobalt(II) et de cadmium(II). La structure de ces ligands et de leurs complexes a été déterminée par spectroscopie infrarouge, par des analyses élémentaires et par cristallographie. Les ligands se présentent tous sous forme thione à l’état solide tandis que les complexes obtenus peuvent revêtir différents états : soit monodentés, mononucléaire ou polynucléaire à deux atomes de soufre provenant du groupement thiosemicarbazone, comme l’étude cristallographique a pu le démontrer, soit bidentés avec des sites decoordination dont l’azote provenant du groupement imine et le soufre du groupement thiol. Les propriétés antifongiques de ces divers composés ont été testées vis-à-vis de champignons pathogènes de l’homme comme Aspergillus fumigatus, Candida albicans, C. glabrata, C. tropicalis, C. krusei, C. parapsilosis et Exophiala dermatitidis. Seuls les complexes avec le cadmium ont montré des activités antifongiques significatives et le ligand de pdiméthylaminobenzaldéhyde thiosemicarbazone a inhibé presque totalement la croissance d’E. dermatitidis / Thiosemicarbazide and 4-methylthiosemicarbazide react with benzaldehyde derivatives by condensation to give different thiosemicarbazone ligands. The latter conduct in ethanolic medium to various complexes by reacting with chlorides and / or bromidesof copper (II), nickel (II), zinc (II), cobalt (II) and cadmium (II). The structures of the ligands and their complexes have been determined mainly by crystallography and by infrared spectroscopy, as well as by elementary analyzes. The ligands are in thion form in solid form.The complexes obtained are either monodentate, mononuclear or polynuclear complexes with two sulfur atoms of the thiosemicarbazone group, such as the determination of the crystal structure has shown either bidentate complexes with coordination sites, imine nitrogen and sulfur of the thio group. Their antifungal properties have been tested against human pathogenic strains: Aspergillus fumigatus, Candida albicans, C. glabrata, C. tropicalis, C. krusei, C. parapsilosis and Exophiala dermatitidis. Only thecomplexes with cadmium exhibited significant activities against the fungal species studied and the thiosemicarbazone of p-dimethylaminobenzaldehyde ligand almost completely inhibited the growth of E. dermatitidis
295

Příprava benzoylovaných derivátů cyklodextrinů / Preparation of benzoylated derivatives of cyclodextrins

Jůza, Radomír January 2017 (has links)
This master thesis deals with the preparation of the cyclodextrin (CD) derivatives that are suitable for complexation of the electron-rich aromatic compounds such as helicenes. The basic skeleton of native CD was perbenzoylated in all positions 2, 3 and 6 in the first place. Then the nucleophilic attack of carboxylates of benzoic acids with electron- withdrawing groups (NO2) or electron-donating group (NH2) to per(6-deoxy-6-iodo)-CD derivatives were used to prepare the perbenzoylated CD derivatives in the postition 6. Binding constant was determined for the prepared benzoylated derivatives of CD and the racemate of the hexahelicene using the NMR titration. Perbenzoylated derivatives of β-CD in all position 2,3 and 6 with one azido group in position 6 were prepared as well. These derivatives could be covalently bonded as chiral selectors in the stationary phase for the HPLC separation of aromatic enantiomers. Keywords: cylodextrins, persubstitution, benzoyl, 4-nitrobenzoyl, 3,5-dinitrobenzoyl, helicenes, NMR titration, binding constants
296

Cell Permeability Studies of AApeptides and Novel Molecular Probes for AD

Bai, Ge 08 April 2016 (has links)
Alzheimer's diseases(AD) has been discovered and under research for more than 70 years, However there is no cure for these progressive and devastating diseases. Based on the following hypothsis: Aß metabolite problem/over production result in the accumulation, and lead to aggregation is the cause of Alzheimer’s disease. AApeptide and Melatonin derivatives can bind to Aß and block the aggregation of β amyloid monomers, decrease the toxicity of Aß to neurons and slow the progressive of Alzheimer’s diseases. In addition, AApeptide which mimic transmembrane peptide Tat will have similar transmembrane function. We have set up our goals as follows: 1) Using newly discovered peptidomimetics, AApeptides. We moved on to research to discover their potential of transmembrane activity and anti-Alzheimer's acitiviy. 2) In Addition, studies of small molecule melatonin derivatives were also progressed. Methods include in this research includes bioorganic synthesis, identification of spectroscopy and relative assays targeting on biological efficiency of Anti-Alzheimer’s diseases. The details of which will be described in Chapters. In conclusions, two sets of transmembrane peptidomimetics for drug transportation has been successfully evaluated and potential of AA peptide small molecules, melatonin derivativesare also evaluated. These works have gained good progress in research between AApeptide and Alzheimer’s Diseases. These works also established basis of research in developing peptidomimimetics as potential pharmacies against Alzheimer’s diseases.
297

Efficient Monte Carlo methods for pricing of electricity derivatives

Nobaza, Linda January 2012 (has links)
>Magister Scientiae - MSc / We discuss efficient Monte Carlo methods for pricing of electricity derivatives. Electricity derivatives are risk management tools used in deregulated electricity markets. In the past,research in electricity derivatives has been dedicated in the modelling of the behaviour of electricity spot prices. Some researchers have used the geometric Brownian motion and the Black Scholes formula to offer a closed-form solution. Electricity spot prices however have unique characteristics such as mean-reverting, non-storability and spikes that render the use of geometric Brownian motion inadequate. Geometric Brownian motion assumes that changes of the underlying asset are continuous and electricity spikes are far from being continuous. Recently there is a greater consensus on the use of Mean-Reverting Jump-Diffusion (MRJD) process to describe the evolution of electricity spot prices. In this thesis,we use Mean-Reverting Jump-Diffusion process to model the evolution of electricity spot prices. Since there is no closed-form technique to price these derivatives when the underlying electricity spot price is assumed to follow MRJD, we use Monte Carlo methods to value electricity forward contracts. We present variance reduction techniques that improve the accuracy of the Monte Carlo Method for pricing electricity derivatives.
298

Dérivés ambiphiles : synthèse et réactivité dephosphine-borane, réactivité d'un complexe possédant un ligand phosphine-alane / Amphibilic derivatives : synthesis and reactivity of phosphine-borane, reactivity of complex with a phosphine-alane ligand

Declercq, Richard 03 November 2016 (has links)
Les dérivés ambiphiles, possèdant un site acide de Lewis (B ou Al) et un site base de Lewis (P), sont connues pour activer les petites molécules, stabiliser des espèces hautement réactives, mais aussi pour se comporter comme des catalyseurs non-métalliques. Dans la mesure où ils présentent différents modes de coordination, ils possèdent des comportements variables en tant que ligands des métaux de transition. Cette thèse porte sur deux aspects des composés ambiphiles. Le premier concerne l'interaction avec les petites molécules et l'organocatalyse, et le second la coordination et la réactivité des complexes métalliques avec des ligands ambiphiles. Le premier chapitre aborde la synthèse et la réactivité de phosphines-boranes possédant un espaceur de type ortho-phénylène. Dans une première partie, des composés possédant des sites base et acide de Lewis de nature différente ont été synthétisés. Dans une seconde partie, les propriétés catalytiques de ces dérivés ont été évaluées lors de la réduction du dioxyde de carbone en présence de boranes. Ces dérivés ambiphiles se sont révélés être des organocatalyseurs efficaces pour cette réaction. Dans une troisième partie, une étude mécanistique a été réalisée. Lors de cette étude, un intermédiaire réactionnel a pu être isolé et caractérisé. Cette espèce, possédant une molécule de formaldéhyde pontante entre les atomes de phosphore et de bore, s'est montrée plus efficace en catalyse que les catalyseurs précédents. En effet, aucune période d'induction n'est observée lors de la réduction du dioxyde de carbone avec ce dernier. Le second chapitre aborde la réactivité d'un complexe de Pt possédant un ligand ambiphile de type phosphine-alane (PAl). Ce complexe comportant une interaction Pt-->Al, avait déjà montré une réactivité intéressante vis-à-vis de l'hydrogène. Dans ce chapitre, sa réactivité vis-à-vis d'autres substrats a été étudiée. Dans une première partie, la capacité du complexe PAl-Pt à activer une liaison N-H polaire a, en particulier, été évaluée. Un complexe issu de l'addition oxydante de PhC(O)NH2 sur le platine a pu être isolé et entièrement caractérisé. Dans une seconde partie, le complexe PAl-Pt a été mis en présence de petites molécules de type CE2 (E = O, S) et différents modes de coordination ont pu être mis en évidence aussi bien en solution et qu'à l'état solide. En particulier, un complexe n1 de CO2 a été isolé. Au cours de ce travail, l'accent a été mis sur la coopérativité d'action métal/acide de Lewis. / Ambiphilic derivatives, which possess a Lewis acid (B or Al) and a Lewis base (P), are known for activating small molecules, stabilizing highly reactive species, but also to be used as metal-free catalyst. Because of their different coordination modes, they show different behaviour as ligand for transition metals. This thesis addresses two aspects of ambiphilic derivatives. The first one is about the interaction with small molecules and the organocatalysis, and the second one the coordination and the reactivity of metallic complexes with ambiphilic ligands. The first chapter deals with the synthesis and the reactivity of phosphine-borane which possess an ortho-phenylene backbone. In the first part, compounds with different kind of Lewis base and acid have been synthesized. In a second part, catalytic properties of these derivatives have been evaluated for the reduction of carbon dioxide in presence of borane. These ambiphilic derivatives have revealed themselves as effective organocatalyst for this reaction. In a third part, a mechanistic study have been realised. During this study, a reaction intermediate has been isolated and characterized. This species, which possess a molecule of formaldehyde bridging between the atoms of phosphorus and boron, revealed itself more effective in catalysis that the previous catalyst. Indeed, no induction period has been observed during the reduction of carbon dioxide with this compound. The second chapter relates the reactivity of a Pt complex which possess a phosphine-alane (PAl) type ambiphilic ligand. This complex involving a Pt-->Al interaction, has already shown an interesting reactivity toward dihydrogene. In this chapter, his reactity toward other kind of substrate has been studied. In a first part, the capacity of the PAl-Pt complex to activate a polar N-H bond has been evaluated. A complex coming from the oxidative addition of PhC(O)NH2 over the platinum has been isolated and fully characterized. In a second part, the PAl-Pt complex has been set to react with CE2 (E = O or S) type small molecules, and different coordination modes have been highlighted both in solution and in solid state. In particular a n1 CO2 coordinated complex has been isolated. During this work, the cooperativity of action metal/Lewis acid has been emphases.
299

Synthetic and spectroscopic studies of indolizine derivatives

Bode, Moira Leanne January 1994 (has links)
The crystalline compound resulting from thermal cyclization of the Baylis-Hillman product, methyl 3-hydroxy-2-methylene-3-(2-pyridyl)propanoate, has been identified as the indolizine derivative, methyl indolizine-2-carboxylate, and this approach involving the reaction of pyridine-2-carboxaldehydes and acrylate analogues has been established as a general route to 2-substituted indolizines. The ease of cyclization the Baylis-Hillman products to indolizines has been shown to increase by converting the hydroxy group to an acetoxy group, and a range of acetylated Baylis-Hillman products were prepared and cyc1ized to the corresponding 2-substituted indolizines, generally in good overall yield. In the reaction of pyridine-2-carboxaldehyde and methyl vinyl ketone, the intermediate cyclized readily and directly to the corresponding indolizine. One- and two-dimensional ¹H and ¹³C NMR analysis of the 2-substituted indolizine products has permitted complete assignment of all ¹H and ¹³C NMR signals, as well as the measurement of all coupling constants for these compounds. A kinetic and mechanistic study has been conducted on the Baylis-Hillman reaction using ¹H NMR spectroscopy. A range of substrates has been examined and the reaction has been found to be third-order overall. A mechanism involving an addition - elimination sequence is proposed, which fits the kinetic data and accounts for observed substituent effects. Reaction of N,N-dimethylacrylamide with pyridine-2-carboxaldehyde in the presence of the tertiary amine catalyst, DABCO, in chloroform, yielded an unexpected product which has been identified by single crystal X-ray diffraction analysis as 1-(2,2,2-trichloro-1-hydroxyethyl)pyridine. Attempted extension of the general indolizine route to the preparation of chromene systems by reacting salicylaldehyde with methyl acrylate in the presence of DABCO, also led to an unexpected, crystalline material, identified by single crystal X-ray diffraction analysis as the coumarin derivative, 3-[(2-formylphenoxy)methyl]coumarin.A series of chloroquine analogues have been prepared from indolizine-2-carboxylic acid, pyrrolo[I,2-a]quinoline-2-carboxylic acid and imidazo[I,2-a]pyridine-2-carboxylic acid by reaction with suitable amines in the presence of the coupling reagent 1, I' -carbonyldiimidazole. This route has been shown to be a vast improvement on earlier procedures and has provided access to both secondary and tertiary indolizine-2-carboxamides. A range of N,N-dialkylindolizine-2-carboxamides have been prepared by this route, and the influence of substituents on their N-CO rotational energy barriers has been determined using variable temperature ¹H and ¹³C NMR techniques. Intercalation with natural DNA by both chloroquine and the synthesized chloroquine analogues has been examined using UV spectrophotometry, and ¹H and ³¹P NMR spectroscopy. The pyrrolo[I,2-a]quinolines have been shown to be DNA intercalators with binding affinities similar to that of the known antimalarial intercalator, chloroquine. In a preliminary study the synthesis of a short oligonucleotide has been undertaken and changes have been observed in the ¹H and ³¹P NMR spectra of the oligonucleotide on addition of the intercalator, chloroquine.
300

Chemical and spectroscopic studies of chromone derivatives

Ramaite, Ipfani David Isaiah 16 November 2012 (has links)
A number of biologically active chromones occur in plants (eg. Khellin) and research in this field has eventually led to the discovery of chromoglycic acid, which is widely used as a sodium salt in asthma therapy. Since biological activity may be related to acidity, a range of chromone-2-carboxylic acids have been prepared via Claisen acylation of substituted o- hydroxyacetophenones and their acid dissociation constants determined potentiometrically to explore substituent effects. From this study it has been found that introduction of certain groups does have a marked effect on acidity. A variety of acrylamide derivatives have been prepared via the dimethylamine-mediated ring opening of chromone-2-carboxamides which, in turn, were prepared from the chromone-2- carboxylic acids via the corresponding acid chlorides. Variable temperature NMR spectroscopy was employed to examine the effect of substituents on the rotational barriers and it has been found that for the acrylamides examined, ring substituents have little effect on the rotational barriers. A combination of low resolution, high resolution and meta-stable peak analysis has been used to study mass fragmentation patterns for a series of acrylamide derivatives. The proposed fragmentation pathways for selected peaks have been found to be common to all the spectra examined when differences in the atomic masses of substituents were taken into account.

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