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Articoli di riviste sul tema "Formation de liaisons C-S"
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Top, Siden, e Gérard Jaouen. "Formation de liaison CC par couplage réducteur d'ions carbéniums arène chrome tricarbonyle". Journal of Organometallic Chemistry 336, n. 1-2 (dicembre 1987): 143–51. http://dx.doi.org/10.1016/0022-328x(87)87164-4.
Testo completo
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Hiemstra, Henk, Floris P. Rutjes, Sape S. Kinderman, Jan H. van Maarseveen e Hans E. Schoemaker. "C-C Bond Formation viaN-Phosphoryliminium Ions". Synthesis 2004, n. 09 (2004): 1413–18. http://dx.doi.org/10.1055/s-2004-822376.
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Peng, Kang, Hui Zhu, Xing Liu, Han-Ying Peng, Jin-Quan Chen e Zhi-Bing Dong. "Chemoselective C-S/S-S Formation between Diaryl Disulfides and Tetraalkylthiuram Disulfides". European Journal of Organic Chemistry 2019, n. 47 (27 novembre 2019): 7629–34. http://dx.doi.org/10.1002/ejoc.201901401.
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Markó, István E., J. Mike Southern e M. Lakshmi Kantam. "Stoichiometric C-C Bond Formation Using Triorganothallium Reagents". Synlett 1991, n. 04 (1991): 235–37. http://dx.doi.org/10.1055/s-1991-20690.
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Wang, Haibo, Lu Wang, Jinsai Shang, Xing Li, Haoyuan Wang, Jie Gui e Aiwen Lei. "Fe-catalysed oxidative C–H functionalization/C–S bond formation". Chem. Commun. 48, n. 1 (2012): 76–78. http://dx.doi.org/10.1039/c1cc16184a.
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Sharma, Upendra, Ritika Sharma, Rakesh Kumar, Inder Kumar e Bikram Singh. "Selective C–Si Bond Formation through C–H Functionalization". Synthesis 47, n. 16 (9 luglio 2015): 2347–66. http://dx.doi.org/10.1055/s-0034-1380435.
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Zhang, Honghua, Huihong Wang, Yi Jiang, Fei Cao, Weiwei Gao, Longqing Zhu, Yuhang Yang et al. "Recent Advances in Iodine‐Promoted C−S/N−S Bonds Formation". Chemistry – A European Journal 26, n. 72 (5 ottobre 2020): 17289–317. http://dx.doi.org/10.1002/chem.202001414.
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Sun, Fengli, Xuemin Liu, Xinzhi Chen, Chao Qian e Xin Ge. "Progress in the Formation of C-S Bond". Chinese Journal of Organic Chemistry 37, n. 9 (2017): 2211. http://dx.doi.org/10.6023/cjoc201703038.
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Jean, Mickaël, Jacques Renault, Pierre van de Weghe e Naoki Asao. "Gold-catalyzed C–S bond formation from thiols". Tetrahedron Letters 51, n. 2 (gennaio 2010): 378–81. http://dx.doi.org/10.1016/j.tetlet.2009.11.025.
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Choudhuri, Khokan, Milan Pramanik e Prasenjit Mal. "Noncovalent Interactions in C–S Bond Formation Reactions". Journal of Organic Chemistry 85, n. 19 (25 agosto 2020): 11997–2011. http://dx.doi.org/10.1021/acs.joc.0c01534.
Testo completoTesi sul tema "Formation de liaisons C-S"
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Leclercq, Elise. "Formation de liaisons C-S et C-C par activation photo- et électrochimique en flux". Electronic Thesis or Diss., Université de Lille (2022-....), 2023. https://pepite-depot.univ-lille.fr/ToutIDP/EDSMRE/2023/2023ULILR037.pdf.
Testo completoAbstract (sommario):
Ce travail de thèse décrit le développement de nouvelles méthodologies pour la formation de liaisons C-C et C-S via une activation électro- et photochimiques afin de mettre au point des procédés plus écocompatibles en réacteur discontinu et en flux continu. L'utilisation de photons offre aux chimistes de synthèse une excellente opportunité d'introduire un niveau élevé de complexité moléculaire dans un environnement «sans réactif». L'électrosynthèse organique permet de remplacer l'utilisation d'agents chimiques oxydants et réducteurs par l'ajout ou le retrait d'un ou plusieurs électrons issus d'électrodes, qui peut être assimilé comme un réactif vert, propre et sans trace et qui peut être issu d'électricité renouvelable. C'est pourquoi l'électrosynthèse est de plus en plus attrayante pour la réalisation de réactions d'oxydo-réductions. De plus, la transposition de procédés photochimiques et électrochimiques en réacteurs fluidiques est d'autant plus intéressante qu'elle permet de réduire considérablement les coûts énergétiques, les temps de réaction mais aussi d'améliorer les sélectivités des réactions.Dans une première partie, ce travail porte sur le développement d'une réaction de sulfonylation électrochimique d'imidazo[1,2-a]pyridines en réacteur conventionnel et en flux. Cette méthode est compatible avec une large gamme d'hétérocycles azotés et de substituants (37 exemples décrits avec un rendement maximal de 90%).Une deuxième partie concerne le développement d'une nouvelle méthode de trifluorométhylation d'hétérocycles azotés via une activation électrochimique en réacteur conventionnel et en flux continu. Dans un premier temps une large gamme de pyridinones trifluorométhylées protégées et non protégées a été obtenue avec des rendements moyens à bons sans électrolyte support. Dans un second temps, une méthode d'oxy- et de trifluorométhylation d'énamides cycliques a été développée. L'utilisation de dispositif en flux étant limitée aux réactions totalement homogènes afin d'éviter tout phénomène de bouchage, seule la réaction d'oxytrifluorométhylation a été réalisée en réacteur fluidique permettant également la suppression d'électrolyte. La réaction tolère de nombreux substituants aussi bien sur le cycle benzylique que sur le cycle énamide. L'influence du nucléophile sur la réaction d'oxytrifluorométhylation a aussi été étudiée et des rendements moyens à excellents (55% à 90%) ont été obtenus.Enfin, dans une troisième partie, nous avons voulu développer une nouvelle méthode de formation de liaison C-C par activation photochimique via de nouveaux photo précurseurs d'arynes. Les résultats préliminaires obtenus sont encourageants pour la suite de l'étude pour une transposition en réacteur fluidique.En conclusion, ce travail permet de montrer les apports et les limitations de la technologie en flux continu notamment pour des procédés photochimiques et d'électrosynthèse. L'utilisation de dispositifs microfluidiques en électrosynthèse permet la décarbonation de réactions d'oxydo-réductions organiques accompagné d'une réduction importante de la consommation d'électricité d'un tiers à productivité constante, tout en limitant l'emploi d'électrolytes support dans une démarche d'économie d'atomes. Cette approche méthodologique couplée à une source d'électricité bas carbone s'avère ainsi vertueuse et propose ainsi une solution aux problématiques environnementales actuelles. De plus, le développement d'une nouvelle méthode de génération d'arynes en utilisant une activation verte peut se révéler prometteur pour l'avenirThis thesis describes the development of new methodologies for the formation of C-C and C-S bonds via electro-and photochemical activation in order to develop eco-friendlier batch and continuous flow processes. The use of photons offers organic chemists an excellent opportunity to introduce a high level of molecular complexity in a “reagent-free” environment. Organic electrosynthesis makes it to replace the use of oxidizing and reducing chemical agents by the addition or removal of one or more electrons from electrodes, which can be assimilated as a green, clean and trace-free reagent and which can be derived form renewable electricity. That's why, electrosynthesis is more and more attractive for carrying out oxidation-reduction reactions. In addition, the transposition of photochemical and electrochemical in flow is also more interesting as it makes possible to considerably reduce energy costs, reaction time but also to improve the selectivity of reactions. In the first part, this work focuses on the development of an imidazo[1,2-a]pyridines electrochemical sulfonylation reaction in conventional and flow reactors. This method is compatible with a wide range of nitrogen heterocycles and substituents (37 examples described with a maximum yield of 90%).The second part concerns the development of a new method for trifluoromethylation of nitrogenous heterocyles by electrochemical activationin conventional and flow reactors. This methodology makes possible to obtain a wide range of protected and unprotected trifluoromethyl pyridinones with average to good yields and without supporting electrolyte. Moreover, the conversion of this reaction to a method of oxy- and trifluoromethylation of cyclic enamides is introduced in a last part. The use of flow devices being limited to completely homogeneous reactions and to avoid any clogging phenomenon, only the reaction of oxy-trifluoromethylation could be carried out in fluidic reactor also allowing electrolyte suppression. The reaction tolerates many substituents both on the benzyl cycle and on the enamide cycle and the influence of the nucleophile on the oxy-trifluoromethylation reaction has been studied and led to average to excellent yields (55% to 90%).Finally, in the last section, we set out to develop a new method for C-C bond formation by photochemical activation via new aryne photoprecursors. The preliminary results obtained are encouraging for further study, with a view to transposition to a fluidic reactor.In conclusion, this work demonstrates the benefits and limitations of continuous flow technology, particularly for photochemical and electrosynthesis processes. The use of microfluidic devices in electrosynthesis enables the decarbonization of organic oxidation-reduction reactions, accompanied by a significant reduction in electricity consumption by a third at constant productivity, while limiting the use of supporting electrolytes in an atom-saving approach. This methodological approach coupled with a low-carbon electricity source is thus virtuous and thus offers a solution to current environmental problems. In addition, the development of a new methodology for generating arynes using green activation may prove promising for the future
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Pagès, Lucas. "Hydrofonctionnalisation d'allénamides terminaux par catalyse au cuivre : formation de liaisons C-C, C-S, C-P et C-O". Electronic Thesis or Diss., Montpellier, Ecole nationale supérieure de chimie, 2022. http://www.theses.fr/2022ENCM0017.
Testo completoAbstract (sommario):
L'objectif de la thèse consiste à découvrir de nouveaux procédés économiques, non toxiques et non polluants pour réaliser la synthèse de molécules à haute valeur ajoutée (dans le domaine de la pharmacie et des matériaux), à partir de molécules de départ simple pouvant éventuellement être issues directement du monde végétal. Ces nouveaux procédés feront principalement appel à la catalyse homogène et à des catalyseurs métalliques peux coûteux et peu toxiques à base par exemple de cuivre (les méthodes que ces nouveaux procédés sont destinés à remplacer font en général appel à des catalyseurs très coûteux et très toxiques à base de palladium et de ligands sophistiqués). Les recherches reposeront sur l'expertise de l'équipe d'accueil dans le domaine l'hydrofonctionnalisation1 de liaisons insaturées (dont l'hydroamination) ainsi que dans celui de l'arylation de nucléophiles carbonés, oxygénés ou azotés,2 par catalyse au cuivre (formation de liaisons C-C et C-hétéroatome). Le projet comportera une partie méthodologie de synthèse ainsi qu'une partie d'étude mécanistique très poussée sur les systèmes catalytiques découverts (RMN, études cinétique, isolation de complexes métalliques intermédiaires, calculs DFT). L'application et le transfert vers le milieu industriel, domaine dans lequel l'équipe a une très grande expérience, seront alors ensuite envisagés et mis en œuvre s'il y a lieu. 1. a) Chem. Comm, 2015, 51, 11210. b) Org. Lett. 2015, 17, 1224. c) Org. Lett. 2016, 18, 1482. d) Adv. Sytnh. Cat., 2017, 349, 4388. e) ACS. Catal. 2017, 7, 425. f) Org. Lett. 2018, 20, 223. g) Synthesis, 2019, 51, 1225. 2. a) Angewandte Chemie, 2007, 46(6), 934. b) Angew. Chem. Int. Ed. 2009, 48, 337. c) Angew. Chem. Int. Ed. 2009, 48, 6954. d) Angew. Chem. Int. Ed. 2009, 48, 8725. d) Angew. Chem. Int. Ed. 2012, 51, 12815. e) Chem. Comm, 2013, 49, 7412. f) Angewandte Chemie, 2015, 54, 1058. g) Angewandte Chemie, 2016, 55, 3785One of the main objective of the thesis is to discover new economic, non-toxic and non-polluting processes for the synthesis of targets with high added value (in the field of pharmacy and materials), starting from simple starting molecules (possibly issues from the plant world). These new processes will mainly use homogeneous catalysis and inexpensive and low-cost metal catalysts based for example on copper (the methods that these new processes are intended to replace generally make use of very expensive and highly toxic palladium based catalysts and sophisticated ligands). The research will be based on the expertise of the host team in the field of hydrofunctionalization (ref 1) of unsaturated bonds (including hydroamination) as well as in the arylation of carbon, oxygenated or nitrogenous nucleophiles (ref 2) by copper catalysis (formation of C-C and C-heteroatom bonds). The project will include a synthesis methodology part as well as a very advanced mechanistic study of the discovered catalytic systems (NMR, kinetic studies, isolation of intermediate metal complexes, DFT calculations). Application and transfer to industry, where the team has a great deal of experience, will then be considered and implemented if necessary. 1. a) Chem. Comm, 2015, 51, 11210. b) Org. Lett. 2015, 17, 1224. c) Org. Lett. 2016, 18, 1482. d) Adv. Sytnh. Cat., 2017, 349, 4388. e) ACS. Catal. 2017, 7, 425. f) Org. Lett. 2018, 20, 223. g) Synthesis, 2019, 51, 1225. 2. a) Angewandte Chemie, 2007, 46(6), 934. b) Angew. Chem. Int. Ed. 2009, 48, 337. c) Angew. Chem. Int. Ed. 2009, 48, 6954. d) Angew. Chem. Int. Ed. 2009, 48, 8725. d) Angew. Chem. Int. Ed. 2012, 51, 12815. e) Chem. Comm, 2013, 49, 7412. f) Angewandte Chemie, 2015, 54, 1058. g) Angewandte Chemie, 2016, 55, 3785
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Doussot, Joël. "Formation selective de liaisons c-n et c-cn par substitution nucleophile oxydante de liaisons c-h". Paris 6, 1993. http://www.theses.fr/1993PA066076.
Testo completoAbstract (sommario):
L'oxydation de substrats aromatiques comportant une chaine alkyle a l'aide de 2,3-dichloro-5,6-dicyano-benzoquinone en presence d'acide hydrazoique ou d'azide de trimethylsilyle conduit a la formation chimio et regioselective d'azides benzyliques. Cette reaction, correspondant a une substitution nucleophile oxydante s#n#o#x, donne acces aux benzylamines par une reduction aisee de ces azides. L'utilisation de cyanure de trimethylsilyle comme agent nucleophile, dans ce type de reaction, ouvre une voie d'acces a des nitriles par fonctionnalisation directe du carbone de la chaine alkyle en position benzylique. L'application de cette methode a des composes 19-nor-steroides (strogenes) permet la creation regio et stereoselective: soit d'une liaison c-n en position 9 (e. D. :80%) ou 12; soit d'une liaison c-cn en position 9 ou 12. La determination des structures des steroides obtenus et l'etude des effets de solvant permettent de proposer un mecanisme reactionnel pour ces reactions. Finalement la reduction des fonctions introduites sur ces structures conduit aux amino et methylamino-19-nor-steroides susceptibles de presenter un interet pharmacologique
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Ritleng, Vincent. "Fonctionnalisation sélective de liaisons C-H dans des conditions douces : formation de liaisons C-C induites par le ruthénium". Université Louis Pasteur (Strasbourg) (1971-2008), 2001. http://www.theses.fr/2001STR13101.
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Frogneux, Xavier. "Transformations réductrices du CO2 pour la formation de liaisons C-N et C-C". Thesis, Paris 11, 2015. http://www.theses.fr/2015PA112136/document.
Testo completoAbstract (sommario):
Dans le monde actuel, le dioxyde de carbone (CO2) est le déchet majoritaire issu de l’utilisation des ressources fossiles mais il est encore peu utilisé dans les applications à grande échelle. Afin de tirer parti de son abondance, le développement de nouvelles transformations chimiques du CO2 pour accéder à des produits de chimie fine connait un intérêt croissant au sein de la communauté scientifique. Tout particulièrement, la formation de liaison(s) C-N à partir du CO2 et d’un substrat azotés permet d’accéder à des produits à hautes valeurs énergétiques et commerciales. Un second type de transformation désirable est la formation de liaison C-C à partir du CO2 afin de synthétiser des dérivés d’acides carboxyliques comme des esters. L’utilisation d’hydrosilanes, réducteurs doux, permet de travailler sous 1 bar de CO2 avec des catalyseurs à base de métaux peu coûteux et abondants tels que le fer et le zinc ou bien avec des organocatalyseurs. Les synthèses de formamides, de méthylamines ou d’aminals à partir du CO2 ont ainsi été développées par hydrosilylation. Enfin, la carboxylation des carbosilanes à partir du CO2 a été développée pour la première fois avec un catalyseur à base de cuivre. Dans le cas des 2-pyridylsilanes, l’utilisation de sels de fluorures pentavalents permet d’activer le substrat efficacement sans catalyseurIn the current world, carbon dioxide (CO2) is the major waste of the massive utilization of fossil resources but only few applications have been developed using this compound. In order to take advantage of its abundancy, the development of novel chemical transformation of CO2 to produce fine chemicals is of high interest in the scientific community. In particular, the formation of C-N bond(s) from CO2 and amine compounds unlocks a new way to access high energy and value-added. A second type of highly desirable transformation is the formation of C-C bonds with CO2 so as to synthesize carboxylic acid derivatives. The utilization of hydrosilanes as mild reductants allows the reactions to proceed under 1 bar of CO2 with abundant and cheap metal-based catalysts (iron, zinc) or with organocatalysts. The synthesis of formamides, methylamines and aminals from CO2 are described herein. Ultimately, the catalytic carboxylation of carbosilanes has been achieved for the first time using copper-based complexes. In the specific case of 2-pyridylsilanes, the use of pentavalent fluoride salts allowed us to perform the reaction without catalyst
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Liu, Yujia. "Formation de liaisons C-C, C-S, C-N et C-P réalisée par catalyse au cuivre, au manganèse ou en absence de métal de transition". Thesis, Montpellier, Ecole nationale supérieure de chimie, 2017. http://www.theses.fr/2017ENCM0016.
Testo completoAbstract (sommario):
Cette thèse se situe dans le cadre général de la recherche de nouvelles méthodes de synthèse, peu coûteuses et éco-compatibles, permettant d’accéder à des molécules intéressantes dans le domaine pharmaceutique, agrochimique ou dans celui des matériaux. Plus particulièrement, l’objectif consiste à créer des liaisons C-C et C-hétéroatome (S, N, P) par la catalyse au cuivre, au manganèse ou à l’aide de méthodes ne faisant pas appel à des métaux de transition.Dans une première partie, une réaction de Sonogashira réalisée par catalyse au cuivre sous des conditions biphasiques (eau / substrats organiques) a été décrite. La charge en catalyseur peut être diminuée jusqu’ à 0,02-0,2 mol% et un intermédiaire potentiel de cette réaction, correspondant à un cluster de cuivre lié à un groupe acétylure, a été identifié par diffraction aux rayons X.Dans une deuxième partie, nous avons décrit un nouveau système catalytique au cuivre permettant de réaliser, sous atmosphère de dioxyde de carbone, la méthylthiolation d’halogénures d’aryle, en utilisant le diméthylsulfoxyde comme source du fragment méthylthio. Le rôle de CO2, dont la présence est un facteur crucial pour la formation des sulfures d’aryle méthyle correspondants, est discuté.La troisième partie décrit des réactions d’homocouplage et d’hétérocouplage, catalysées au manganèse, et mettant en jeu des dérivés aryllithiens synthétisés in situ à partir d’halogénures d’aryle. Selon les conditions expérimentales, des biaryles symétriques ou dissymétriques peuvent être obtenus. Un complexe intermédiaire du manganèse pouvant intervenir dans les mécanismes réactionnels a été détecté par l’ESI-MS.Enfin, un système associant DMF et t-BuOK et ne faisant pas appel au complexe de métaux de transition a été développé pour réaliser l’arylation de nucléophiles variés tels que le pyrazole, l’imidazole, le disulfure de dialkyle ou l’oxyde de diarylphosphine à partir de dérivés halogénés aromatiques. Pour ce sujet, les travaux sont à un stade préliminaireThis thesis is one part of a general research of the novel, non-expensive and environmentally friendly methods for the synthesis of the interesting molecules in the pharmaceutical, agrochemical or material field. In particular, the objective consists of creating the C-C and C-heteroatom (S, N, P) bonds by using copper, manganese catalysis or transition-metal-free system.In the first part, a copper-catalyzed palladium-free Sonogashira reaction has been realized under biphasic conditions (water / organic substrates) allowing decreasing the copper loading up to 0.02 – 0.2 mol% and a potential intermediate species of this reaction, corresponding to a copper cluster linked with acetylide moiety, has been identified by X-ray diffraction.In the second part, we described a novel carbon dioxide involved copper-catalyzed system for the methylthiolation of aryl halides using dimethylsufoxide as a source of methylthio group. The presence of carbon dioxide is a crucial factor for the formation of aryl methyl sulfides products and its role is discussed.The third part describes the manganese-catalyzed homocoupling and cross-coupling reactions via the formation in situ of aryllithium from corresponding aryl halides or arenes. According to the experimental conditions, the symmetrical or unsymmetrical biaryls could be obtained. An intermediate complex of manganese which could involve in the reaction mechanism was detected by ESI-MS.Finally, a transition-metal-free system associating DMF with t-BuOK has been developed to realize the arylation of aromatic halide derivatives and various nucleophiles such as pyrazol, imidazole, dialkyl disulfide or diarylphosphine oxide. This project is at a preliminary stage
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Vabre, Roxane. "Fonctionnalisation directe de liaisons C-H et couplages croisés pour la formation de liaisons C-C et C-N : synthèse de purines 6,8,9-trisubstituées". Phd thesis, Université Paris Sud - Paris XI, 2013. http://tel.archives-ouvertes.fr/tel-00923198.
Testo completoAbstract (sommario):
La grande variété de propriétés biologiques associées au noyau purine en fait une structure privilégiée pour la conception et la synthèse de nouvelles molécules à visée thérapeutique. Cette spécificité est étroitement liée à la grande diversité de substituants pouvant être introduits sur les différentes positions du noyau purine et en particulier sur C2, C6, C8 et N9. Par conséquent, le développement de méthodes de fonctionnalisation rapides de cette famille de composés est d'un grand intérêt synthétique. Nous nous sommes focalisés sur la formation de liaisons C-C et C-N sur les positions 6 et 8 du noyau purine pour pouvoir présenter de nouveaux outils de synthèse permettant d'introduire une plus grande diversité fonctionnelle. D'une part, nous avons étudié la fonctionnalisation directe de liaisons C-H de purines, sujet encore peu exploré. En effet, de nos jours, le traditionnel couplage croisé (Negishi, Suzuki-Miyaura), utilisé pour la création de liaisons C-C, se voit de plus en plus concurrencé par ces réactions puisqu'elles ne nécessitent pas la préparation d'un partenaire organométallique. Ce sont des réactions dites à économie d'atomes. En nous basant sur l'expérience du laboratoire dans le domaine de la fonctionnalisation directe de liaisons C-H, nous avons envisagé l'alcénylation et l'alcynylation directes en position 8 de la purine, les motifs alcényle et alcynyle étant présents dans certaines purines d'intérêt biologique. D'autre part, nous nous sommes intéressés à deux méthodes de couplage croisé pallado-catalysé permettant la formation de liaisons C-N et C-C : le couplage de Buchwald - Hartwig entre une 8-iodopurine et des amides ou des amines aromatiques, et le couplage de Liebeskind - Srogl entre une 6-thioétherpurine et divers acides boroniques.
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Vece, Vito. "Formation de liaisons C-C et C-O par activation électrophile de doubles liaisons catalysée par des superacides de Brönsted et de Lewis". Nice, 2011. http://www.theses.fr/2011NICE4028.
Testo completoAbstract (sommario):
En synthèse organique, l’utilisation des superacides de Brönsted (TfOH et Tf2NH) ou superacides de Lewis (M(n)(OTf)n et M(n)(NTf2)n) présente un intérêt considérable dans de nombreuses réactions, plus particulièrement en tant que catalyseurs pour la formation de liaisons C-O, C-N et C-C au cours desquels une activation électrophile de double liaison est nécessaire. Ces superacides peuvent ainsi être utilisés en quantité sous-stoechiométrique et demeurer souvent plus actifs et plus sélectifs que des acides de Lewis plus classiques, ce qui inscrit ces travaux de méthodologie dans la chimie verte. Nous avons mis à profit l’activité de ces catalyseurs pour réaliser des réactions de type Friedel-Crafts, des réactions tandem Friedel-Crafts-hydroalcoxylation et des réactions de cycloisomerisation. Les composés polyfonctionnalisés auxquels nous proposons un nouvel accès constituent sont porteurs d’applications potentielles nombreuses, non seulement dans le cadre de la synthèse de produits pharmaceutiques mais aussi en agrochimie ou dans l’industrie des parfums. Dans un premier chapitre, nous présentons une étude bibliographique des thèmes abordés au cours de ce travail de thèse. Dans un second chapitre, la réaction d’allylation de type Friedel-Crafts à partir de cycles aromatiques, phénoliques ou non, est étudiée et orientée vers des applications dans des synthèses d’intérêt industriel. Dans un troisième chapitre, une discussion mécanistique de cette réaction de Friedel-Crafts est ensuite présentée, appuyée par des expériences de cinétiques et par des calculs théoriques ab initio. Dans un quatrième chapitre, nous présentons ensuite une discussion sur les réactions de cyclisation de composés polyinsaturés de type diènes-1,6 ou aza-diènes. La cycloisomérisation de diènes-1,6 substitués permet l’accès à des composés nouveaux dont les squelettes présentent un intérêt dans le domaine de la parfumerie, et s’insère ainsi dans une des thématiques principales développées au laboratoire. L’application des systèmes catalytiques développés au cours de cette thèse dans la synthèse de composés possédant des propriétés odorantes a été un des objectifs de ce travailThe use of Brönsted superacids (TfOH and Tf2NH) or Lewis superacids (M(n)(OTf)n and M(n)(NTf2)n) in organic synthesis presents a high interest in a wide number of reactions, particularly for the C-O, C-N and C-C bond formation involving the electrophilic activation of a double bond. These superacids could be used in sub-stoichiometric amounts whiole remaining more active and selective than more conventional Lewis acids, therefore improving the Green Chemistry aspects of our studies. We have used these catalysts to carry out Friedel-Crafts type reactions, tandem Friedel-Crafts-hydroalkoxylation processes and cycloisomerisations. The polyfunctionalised compounds for which a novel and efficient access is proposed present potential applications in medicinal, agricultural and perfume chemistry. A first chapter is devoted to the bibliographical studies of the various topics presented in this manuscript. In a second chapter, the Friedel-Crafts type allylation reaction from aromatic cycles, phenolic or not, have been studied and oriented towards the synthesis of valuable chemicals of industrial relevance. In a third chapter, mechanistic studies based on kinetic measurements and theoretical calculations on this reaction are presented. In a fourth chapter, cyclisation reactions of polyinsaturated compounds such as 1,6-dienes and aza-dines are presented. The cycloisomerisation of substituted 1,6-dienes allowed the access to several new compounds of interest in fragrance chemistry, a central interest of our laboratory. The application of the catalytic systems studied in the synthesis of compounds with odorant properties has
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Tremel, Pascale. "Formation de liaisons C-C dans des réactions catalysées par des "superacides" de Lewis". Nice, 2011. http://www.theses.fr/2011NICE4126.
Testo completoAbstract (sommario):
La réaction de carbonyle-ène, la cyclisation d’alcools homoallyliques et allyliques sur une double liaison et la cyclisation de diènes-1,6 par voie électrochimiques sont des méthodes utiles pour la synthèse organique afin d’obtenir de nouveaux composés de structures variées et diversement substitués. L’objectif de ce travail de thèse a consisté en l’étude de ces diverses réactions par la catalyse avec des triflates et des triflimidures métalliques, à caractère plus acide que les acides de Lewis classiques. La réaction de carbonyle-ène par du triflimidure de fer (II) ou par du triflate de bismuth (III) conduit à la formation de dérivés hydroxylés à partir d’aldéhydes et de cétones avec un taux catalytique compris entre 0,1 et 10 mol%. Les dérivés cétones fournissent également des réactions en cascade. La cyclisation d’alcool homoallyliques conduit à la formation d’éthers cycliques à cinq chaînons en présence de 1 mol% de triflate d’aluminium. La cyclisation d’alcools allyliques fournit des cycles à cinq ou six chaînons en présence de 5 à 10 mol% de triflate d’aluminium. Enfin, l’étude spécifique de la cyclisation oxydative de diènes-1,6 par voie électrochimique conduit à la formation de cycles à cinq chaînons avec l’addition d’une ou deux molécules de méthanol en présence de 10 mol% de Ce(OTf)3The carbonyl ene reaction, the cyclization of homoallylic and allylic alcohols to double bonds and the anodic cyclization of 1,6-dienes are useful methods in organic synthesis in order to obtain new compounds, with variable substitutions. The purpose of this work deals with the catalysis of these reactions by metal triflates and triflimides, more acidic than classical Lewis Acids. The carbonyl ene reaction with iron (II) triflimide led to the formation of cyclic hydroxylic compounds from aldehydes and ketones with only 0,1 to 10 mol% of catalyst. Ketone derivatives provided also cascade reactions. Five membered ring ethers were obtained by the cyclization of homoallylic alcohols with 1 mol% of Al(OTf)3. The cyclization of allylic alcohols led to five and six membered rings with 5 to 10 mol% of Al(OTf)3. The study of the anodic 1,6-diene cyclization provided a series of five membered ring compounds with addition of one or two methanol molecules with 10 mol% of Ce(OTf)3
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Maillos, Philippe. "Formation de liaisons Carbone-Azote par réaction SRN¹ en série aliphatique". Paris 11, 1988. http://www.theses.fr/1988PA112185.
Testo completoAbstract (sommario):
Les anions dérivés des azoles sont des nucléophiles efficaces pour des réactions de SRN1 avec des gem bromonitro alcanes simples, monofonctionnalisés, ou bifonctionnalisés , menant à des dérivés gemnitroazoliques, avec formation de liaisons carbone-azote inédites jusqu'alors dans le domaine de la SRN1. Les composés ainsi obtenus réagissent efficacement avec des nitronates dans une seconde réaction de SRN1 et conduisent à des composés azolés à chaîne ramifiée. Certaines propriétés chimiques des dérivés obtenus sont étudiées en vue d'essais de synthèse de composés ayant une structure originale, et appartenant à des familles connues pour leurs activités biologiques importantes acyclonucléosides et dérivés pyridinaldoximes (réactivateurs d'enzyme cholinestérase inhibé par les organophosphorés).
Libri sul tema "Formation de liaisons C-S"
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Lewis, C. S. The C. S. Lewis Bible. New York: HarperOne, 2010.
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Vanderlippe, John M., e VanderLippe John M. The Politics Of Turkish Democracy: Ismet Inonu And The Formation Of The Multi-party System, 1938-1950 (S U N Y Series in the Social and Economic History of the Middle East). State University of New York Press, 2005.
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Morgan, Marina. Other bacterial diseasesStreptococcosis. Oxford University Press, 2011. http://dx.doi.org/10.1093/med/9780198570028.003.0023.
Testo completoAbstract (sommario):
Many pyogenic (β -haemolytic) streptococci of clinical significance have animal connections. In the last edition of this book two species of streptococci were considered of major zoonotic interest, namely Streptococcus suis and S. zooepidemicus. Since then, numerous sporadic zoonoses due to other streptococci have been reported, and a newly recognized fish pathogen with zoonotic potential termed S. iniae has emerged. Changes in nomenclature make the terminology confusing. For example, the organism known as S. zooepidemicus — now termed S. dysgalactiae subsp. zooepidemicus — still causes pharyngitis in humans, complicated rarely by glomerulonephritis after ingestion of unpasteurized milk. Pigs remain the primary hosts of S. suis with human disease mainly affecting those who have contact with pigs or handle pork.Once a sporadic disease, several major epidemics associated with high mortality have been reported in China. The major change in reports of zoonotic streptococcal infections has been the emergence of severe skin and soft tissue infections, and an increasing prevalence of toxic shock, especially due to S. suis (Tang et al. 2006), group C (Keiser 1992) and group G β -haemolytic streptococci (Barnham et al. 2002). Penicillin remains the mainstay of treatment for most infections, although some strains of group C and G streptococci are tolerant (minimum bactericidal concentration difficult or impossible to achieve in vivo) (Portnoy et al. 1981; Rolston and LeFrock 1984) and occasionally strains with increased minimum inhibitory concentrations (MIC) for penicillin are reported.Agents preventing exotoxin formation, such as clindamycin and occasionally human intravenous immunoglobulin, may be used in overwhelming infection where circulating exotoxins need to be neutralized in order to damp down the massive release of cytokines generated by their production (Darenberg et al. 2003). Prevention of human disease focuses on maintaining good hygienic practice when dealing with live animals or handling raw meat or fish products, covering skin lesions, thorough cooking of meats and pasteurization of milk.
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Trieloff, Mario. Noble Gases. Oxford University Press, 2017. http://dx.doi.org/10.1093/acrefore/9780190647926.013.30.
Testo completoAbstract (sommario):
This is an advance summary of a forthcoming article in the Oxford Encyclopedia of Planetary Science. Please check back later for the full article.Although the second most abundant element in the cosmos is helium, noble gases are also called rare gases. The reason is that they are not abundant on terrestrial planets like our Earth, which is characterized by orders of magnitude depletion of—particularly light—noble gases when compared to the cosmic element abundance pattern. Indeed, such geochemical depletion and enrichment processes make noble gases so versatile concerning planetary formation and evolution: When our solar system formed, the first small grains started to adsorb small amounts of noble gases from the protosolar nebula, resulting in depletion of light He and Ne when compared to heavy noble gases Ar, Kr, and Xe: the so-called planetary type abundance pattern. Subsequent flash heating of the first small mm to cm-sized objects (chondrules and calcium, aluminum rich inclusions) resulted in further depletion, as well as heating—and occasionally differentiation—on small planetesimals, which were precursors of larger planets and which we still find in the asteroid belt today from where we get rocky fragments in form of meteorites. In most primitive meteorites, we even can find tiny rare grains that are older than our solar system and condensed billions of years ago in circumstellar atmospheres of, for example, red giant stars. These grains are characterized by nucleosynthetic anomalies and particularly identified by noble gases, for example, so-called s-process xenon.While planetesimals acquired a depleted noble gas component strongly fractionated in favor of heavy noble gases, the sun and also gas giants like Jupiter attracted a much larger amount of gas from the protosolar nebula by gravitational capture. This resulted in a cosmic or “solar type” abundance pattern, containing the full complement of light noble gases. Contrary to Jupiter or the sun, terrestrial planets accreted from planetesimals with only minor contributions from the protosolar nebula, which explains their high degree of depletion and basically “planetary” elemental abundance pattern. Indeed this depletion enables another tool to be applied in noble gas geo- and cosmochemistry: ingrowth of radiogenic nuclides. Due to heavy depletion of primordial nuclides like 36Ar and 130Xe, radiogenic ingrowth of 40Ar by 40K decay, 129Xe by 129I decay, or fission Xe from 238U or 244Pu decay are precisely measurable, and allow insight in the chronology of fractionation of lithophile parent nuclides and atmophile noble gas daughters, mainly caused by mantle degassing and formation of the atmosphere.Already the dominance of 40Ar in the terrestrial atmosphere allowed C. F v. Weizsäcker to conclude that most of the terrestrial atmosphere originated by degassing of the solid Earth, which is an ongoing process today at mid ocean ridges, where primordial helium leaves the lithosphere for the first time. Mantle degassing was much more massive in the past; in fact, most of the terrestrial atmosphere formed during the first 100 million years of Earth´s history, and was completed at about the same time when the terrestrial core formed and accretion was terminated by a giant impact that also formed our moon. However, before that time, somehow also tiny amounts of solar noble gases managed to find their way into the mantle, presumably by solar wind irradiation of small planetesimals or dust accreting to Earth. While the moon-forming impact likely dissipated the primordial atmosphere, today´s atmosphere originated by mantle degassing and a late veneer with asteroidal and possibly cometary contributions. As other atmophile elements behave similar to noble gases, they also trace the origin of major volatiles on Earth, for example, water, nitrogen, sulfur, and carbon.
Capitoli di libri sul tema "Formation de liaisons C-S"
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Eisen, Moris S. "Catalytic C–N, C–O, and C–S Bond Formation Promoted by Organoactinide Complexes". In C-X Bond Formation, 157–84. Berlin, Heidelberg: Springer Berlin Heidelberg, 2010. http://dx.doi.org/10.1007/978-3-642-12073-2_7.
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Di Giuseppe, Andrea, Ricardo Castarlenas e Luis A. Oro. "Rhodium Catalysts for C–S Bond Formation". In Topics in Organometallic Chemistry, 31–67. Cham: Springer International Publishing, 2016. http://dx.doi.org/10.1007/3418_2016_171.
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Della Sala, Giorgio, e Alessandra Lattanzi. "C-Other Atom Bond Formation (S, Se, B)". In Stereoselective Organocatalysis, 493–527. Hoboken, New Jersey: John Wiley & Sons, Inc., 2013. http://dx.doi.org/10.1002/9781118604755.ch14.
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Kibayashi, C., e N. Yamazaki. "C—C Bond Formation Using Allyltrimethylsilane". In Acetals: O/N, S/S, S/N, and N/N and Higher Heteroatom Analogues, 1. Georg Thieme Verlag KG, 2007. http://dx.doi.org/10.1055/sos-sd-030-00042.
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Kibayashi, C., e N. Yamazaki. "C—C Bond Formation Using Organometallic Reagents". In Acetals: O/N, S/S, S/N, and N/N and Higher Heteroatom Analogues, 1. Georg Thieme Verlag KG, 2007. http://dx.doi.org/10.1055/sos-sd-030-00041.
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Toffano, M. "Formation of C—S Bonds". In Organophosphorus Compounds (incl. RO-P and RN-P), 1. Georg Thieme Verlag KG, 2009. http://dx.doi.org/10.1055/sos-sd-042-00446.
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Mase, N. "C—S and C—Se Bond Formation". In Water in Organic Synthesis, 1. Georg Thieme Verlag KG, 2012. http://dx.doi.org/10.1055/sos-sd-206-00162.
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Pedersen, C. Th. "By Formation of Two S—S, Three S—C, and One C—C Bond". In Five-Membered Hetarenes with One Chalcogen and One Additional Heteroatom, 1. Georg Thieme Verlag KG, 2002. http://dx.doi.org/10.1055/sos-sd-011-00213.
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Pedersen, C. Th. "By Formation of One S—S, One S—C, and One C—C Bond". In Five-Membered Hetarenes with One Chalcogen and One Additional Heteroatom, 1. Georg Thieme Verlag KG, 2002. http://dx.doi.org/10.1055/sos-sd-011-00217.
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Stien, D. "C—C Bond Formation". In Three Carbon-Heteroatom Bonds: Esters and Lactones; Peroxy Acids and R(CO)OX Compounds; R(CO)X, X=S, Se, Te, 1. Georg Thieme Verlag KG, 2005. http://dx.doi.org/10.1055/sos-sd-021-00020.
Testo completoAtti di convegni sul tema "Formation de liaisons C-S"
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Williams, Spencer. "UNDERSTANDING THE C-S-FE SYSTEMATICS OF THE MARCELLUS FORMATION". In GSA Annual Meeting in Indianapolis, Indiana, USA - 2018. Geological Society of America, 2018. http://dx.doi.org/10.1130/abs/2018am-321858.
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Hopple, Sara, Mark Bushfield, Fiona Murdoch e D. Euan MacIntyre. "REGULATION OF PLATELET cAMP FORMATION BY PROTEIN KINASE C". In XIth International Congress on Thrombosis and Haemostasis. Schattauer GmbH, 1987. http://dx.doi.org/10.1055/s-0038-1644512.
Testo completoAbstract (sommario):
Exogenous synthetic 1,2-diacylglycerols (e.g. 1,2-dioctanoylglycerol, DiC8) and 4β Phorbol esters (e.g. phorbol myristate acetate, PMA) routinely are used to probe the effects of protein Kinase C (PKC) on cellular responsiveness. Such agents act either independently or synergistically with elevated [Ca2+]i to induce platelet activation, but also inhibit agonist-induced inositol lipid metabolism and Ca2+ flux. These findings led to the concept that activated PKC can function as a bi-directional regulator of platelet reactivity. Therefore, DiCg and PMA were utilized to examine the effects of activated PKC on receptor-mediated stimulation and inhibition of adenylate cyclase, as monitored by cAMP accumulation. All studies were performed using intact human platelets in a modified Tyrodes solution, and cAMP was quantified by radioimmunoassay. Pretreatment (2 min.; 37°C) of platelets with PMA (≤ 300 nM) but not DiCg (200 μM) attenuated the elevation of platelet cAMP content evoked by PGD2 300 nM) but not by PGE1 (≤300 nM), PGI2 (≤100 nM) or adenosine (≤ 100 μM).These effects of PMA were unaffected by ADP scavengers, by Flurbiprofen (10 μM) or by cAMP phosphodiesterase inhibitors (IBMX, 1 mM) but were abolished by the PKC inhibitor Staurosporine (STP, 100 nM). In contrast, DiC8 (200 μM), but not PMA ( ≤ 300 nM), reduced the inhibitory effect of adrenaline (5 μM) on PGE1 (300 nM)-induced cAMP formation. This effect of DiCg was unaltered by STP (100 nM). Selective inhibition of PGD2-induced cAMP formation by PMA most probably can be attributed to PKC catalysed phosphorylation of the DP receptor. Reduction of the inhibitory effect of adrenaline by DiC8 could occur via an action at the α2 adrenoreceptor or Ni. These differential effects of PMA and DiC8 may result from differences in their distribution or efficacy, or to heterogeneity of platelet PKC.
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"Graphite Nanoplatelets and Graphene Oxide Influence on C-S-H Formation". In "SP-329: Superplasticizers and Other Chemical Admixtures in Concrete Proceedings Twelfth International Conference, Beijing, China". American Concrete Institute, 2018. http://dx.doi.org/10.14359/51711218.
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Barbarulo, R. "The role of C-S-H and temperature in delayed ettringite formation". In International RILEM Workshop on Internal Sulfate Attack and Delayed Ettringite Formation. RILEM Publications SARL, 2004. http://dx.doi.org/10.1617/2912143802.010.
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Schwarz, N., H. L. McRae, J. Müller, J. Oldenburg, S. Reda, B. Pötzsch e H. Rühl. "Activated Protein C Formation on Endothelial Cells is Impaired in Hereditary Protein C Deficiency Independent of the Type of Protein C Gene Mutation and Residual Activity". In GTH Congress 2024 – 68th Annual Meeting of the Society of Thrombosis and Haemostasis Research – Building Bridges in Coagulation. Georg Thieme Verlag, 2024. http://dx.doi.org/10.1055/s-0044-1779076.
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Aydar, S., S. Alataş, L. Numanoğlu e A. Sönmezdağ. "EFFECT OF ORAL ANTICOAGULANTS ON STABLE ROSETTE FORMATION". In XIth International Congress on Thrombosis and Haemostasis. Schattauer GmbH, 1987. http://dx.doi.org/10.1055/s-0038-1643271.
Testo completoAbstract (sommario):
Human peripheral blood T lymphacytes when cultered in the presence of mitogen Phytohemogglutinin (PHA) acquire the capacity to form E rosettes with sheep erythrocytes that are resistant to incubation at 37° C. Whereas human thymus lymphocytes form 37° C stable E rosettes. On the other hand, it is shown that the use of anticoagulants can prevent cancer metastases which brings forth the importance of explaining the relationship between the lymphocyte functions and anticoagulant action mecha-nismus. In order to investigate this relationship, we did a group af experiments with lymphocytes of normal children and of children with severe burn wounds. Peripheral blood lymphocytes were seperated by “Lymphoprep” centrifugation technique. The lymphocytes of normal children and patients with burn were divided in two groups: A-Activated lymphocytes: 1×106 /ml lymphocytes were cultured and activated by PHAfor 48 hours at 37° C in RPMI 1640. B-Non activated lymphocytes were in culture witout PHA. 1×10™6 M/ml warfarin sulfate was added to some of the cultures of each group prior to the culture conditions. At the end of the 48 hour incubation, heat stable rosette formation was determined by the method of Wauve and co-workers. Significantly elevated levels of heat stable rosette forming cells were found in the PHA activated culture treated with warfarin sulfate in normals and patients with burn. Although the blastic transformation of T lymphocytes was found to be depressed, heat stable rosette formation of warfarin sulfate treated lymphocytes abtained from burn patients was observed to be significantly elevated. It is concluded that warfarin sulfate increases the activity of T lymphocytes by interfering with the resynthesis of heai stable E receptors.
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de Four, N. J., R. M. Bertina e F. Havgrkate. "STIMULATION OF FIBRINOLYSIS BY ACTIVATED PROTEIN C (APC)". In XIth International Congress on Thrombosis and Haemostasis. Schattauer GmbH, 1987. http://dx.doi.org/10.1055/s-0038-1642961.
Testo completoAbstract (sommario):
In 1960 Mammen and Seegers reported the discovery of a new protein (autoprothrombin II-A, APC) with both anticoagulant and profibrinolytic activity. They found that APC accelerated clot lysis in vitro and proposed that this was due to a reduction of plasmin - inhibitory activity. Many years later Comp et al (J Clin Inv 68: 1221) reported that the infusion of APC into dogs resulted in an increase in circulating plasminogen activator activity. This observation stimulated more extensive studies of the profibrinolytic effects of APC.In our laboratories we have studied the effect of human APC on clot lysis both in whole blood (human) and in a system of purified human proteins. In these systems 125I-labelled fibrinogen was incorporated in a clot formed after the addition of Jombin (complete clot formation within 5 min) and the subsequent lysis of this clot was followed by measuring the release of I-labelled fibrin degradation products (FDP) into the supernatant. Human t-PA was added to the system to achieve complete lysis of the clot within a few hours.When APC was added to citrated whole blood before clot formation, it was found to accelerate clot lysis in a dose dependent way. This effeg| was specific for APC and dependent on an intact active site, on the presence of protein S (the protein cofactor of APC) and Ca . The presence of APC did not influence the composition of the FDP formed, as analysed by means of SDS-polyacry-1 amide gel electroforesis, and its effect was found to be independent of the presence or absence of a.-antiplasmin.Subsequently we developped a clot lysis system using the purified human proteins of the fibrinolytic system: fibrinogen, FXIII, t-PA, PAI-1 (from human endothelial cells), glu-plasminogen and a -antiplasmin. In this system clot lysis was dependent on the concentrations of plasminogen, -antiplasmin, t-PA and PAI-1, but independent on the thrombin concentration and the presence or absence of phospholipids (purified from human brain). In the absence of PAI-1, no effect of APC on clot lysis was observed. However, in the presence of PAI-1, APC accelerated clot lysis. This effect was independent of the presence or absence of phospholipids and/or protein S and could be explained by the observation that APC can form a complex with PAI-1 (~ 95 kd) and under certain conditions even can convert active PAI-1 (~ 46 kd) into an inactive degradation product (~ 42 kd). However, complex formation is relatively slow anti high PAI-1 concentrations are needed to observe the reaction. The addition of protein S or phospholipids in the presence of Ca did not stimulate complex formation. Therefore, it seems highly unlikely that neutralization of PAI-1 by APC is responsible for the profibrinolytic effect of APC in the whole blood clot lysis.A completely different explanation for the profibrinolytic effect of APC was suggested by the observation that the addition of blood-platelets to the system of purified fibrinolytic components introduced a dependence of the clot lysis rate on the thrombin concentration (decrease in clot lysis at increasing thrombin concentration). This finding opened the possibility that APC stimulated fibrinolysis by reducing the effective thrombin concentration. Subsequent experiments using the whole blood clot lysis system revealed that in the presence of anti-FX antibodies clot lysis was no longer accelerated by APC, while the actual rate of clot lysis depended on the concentration of thrombin added.We like to propose, that in a blood clot lysis system APC most likely accelerates fibrinolysis by reducing the effective thrombin concentration; if at all, neutralization of PAI-1 may play only a minor role.
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Brass, L. F., D. R. Manning e M. J. Woolkalis. "G PROTEIN REGULATORS OF PHOSPHOLIPASE C AND ADENYLATE CYCLASE IN PLATELETS". In XIth International Congress on Thrombosis and Haemostasis. Schattauer GmbH, 1987. http://dx.doi.org/10.1055/s-0038-1644630.
Testo completoAbstract (sommario):
The hydrolysis of polyphosphoinositides (PI) by phospholipase C during platelet activation produces two key intracellular messengers, inositol triphosphate and diacylglycerol. This process is thought to be regulated by a guanine nucleotide binding protein referred to as Gp. Although the evidence that Gp exists is compelling, to date it has not been isolated. Uncertainty about its identity has been compounded by variations between tissues in the susceptibility of Gp to pertussis toxin and by reconstitution studies which show that pertussis toxin-inhibited PI hydrolysis can be restored by purified Gi, the pertussis toxin-sensitive G protein which inhibits adenylate cyclase. Therefore, it remains unclear whether Gp represents a new G protein or a second role for Gj. When platelets permeabilized with saponin were incubated with pertussis toxin and 32P-NAD, a single 42 kDa protein was 32P-ADP-ribosylated which co-migrated with the purified a subunit of Gi. Preincubating the platelets with an agonist inhibited labeling of this protein by dissociating the G protein into subunits. The extent of inhibition correlated with the number of toxin-sensitive functions caused by the agonist. Labeling was abolished by thrombin, which inhibited cAMP formation and caused toxin-inhibitable PI hydrolysis. Labeling was partially inhibited by vasopressin and platelet activating factor, which caused toxin-inhibitable PI hydrolysis, but had no effect on cAMP formation and by epinephrine, which inhibited cAMP formation, but did not cause PI hydrolysis. Labeling was unaffected by the TxA2 analog U46619, which neither caused toxin-sensitive PI hydrolysis nor inhibited cAMP formation. These observations suggest that the 42 kDa band may contain a subunits from both Gp and Gi and, in fact, 2D electrophoresis resolved the 42 kDa protein band into two proteins with distinct pi. However, those agonists linked functionally only to Gp or only to Gi decreased the labeling of both proteins. Therefore, our data suggest (1) that Gj and Gp are the same protein and (2) that whether a aiven platelet agonist affects adenylate cyclase or phospholipase C or both depends upon factors extrinsic to the G protein.
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David, J. L., M. Lambrichts e M. T. Closon. "INFRACLINIC ACTIVATION OF PLATELETS AND FIBRIN FORMATION IN CANCER PATIENTS". In XIth International Congress on Thrombosis and Haemostasis. Schattauer GmbH, 1987. http://dx.doi.org/10.1055/s-0038-1643198.
Testo completoAbstract (sommario):
Thromboembolism has been frequently reported in cancer patients, mainly in cases with solid tumors. Besides in several animal models, fibrin deposition around the tumor and platelet aggre gates appear to be involved in invasion and metastasis. This study was aimed at evaluating the extent of in vivo platelet activation and fibrin formation in several kinds of human cancer. We excluded from this study patients whose blood was sampled with difficulty as well as those having clinical evidence of thrombosis or embolism, those with thrombocytopenia, increased fibrinogen degradation products or biological pattern of disseminated intravascular coagulation. Fibrinopeptide A (fpA) and β-thrombo-globulin (β-tg) were determined by RIA. Free platelet count ratio (PCR) was determined on whole blood samples as an index of circulating aggregates. Usual coagulation tests, antithrombin III activity, protein C plasma level, F VIII related antigen (F VIII RAG), F VIII Ristocetin cofactor (F VIII RCF) and F VIII procoagulant activity (F VIII C) were also determined.It was found that in more than fifty percent of patients, fpA was significantly increased above the upper reference limit. Cases with increased B-tg were less frequent. Separate increases in β-tg or fpA levels were often observed. PCR remained within the reference values in almost all patients. F VIII RAG, RCF and C were usually above 150 % of the reference mean.We conclude that platelet release and fibrinoformation frequently occur in cancer patients showing no sign of thrombotic process. Increased level of fpA with normal plasma β-tg level suggests that thrombin generation occurs only in the extravascular compart ment, probably next to the tumoral tissues. Increased levels of plasma β-tg with normal fpA levels may result from platelet activation by other stimuli than thrombin. It must be emphasized that normal PCR does not exclude the presence of fibrinous circulating aggregates which cannot be dispersed by EDTA. High F VIII activities may be due to the release of the von Willebrand factor from tumoral vessels.
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Lobel, P., M. Palmer e K. Schor. "CHRONIC ORAL DEFIBROTIDE STIMULATES VASCULAR PGI2 AND INHIBITS ATHEROSCLEROTIC PLAQUE FORMATION IN CHOLESTEROL-FED RABBITS". In XIth International Congress on Thrombosis and Haemostasis. Schattauer GmbH, 1987. http://dx.doi.org/10.1055/s-0038-1643150.
Testo completoAbstract (sommario):
Defibrotide (DEF) is a polydeoxyribonucleotide fraction from bovine lung, possessing profibrinolytic and PGI2 stimulating properties. Male rabbits were fed for 4 months a standard laboratory diet (150 g/day) without (A) or with (B) DEF or a cholesterol (1%) supplemented diet without (C) or with (D) DEF (60 mg/kg x day) was administered orally (drinking water) and withdrawn 24-36 h prior to the acute experiments.DEF did not change the elevated serum cholesterol: 18 ± 2 (C) vs. 26 ± 5 (D) mM but significantly reduced the plaque formation in the aorta from 4.5 ± 0.3 (C) to 3.3 ± 0.2 (D) (subjective score). Collagen induced (0.6 pg/ml) thromboxane formation and ATP release was significantly reduced by DEF: 55+2 (C) vs. 42 ± 2 (D) ng/ml TXB2; 152 ± 11 (C) vs. 74±5 (D) AU ATP (platelet rTch plasma). DEF significantly increased the basal and bradykinin (Bk, 30 nM) stimulated PGI2 release from rabbit aorta preparations in Krebs buffer, while the PGI2 forming capacity (arachidonic acid, AA, 30 pg/ml) was unchanged Furthermore, the iloprost (30 nM) stimulated cAMP was significantly elevated by DEF in both control: 115 ± 10 (A) vs. 155 ± 18 (B) pmoles/1 and cholesterol-fed rabbits: 120 ± 14 (C) vs. 172 ± 9 (D). DEF, directly added to the platelets in vitro did not inhibit platelet activation up to 100 pg/ml.The data demonstrate a 2-3-fold stimulation of basal and hormone (Bk) induced PGI2 formation of control and sclerotic rabbit aorta after 4 months DEF treatment while the atherosclerosis per se does not significantly change these parameters. DEF treatment also significantly reduces platelet hyperreactivity at unchanged serum ch() lesterol. Both properties might be useful to prevent complication’s of atherosclerosis, such as myocardial infarction and stroke.
Rapporti di organizzazioni sul tema "Formation de liaisons C-S"
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Kontak, D. J., S. Paradis, Z. Waller e M. Fayek. Petrographic, fluid inclusion, and secondary ion mass spectrometry stable isotopic (O, S) study of Mississippi Valley-type mineralization in British Columbia and Alberta. Natural Resources Canada/CMSS/Information Management, 2022. http://dx.doi.org/10.4095/327994.
Testo completoAbstract (sommario):
A comprehensive study of Mississippi Valley-type base-metal deposits across the Canadian Cordillera was done to compare and contrast their features. Extensive dissolution of host rocks is followed by multiple generations of dolomite cements from early, low-temperature, fine-grained to coarser, higher temperature types that overlap with Zn-Pb sulfide minerals; late-stage calcite occludes residual porosity. Dolomite is generally chemically stoichiometric, but ore-stage types are often rich in Fe (<1.3 weight per cent FeO) with small sphalerite inclusions. Sphalerite-hosted fluid inclusions record ranges for homogenization temperatures (77-214°C) and fluid salinity (1-28 weight per cent equiv. NaCl±CaCl2). These data suggest fluid mixing with no single fluid type related to all sulfide mineralization. In situ secondary ion mass spectrometry (SIMS) generated delta-18OVSMOW values for carbonate minerals (13-33 permille) reflect dolomite and calcite formation involving several fluids (seawater, basinal, meteoric) over a large temperature range at varying fluid-rock ratios. Sphalerite and pyrite SIMS delta-34SVCDT values vary (8-33 permille) but in single settings have small ranges (<2-3 permille) that suggest sulfur was reduced via thermochemical sulfate reduction from homogeneous sulfur reservoirs. Collectively, the data implicate several fluids in the mineralizing process and suggest mixing of a sulfur-poor, metal-bearing fluid with a metal-poor, sulfide-bearing fluid.
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Dickman, Martin B., e Oded Yarden. Genetic and chemical intervention in ROS signaling pathways affecting development and pathogenicity of Sclerotinia sclerotiorum. United States Department of Agriculture, luglio 2015. http://dx.doi.org/10.32747/2015.7699866.bard.
Testo completoAbstract (sommario):
Abstract: The long-term goals of our research are to understand the regulation of sclerotial development and pathogenicity in S. sclerotior11111. The focus in this project was on the elucidation of the signaling events and environmental cues involved in the regulation of these processes, utilizing and continuously developing tools our research groups have established and/or adapted for analysis of S. sclerotiorum, Our stated objectives: To take advantage of the recent conceptual (ROS/PPs signaling) and technical (amenability of S. sclerotiorumto manipulations coupled with chemical genomics and next generation sequencing) developments to address and extend our fundamental and potentially applicable knowledge of the following questions concerning the involvement of REDOX signaling and protein dephosphorylation in the regulation of hyphal/sclerotial development and pathogenicity of S. sclerotiorum: (i) How do defects in genes involved in ROS signaling affect S. sclerotiorumdevelopment and pathogenicity? (ii) In what manner do phosphotyrosinephosphatases affect S. sclerotiorumdevelopment and pathogenicity and how are they linked with ROS and other signaling pathways? And (iii) What is the nature of activity of newly identified compounds that affect S. sclerotiori,111 growth? What are the fungal targets and do they interfere with ROS signaling? We have met a significant portion of the specific goals set in our research project. Much of our work has been published. Briefly. we can summarize that: (a) Silencing of SsNox1(NADPHoxidase) expression indicated a central role for this enzyme in both virulence and pathogenic development, while inactivation of the SsNox2 gene resulted in limited sclerotial development, but the organism remained fully pathogenic. (b) A catalase gene (Scatl), whose expression was highly induced during host infection is involved in hyphal growth, branching, sclerotia formation and infection. (c) Protein tyrosine phosphatase l (ptpl) is required for sclerotial development and is involved in fungal infection. (d) Deletion of a superoxidedismutase gene (Sssodl) significantly reduced in virulence on both tomato and tobacco plants yet pathogenicity was mostly restored following supplementation with oxalate. (e) We have participated in comparative genome sequence analysis of S. sclerotiorumand B. cinerea. (f) S. sclerotiorumexhibits a potential switch between biotrophic and necrotrophic lifestyles (g) During plant microbe interactions cell death can occur in both resistant and susceptible events. Non pathogenic fungal mutants S. sclerotior111n also cause a cell death but with opposing results. We investigated PCD in more detail and showed that, although PCD occurs in both circumstances they exhibit distinctly different features. The mutants trigger a restricted cell death phenotype in the host that unexpectedly exhibits markers associated with the plant hypersensitive (resistant) response. Using electron and fluorescence microscopy, chemical effectors and reverse genetics, we have established that this restricted cell death is autophagic. Inhibition of autophagy rescued the non-pathogenic mutant phenotype. These findings indicate that autophagy is a defense response in this interaction Thus the control of cell death, dictated by the plant (autophagy) סr the fungus (apoptosis), is decisive to the outcome of certain plant microbe interactions. In addition to the time and efforts invested towards reaching the specific goals mentioned, both Pls have initiated utilizing (as stated as an objective in our proposal) state of the art RNA-seq tools in order to harness this technology for the study of S. sclerotiorum. The Pls have met twice (in Israel and in the US), in order to discuss .נחd coordinate the research efforts. This included a working visit at the US Pls laboratory for performing RNA-seq experiments and data analysis as well as working on a joint publication (now published). The work we have performed expands our understanding of the fundamental biology (developmental and pathogenic) of S. sclerotioז111וז. Furthermore, based on our results we have now reached the conclusion that this fungus is not a bona fide necrotroph, but can also display a biotrophic lifestyle at the early phases of infection. The data obtained can eventually serve .נ basis of rational intervention with the disease cycle of this pathogen.
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Xu, Jin-Rong, e Amir Sharon. Comparative studies of fungal pathogeneses in two hemibiotrophs: Magnaporthe grisea and Colletotrichum gloeosporioides. United States Department of Agriculture, maggio 2008. http://dx.doi.org/10.32747/2008.7695585.bard.
Testo completoAbstract (sommario):
Plant pathogenic fungi have various life styles and different plant infection strategies. Hemibiotrophs like Magnaporthe grisea and Colletotrichum species develop specialized structures during plant infection. The goal of this study was to identify, characterize, and compare genes required for plant infection in M. grisea and C. gloeosporioides. Specific objectives are to: 1) further characterize genes identified in the preliminary studies of C. gloeosporioides and M. grisea;2) identify and characterize additional fungal genes tagged by GFP; and 3) identify in planta growth and appressorium-specific genes by subtractive hybridization and transcript profiling by the LongSAGE method. In this study, the PI and Co-PI collaborated closely on studies in M. grisea and C. gloeosporioides. In M. grisea, REMI and ATMT were used to transform the wildtype with promoter-less EGFP constructs. A total of 28 mutants defective in different plant infection processes or expressing EGFP during plant infection were identified. Genes disrupted in five selected mutants have been identified, including MG03295 that encodes a putative Rho GTPase. In transformant L1320, the transforming vector was inserted in the MIRI gene that encodes a nuclear protein. The expression of MIRI was highly induced during infection. Deletion and site-directed mutagenesis analyses were used to identify the promoter regions and elements that were essential for induced in planta expression of MIRI. This was the first detailed characterization of the promoter of an in planta gene in M. grisea and the MIRI promoter can be used to monitor infectious growth. In addition, the Agilent whole-genome array of M. grisea was used for microarray analyses with RNA samples from appressoria formed by the wild-type shain and the pmkl and mstl2 mutants. Over 200 genes were downregulated in the mst I 2 and pmkl mutants. Some of them are putative transcription factors that may regulate appressorium formation and infectious hyphal growth. In C. gloeosporioides, various REMI mutants showing different pathogenic behavior were identified and characterized. Mutants N3736 had a single insertion and was hyper-virulent. The gene disrupted in mutant3736 (named CgFMOI) encodes a FAD-dependent monooxygenase. Expression analyses linked the expression of the CgFMOI gene with the necrotrophic phase of fungal infection, and also suggest that expression of CgFMOl is unnecessary for the first stages of infection and for biotrophy establishment. All CgFMOl-silenced mutants had reduced virulence. In REMI mutant N159, the tagged gene encodes a putative copper transporter that is homologue of S. cerevisiae CTR2. In yeast, Ctr2 is a vacuolar transporter for moving copper from the vacuole to the cytoplasm. The gene was therefore termed CgCTR2. In addition to characterization of CgCTR2, we also conducted comparative analyses in M. grisea. The M. grisea CgCTR-2 homolog was isolated, knockout strains were generated and characterized and the M. grisea was used to complement the Nl 59 C. gloeosporioides mutant. Overall, we have accomplished most of proposed experiments and are in the process of organizing and publishing other data generated in this project. For objective 3, we used the microarray analysis approach. Several genes identified in this study are novel fungal virulence factors. They have the potential to be used as targets for developing more specific or effective fungicides. In the long run, comparative studies of fungal genes, such as our CgCTR2 work, may lead to better disease control strategies.
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Choudhary, Ruplal, Victor Rodov, Punit Kohli, Elena Poverenov, John Haddock e Moshe Shemesh. Antimicrobial functionalized nanoparticles for enhancing food safety and quality. United States Department of Agriculture, gennaio 2013. http://dx.doi.org/10.32747/2013.7598156.bard.
Testo completoAbstract (sommario):
Original objectives The general goal of the project was to utilize the bactericidal potential of curcumin- functionalizednanostructures (CFN) for reinforcement of food safety by developing active antimicrobial food-contact surfaces. In order to reach the goal, the following secondary tasks were pursued: (a) further enhancement of the CFN activity based on understanding their mode of action; (b) preparing efficient antimicrobial surfaces, investigating and optimizing their performance; (c) testing the efficacy of the antimicrobial surfaces in real food trials. Background to the topic The project dealt with reducing microbial food spoilage and safety hazards. Cross-contamination through food-contact surfaces is one of the major safety concerns, aggravated by bacterial biofilm formation. The project implemented nanotech methods to develop novel antimicrobial food-contact materials based on natural compounds. Food-grade phenylpropanoidcurcumin was chosen as the most promising active principle for this research. Major conclusions, solutions, achievements In agreement with the original plan, the following research tasks were performed. Optimization of particles structure and composition. Three types of curcumin-functionalizednanostructures were developed and tested: liposome-type polydiacetylenenanovesicles, surface- stabilized nanoparticles and methyl-β-cyclodextrin inclusion complexes (MBCD). The three types had similar minimal inhibitory concentration but different mode of action. Nanovesicles and inclusion complexes were bactericidal while the nanoparticlesbacteriostatic. The difference might be due to different paths of curcumin penetration into bacterial cell. Enhancing the antimicrobial efficacy of CFN by photosensitization. Light exposure strengthened the bactericidal efficacy of curcumin-MBCD inclusion complexes approximately three-fold and enhanced the bacterial death on curcumin-coated plastic surfaces. Investigating the mode of action of CFN. Toxicoproteomic study revealed oxidative stress in curcumin-treated cells of E. coli. In the dark, this effect was alleviated by cellular adaptive responses. Under light, the enhanced ROS burst overrode the cellular adaptive mechanisms, disrupted the iron metabolism and synthesis of Fe-S clusters, eventually leading to cell death. Developing industrially-feasible methods of binding CFN to food-contact surfaces. CFN binding methods were developed for various substrates: covalent binding (binding nanovesicles to glass, plastic and metal), sonochemical impregnation (binding nanoparticles to plastics) and electrostatic layer-by-layer coating (binding inclusion complexes to glass and plastics). Investigating the performance of CFN-coated surfaces. Flexible and rigid plastic materials and glass coated with CFN demonstrated bactericidal activity towards Gram-negative (E. coli) and Gram-positive (Bac. cereus) bacteria. In addition, CFN-impregnated plastic material inhibited bacterial attachment and biofilm development. Testing the efficacy of CFN in food preservation trials. Efficient cold pasteurization of tender coconut water inoculated with E. coli and Listeriamonocytogeneswas performed by circulation through a column filled with CFN-coated glass beads. Combination of curcumin coating with blue light prevented bacterial cross contamination of fresh-cut melons through plastic surfaces contaminated with E. coli or Bac. licheniformis. Furthermore, coating of strawberries with CFN reduced fruit spoilage during simulated transportation extending the shelf life by 2-3 days. Implications, both scientific and agricultural BARD Report - Project4680 Page 2 of 17 Antimicrobial food-contact nanomaterials based on natural active principles will preserve food quality and ensure safety. Understanding mode of antimicrobial action of curcumin will allow enhancing its dark efficacy, e.g. by targeting the microbial cellular adaptation mechanisms.
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EGR Cooler Fouling Reduction: A New Method for Assessment in Early Engine Development Phase. SAE International, marzo 2022. http://dx.doi.org/10.4271/022-01-0589.
Testo completoAbstract (sommario):
High pressure EGR provides NOx emission reduction even at low exhaust temperatures. To maintain a safe EGR system operation over a required lifetime, the EGR cooler fouling must not exceed an allowable level, even if the engine is operated under worst-case conditions. A reliable fouling simulation model represents a valuable tool in the engine development process, which validates operating and calibration strategies regarding fouling tendency, helping to avoid fouling issues in a late development phase close to series production. Long-chained hydrocarbons in the exhaust gas essentially impact the fouling layer formation. Therefore, a simulation model requires reliable input data especially regarding mass flow of long-chained hydrocarbons transported into the cooler. There is a huge number of different hydrocarbon species in the exhaust gas, but their individual concentration typically is very low, close to the detection limit of standard in-situ measurement equipment like GC-MS. Therefore, a new measurement and analysis approach has been developed, where the exhaust gas is guided to a metal foam collector, in which HC`s are deposited. The probe is then analyzed in a suited thermogravimetrical system (TGA) in nitrogen atmosphere, temperature range 25°C to 650°C. Analyzing the TGA curve, HC concentration data for 6 different boiling temperature ranges are obtained, provided to an adapted 1-d fouling simulation model. Using these data along with further input parameters like cooler geometry, gas temperature, pressure, flow, particle size distribution and coolant temperature, the simulation model has proven as a suitable tool to predict the fouling and identify engine settings for fouling reduction.