Dissertations / Theses on the topic 'C - hetero'
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Devaraj, Karthik. "Ruthenium-catalyzed C-H Functionalization of (Hetero)arenes." Doctoral thesis, Uppsala universitet, Organisk kemi, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-310998.
Full textSubba, Raju. "Studies on the reactions of C - hetero bond formation." Thesis, University of North Bengal, 2015. http://ir.nbu.ac.in/handle/123456789/1854.
Full textSaha, Bittu. "Development of Novel methodologies for the construction of c-hetero bond." Thesis, University of North Bengal, 2018. http://ir.nbu.ac.in/handle/123456789/2823.
Full textLi, Haoran. "Pd-catalyzed C-H bond functionalizations of (hetero)arenes and alkenes : A one step access to poly(hetero)aromatics and styrene derivatives." Thesis, Rennes, Ecole nationale supérieure de chimie, 2020. http://www.theses.fr/2020ENCR0068.
Full textIn order to explain the background of my research work, in the first chapter, I summarized general mechanistic information on palladium-catalyzed C-H bond arylation and detailed some literature on direct arylation related to my research work. My objectives were to study the reactivity of new synthetic units allowing the straightforward access to bi-(hetero)aryls compounds or styrene derivatives using aryl halides or benzenesulfonyl chloride derivatives as the aryl-sources. Then, in the chapters 2-6, I summarized my research work. I studied the regiocontrolled palladium-catalyzed direct C2-arylations of Methoxsalen using benzenesulfonyl chlorides and C2,C3-diarylations using aryl bromides as the aryl sources. These results are summarized in the chapter 2. Then, I found that Pd-catalyzed direct arylation reaction allows the easy access to Ticlopidine derivatives arylated at the C5-position of the thienyl ring in one step. These results are reported in the chapter 3. In the chapter 4, we studied the reactivity of Diflufenican which contains a 1,3-difluorobenzene ring and a pyridine unit using Ru and Pd catalysis. Under appropriate conditions, two different C-H bonds of Diflufenican could be arylated. In the chapter 5, I employed different aryl sources to functionalize the C10- and C11-positions of dibenzo[b,f]azepines, and obtained asymmetric products. Through these reactions, a wide diversity of functional group were introduced on the dibenzo[b,f]azepine derivatives. Finally, in the Chapter 6, I report the first method allowing to prepare C10-arylated Cyproheptadine derivatives
Zhao, Liqin. "Palladium-catalyzed direct arylation via sp² and sp³ C-H activation of hetero(aromatics) and hydrocarbons for C-C bond formation." Thesis, Rennes 1, 2014. http://www.theses.fr/2014REN1S038/document.
Full textDuring this thesis, we were interested in the sp² and sp³ C-H bond activation catalyzed by palladium catalysts for the preparation of (hetero)aryl-aryls and biaryls. This method is considered as cost effective and environmentally attractive compared to the classical couplings such as Suzuki, Heck, or Negishi. First we described the palladium-catalyzed direct C2-arylation of benzothiophene in the absence of phosphine ligand with high selectivity. We also demonstrated that it is possible to active both C2 and C5 C-H bonds for access to 2,5-diarylated compounds in one step, and also to non-symmetrically substituted 2,5-diarylpyrroles via sequential C2 arylation followed by C5 arylation. We also studied the reactivity of polychlorobenzenes via palladium-catalyzed C-H activation. We finally examined the palladium-catalysed selective sp² and sp³ C-H bond activation of guaiazulene. The selectivity depends on the solvent and base: sp² C2-arylation (KOAc in ethylbenzene), sp² C3-arylation (KOAc in DMAc) and sp³ C4-Me arylation (CsOAc/K₂CO₃ in DMAc). Through this method, a challenging sp³ C-H bond was activated
Öhlenschläger, Kim K. [Verfasser], and C. [Akademischer Betreuer] Barner-Kowollik. "Hetero Diels-Alder Reactions in Material Science / Kim K. Öhlenschläger. Betreuer: C. Barner-Kowollik." Karlsruhe : KIT-Bibliothek, 2014. http://d-nb.info/1082294411/34.
Full textKirchberg, Sylvia [Verfasser]. "Palladium-katalysierte C-H-Arylierungen von (Hetero)-Arenen mit Arylboronsäuren und TEMPO / Sylvia Kirchberg." München : Verlag Dr. Hut, 2011. http://d-nb.info/1017353379/34.
Full textSala, Fernanda Angélica. "Estudo da interação entre domínios C-terminais de septinas humanas: implicação na formação e estabilidade do filamento." Universidade de São Paulo, 2015. http://www.teses.usp.br/teses/disponiveis/75/75133/tde-10082015-140053/.
Full textSeptins comprise a conserved protein family that binds guanidine nucleotide and forms heterofilaments. In structural terms they have a common organization: a central GTPase domain, a N-terminal domain and a C-terminal domain, this last one is predicted to form coiled coil structures. Currently, the human septin heterocomplex best characterized (SEPT2/SEPT6/SEPT7) reveals the importance of the GTPase domain in filament assembly, however the absence of electron density for the C-terminal domains makes its function still unknown. Studies with mammals septins, and of others organisms like C. elegans and S. cerevisea suggests that some septins groups (e.g. II e IV in mammals) interact via its C-terminal domains and this could act in a determinative way to correct filament assembly. In this way, this project aimed to study the homo/heterotypical affinity for the C-terminal domains of human septins belonging to groups II (SEPT6C/8C/10C/11C) e IV (SEPT7C), investigating whether this domain contributes with the preference of septins to interact with proteins of different groups during assembly of the heterofilament. The C-terminal domains were expressed in E. coli and purificated. It was carried out studies using analytical ultracentrifugation and circular dichroism spectropolarimetry tecniques which allowed identification of major affinity and stability in the heterotypical association compared to homotypical. It was measured apparent dissociation constants for homodimers of low µM range while for heterodimers our group\'s data shows dissociation constants in the nM range. To understand at atomic level the factors responsible for this significant preference in the C-terminal domains interaction between groups II and IV was performed molecular modelling studies and analysis of the primary sequence. These analysis suggests the presence of a high number of charged residues in position a of the coiled coil as responsible for selectivity. Consequently, the heterodimer would be therefore favoured because of the minor repulsive effect coming from the staggered of charged residues in a. Thus, these results indicate the crucial or cooperative action of C-terminal domains in preferential organization of septins during filament assembly, favouring the NC interface between septins of groups II and IV.
Clouston, Laurel L. "The design and synthesis of C¦3 symmetric ligands for lanthanide Lewis acid catalysis of the inverse demand hetero Diels-Alder reaction." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp02/NQ37336.pdf.
Full textO'Connor, Sean M. J. "Application of Tridentate Schiff Base Chromium (III) Complex Catalysts Towards the Total Synthesis of (-)- Lasonolide A and C-Disaccharide Mimics." Thesis, Griffith University, 2012. http://hdl.handle.net/10072/366217.
Full textThesis (PhD Doctorate)
Doctor of Philosophy (PhD)
School of Biomolecular and Physical Sciences
Science, Environment, Engineering and Technology
Full Text
Cuba, Supanta Gustavo. "Efectos del dopaje y la temperatura sobre las propiedades térmicas de hetero-estructuras de C/BN y su potencial uso como sensor ambiental del formaldehído." Doctoral thesis, Universidad Nacional Mayor de San Marcos, 2019. https://hdl.handle.net/20.500.12672/12312.
Full textConsejo Nacional de Ciencia y Tecnología (Perú). Fondo Nacional de Desarrollo Científico y Tecnológico (Fondecyt)
Tesis
Potukuchi, Harish Kumar [Verfasser], Lutz [Akademischer Betreuer] Ackermann, and Dietmar [Akademischer Betreuer] Stalke. "Catalytic syntheses and copper- or ruthenium-catalyzed direct C H bond arylations of (hetero)arenes / Harish Kumar Potukuchi. Gutachter: Lutz Ackermann ; Dietmar Stalke. Betreuer: Lutz Ackermann." Göttingen : Niedersächsische Staats- und Universitätsbibliothek Göttingen, 2011. http://d-nb.info/1043939148/34.
Full textWeisz, Mario. "Electrothermal device-to-circuit interactions for half THz SiGe∶C HBT technologies." Thesis, Bordeaux 1, 2013. http://www.theses.fr/2013BOR14909/document.
Full textThe power generate by modern silicon germanium (SiGe) heterojunction bipolar transistors (HBTs) can produce large thermal gradients across the silicon substrate. The device opering temperature modifies model parameters and can significantly affect circuit operation. This work characterizes and models self-heating and thermal coupling in SiGe HBTs. The self-heating effect is evaluated with low frequency and pulsed measurements. A novel pulse measurement system is presented that allows isothermal DC and RF measurements with 100ns pulses. Electrothermal intra- and inter-device feedback is extensively studied and the impact on the performance of two analog circuits is evaluated. Novel test structures are designed and fabricated to measure thermal coupling between single transistors (inter-device) as well as between the emitter stripes of a multi-finger transistor (intra-device). Thermal coupling factors are extracted from measurements and from 3D thermal simulations. Thermally coupled simulations of a ring oscillator (RO) with 218 transistors and of a 60GHz power amplifier (PA) are carried out. Current mode logic (CML) ROs are designed and measured. Layout optimizations lead to record gate delay of 1.65ps. The thermal performance of a 60GHz power amplifier is compared when realized with a multi-transistor array (MTA) and with a multi-finger trasistor (MFT). Finally, perspectives of this work within a CAD based circuit design environment are discussed
Sahoo, Amit Kumar. "Electro-thermal Characterizations, Compact Modeling and TCAD based Device Simulations of advanced SiGe : C BiCMOS HBTs and of nanometric CMOS FET." Thesis, Bordeaux 1, 2012. http://www.theses.fr/2012BOR14557/document.
Full textAn extensive evaluation of different techniques for transient and dynamic electro-thermal behavior of microwave SiGe:C BiCMOS hetero-junction bipolar transistors (HBT) and nano-scale metal-oxide-semiconductor field-effect transistors (MOSFETs) have been presented. In particular, new and simple approach to accurately characterize the transient self-heating effect, based on pulse measurements, is demonstrated. The methodology is verified by static measurements at different ambient temperatures, s-parameter measurements at low frequency region and transient thermal simulations. Three dimensional thermal TCAD simulations are performed on different geometries of the submicron SiGe:C BiCMOS HBTs with fT and fmax of 230 GHz and 290 GHz, respectively. A comprehensive evaluation of device self-heating in time and frequency domain has been investigated. A generalized expression for the frequency-domain thermal impedance has been formulated and that is used to extract device thermal impedance below thermal cut-off frequency. The thermal parameters are extracted through transistor compact model simulations connecting electro-thermal network at temperature node. Theoretical works for thermal impedance modeling using different networks, developed until date, have been verified with our experimental results. We report for the first time the experimental verification of the distributed electrothermal model for thermal impedance using a nodal and recursive network. It has been shown that, the conventional single pole thermal network is not sufficient to accurately model the transient thermal spreading behavior and therefore a recursive network needs to be used. Recursive network is verified with device simulations as well as measurements and found to be in excellent agreement. Therefore, finally a scalable electro-thermal model using this recursive network is developed. The scalability has been verified through numerical simulations as well as by low frequency measurements and excellent conformity has been found in for various device geometries
van, Heteren Peer [Verfasser]. "Cystatin C als Risikofaktor für kardiovaskuläre Ereignisse bei Nierentransplantierten / Peer van Heteren." Bonn : Universitäts- und Landesbibliothek Bonn, 2013. http://d-nb.info/1047185237/34.
Full textDrews, Thorsten [Verfasser], C. [Gutachter] Huth, H. P. [Gutachter] Schultheiss, and R. [Gutachter] Hetzer. "Halteapparatkonservierende Mitralchirurgie / Thorsten Drews ; Gutachter: C. Huth, H. P. Schultheiss, R. Hetzer." Berlin : Humboldt-Universität zu Berlin, 2001. http://d-nb.info/1207622540/34.
Full textRodrigues, Daniela Maffi. "Poli (l?quidos i?nicos) celul?sicos aplicados como catalisadores heterog?neos para transforma??o qu?mica do CO2 em carbonatos c?clicos." Pontif?cia Universidade Cat?lica do Rio Grande do Sul, 2018. http://tede2.pucrs.br/tede2/handle/tede/8367.
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Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior - CAPES
Carbon capture and storage (CCS) and carbon capture and utilisation(CCU) technologies has been pointed out as possibilities to mitigate the effects caused by the massiverelease of CO2 into the atmosphere. The use of CO2 in cycloaddition reactions toepoxides obtaining cyclic carbonates is an interesting possibility to reduce CO2emission. Cyclic carbonates are products of great applicability as solvents in the chemical industry and are used as raw material for a wide range of products. Meanwhile, the use of CO2 for a cycloaddition reaction requires a large amount of energy being necessary the use of catalysts in order to optimize such reactions. Poly (ionic liquids) (PIL) are alternative catalysts due its selective, recyclability and conversion. In this work, cellulosic poly(ionic liquids) (CPIL) obtained from rice husk were testedas heterogeneous catalyst. Cellulose extraction was carried out by chemical method. A chemical modification of the cellulose fibers was carried out by the treatment with citric acid and functionalization with 3 mmol of the ionic liquids BMIM Cl, TBAB, TBPB and BMPYRR to form CPIL-BMIM, CPIL-TBA, CPIL-TBP and CPIL-BMPYRR), without addition of solvents. Cyclo addition reactions were carried out with propylene and styrene oxides with different CO2 pressures(25, 30 and 40 bar) and temperatures (90, 110 and 120 ?C) for 6 h. The obtained product was characterized by gas chromatography (GC), Fourier Transform Infrared Spectroscopy(FTIR)and Nuclear Magnetic Resonance (1H NMR). The results showed better yields for CPIL-TBP and CPIL-TBA, whose values were 53.2% and 39% respectively for propylene carbonate and 67.3% for styrene carbonate using CPIL-TBP. When the ZnBr2 cocatalyst was used, there was an increase in the catalytic activity of these catalysts. For CPIL-TBP the yields were 71.4% for propylene carbonate and 78.7% for styrene carbonate. For CPIL-TBA the increase in propylene carbonate yield was 67.7%.
O uso das tecnologias de captura e armazenamento de carbono (CCS) e de captura utiliza??o do carbono (CCU) v?m sendo apontadas como possibilidades para mitigar os efeitos causados pela libera??o deliberada de elevadas concentra??es de CO2 na atmosfera. A utiliza??o do CO2 em rea??es de cicloadi??o em ep?xidos para obter carbonatos c?clicos vem se mostrando uma possibilidade interessante para reduzir a emiss?o de CO2 na atmosfera. Os carbonatos c?clicos s?o produtos de grande aplicabilidade como solventes na ind?stria qu?mica e s?o utilizados como mat?ria prima para uma vasta gama de produtos. Entretanto, o CO2 apresenta baixa reatividade tornando-se necess?rio o uso de catalisadores para otimizar tais rea??es. Os poli(l?quidos i?nicos) (PILs) v?m se mostrando como poss?veis catalisadores alternativos, demonstrando-se seletivos, recicl?veis e gerando consider?vel convers?o. Neste trabalho foram testados poli(l?quidos i?nicos) celul?sicos (CPIL), obtidos a partir da casca do arroz, como catalisador heterog?neo. A extra??o da celulose foi realizada por um m?todo qu?mico. A modifica??o qu?mica das fibras de celulose foi realizada a partir do tratamento com ?cido c?trico e a funcionaliza??o desta com 3 mmol dos l?quidos i?nicos BMIM Cl, TBAB, TBPB e BMPYRR formando CPIL-BMIM, CPIL-TBA, CPIL-TBP e CPIL-BMPYRR. As rea??es de cicloadi??o foram realizadas com os ?xidos de propileno e estireno com diferentes press?es de CO2 (15, 25, 30 e 40 bar) e temperaturas (90, 110, 120 e 130?C) durante (3, 6 e 9h), todas as rea??es foram realizadas sem a utiliza??o de solventes. O produto obtido foi caracterizado por cromatografia gasosa (CG) , espectroscopia de infravermelho com transformada de Fourier (FTIR) e Resson?ncia Magn?tica Nuclear (1H RMN). Os resultados demonstraram melhores rendimentos para CPIL-TBP e CPIL-TBA, cujos valores foram de 53,2% e 39% respectivamente para o carbonato de propileno e de 67,3% para o carbonato de estireno utilizando o CPIL-TBP. Quando o cocatalisador ZnBr2 foi utilizado, houve um aumento na a atividade catal?tica destes catalisadores, para o CPIL-TBP os rendimentos foram de 71,4 % para o carbonato de propileno e 78,7% para o carbonato de estireno. Para o CPIL-TBA o aumento no rendimento de carbonato de propileno foi de 67,7%.
Rao, Santhosh. "Molecular Construction Using Carbene and Diboron Systems: Catalytic Transformation of C-C and C-Hetero Atom Bonds." Thesis, 2018. https://etd.iisc.ac.in/handle/2005/5327.
Full textOjha, Devi Prasan. "Palladium Catalyzed Refunctionalizations of Olefins : Novel Strategies for Construction of C-C, C-Hetero Bonds and Homogeneous Hydrogenation." Thesis, 2015. http://etd.iisc.ac.in/handle/2005/3841.
Full textOjha, Devi Prasan. "Palladium Catalyzed Refunctionalizations of Olefins : Novel Strategies for Construction of C-C, C-Hetero Bonds and Homogeneous Hydrogenation." Thesis, 2015. http://etd.iisc.ernet.in/2005/3841.
Full textPotukuchi, Harish Kumar. "Catalytic syntheses and copper- or ruthenium-catalyzed direct C H bond arylations of (hetero)arenes." Doctoral thesis, 2011. http://hdl.handle.net/11858/00-1735-0000-0006-B0A3-7.
Full textRokade, Balaji Vasantrao. "Copper-Catalyzed Novel Oxidative Transformations : Construction of Carbon-Hetero Bonds." Thesis, 2014. http://etd.iisc.ac.in/handle/2005/3479.
Full textRokade, Balaji Vasantrao. "Copper-Catalyzed Novel Oxidative Transformations : Construction of Carbon-Hetero Bonds." Thesis, 2014. http://etd.iisc.ernet.in/2005/3479.
Full textFenner, Sabine. "Sustainable Strategies for Site-Selective C−VC Bond Formations through Direct C−H Bond Functionalizations." Doctoral thesis, 2012. http://hdl.handle.net/11858/00-1735-0000-0006-B090-4.
Full textHsu, Yuan-Shi, and 許元錫. "The comparative study of electrical and conversion efficiency performance for homo-junction and hetero-junction c-Si solar cells." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/26085868041302747750.
Full text國立中央大學
光電科學與工程學系
102
In this study, ECR-CVD was used for the deposition of high doping silicon thin films and passivation layers, PE-CVD was used for the deposition of passivation layers. These thin films were deposited on single-crystalline silicon substrate to fabricate the homo-junction and hetero-junction c-Si solar cells. The electrical properties and solar cell performance of homo-junction and hetero-junction c-Si solar cells were investigated. ECR-CVD has advantages about high deposition rate, low working pressure, low ion bombardment and no electrode pollution. But high deposition rate makes the thin films more defects and loose structure, these feature are not good for passivation layers in HIT solar cells. Therefore, the better quality passivation layers were deposited by PE-CVD to improve the HIT solar cells. In the first part, we will modulate the experimental parameters of doping concentration of BSF, oxygen content of emitter, single-crystalline silicon substrate types, and the electrode in homo-junction solar cells to investigate the electrical properties and conversion efficiency. The emitter and back surface field layers of homo-junction solar cell were deposited by ECR-CVD. The characteristics of homo-junction solar cell with screen printing electrode on p-type planar substrate were shown as follow: VOC = 0.616 V, JSC = 37.397 mA/cm2, F.F. = 75 %, efficiency = 17.29 % in the area of 1 cm2. In second part, the passivation quality on different wafer and the variation of the passivation layer thickness were performed in hetero-junction solar cells. The passivation layer were deposited by ECR-CVD or PE-CVD, the emitter and back surface field layers were deposited by ECR-CVD. In addition, the characteristics of hetero-junction solar cell on p-type planar substrate with 3 nm passivation layer deposited by PE-CVD that were shown as follow: VOC = 0.644 V, JSC = 34.04 mA/cm2, F.F. = 68 %, efficiency = 14.8 % in the area of 1 cm2.
Clouston, Laurel L. "The design and synthesis of C₃ symmetric ligands for lanthanide Lewis acid catalysis of the inverse demand hetero Diels-Alder reaction." Thesis, 1998. https://dspace.library.uvic.ca//handle/1828/8721.
Full textGraduate
Giguère, Denis. "Synthèse de 4-désoxy hexopyrannoses, C-disaccharides et C-glycosides biologiquement actifs." Thèse, 2009. http://hdl.handle.net/1866/4191.
Full textCarbohydrates represent a large family of organic molecules that play key roles in various biological processes. Due to their medicinal importance, preparation of deoxy-sugars, C-glycosides and C-disaccharides have become an important topic in organic synthesis. Mostly, this thesis presents a new de novo synthesis of 4-deoxy hexopyranoses, along with the preparation of biologically relevant C-glycosides. Moreover, a special attention has been focussed on the de novo synthesis of 4-deoxy-C-disaccharides. Firstly, Jacobsen Cr(III) catalyst and a binaphthol/titanium complex have been used to catalyze enantioselective hetero-Diels-Alder reactions. The dihydropyran thus formed has been transformed into naturally occurring 4-deoxy hexopyranoses. Therefore, the ezoaminuroic acid core, a desosamine precursor and neosidomycin have been prepared following a de novo approach. Moreover, as a comparative study, neosidomycin has also been synthesized using a chiron approach from methyl alpha-D-mannopyranoside. Finally, a preliminary biological evaluation of neosidomycin has been applied on concanavalin-A (Chapter 2). Secondly, homoallylic alcohols have been generated from a stereoselective allylation on aldehyde linked via C-C bonds to a mannoside residue. Then, the homoallylic alcohols have been transformed into 4-deoxy hexopyranoses in various configurations (D or L). Thereby, the syntheses of pseudo 4-deoxy-C-disaccharides, 4-deoxy-C-disaccharides and pseudo 4-deoxy aza-C-disaccharides have been easily performed. Determinations of the diastereoisomeric ratio of the allylation reactions along with the absolute configuration of the newly formed chiral center have been easily achieved. Various members of this new family have been deprotected for a preliminary biological evaluation on concanavalin-A (Chapter 3). Finally, the syntheses of relevant C-glycosides have been realized regarding two aspects: i) 3-C-mannopyranosyl coumarin synthesis and ii) synthesis of C-galactosides as PA-IL inhibitors. Methyl glycosyl cinnamates have been isolated using a Heck coupling on alpha,beta-insaturated ester linked to glycosidic moieties via C-C bonds. However, when 2-iodophenol is used as a Heck partner, the corresponding coumarins have been isolated. C-Galactosyl methyl cinnamate derivatives represent good monovalent inhibitors with Kd as low as 37 micro M against PA-IL (Chapter 4).
Chen, Zhong-Yi, and 陳忠毅. "1. 1. Studies in Synthesis of C-1 Substituted Fulvenes via the Oxidation-Addition of Haloacetyl Halide to fulveneketene Acetal. 2. Traceless Solid-Phase Synthesis of Cyclopenta[c]quinolines and Cyclopenta[c]chromenes via Hetero [6+3] Cycloadditions of Fu." Thesis, 2003. http://ndltd.ncl.edu.tw/handle/12983595954471742161.
Full text國立中正大學
化學研究所
91
1.Studies in Synthesis of C-1 Substituted Fulvenes via the Oxidation-Addition of Haloacetyl Halide to fulveneketene Acetal. In contrast to the [2+2] cycloaddition of fulvenes and ketenes, fulveneketene acetal, 2-chloropentadienylidene-1,3-dioxalane, reacts with a-halo acyl halides to give various C-1 substituted fulvene. Herein we describe the first example of oxidative-addition of a-chloroacetyl chloride to fulveneketene acetal, and formal synthesis of the carbocyclic analogs of Captopril. 2.Traceless Solid-Phase Synthesis of Cyclopenta[c]quinolines and Cyclopenta[c]chromenes via Hetero [6+3] Cycloadditions of Fulvene. A Facile Approach to the 11-Heterosteroids Framework. The hetero [6+3] cycloaddition of fulvenes to benzoquinones and indoanilines provides an efficient route to the synthesis cyclopenta[c]-4H-chromen-8-ol, benzo[d]cyclopenta[e]-3H-3-azin-8-ol and other 11-hetero steroids. The structure of the cyclopenta[c]chromene skeleton was confirmed by the X-ray structure analysis of the p-bromobenzoate of 109. The traceless solid-phase synthesis of the scaldfold, consist of 110 examples, was achieved by the reaction of benzoquinones or iodoanilines with aminofulvene resin 140 which was prepared from polystyrene amino resin 138 via 2-step reaction.
Costa, Gustavo Franco Ferreira da. "Cymbopogon citratus and its polyphenols as potential phytotherapeutic products: an in vivo approach." Doctoral thesis, 2016. http://hdl.handle.net/10316/29994.
Full textCymbopogon citratus (DC). Stapf (Poaceae), commonly known as lemongrass, is a tropical perennial shrub originated from the Southeast Asia. This plant is reported to possess antifungal, insecticidal, anti-diabetic, anti-septic, anti-mutagenic, anti-carcinogenic activities as well as anti-inflammatory. In fact, aqueous extracts of dried leaves are used all over the year in folk medicine for the treatment of peptic ulcers and inflammatory conditions. Recently, some phenolic compounds, such as luteolin and apigenin glycosides and condensed tannins, were identified and related to both antioxidant and anti-inflammatory properties. The purposes of this work were to i) validate an analytical method for quantification of phenolic compounds of C. citratus; ii) study the influence of harvest time and plant quality on the phenolic composition and antioxidant activity; iii) characterize the tannins; iv) validate the traditional uses of lemongrass infusion as anti-inflammatory in vivo; v) obtain a topical formulation to evaluate the phenolic compounds permeation and their anti-inflammatory activity; vi) trace the pharmacokinetic profile of the main phenolic compounds in rats. Three different extracts: infusion (CcI), 50% aqueous ethanol (CcM50%) and ethanol (CcM100%) extracts were prepared and a simple and efficient RP-HPLC-PDA method was successfully validated for simultaneous identification and quantification of phenolic acids and flavonoids. Infusions were also obtained from different harvest dates (April, June, July, August and September) and quality grades (High, Medium and Low). It was verified that the content on polyphenols and the antioxidant capacity of CcI is strongly related with the quality of the plant. The total phenols assay showed a substantial loss from August to September. It was possible to find out the best month to harvest the plant to get the most of each phenolic group: April and June for hydroxycinnamic acids; June and September for flavonoids; June, July and August for tannins. Regardless the group of phenolic compound addressed, its content was always inversely proportional to the degree of leaves ageing. For all tested oxidant species, the high-quality samples exhibited the best antioxidant results. CcI was fractionated by column chromatography and polyphenol-rich fractions, namely phenolic acids (CcPA), flavonoids (CcF) and tannins (CcT) were obtained. CcT was characterized by HPLC-PDA-ESI/MSn, revealing the presence of proanthocyanidin hetero-dimers, along with some common procyanidin dimers. These hetero-dimeric flavan structures have been described for the first time in lemongrass and consist of apigeniflavan or luteoliflavan units linked to a flavanone, either naringenin or eriodictyol, and may occur as aglycone or glycosylated forms. For the in vivo assays, CcI, CcF and CcT were tested. CcI administered before and after ethanol stimulus, significantly reduced the incidence and severity of gastric lesions and, consequently, the ulcer index, corroborating the traditional medicinal use of this plant to ameliorate gastritis and/or peptic ulcers symptoms. On the other hand, CcI, CcF and CcT were orally administered to rats, in order to evaluate the anti-inflammatory effect at the carrageenan-induced paw edema assay. The observed effect by CcI (68.24 mg/kg), 82.30% of edema inhibition, was very similar to that obtained by the reference NSAID used (diclofenac, 10 mg/kg), 84.00%. On the other hand, flavonoid (7.42 mg/kg) and the tannin-rich (5.96 mg/kg) fractions significantly contributed for the anti-inflammatory activity on the edema volume (59 and 61%, respectively). The topical anti-inflammatory activity of CcI was also addressed. The results suggest that flavonoids, mainly, luteolin 7-O-neohesperidoside, cassiaoccidentalin B, carlinoside and cynaroside, may contribute to the topical anti-inflammatory effect. CcF (0.6%), CcT (0.3%) and CcF+CcT (0.66%+0.34%) topical formulations were also tested, and the results obtained suggest that tannins and flavonoids also possess a significant activity and that a synergistic mechanism of action may occur. In fact, edema inhibitions of 43%, 47% and 59% were respectively verified, being CcF+CcT effect very close to that of 1% diclofenac (65.9%). Pharmacokinetic analysis was performed in plasma, liver and kidney and showed that the compounds present in CcI are not detected in vivo after a single-dose oral administration. In contrary, the metabolites, luteolin 7-O-glucuronide and luteolin 3’-O-sulfate, present at the highest bioavailability, are probably the main responsible for the anti-inflammatory activity previously reported. In conclusion, this work has developed a method to quantify the phenolic compounds contained in C. citratus; pointed the importance of harvesting and storing the plant material, in order to take the maximum advantages from the phenolic compounds use; and demonstrated, in safe doses, its anti-inflammatory activity, using an in vivo approach, which supports the traditional use of lemongrass infusion. Furthermore, C. citratus leaves flavonoids and tannins were highlighted as bioactive compounds, encouraging the development of new anti-inflammatory drugs or nutraceuticals.