44 research outputs found
SynthÚse de glycomimétiques inhibiteurs sélectifs des galectines
Les galectines sont une famille de protĂ©ines cytosoliques possĂ©dant un domaine de reconnaissance pour les rĂ©sidus ÎČ-D-galactosides et dont quatorze membres ont Ă©tĂ© identifiĂ©s chez les mammifĂšres. Le rĂŽle prĂ©cis de ces lectines n'est pas trĂšs bien dĂ©fini, mais tous les membres des galectines ont une trĂšs forte modulation de leurs expressions durant une Ă©tape de leurs dĂ©veloppements spĂ©cifiques, sous diffĂ©rentes conditions physiologiques et pathologiques. Les galectines semblent ĂȘtre impliquĂ©es dans le processus d'apoptose, dans les rĂ©actions du systĂšme immunitaire et dans le processus de l'infection du VIH. Ainsi, une inhibition sĂ©lective de celles-ci pourrait mener Ă des traitements anti-cancers, anti-inflammatoires ou mĂȘme anti-VIH. Dans le but de synthĂ©tiser des inhibiteurs sĂ©lectifs des galectines avec une augmentation de l'affinitĂ©, une rĂ©action catalysĂ©e par transfert de phase a Ă©tĂ© utilisĂ©e pour la synthĂšse d'aryle O-et \ud
S-galactosides et lactosides. En plus d'obtenir des inhibiteurs ayant une affinitĂ© supĂ©rieure au ligand naturel, une corrĂ©lation a Ă©tĂ© dĂ©couverte, soit entre la densitĂ© Ă©lectronique de l'oxygĂšne en position-3 du glucoside avec la propriĂ©tĂ© d'inhibition pour les dĂ©rivĂ©s lactosides pour la galectine-1. Ensuite, la synthĂšse rĂ©giosĂ©lective de dĂ©rivĂ©s triazoles et d'isoxazoles a aussi Ă©tĂ© exploitĂ©e pour l'obtention d'hĂ©tĂ©rocycles non-naturels dans le but de crĂ©er des interactions favorables avec les galectines. Le triazole Câ-symĂ©trique s'est avĂ©rĂ© ĂȘtre le meilleur inhibiteur pour les galectines-1 et -3. De plus, l'exploitation d'espaceurs rigides a Ă©tĂ© utilisĂ©e dans le but de synthĂ©tiser des inhibiteurs avec une augmentation de la sĂ©lectivitĂ© vis-Ă -vis la Concanavalin A. Des mĂ©taux de transition ont Ă©tĂ© utilisĂ©s tels que le palladium(0) pour la rĂ©action de Sonogashira et l'octacarbonyle de dicobalt pour une rĂ©action de benzannĂ©lation Ă partir de mannosides acĂ©tylĂ©niques. Cette mĂ©thode peut ĂȘtre appliquĂ©e pour d'autres protĂ©ines ou lectines telles que les galectines. Finalement, le premier modĂšle QSAR pour la galectine-3 a Ă©tĂ© dĂ©veloppĂ© dans le but de concevoir une base de donnĂ©es fiable pour le dĂ©veloppement de futurs antagonistes sĂ©lectifs de la galectine-3. L'Ă©tude rĂ©alisĂ©e suggĂšre que les interactions non-covalentes telles que la lipophilie et la structure de l'inhibiteur sont des points importants pour l'obtention d'un inhibiteur sĂ©lectif de la galectine-3. ______________________________________________________________________________ MOTS-CLĂS DE LâAUTEUR : Galectine, Glycochimie, Cycloaddition, Catalyse par transfert de phase
SynthÚse de 4-désoxy hexopyrannoses, C-disaccharides et C-glycosides biologiquement actifs
Les glucides constituent la classe de molécules organiques la plus abondante et ceux-ci jouent des rÎles cruciaux dans divers processus biologiques. De part leur importance médicinale, la préparation des désoxy-sucres, des C-glycosides et des C-disaccharides est devenue un sujet de pointe en synthÚse organique. De façon générale, cette thÚse décrit une nouvelle synthÚse de novo des 4-désoxy hexopyrannoses en plus de la préparation de C-glycosides biologiquement actifs. De plus, une attention particuliÚre a été portée à la préparation de novo de 4-désoxy-C-disaccharides.
Dans un premier temps, le catalyseur de Cr(III) de Jacobsen et un complexe binaphtol/titane ont Ă©tĂ© utilisĂ©s pour rĂ©aliser des hĂ©tĂ©ro-Diels-Alder Ă©nantiosĂ©lectives. Les dihydropyrannes ainsi gĂ©nĂ©rĂ©s ont Ă©tĂ© transformĂ©s en 4-dĂ©soxy hexopyrannoses prĂ©sents dans la nature. De cette façon, un dĂ©rivĂ© de lâacide Ă©zoaminuroĂŻque, un prĂ©curseur de la dĂ©sosamine et de la nĂ©osidomycine, a Ă©tĂ© prĂ©parĂ© suivant cette approche de novo. De plus, Ă titre comparatif, la nĂ©osidomycine a Ă©galement Ă©tĂ© fabriquĂ©e selon une approche chiron, Ă partir du mĂ©thyl alpha-D-mannopyrannoside. Finalement, une Ă©valuation biologique prĂ©liminaire de la nĂ©osidomycine a Ă©tĂ© effectuĂ©e sur une la concanavaline-A (Chapitre 2).
Dans un deuxiĂšme temps, une allylation stĂ©rĂ©osĂ©lective sur un aldĂ©hyde liĂ© via des liens C-C Ă une unitĂ© mannoside a permis de gĂ©nĂ©rer un alcool homoallylique. Cette derniĂšre fonctionnalitĂ© a Ă©tĂ© transformĂ©e en 4-dĂ©soxy hexopyrannose de configuration D ou L. De cette façon, la prĂ©paration de pseudo 4-dĂ©soxy-C-disaccharides, de 4-dĂ©soxy-C-disaccharides et de pseudo 4-dĂ©soxy aza-C-disaccharides a facilement Ă©tĂ© rĂ©alisĂ©e. Les rapports diastĂ©rĂ©oisomĂ©riques de la rĂ©action dâallylation ont Ă©tĂ© dĂ©terminĂ©s en plus de la configuration absolue des nouveaux centres stĂ©rĂ©ogĂ©niques formĂ©s. La transformation des alcools homoallyliques en pyrannes poly hydroxylĂ©s ou en lactames poly hydroxylĂ©s a Ă©tĂ© rĂ©alisĂ©e, en plus de la dĂ©protection de certains membres de cette famille pour une Ă©valuation biologique prĂ©liminaire sur la concanavaline-A (Chapitre 3).
Finalement, la synthĂšse de C-glycosides biologiquement actifs a Ă©tĂ© rĂ©alisĂ©e selon deux volets: i) prĂ©paration de 3-C-mannopyrannosyl coumarines et ii) synthĂšse de C-galactosides, inhibiteurs de la lectine PA-IL. Pour ce faire, le couplage de Heck a Ă©tĂ© utilisĂ© Ă partir dâun ester alpha,bĂȘta-insaturĂ©, attachĂ© Ă une unitĂ© glycosidique via des liens C-C, pour gĂ©nĂ©rer un dĂ©rivĂ© glycosyl cinnamate de mĂ©thyle. Cependant, lorsque le 2-iodophĂ©nol est utilisĂ© comme partenaire de Heck, la coumarine correspondante a Ă©tĂ© isolĂ©e. Les dĂ©rivĂ©s C-galactopyrannosyl cinnamates de mĂ©thyle reprĂ©sentent de bons inhibiteurs monovalents de la PA-IL avec un Kd aussi bas que 37 micro M (Chapitre 4).Carbohydrates represent a large family of organic molecules that play key roles in various biological processes. Due to their medicinal importance, preparation of deoxy-sugars, C-glycosides and C-disaccharides have become an important topic in organic synthesis. Mostly, this thesis presents a new de novo synthesis of 4-deoxy hexopyranoses, along with the preparation of biologically relevant C-glycosides. Moreover, a special attention has been focussed on the de novo synthesis of 4-deoxy-C-disaccharides.
Firstly, Jacobsen Cr(III) catalyst and a binaphthol/titanium complex have been used to catalyze enantioselective hetero-Diels-Alder reactions. The dihydropyran thus formed has been transformed into naturally occurring 4-deoxy hexopyranoses. Therefore, the ezoaminuroic acid core, a desosamine precursor and neosidomycin have been prepared following a de novo approach. Moreover, as a comparative study, neosidomycin has also been synthesized using a chiron approach from methyl alpha-D-mannopyranoside. Finally, a preliminary biological evaluation of neosidomycin has been applied on concanavalin-A (Chapter 2).
Secondly, homoallylic alcohols have been generated from a stereoselective allylation on aldehyde linked via C-C bonds to a mannoside residue. Then, the homoallylic alcohols have been transformed into 4-deoxy hexopyranoses in various configurations (D or L). Thereby, the syntheses of pseudo 4-deoxy-C-disaccharides, 4-deoxy-C-disaccharides and pseudo 4-deoxy aza-C-disaccharides have been easily performed. Determinations of the diastereoisomeric ratio of the allylation reactions along with the absolute configuration of the newly formed chiral center have been easily achieved. Various members of this new family have been deprotected for a preliminary biological evaluation on concanavalin-A (Chapter 3).
Finally, the syntheses of relevant C-glycosides have been realized regarding two aspects: i) 3-C-mannopyranosyl coumarin synthesis and ii) synthesis of C-galactosides as PA-IL inhibitors. Methyl glycosyl cinnamates have been isolated using a Heck coupling on alpha,beta-insaturated ester linked to glycosidic moieties via C-C bonds. However, when 2-iodophenol is used as a Heck partner, the corresponding coumarins have been isolated. C-Galactosyl methyl cinnamate derivatives represent good monovalent inhibitors with Kd as low as 37 micro M against PA-IL (Chapter 4)
Stereoselective synthesis of fluorinated galactopyranosides as potential molecular probes for galactophilic proteins : assessment of monofluorogalactosideâLecA interactions
The replacement of hydroxyl groups by fluorine atoms on hexopyranoside scaffolds may allow access to invaluable tools for studying various biochemical processes. As part of ongoing activities toward the preparation of fluorinated carbohydrates, a systematic investigation involving the synthesis and biological evaluation of a series of monoâ and polyfluorinated galactopyranosides is described. Various monofluorogalactopyranosides, a trifluorinated, and a tetrafluorinated galactopyranoside have been prepared using a Chiron approach. Given the scarcity of these compounds in the literature, in addition to their synthesis, their biological profiles were evaluated. Firstly, the fluorinated compounds were investigated as antiproliferative agents using normal human and mouse cells in comparison with cancerous cells. Most of the fluorinated compounds showed no antiproliferative activity. Secondly, these carbohydrate probes were used as potential inhibitors of galactophilic lectins. The first transverse relaxationâoptimized spectroscopy (TROSY) NMR experiments were performed on these interactions, examining chemical shift perturbations of the backbone resonances of LecA, a virulence factor from Pseudomonas aeruginosa. Moreover, taking advantage of the fluorine atom, the 19Fâ
NMR resonances of the monofluorogalactopyranosides were directly monitored in the presence and absence of LecA to assess ligand binding. Lastly, these results were corroborated with the binding potencies of the monofluorinated galactopyranoside derivatives by isothermal titration calorimetry experiments. Analogues with fluorine atoms at Câ3 and Câ4 showed weaker affinities with LecA as compared to those with the fluorine atom at Câ2 or Câ6. This research has focused on the chemical synthesis of âdrugâlikeâ lowâmolecularâweight inhibitors that circumvent drawbacks typically associated with natural oligosaccharides
Vitamin D status, cognitive decline and incident dementia : the Canadian Study of Health and Aging
Objective: Vitamin D could prevent cognitive decline because of its neuroprotective, anti-inflammatory and antioxidant properties. This study aimed to evaluate the associations of plasma 25-hydroxyvitamin D (25(OH)D) concentrations with global cognitive function and incident dementia, including Alzheimerâs disease (AD). Methods: The Canadian Study of Health and Aging is a 10-year cohort study of a representative sample of individuals aged 65years or older. A total of 661 subjects initially without dementia with frozen blood samples and follow-up data were included. Global cognitive function was measured using the validated Modified Mini-Mental State (3MS) examination. A consensus diagnosis of all-cause dementia and AD was made between the physician and the neuropsychologist according to published criteria. Cognitive decline for a 5-year increase in age at specific 25(OH)D concentrations was obtained using linear mixedmodels with repeated measures. Hazard ratios of incident dementia and AD were obtained using semi-parametric proportionalhazards models with age as time scale. Results: Over a mean follow-up of 5.4 years, 141 subjects developed dementia of which 100 were AD. Overall, no significant association was found between 25(OH)D and cognitive decline, dementia or AD. Higher 25(OH)D concentrations were associated with an increased risk of dementia and AD in women, but not in men. Conclusion: This study does not support a protective effect of vitamin D status on cognitive function. Further research is needed toclarify the relation by sex.Objectif : La vitamine D pourrait avoir un effet protecteur sur le dĂ©clin cognitif en raison de ses propriĂ©tĂ©s neuroprotectrices, anti-inflammatoires et antioxydantes. Lâobjectif de cette Ă©tude Ă©tait dâĂ©valuer les associations entre la concentration plasmatique de 25-hydroxyvitamine D (25(OH)D), la fonction cognitive globale et lâincidence de la dĂ©mence incluant la maladie dâAlzheimer (MA). MĂ©thodes: LâĂtude sur la santĂ© et le vieillissement au Canada est une Ă©tude de cohorte de 10 ans rĂ©alisĂ©e dans un Ă©chantillon reprĂ©sentatif des Canadiens ĂągĂ©s de 65 ans et plus. Un total de 661 participants sans dĂ©mence, pour lesquels un Ă©chantillon sanguin congelĂ© et des donnĂ©es au suivi Ă©taient disponibles, ont Ă©tĂ© inclus dans lâanalyse. La fonction cognitive globale a Ă©tĂ© mesurĂ©e Ă lâaide dâun outil validĂ©, le Modified Mini-Mental State(3MS) Examination. Les diagnostics de dĂ©mence toutes cause set de MA ont Ă©tĂ© obtenus par consensus entre un mĂ©decin gĂ©nĂ©raliste et un neuropsychologue selon des critĂšres publiĂ©s. Le dĂ©clin cognitif pour chaque augmentation de 5 ans dâĂąge Ă des concentrations spĂ©cifiques de 25(OH)D a Ă©tĂ© mesurĂ© Ă lâaide de modĂšles linĂ©aires mixtes avec donnĂ©es rĂ©pĂ©tĂ©es. Des rapports de risques de la dĂ©mence et de la MA ont Ă©tĂ© obtenus Ă lâaide de modĂšles Ă risques proportionnels semi-paramĂ©triques en utilisant lâĂąge comme Ă©chelle du temps. RĂ©sultats : En cours de suivi (moyenne : 5,4 ans), 141 individus ont dĂ©veloppĂ© une dĂ©mence dont 100 Ă©taient la MA. Globalement, aucune association statistiquement significative nâa Ă©tĂ© observĂ©e entre le 25(OH)D et le dĂ©clin cognitif, la dĂ©mence ou la MA. Des concentrations plus Ă©levĂ©es de 25(OH)D Ă©taient associĂ©es Ă une augmentation du risque de dĂ©mence et de MA chez les femmes, mais pas chez les hommes. Conclusion : Cette Ă©tude nâappuie pas lâhypothĂšse dâun effet protecteur de la vitamine D sur la fonction cognitive. Dâautres Ă©tudes seraient nĂ©cessaires pour clarifier la relation selon le sexe
Diversityâoriented synthesis of diolâbased peptidomimetics as potential HIV protease inhibitors and antitumor agents
Peptidomimetic HIV protease inhibitors are an important class of drugs used in the treatment of AIDS. The synthesis of a new type of diol-based peptidomimetics is described. Our route is flexible, uses d-glucal as an inexpensive starting material, and makes minimal use of protection/deprotection cycles. Binding affinities from molecular docking simulations suggest that these compounds are potential inhibitors of HIV protease. Moreover, the antiproliferative activities of compounds 33âa, 35âa, and 35âb on HT-29, M21, and MCF7 cancer cell lines are in the low micromolar range. The results provide a platform that could facilitate the development of medically relevant asymmetrical diol-based peptidomimetic
Ăvaluation d'un modĂšle de luminance artificielle du ciel nocturne
Simulation models play an important role in decision making and developement of new scientific theories. In view of their critical role, everyone can expect complete and relevant information about the confidence level that are associated with them. To achieve this goal, we must perform validation and verification (V&V) operations. This represents an important challenge in Earth Faculté des sciences where modelized systems are complex and open. An anthropic night-sky radiance model was studied to establish a V&V strategy that might be applied to Earth Faculté des sciences models in general. This strategy include qualification (are we modeling the right phenomenon?), verification (does implemantation respect the specifications?), and validation (does software simulate the phenomenon correctly?). Qualification and verification show the relevance of the selected governing equations and allow us to identify paths to improve software management maturity. Effects of distance and angle of view on anthropic night-sky radiance were studied in validation. Comparison of simulations and measurements show interesting similarities
Ăvaluation d'un modĂšle de luminance artificielle du ciel nocturne
Simulation models play an important role in decision making and developement of new scientific theories. In view of their critical role, everyone can expect complete and relevant information about the confidence level that are associated with them. To achieve this goal, we must perform validation and verification (V&V) operations. This represents an important challenge in Earth Faculté des sciences where modelized systems are complex and open. An anthropic night-sky radiance model was studied to establish a V&V strategy that might be applied to Earth Faculté des sciences models in general. This strategy include qualification (are we modeling the right phenomenon?), verification (does implemantation respect the specifications?), and validation (does software simulate the phenomenon correctly?). Qualification and verification show the relevance of the selected governing equations and allow us to identify paths to improve software management maturity. Effects of distance and angle of view on anthropic night-sky radiance were studied in validation. Comparison of simulations and measurements show interesting similarities