61 |
Scanning and Host Fingerprinting Methods for Command and Control Server DetectionNakamura, Yuki, Åström, Björn January 2021 (has links)
Background. Detecting malware command and control infrastructure has impor-tant applications for protecting against attacks. Much research has focused on thisproblem, but a majority of this research has used traffic monitoring methods fordetection. Objectives. In this thesis we explore methods based on network scanning and active probing, where detection is possible before an attack has begun, in theory resulting in the ability to bring the command and control server down preemptively. Methods. We use network scanning to discover open ports which are then fed into our probing tool for protocol identification and data gathering. Fingerprinting is performed on the open ports and running services of each host.We develop two methods for fingerprinting and classification of hosts. The first method uses a machine learning algorithm over the open ports and probe data, while the other computes distance scores between hosts. We compare these methods to the new but established JARM method for host fingerprinting, as well as to two other simple methods. Results. Our findings suggest that our general active probing method is feasible for use in detecting command and control infrastructure, but that the results vary strongly depending on the malware family, with certain malware families providing much better results than others. Conclusions. We end with discussions on the limitations of our methods and how they can be improved, as well as bring up our opinions on the potential for future work in this area. / Bakgrund. Att kunna upptäcka command-and-control-infrastruktur kopplad till malware har viktiga tillämpningar för syftet att skydda mot attacker. Mycket forskning existerar som fokuserar på detta problem, men en majoritet använder metoder baserade på trafikmonitorering. Syfte. I denna uppsats utforskar vi istället metoder baserade på scanning och probing av nätverk, genom vilka detektering är möjlig innan en attack har ägt rum, med fördelen att en command-and-control-server i teorin kan tas ner förebyggande. Metod. Vi använder nätverks-scanning för att upptäcka öppna portar vilka matas in i vårt probing-verktyg som sedan utför protokoll-identifiering och datainsamling. Vi skapar ett fingeravtryck av varje server från de öppna portarna och de hostade tjänsterna. Två metoder för klassifiering av servrar togs fram. Den första metoden använder en maskininlärningsalgoritm över de öppna portarna och probe-datan, medan den andra beräknar en distans mellan två servrar. Vi jämför dessa metoder med den nya men etablerade JARM-metoden, som tar fram fingeravtryck av servrar från TLS-data, samt med två andra, simplare metoder. Resultat. Våra upptäckter visar att vår metod, som bygger på generell, aktiv probing är möjlig att använda för detektering av command-and-control-infrastruktur, men att resultaten varierar kraftigt beroende på malware-familj, där vissa familjer erbjuder mycket bättre resultat än andra. Slutsatser. Vi avslutar med att diskutera begränsningar i våra metoder och hur dessa kan förbättras, samt tar upp våra åsikter om potentialen för framtida forskning inom detta område.
|
62 |
Identifikation und Charakterisierung von porenbildenden Proteinen der inneren ChloroplastenmembranGötze, Tom Alexander 07 July 2009 (has links)
PRAT-C2 In elektrophysiologischen Untersuchungen heterolog exprimierter PRAT-C2 Proben wurde eine Kationen-selektive Kanalaktivität mit einer dreifachen Porenstöchiometrie beobachtet. Durch Variation der experimentellen Parameter und eine detaillierte Analyse der Ergebnisse konnten seitenspezifische Eigenschaften des Kanals aufgedeckt werden, die auf eine ungleiche Ladungsverteilung hindeuten. Auf der Grundlage von Strukturvorhersagen wurde ein Topologiemodell mit vier transmembranen alpha-Helices für PRAT-C2.2 aus Arabidopsis thaliana erstellt. Die zum Stroma und Intermembranraum exponierten Sequenzabschnitte weisen eine sehr unterschiedliche Verteilung geladener Aminosäuren auf. Das Schaltverhalten des Kanals wurde sowohl durch das Signalpeptid eines chloroplastidären als auch eines mitochondrialen Präproteins beeinflusst. Trotz einer Reaktion auf den spezifischen Antikörper gegen PRAT-C2.1 wurden Hinweise dafür erbracht, dass es sich bei der Kanalaktivität um eine porenbildende Kontamination aus dem bakteriellen Expressionssystem handelte. Tic110 Durch den Vergleich der Eigenschaften von Tic110, aufgereinigt aus Chloroplasten von Pisum sativum, und einer verkürzten, heterolog exprimierten Form konnte gezeigt werden, dass der porenbildende Sequenzabschnitt jenseits der ersten 96 Aminosäuren liegt. Die Kanalaktivität zeichnete sich durch ein charakteristisches Schaltverhalten aus, wobei die Schaltfrequenz durch eine Wechselwirkung mit Ca2 -Ionen beeinflusst wurde. Tic110 zeigte eine Präferenz gegenüber Kationen, die jedoch von der Konformation des Kanals abhängig war und in Anwesenheit zweiwertiger Kationen abnahm. Cu2 -Ionen führten ab Konzentrationen von 2 mM zu einem kompletten Stromblock. Ob dieser Effekt auf der Bildung einer Disulfidbrücke basiert und damit biochemische Ergebnisse bekräftigt werden, die eine Regulation durch das Thioredoxin-System im Chloroplasten vermuten lassen, konnte anhand der vorliegenden Ergebnisse nicht eindeutig geklärt werden.
|
63 |
The Role of MCTP2 in Health and DiseaseAlkhouli, Mohammed A. 01 1900 (has links)
Indiana University-Purdue University Indianapolis (IUPUI) / MCTP2 (multiple C2 domain transmembrane containing protein 2) encodes a protein with poorly understood roles in lipid metabolism and lipid droplet biogenesis. Genetic studies previously identified variations in MCTP2 in conjunction with left ventricular outflow tract obstructive forms of congenital heart disease (CHD). This dissertation research aimed to delineate the biomedical significance of Mctp2 by investigating its expression and consequences of its genetic deletion in mouse models.
Temporal and spatial expression of Mctp2 was investigated by RT-PCR and in-situ hybridization. A novel isoform, designated as isoform 2 in mice, results from alternative pre-mRNA splicing. Similar levels of Mctp2 isoforms 1 and 2 are present in embryonic tissues, whereas isoform 1 is preferentially expressed in adult tissues with high lipid metabolism. During mouse embryonic development, in-situ hybridization suggests expression of Mctp2 at the gut tube, liver bud and near the pharyngeal arches from E8.5 – E10.5.
Given association of MCTP2 with CHD, the biological significance of Mctp2 was addressed using gene trap (GT) and conditional mouse models. Survival of Mctp2 GT mice was dependent on the genetic background strain, suggesting a role for strain-specific modifiers. Conditional knockout of Mctp2 in cardiac progenitor cells displayed no effect on survival. The role of Mctp2 in cardiac development remains to be delineated.
The role of Mctp2 in cardiac function was addressed in both mouse models. Initial findings suggest Mctp2 allele dosage effects on the development of heart failure. GT mice lacking one, or both, copies of Mctp2 display cardiac systolic dysfunction, with upregulation of heart failure markers at 50 weeks of age in heterozygotes and increases in cardiac fibrosis in homozygotes. Systemic conditional deletion of Mctp2 did not show heart failure phenotypes using the strain protective from lethality. However, cardiac specific deletion of Mctp2 using the Nkx2.5-Cre driver, a line that is sensitized for cardiac dysfunction, led to decreased ejection fraction and fractional shortening in mice with conditional deletion of both copies of Mctp2 as well as Mctp2 dosage dependent penetrance of cardiac dilation. These studies of knockout mice suggest a role for Mctp2 in maintenance of cardiac function and possible genetic interaction with Nkx2.5. / 2022-02-02
|
64 |
Application of laser-induced breakdown spectroscopy (LIBS) to the expansion of strontium (Sr) analysis options and to used engine oilBinzowaimil, Ayed M 06 August 2021 (has links)
Laser-induced breakdown spectroscopy (LIBS) is a technique that allows quantitative and qualitative analysis of many materials. In this study, the LIBS analysis options for strontium mixture powders is expanded by increasing the number of usable strontium atomic transitions to avoid incorrect results due to spectral congestion or high strontium concentrations. The research employs double-sided tape affixed to a glass slide to hold the sample where the powder is poured onto one surface of the tape and excess dust that has not adhered is removed. This method minimizes the sample quantity needed and keeps the sample on the slide during experimentation, which also reduces costs. Herein, LIBS was used to detect and quantify the level of metal concentrations in used engine oil samples to provide valuable information about the composition of the selected material in a liquid sample. Data were obtained using multivariate analysis to develop calibration curves using LIBS spectra, which was employed for the quantification of the elements Al, Ca, Fe, Mg, and Mn. The relationship between the peak intensity of the metals in new engine oil samples and the metal concentrations in used engine oil samples were analyzed to minimize the matrix effect and the interference of element lines after which the atomic emission observed in LIBS spectra of used engine oil and new engine oil were compared. C2 molecular band emissions were also used to determine the degree of the engine oil degradation. Next, calibration models were developed for samples with high species concentrations. A partial least squares regression model was developed for calibration models to overcome matrix effect problems of some lines of each metal. This research successfully used the LIBS technique to determine the degree of engine oil degradation. This study established that used engine oil analysis using the LIBS technique can be utilized to maintain engines in good condition and to prevent engine failure. This paper presents the key findings and conclusions regarding the application of LIBS. Finally, although this technique shows many benefits and reliable results, challenges remain in terms of matrix effects, spectral pre-processing, model calibration, and instrumentation.
|
65 |
La spécification et la certification pour le francais des niveaux C1 et C2 du Cadre européen commun de référence pour les langues / Specification and certification for French of the C1 and C2 Levels of the Common European Framework of Reference for LanguagesRiba, Patrick 16 June 2010 (has links)
Cette thèse a pour objet la problématique de la description et la spécification des niveaux C du Cadre européen commun de référence pour les langues, dits niveaux de l’utilisateur expérimenté [C1 autonome, C2 maîtrise] pour le français. Elle s’inscrit dans la dynamique de référentialisation souhaitée par le Conseil de l’Europe et engagée dans plusieurs pays européens, y compris en France, où les niveaux A et B ont déjà été décrits : B2, J.C. Beacco, S. Bouquet, R. Porquier, [2004], A1, J.C. Beacco, R. Porquier, [2007], A2, J.C. Beacco, S. Lepage, R. Porquier, P. Riba, [2008], B1, J.C. Beacco, B. Blin, E. Houles, S. Lepage, P. Riba, à paraître]. La description des éléments notionnels et fonctionnels des niveaux C1 et C2, genres discursifs, fonctions, notions, catégories morphosyntaxiques, matière graphique, compétences culturelles et stratégies d’apprentissage, a été établie en suivant trois voies méthodologiques, intuitive, expérimentale et d’étalonnage. Elle se focalise sur la recherche des points de césure entre B2, C1 et C2 utiles pour les auteurs de méthodes ou de curriculums, les concepteurs d’examens et les enseignants et elle propose une spécification d’un niveau C2+, didactiquement compatible avec les notions paradoxales de « dernier niveau de langue » et d’apprentissage tout au long de la vie. / This investigation describes and specifies for French the contents of C1 and C2 levels of the Common European Framework of Reference for Languages. It joins in the dynamics wished by the Council of Europe, and engaged in several European countries, including in France, where the levels A and B were already described: B2, J.C. Beacco, S Bouquet, R. Porquier, 2004, A1, J.C. Beacco, R. Porquier, 2007, A2, J.C. Beacco, S Lepage, R. Porquier, p. Riba, 2008, B1, J.C. Beacco, B. Blin, E. Swells, S Lepage, p. Riba, to be published]. The description of the notional and functional elements of C1 and C2 levels: discursive genders, functions, notions, morphosyntactic categories, graphic material, cultural skills and strategies of learning, were established by following methodological, intuitive and experimental ways and by calibration. This investigation focuses on the research of cutscores between B2, C1 and C2, in order to help authors of methods, designers of examinations and teachers, and it proposes a specification of a level C2 +, didactically compatible with the paradoxical notions of " last level " and “learning throughout the life”.
|
66 |
Caracterização molecular dos componentes C1q, C4 e C2 do sistema complemento em pacientes pediátricos com lúpus eritematoso sistêmico / Molecular characterization of complement components C1q, C4, and C2 in pediatric patients with Systemic Lupus ErythematosusUmetsu Sobrinho, Natália 08 August 2013 (has links)
Objetivo: Realizar a caracterização molecular dos genes C1q, C4 e C2 em pacientes com lúpus eritematoso sistêmico juvenil (LESJ). Métodos: Quatro pacientes com LESJ e deficiências de C1q,C4 e/ou C2 foram selecionados. O paciente P1 apresentava níveis séricos indetectáveis de C1q e níveis normais de C3 e C4; paciente P2 níveis baixos de C2 e C4 no soro; P3 apresentava níveis baixos de C2 e normais de C3 e C4 e P4 constantes níveis baixos de C4 e níveis normais de C1q, C2 e C3 no soro. Foram sequenciados os genes C1q e C2. Células mononucleares dos pacientes P1, P3 e P4 e de três indivíduos saudáveis foram cultivadas, estimuladas com interferon gama e incubadas por 36 horas e PCR quantitativo (qRTPCR) foi realizado para verificar a expressão de mRNA. Resultados: A caracterização molecular do gene C1q (P1) mostrou trocas heterozigotas na cadeia A (c.276 A>G Gly) e na cadeia C (c.126 C>T Pro). Foram observadas também duas trocas de base em homozigose na região 5\'UTR (c. -159 T>G) e na região 3\'UTR (c*78 A>G) da cadeia B. O qRT-PCR mostrou que a expressão de mRNA de C1qA no paciente P1 sem estimulo estava 1,3 vezes mais baixo e com estímulo de interferon gama estava 1,6 vezes mais expresso se comparado aos indivíduos saudáveis. A expressão de mRNA de C1qB sem estímulo foi 2,2 vezes mais baixo e com estímulo foi 1,5 vezes mais expresso quando comparados aos controles. Para C1qC os indivíduos controles não expressaram mRNA porém o paciente P1 apresentou pequena expressão com e sem estímulo. O sequenciamento do gene C2 dos pacientes P2 e P3 apresentou 100% de similaridade com a sequência de referência com exceção da deleção de 28pb no exon 6 (deficiência heterozigota de C2 do tipo I). A expressão de mRNA de C2 do paciente P3 foi sem estímulo 23 vezes mais baixo e com interferon 4,2 vezes menos expresso quando comparado aos controles. P4 apresentou 2 copias de C4A e 3 copias de C4B e no qRT-PCR o gene C4B estava 14 vezes menos expresso sem estímulo e com estímulo estava semelhante aos controles. Conclusões: As trocas de base em homozigose nas regiões 5\'UTR (região promotora) e 3\'UTR (região de estabilização do mRNA) na cadeia B do gene C1q podem ter modificado a região de transcrição do mRNA pois sua expressão sem estimulo foi baixa. Outras investigações são necessárias para relacionar as variações do gene C1q encontradas com os níveis séricos indetectáveis de C1q. A deficiência de C2 do tipo I heterozigota pode levar a redução na expressão de mRNA e pode estar presente em pacientes lúpicos com níveis séricos detectáveis de C2. Por fim, a baixa expressão de mRNA de C4B mostrou que as dosagens séricas e a avaliação do número de copias podem não ser suficientes para estabelecer a deficiência de C4 / Objective: To perform the molecular characterization of C1q, C4 and C2 genes in patients with Juvenile Systemic Lupus Erythematosus (JSLE). Methods: Four patients with JSLE and C1q, C4 and/or C2 deficiencies were chosen. Patient P1 had undetectable C1q serum level and normal levels of C3 and C4; Patient P2 had decreased levels of C2 and C4 serum while P3 had decreased C2 with normal C3 and C4 levels. Lastly P4 had repeated decreased C4 and normal C1q, C2 and C3 serum levels. C1q and C2 genes were sequenced. Peripheral mononuclear cells from patients P1, P3 and P4 and from three healthy individuals were both cultivated and stimulated with interferon gamma and a quantitative PCR (qRT-PCR) was also performed to verify mRNA expression. Results: C1q molecular characterization for P1 revealed heterozygous silent mutations in A chain (c.276 A>G Gly) and in C chain (c.126 C>T Pro). Additionally, in B chain two homozygous single-base exchanges were detected in the 5´UTR (c. -159 T>G) and 3\'UTR region (c*78 A>G). The qRTPCR revealed that C1qA gene mRNA expression without stimulation was decreased 1.3 times and with interferon gamma was 1.6 times more expressed compared with controls samples. C1qB gene expression without stimulation was 2.2 times decreased and when stimulated was 1.5 times more expressed. Controls did not expressed C1qC gene and patient P1 had low expression both with and without stimulation. P2 had 2 copies of C4A and 1 copy of C4B. C2 gene sequencing (P2 and P3) showed 100% match with referenced sequence, with exception to 28bp deletion at the exon 6 (heterozygous C2 deficiency type I). C2 mRNA expression from P3 without stimulation was 23 times decreased and with interferon was 4.2 times decreased compared with controls. P4 had 2 copies of C4A and 3 copies of C4B. The qRT-PCR were performed only in C4B gene showed without stimulation a 14 times decreased expression and with interferon stimulation the expression were similar to controls. Conclusions: The two homozygous single-base exchanges in 5\'UTR and 3\'UTR that correspond to the promoter region and stabilization mRNA region in B chain of C1q gene, may have modified mRNA transcription as its expression was decreased without stimulation. Further analysis is necessary to relate C1q gene variations and undetectable serum C1q. In addition, heterozygous C2 deficiency type I may lead to reduced mRNA expression and may be present in JSLE patients with detectable C2 levels. Finally, the decreased C4B gene expression showed that serum dosage and gene copy number may not be sufficient to assess C4 deficiency
|
67 |
Caracterização molecular dos componentes C1q, C4 e C2 do sistema complemento em pacientes pediátricos com lúpus eritematoso sistêmico / Molecular characterization of complement components C1q, C4, and C2 in pediatric patients with Systemic Lupus ErythematosusNatália Umetsu Sobrinho 08 August 2013 (has links)
Objetivo: Realizar a caracterização molecular dos genes C1q, C4 e C2 em pacientes com lúpus eritematoso sistêmico juvenil (LESJ). Métodos: Quatro pacientes com LESJ e deficiências de C1q,C4 e/ou C2 foram selecionados. O paciente P1 apresentava níveis séricos indetectáveis de C1q e níveis normais de C3 e C4; paciente P2 níveis baixos de C2 e C4 no soro; P3 apresentava níveis baixos de C2 e normais de C3 e C4 e P4 constantes níveis baixos de C4 e níveis normais de C1q, C2 e C3 no soro. Foram sequenciados os genes C1q e C2. Células mononucleares dos pacientes P1, P3 e P4 e de três indivíduos saudáveis foram cultivadas, estimuladas com interferon gama e incubadas por 36 horas e PCR quantitativo (qRTPCR) foi realizado para verificar a expressão de mRNA. Resultados: A caracterização molecular do gene C1q (P1) mostrou trocas heterozigotas na cadeia A (c.276 A>G Gly) e na cadeia C (c.126 C>T Pro). Foram observadas também duas trocas de base em homozigose na região 5\'UTR (c. -159 T>G) e na região 3\'UTR (c*78 A>G) da cadeia B. O qRT-PCR mostrou que a expressão de mRNA de C1qA no paciente P1 sem estimulo estava 1,3 vezes mais baixo e com estímulo de interferon gama estava 1,6 vezes mais expresso se comparado aos indivíduos saudáveis. A expressão de mRNA de C1qB sem estímulo foi 2,2 vezes mais baixo e com estímulo foi 1,5 vezes mais expresso quando comparados aos controles. Para C1qC os indivíduos controles não expressaram mRNA porém o paciente P1 apresentou pequena expressão com e sem estímulo. O sequenciamento do gene C2 dos pacientes P2 e P3 apresentou 100% de similaridade com a sequência de referência com exceção da deleção de 28pb no exon 6 (deficiência heterozigota de C2 do tipo I). A expressão de mRNA de C2 do paciente P3 foi sem estímulo 23 vezes mais baixo e com interferon 4,2 vezes menos expresso quando comparado aos controles. P4 apresentou 2 copias de C4A e 3 copias de C4B e no qRT-PCR o gene C4B estava 14 vezes menos expresso sem estímulo e com estímulo estava semelhante aos controles. Conclusões: As trocas de base em homozigose nas regiões 5\'UTR (região promotora) e 3\'UTR (região de estabilização do mRNA) na cadeia B do gene C1q podem ter modificado a região de transcrição do mRNA pois sua expressão sem estimulo foi baixa. Outras investigações são necessárias para relacionar as variações do gene C1q encontradas com os níveis séricos indetectáveis de C1q. A deficiência de C2 do tipo I heterozigota pode levar a redução na expressão de mRNA e pode estar presente em pacientes lúpicos com níveis séricos detectáveis de C2. Por fim, a baixa expressão de mRNA de C4B mostrou que as dosagens séricas e a avaliação do número de copias podem não ser suficientes para estabelecer a deficiência de C4 / Objective: To perform the molecular characterization of C1q, C4 and C2 genes in patients with Juvenile Systemic Lupus Erythematosus (JSLE). Methods: Four patients with JSLE and C1q, C4 and/or C2 deficiencies were chosen. Patient P1 had undetectable C1q serum level and normal levels of C3 and C4; Patient P2 had decreased levels of C2 and C4 serum while P3 had decreased C2 with normal C3 and C4 levels. Lastly P4 had repeated decreased C4 and normal C1q, C2 and C3 serum levels. C1q and C2 genes were sequenced. Peripheral mononuclear cells from patients P1, P3 and P4 and from three healthy individuals were both cultivated and stimulated with interferon gamma and a quantitative PCR (qRT-PCR) was also performed to verify mRNA expression. Results: C1q molecular characterization for P1 revealed heterozygous silent mutations in A chain (c.276 A>G Gly) and in C chain (c.126 C>T Pro). Additionally, in B chain two homozygous single-base exchanges were detected in the 5´UTR (c. -159 T>G) and 3\'UTR region (c*78 A>G). The qRTPCR revealed that C1qA gene mRNA expression without stimulation was decreased 1.3 times and with interferon gamma was 1.6 times more expressed compared with controls samples. C1qB gene expression without stimulation was 2.2 times decreased and when stimulated was 1.5 times more expressed. Controls did not expressed C1qC gene and patient P1 had low expression both with and without stimulation. P2 had 2 copies of C4A and 1 copy of C4B. C2 gene sequencing (P2 and P3) showed 100% match with referenced sequence, with exception to 28bp deletion at the exon 6 (heterozygous C2 deficiency type I). C2 mRNA expression from P3 without stimulation was 23 times decreased and with interferon was 4.2 times decreased compared with controls. P4 had 2 copies of C4A and 3 copies of C4B. The qRT-PCR were performed only in C4B gene showed without stimulation a 14 times decreased expression and with interferon stimulation the expression were similar to controls. Conclusions: The two homozygous single-base exchanges in 5\'UTR and 3\'UTR that correspond to the promoter region and stabilization mRNA region in B chain of C1q gene, may have modified mRNA transcription as its expression was decreased without stimulation. Further analysis is necessary to relate C1q gene variations and undetectable serum C1q. In addition, heterozygous C2 deficiency type I may lead to reduced mRNA expression and may be present in JSLE patients with detectable C2 levels. Finally, the decreased C4B gene expression showed that serum dosage and gene copy number may not be sufficient to assess C4 deficiency
|
68 |
Structure and Biochemistry of otoferlin C2-domains / Struktur und Biochemie von Otoferlin C2-DomänenHelfmann, Sarah 04 July 2011 (has links)
No description available.
|
69 |
Regioselective Functionalization of Indoles using Directing Group Strategy : An Efficient Transition Metal CatalysisLanke, Veeranjaneyulu January 2016 (has links) (PDF)
The thesis entitled “Regioselective Functionalization of Indoles using Directing Group Strategy: An Efficient Transition Metal Catalysis” is divided into two sections. Section A, which is presented in three chapters, describes the regioselective alkenylation of indoles using directing group strategy. Whereas, Section B, which is divided in to two chapters, narrates the synthesis of 4-amino indoles using directing group strategy and site selective addition of maleimide to indole at C2-position.
Section A
Chapter 1. C2-Alkenylation of indoles
The indole ring system is one of the most abundant heterocycles present in nature. The synthesis and functionalization of indoles is one of the major areas of focus for synthetic organic chemists.1 Alkenylation of indole at C2-position is a challenging task due to the electrophilic nature of the reaction. For this reason, the functionalization of indole at C2-position is less addressed. In this chapter, a highly regioselective alkenylation of indole at the C2-position has been described by using the Ru(II) catalyst and employing a directing group (DG) strategy.2 This directing group strategy offers rare selectivity for the alkenylation of N-benzoylindole at the C2-position in the presence of the more reactive C3-position. A variety of N-benzoylindole derivatives are shown to undergo alkenylation at C2-positon. Deprotection of the benzoyl group has also been demonstrated, and the resulting products serve as a useful synthon for synthesizing a variety of natural products. A few representative examples are highlighted in Scheme 1.3
1 (a) Cacchi, S.; Fabrizi, G. Chem. Rev. 2005, 105, 2873.
(b) Karamyan, K. A. J.; Hamann, M. T. Chem. Rev. 2010, 110, 4489.
2 (a) Lyons, T. W.; Sanford, M. S. Chem. Rev. 2010, 110, 1147.
(b) Engle, K. M.; Mei, T.-S.; Wasa, M.; J.-Q. Yu, Acc. Chem. Res. 2012, 45, 788.
(c) Neufeldt, S. R.; Sanford, M. S. Acc. Chem. Res. 2012, 45, 936.
(d) Arockiam, P. B.; Bruneau, C.; Dixneuf, P. H. Chem. Rev. 2012, 112, 5879.
3 Lanke, V.; Prabhu, K. R. Org. Lett. 2013, 15, 2818.
Scheme 1: C2- Alkenylation of indoles
Chapter 2 describes a highly regioselective alkenylation of indoles at the C4-position by employing aldehyde functional group as a directing group, and Ru as a catalyst, under a mild reaction conditions. This approach leads to a short synthetic route for C4-alkenylated indoles, which serve as precursors for ergot alkaloids and related heterocyclic compounds.4 Further The potential of the present strategy has been demonstrated by performing (i) scale up reaction, (ii) selective reduction of olefin double bond and (iii) synthesizing substituted 1,3,4,5-tetrahydrobenzo[cd] in two steps with an overall yield of 68%. 1,3,4,5-Tetrahydrobenzo[cd] is one of the key intermediates for synthesizing ergot alkaloids. A few examples are highlighted in Scheme 2.5
4 (a) Horwell, D. C. Tetrahedron 1980, 36, 3123.
(b) Kozikowski, A. P.; Ishida, H. J. Am. Chem. Soc. 1980, 102, 4265.
(c) Oppolzer, W.; Grayson, J. I.; Wegmann, H.; Urrea, M. Tetrahedron 1983, 39, 3695.
(d) Hatanaka, N.; Ozaki, O.; Matsumoto, M. Tetrahedron Lett. 1986, 27, 3169.
(e) Horwell, D. C.; Verge, J. P. Phytochemistry 1979, 18, 519.
5 anke, V.; Prabhu, K. R. Org. Lett. 2013, 15, 6262.
Scheme 2: C4- Alkenylation of indoles
Chapter 3 of Section A, presents a novel mode of selective alkenylation of indoles using Ru and Rh catalyst. In these alkenylation reactions, selectivity between C2- and C4-positions of indole framework has been achieved by altering the property of directing group. Methyl ketone, as directing group, furnishes exclusively C2-alkenylated product, whereas trifluoromethyl ketone as a directing group changes the selectivity to C4, indicating that electronic nature of the directing group controls the choice between a 5-membered and 6-membered metallacycle. Developing such divergent and selective C-H functionalizations, between C2- and C4-positions, on the indole framework can lead to easy and short synthetic routes for natural, unnatural and biologically-active compounds.6 Further screening of other carbonyl derived directing groups revealed that strong and weak directing groups exhibit opposite selectivity. Experimental
6 (a) Bronner, S. M.; Goetz, A. E.; Garg, N. K. J. Am. Chem. Soc. 2011, 133, 3832.
(b) Nathel, N. F. F.; Shah, T. K.; Bronner, S. M.; Garg, N. K. Chem. Sci., 2014, 5, 2184.
(c) A Beilstein/Crossfire search shows that more than 600 C4- substituted indole-containing natural products exist and nearly 10,000 bioactive C4-substituted indoles have been reported. controls, deuteration experiments and preliminary DFT calculations lend support to the proposed mechanism. A few representative examples are highlighted in Scheme 3.7
Scheme 3: C4- vs C2-Alkenylation of ndoles
Deuterium Labeling studies were carried out to shed light on the site of metallacycle formation and hence the origin of selectivity. Both COCF3 and COCH3 substrates were independently subjected to both standard conditions A and B, along with either D2O or AcOD as deuterium sources (Scheme 4).
7 Lanke, V.; Bettadapur, K. R.; Prabhu, K. R. Manuscript submitted.
Scheme 4: Deuterium labeling studies
The Section B is divided into 2 chapters.
Chapter 1 presents a method for synthesizing of 3-(indol-2-yl) succinimide derivatives by using a directing group strategy. Selective functionalization at C2-position of indole in the presence of highly reactive C3-position has been achieved. A conjugate addition, instead of Heck-type reaction, has been achieved by careful selection of the alkene partner (maleimides and maleate esters). This selectivity has been achieved by avoiding β-hydride elimination. Succinimide derivatives are structural motifs that are found in many natural products and drug molecules. Moreover, succinimides can be easily reduced into 5-membered pyrrolidine rings, γ-lactams and lactims, which are part of structural scaffolds of useful natural products.8 Further the application of the protocol has been showcased by performing reduction to obtain pyrrolidine and 1,4 diols. A few representative examples are highlighted in Scheme5.9 8 (a)Crider, A. M.; Kolczynski, T. M.; Yates, K. M. J. Med. Chem. 1980, 23, 324.
(b) Isaka, M.; Rugseree, N.; Maithip, P.; Kongsaeree, P.; Prabpai, S.; Thebtaranonth, Y. Tetrahedron 2005, 61, 5577.
(c) Uddin, J.; Ueda, K.; Siwu, E. R. O.; Kita, M.; Uemura, D. Bioorg. Med. Chem. 2006, 14, 6954. (d) Hubert, J. C.; Wijnberg, J. B. P. A.; Speckamp, W. N. Tetrahedron 1975, 31, 1437.
(e) Wijnberg, J. B. P. A.; Schoemaker, H. E.; Speckamp, W. N. Tetrahedron 1978, 34, 179.
9 Lanke, V.; Bettadapur, K. R.; Prabhu, K. R. Org. Lett. 2015, 17, 4662.
Scheme 5: Addition of Maleimide to Indole at C2-position
Chapter 2 describes a highly regioselective amidation of unprotected indoles at the C4-position by employing aldehyde functional group as a directing group. This reaction has been performed using Ir(III) catalyst, under mild reaction conditions. Thus, an efficient, simple, short synthetic route for C4-amido indoles has been achieved. C4-Amido indoles are privileged molecules, which serve as precursors for indolactum V,10 teleocidin and related heterocyclic compounds.11 To the best our knowledge, this is the first report of using aldehyde as a directing group for amidation reactions. The potential of the present strategy has been demonstrated by performing scaling up reaction, and deprotection of tosyl group to obtain corresponding amines. A few representative examples are highlighted in Scheme 6.12
10 Garg, N. K. et al., J. Am. Chem. Soc. 2011, 133, 3832
11 Kehler, J. J. Med. Chem. 2014, 57, 5823
12 Lanke, V.; Prabhu, K. R. (Manuscript submitted).
Scheme 6: C4- amidation of indoles 7
|
70 |
Optilmisation de l'utilisation du gadolinium comme poison consommable dans le combustible nucléaire : Vers une REP sans bore / Optimizing the use of gadolinium as burnable poison in nuclear fuel : towards a boron free PWRPieck, Dario 22 October 2013 (has links)
L’excès de réactivité neutronique dans les centrales nucléaires est compensé par des sys-tèmes actifs de contrôle du réacteur : acide borique et barres de contrôle. L’apport d’antiréactivité peut se faire passivement avec des poisons consommables, c'est-à-dire des absorbants de neutrons, en particulier du gadolinium (Gd).Dans le cadre d’une augmentation de l’enrichissement en U²³⁵ et de réduction de l’utilisation d’acide borique, cette thèse a pour objectif d’optimiser la distribution du ga-dolinium dans des céramiques d’UO₂ afin d’obtenir un apport optimisé d’antiréactivité dans un Réacteur à Eau sous Pression.Dans ce sens, le travail est orienté à trouver des nouveaux matériaux riches en gadolinium. Le diagramme de phase U-O-Gd a donc été exploré dans le domaine des fortes teneurs en Gd. Deux phases cubiques ont été trouvées et caractérisées : les phases C1 et C2. En vue d’une application industrielle, la phase C1 a été retenue comme candidate pour l’ajout du Gd dans les pastilles d’UO₂.La distribution optimale de cette phase C1 dans les assemblages de combustible nucléaire a été étudiée avec le code de calcul neutronique APOLLO2.8. Des études paramétriques ont été réalisées. Ces études neutroniques ont aboutit à un concept performant de pastille empoisonnée. Finalement, des pastilles prototype ont été fabriquées en laboratoire suivant ce concept. L’ensemble des résultats obtenus montre qu’un concept de pastille avec un dépôt superficiel neutrophage de phase C1 est une manière d’apporter de l’antiréactivité de manière optimisée dans le cadre de cycles longs. Ceci pourrait potentiellement être appliquée à l‘échelle industrielle. Un brevet a été déposé en ce sens. / Reactivity excess in Nuclear Power Plants is controlled by reactor’s active systems: boric acid dilution and control rods. Alternatively, negative reactivity insertion can be made in a passive way using burnable poisons, i.e. neutron absorbers, this is the case of gadolinium (Gd).In the industrial framework of U²³⁵ enrichment increase and boric acid restraint, the goal of this thesis is to optimize the distribution of gadolinium in UO₂ ceramics to obtain a high-performance provision of negative reactivity in Pressurized Water Reactors.In this sense, the work is focus on new gadolinium-rich materials. Thus, U-Gd-O phase diagram was explored in the field of high Gd contents. Two cubic phases were found and characterized: the C1 and C2 phases. With the aim of an industrial application, C1 phase was selected as candidate for Gd addition into UO₂ pellets.The optimal distribution of C1 phase within a nuclear fuel assembly was studied using APOLLO 2.8 neutron transport code. Parametrical calculations were performed. These neutronic studies have ends in a successful “concept of poisoned pellet”.Finally, some prototype pellets following this concept were made in laboratory to proof it feasibility.All the obtained results shows that the proposed concept of a neutrophage C1-phase coating on UO₂ pellets is a convenient way to reduce reactivity excess within the framework of long irradiation cycles. This concept could be potentially applied in industrial scale. Consequently a patent application process was initiated.
|
Page generated in 0.058 seconds