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Ahn, Young Ock. "A new class of glycosidases specific to disaccharide glycosides." Kyoto University, 2005. http://hdl.handle.net/2433/145447.
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Kyoto University (京都大学)0048
新制・課程博士
博士(農学)
甲第11237号
農博第1452号
新制||農||901(附属図書館)
学位論文||H17||N3982(農学部図書室)
22846
UT51-2004-U442
京都大学大学院農学研究科応用生命科学専攻
(主査)教授 坂田 完三, 教授 江崎 信芳, 教授 矢崎 一史
学位規則第4条第1項該当
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DONG, DONG XIA-CATHERINE. "Synthese de glycosides d'aryle et de glycosides d'ether d'enol d'interet biologique." Paris 11, 1990. http://www.theses.fr/1990PA112319.
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Les phenyl 2-o-(3-amino-2,3,6-tridesoxy-alpha-l-arabino et alpha-l-ribohexopyranosyl)-beta-d-glucopyranosides sont prepares en tant que modeles representatifs d'un fragment structural commun aux antibiotiques du groupe de la vancomycine (actinoidine, avoparcine, vancomycine). La synthese de ces chaines laterales heterosaccharidiques est basee sur le couplage de derives du beta-d-glucopyranoside de phenyle avec les glycals totalement proteges de la l-acosamine et de la l-ristosamine, ces derniers etant les precurseurs des fragments 3-amino-2,3,6-tridesoxy-, respectivement de configuration l-arabino et l-ribo. La deprotection partielle ou totale de ces disaccharides fournit les molecules-cibles. La synthese de prodrogues d'anthracyclines antitumorales, comme la daunorubicine, a ete entreprise. Elle comprend la synthese de glycosides d'aryle et d'ether d'enol. Une fois verifiee l'absence de cytotoxicite de ces derives, l'hydrolyse enzymatique a ete etudiee de facon a controler si la liberation de la daunorubicine elle-meme se produisait de facon satisfaisante
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Åberg, Per-Mikael. "Synthesis of blood group A and B determinants and studies towards catalytic glycosidations." Lund : Organic Chemistry 2, Lund Institute of Technology, Lund University, 1994. http://books.google.com/books?id=3J1qAAAAMAAJ.
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Fleury, Adeline. "Synthèse de c-glycosides et daminoacides glycosyles trifluoromethyles." Thesis, Cergy-Pontoise, 2011. http://www.theses.fr/2011CERG0509/document.
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L’objectif de nos travaux consiste en la préparation de C-glycosides et d’aminoacides glycosylés trifluorométhylés dans le but d'obtenir des structures biologiquement actives stabilisées. L'intérêt des C-glycosides est lié à leur stabilité autorisant une pharmacocinétique plus appropriée pour un usage thérapeutique. La 1ière partie de mon travail a été de créer une liaison C-C en position anomérique d'un sucre par différentes méthodes d’alkylation, d’alcynylation à l’indium et par la réaction de Réformatsky. Ensuite après avoir fonctionnalisé les C-glycosides synthétisés, une étude tournée vers la synthèse d’aminoacides C-glycosylés par le biais d’alkylations énantiosélectives a été réalisée. Ensuite nous avons étudié la synthèse d’aminoacides glycosylés stabilisés par l’introduction d’un groupement trifluorométhylé en une position stratégique. D’abord nous avons étudié la synthèse d’aminoacides N-glycosylés obtenus par la réaction entre un aminoacide trifluorométhylé et un sucre. Le groupe fluoré, en de l’azote, diminue la basicité de l’amine et empêche sa protonation. Ainsi, l’hydrolyse du lien anomérique est très défavorisée. Plusieurs conditions réactionnelles ont été étudiées. Le milieu acide protonique a montré des résultats encourageant notamment entre le 2-déoxy-glucose et un dipeptide trifluorométhylé. Ensuite nous avons travaillé sur la synthèse de O-glycosides. 2 stratégies ont été développé à partir d’un sucre trifluorométhylé. D’abord l’éthérification de Williamson a été étudié entre un sucre trifluorométhylé et différents dérivés halogénés. Cette voie a donné des résultats satisfaisant avec des dérivés halogénés linéaires uniquements. Puis la réaction de Mitsunobu a été étudié entre un sucre trifluorométhylé et différents alcools. La réaction donne des résultats variés dépendant de l’alcool. Cette voie nous a aussi permis de synthétiser des aminoacides O-glycosylés trifluorométhylé en utilisant la sérine comme alcoolThe aim of our work consists in the preparation of C-glycosides and trifluorinated glycosylated aminoacids in order to obtain biogically active structures. The interest of such C-glycosides, is due to its stability. It allows a better pharmacokinetics to a therapeutic use. The first part of my work was to create a C-C bond at the anomeric position of a carbohydrate by different methods such as alkylation, alcynylation and Reformatsky reaction. Then, after functionalized these C-glycosides, a study on C-glycosylated aminoacids synthetized by an enantioselectiv alkylation way was made. The second part of my work was to synthesized stabilized glycoaminoacidsby the introduction of a trifluoromethylated group at a strategic position: at the anomeric position of the carbohydtare or at position of the anomeric position of the carbohydtare. We first studied the synthesis of N-glycosides with a trifluoromethylated group at position of the anomeric position of the carbohydtare. This strategy is based on the reaction of a protected sugar with a trifluoromethylated amine catalysed by an acid. Then we studied the synthesis of O-glycoaminoacids with a trifluoromethylated group at the anomeric position of the carbohydtare. Two strategies have been developed. The first one is the alkylation of Williamson. The second one is the reaction of Mitsunobu
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Korkashvili, Tamar. "Steroidal Glycosides of Cordyline australis." The University of Waikato, 2006. http://hdl.handle.net/10289/2237.
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The n-butanol extract of aerial parts of Cordyline australis demonstrated antifungal activity. n-Butanol and chloroform extracts of dried or fresh leaves of C. australis afforded a steroidal glycoside, which was identified as 5α-spirost-25(27)-en-3β-ol 3-O{O-α-L-rhamnopyranosyl-(1→2)-β-D-glucopyranoside}, saponin 1. This spirostanol glycoside showed strong antifungal activity towards Trichophyton mentagrophytes and some aspecific activity and cytotoxicity against MRC5 cell. The chloroform extract of fresh leaves of C. australis yielded a second new spirostanol glycoside which was identified as 5α-spirost-25(27)-ene-1β,3β-diol 1-{O-α-L-rhamnopyranosyl-(1→2)-β-D-fucopyranoside}, saponin 2. The n-butanol extracts of senescent leaves of C. australis afforded a third new spirostanol glycoside that was identified as 5α-spirost-25(27)-ene-1β,3β-diol 1-{O-β-D- fucopyranoside, saponin 3. A mixture of two isomeric flavonoid glycosides was isolated from dried leaves of C. australis and shown to be a ca 1:1 mixture of isorhamnetin-3-O-{O-α-L-rhamnopyranosyl-(1→6)-β-D-glucopyranoside}, 4 and isorhamnetin-3-O-{O-α-L-rhamnopyranosyl-(1→6)-β-D-galactopyranoside}, 5. Three other known steroidal glycosides, β-sitosterol glucoside, 6, prosapogenin A of dioscin, 7, and trillin, 8 were also isolated from the leaves of C. australis. The n-butanol extract of dried stems of C. australis afforded (25S)-5α-spirostane-1β,3α-diol 1-{O-β-D-glucopyranoside}, 9. This spirostanol glycoside showed moderate cytotoxicity against Herpes simplex type I virus (ATCC VR733) and Polio Virus Type I (Pfiser vaccine strain).
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Ibrahim, Jamal. "Hydroxylysine glycosides of corneal collagen." Thesis, University of Oxford, 1986. http://ora.ox.ac.uk/objects/uuid:2442f75c-6a1c-4575-98b0-a4475a3df1f2.
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These findings are discussed with respect to the possible role of hydroxylysine glycosides in limiting collagen fibril diameter. Comparisons of the amino acid sequences around the seven glycoside sites however gave no clues as to what makes some lysyl residues more susceptible to modification than others. The possible reasons for the high extent of lysyl modification in the cornea are also discussed.
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Hindle, Neil. "Amino sugars and their glycosides." Thesis, University of Oxford, 1995. http://ora.ox.ac.uk/objects/uuid:78ab400f-4a4c-47bb-9d18-1b3bef205044.
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This thesis describes approaches to the transformation of simple carbohydrates into a polyhydroxylated pyrrolidine and the formation of its glucosides. Chapter one describes the synthesis of the naturally occurring pyrrolidine 2,5-dideoxy-2,5-imino-D-mannitol. Synthesised from di-O-isopropylidene-D-glucose, the key steps are the introduction of nitrogen at C-5 with retention of configuration. Then cyclisation of the nitrogen onto the C-2 position with inversion to form the pyrrolidine ring. Reduction of the aldehyde furnished the polyhydroxylated heterocycle in 3.4% yield over 16 steps. The synthetic compound matched the naturally occurring compound in all respects. Chapter two contains a review of commonly used glycosylation methods. It also describes the glycosylation of di-O-isopropylidene-α-D-glucose as a model system comparing the Koenig-Knorr method to the trichloroacetimidate method using several reaction conditions. Glycosylation of 2,5-dideoxy-2,5-imino-D-mannitol was carried out using the trichloroacetimidate method to synthese all four glucosides. Boron trifluoride etherate and trimethylsilyl trifluoromethanesulphonate were used as catalysts in dichloromethane, diethyl ether and acetonitrile under strictly anhydrous conditions. All four glucosides were prepared 1-O-(αβ-D-glucopyranosyl)-2,5-dideoxy-2,5-imino-D-mannitol and 3-O-(αβ-D-glucopyranosyl)-2,5-dideoxy-2,5-imino-D-mannitol. Biological screening carried out against a wide range of glycosidases and glycosyl transferases indicated that the glucosides showed little inhibition in comparison to 2,5-dideoxy-2,5-imino-D-mannitol. Chapter three describes the isolation and identification of 1-O-(β-D-glucopyranosyl)- 2,5-dideoxy-2,5-imino-D-mannitol from Nephthytis poisonii N.E.Br. a member of the Araceae family found in tropical Africa. Identification was made by comparison with the previously synthesised glucosides of 2,5-dideoxy-2,5-imino-Dmannitol. Investigations of Hyacinthoides non-scriptus (L.) chouard ex Rothm are also discussed. Chapter four describes the synthesis of a diazidolactone that could be used to form a 1,5 disubstituted tetrazole. This would have a second nitrogen functionality in the molecule allowing the possibility of the inclusion of the tetrazole into a peptide sequence. The synthesis was carried out from L-gulono-1,4-lactone. An azido group was introduced selectively at C-2, this unexpectedly occurred with retention of configuration. A second azide was then introduced at C-5, this occurring with the more commonly observed inversion of configuration to afford the 2,5-diazido-2,5-dideoxy-D-manno-1,4-lactone.
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Lacy, Christopher. "The syntheses of morphine glycosides." Thesis, University of Bath, 1995. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.760686.
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JEGOU, ANNE. "Nouvelles syntheses de c-glycosides." Rennes 1, 1998. http://www.theses.fr/1998REN10128.
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Les c-glycosides sont des analogues de sucres dans lesquels un atome de carbone remplace l'atome d'oxygene anomerique. En tant qu'analogue, un c-glycoside, de surcroit stable a l'hydrolyse chimique ou enzymatique, peut interferer dans le metabolisme des glucides en inhibant les enzymes (glycosidases ou glycosyltransferases) qui sont necessaires a l'elaboration d'un glycoconjugue fonctionnel. Les acetals bicycliques 2:2:1 derivent du 6-o-pivaloyl-d-galactal via une reaction d'iodocyclisation. Leur ouverture regioselective par des c-nucleophiles nous a permis d'exploiter la geometrie particuliere de ces molecules pour synthetiser stereoselectivement des motifs c-furanosides. L'allyltrimethylsilane et le 2-(trimethylsilyloxy)furane ont ete en particulier utilises. La reactivite du 2-(trimethylsilyloxy)furane, ainsi que celle du 3-trimethylsilylmethyl-but-3-enoate de methyle, derive du dicetene, vis-a-vis de donneurs de glycopyranosyle, ont ete egalement etudiees. Ces deux nucleophiles permettent d'introduire, des l'etape de c-glycosylation, une chaine fonctionnalisee en position anomerique.
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Tan, Jingjun. "Dietary isoflavones : aglycones and glycosides." Thesis, University of Leeds, 2011. http://etheses.whiterose.ac.uk/2092/.
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Flavonoids are non-nutrient secondary metabolites ubiquitous in plants, associated with protection against various diseases, such as cancer and cardiovascular diseases. Dietary flavonoids are normally found as conjugated glycosides except, notably, in fermented foods where although there may be losses in total flavonoid content, levels of liberated aglycones can be relatively high. There has been considerable interest in the relationship between the form and structure of the ingested flavonoids and the consequences for efficiency of absorption. The research focused firstly on β-D-glucosidases (β-D-glycoside glucohydrolase, EC 3.2.1.21) extracted from different plant sources and characterised. The enzyme was found at the highest levels in almond and apple seeds. The optimum reaction conditions of the enzyme from apple seeds were determined to be pH 5.5 at 65ºC, and the enzyme extract was stable at 4ºC for at least 12 weeks. Kinetic characterisation of the enzyme from selected materials was carried out by using para-nitrophenyl-β-D-glucopyranoside (p-NP-Glc) as substrate. The Km and Vmax of the enzyme from apple seed extract were determined, for the first time, to be 5.48 ± 0.34 mM and 15.60 ± 0.95 U/mg protein (n = 8), respectively, with the protein content of the extract being 0.728 ± 0.019 mg/ml. Secondly, isoflavone contents from different sources were investigated. Soy bean and its products are were found to be good sources of daidzin and genistin; kudzu was the best source of puerarin; red clover and chickpea were good sources of formononetin and biochanin A. Passion fruit was found to be an interesting source of isoflavones outside the legume family. By using selected enzyme sources and isoflavone sources, a novel natural style soy-based food was developed in which isoflavones existed predominately as aglycones. The food, derived using soya and enzymes from waste sources, may have further potential.
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Bolarinwa, Islamiyat. "Cyanogenic glycosides in plant foods." Thesis, University of Leeds, 2013. http://etheses.whiterose.ac.uk/5002/.
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Consumption of cyanogenic plants can cause serious health problems for humans. The ability to detect and quantify cyanogenic glycosides, capable of generating cyanide, could contribute to prevention of cyanide poisoning from the consumption of improperly processed cyanogenic plants. In the first part of the present study, an efficient extraction method for amygdalin from foods was developed by comparing the extraction efficiency of water and ethanol at room and boiling temperature for various extraction times. Efficiencies of the extraction methods were evaluated by using a modified HPLC method. In general, boiling ethanol was more efficient for amygdalin extraction from foods. Amygdalin contents of a wide range of commercially-available food products were determined for the first time. In the second part, the effect of processing on amygdalin levels in apple juice was investigated. Apple juices produced from different apple varieties were subjected to various processing conditions such as freezing, pasteurization and holding for various times. The results obtained showed that processing can result in reduction of amygdalin level in apple juice and that the reduction of amygdalin by enzymatic degradation probably depends on the level of the enzyme in the processed foods and the utilisation of optimum conditions for the enzyme activities. High-temperature treated commercially-available apple juice had lower amygdalin levels compared to low-temperature treated juices, indicating the degradation of amygdalin at high processing temperatures. In the last part, the development of a sensitive ELISA method for amygdalin was investigated. Antibody produced by using an immunogen that was synthesized using the cyanuric chloride method for coupling of hapten to carrier protein was highly immunoreactive and very specific for amygdalin. The ELISA developed using this antibody was very sensitive (LOD = 0.2ng/ml). The results obtained from the determination of amygdalin in foods using the ELISA method showed excellent correlation with those obtained from HPLC method. The work described is the first comprehensive study on detection of a particular cyanogenic glycoside and use of an antibody-based method for determination of amygdalin in processed foods. The results obtained suggested that while the consumption of products available in the UK with the potential for containing amygdalin are unlikely to present a health risk to consumers, monitoring of new processing protocols would be wise.
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McMahon, Heather. "The effects of different processing parameters (cold soak and percent alcohol (v/v) at dejuicing) on the concentrations of grape glycosides and glycoside fractions and glycosidase activities in selected yeast and lactic acid bacteria." Thesis, Virginia Tech, 1998. http://hdl.handle.net/10919/46209.
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Grape-derived aroma and flavor precursors exist partially as non-volatile, sugar-bound glycosides. Hydrolysis of these compounds may modify sensory attributes and potentially enhance wine quality. Cold soak (prefermentation skin contact) at two temperatures and alcohol content (%, v/v) at dejuicing were monitored to determine effects on Cabernet Sauvignon glycoside concentration. Total, phenolic-free, and red-free glycoside concentrations were estimated by the quantification of glycosyl-glucose. Cold soak (5 days at 10° C) increased total glycosides by 77%, red-free glycosides by 80%, and phenolic-free glycosides by 96%. Ambient soak (3 days at 20° C) enhanced color extraction, and increased total glycosides by 177%, red-free glycosides by 144%, and phenolic-free glycosides by 106%. Wines produced by early pressing (10% sugar) had 25% more total and red-free glycosides than late press (0.25% sugar). After post-fermentation malolactic fermentation, total glycosides were 14% lower and phenolic-free glycosides were 35% lower.
In a second study, the activities of a-L-arabinofuranosidase, b-glucosidase, and a-L-rhamnoyranosidase were determined in model systems for thirty-two strains of yeasts belonging to the following genera: Aureobasidium, Candida, Cryptococcus, Hanseniaspora, Hansenula, Kloeckera, Metschnikowia, Pichia, Saccharomyces, Torulaspora, and Brettanomyces (10 strains); and seven bacteria (Leuconostoc oenos strains). Only one Saccharomyces strain exhibited -glucosidase activity, but several non-Saccharomyces yeast species had substantial production. Aureobasidium pullulans hydrolyzed a-L-arabinofuranoside, b-glucoside, and a-L-rhamnoyranoside. Eight Brettanomyces strains had -glucosidase activity. Location of enzyme activity was determined for those species with enzymatic activity. The majority of -glucosidase was located in the whole cell fraction (66%), followed by the permeabilized fraction (35%), and extracellular production (2%). Aureobasidium pullulans was also capable of hydrolyzing grape glycosides.Master of Science
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Levoirier, Eric. "Synthèse organique en phase aqueuse : nouvelle méthodologie d'accès aux C-glycosides, glycosides branchés et C-disaccharides." Paris 11, 2002. http://www.theses.fr/2002PA112284.
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L'intérêt porté aux C-glycosides ainsi qu'aux C-disaccharides s'est considérablement accentué depuis ces dernières années. Contrairement aux O-glicosides, ceux-ci sont en effet stables en milieu biologique car peu ou pas métabolisables. Ils présentent par affleurs souvent, des caractéristiques structurales similaires aux oligosaccharides naturels, gardant ainsi l'essentiel des propriétés biologiques. Toutefois, la préparation de ces dérivés est bien souvent longue et fastidieuse et nécessite notamment de nombreuses étapes successives de protection-déprotection. D'autre part, il a été récemment démontré l'intérêt synthétique de la réaction d'allylation de composés carbonyles dans les conditions de Barbier dans l'eau. Ce type de réactivité a donc été appliqué à la synthèse de C-glicosides et de C-disaccharides. Pour cela, la synthèse de deux dérivée glycosidiques présentant un motif halogénure allylique a été mise au point. Les dérivés 4-bromo-2-énopyranoside et 6-bromo-4-énopyranoside obtenus ont été utilisés pour l'allylation de différents aldéhydes en présence d'indium. Après fonctionnalisation de la double liaison, différents 2-C- et 4-C-hexoses ont ainsi sélectivement été obtenu. L'utilisation comme composé carbonylé d'un β-C-glycosylaldéhyde, a permis la préparation de β(1->2)- et β(1->4)-C-disaccharides avec des rendements satisfaisants. Enfin, un accès rapide à ce type d'aldéhydes a été trouvé. Cette stratégie utilise comme étape clé la préparation d'une β-C-glycosylcétone en une seule étape depuis l'hexose libre. Le β-C-glycosylaldéhyde est ensuite obtenu après trois étapes supplémentaires avec un bon rendementThe Synthesis of carbon-carbon linked disaccharides (C-disaccharides) is the subject of widespread current interest. Among the many methods developed for the synthesis of C-glycosides, C-branched sugars and C-disaccharides during the last 20 years, some have been efficient, although they still remain relatively complex, generally requiring many protection-deprotection steps. Recently, organic reactions in water have received much attention not only because water is an economical and environmentally friendly solvent but more especially because unique reactivities and selectivities are often exhibited in water. Among them, indium chemestry has captured much recent attention largely due to the discovery that indium can mediate the smooth coupling of allylic halide with aldehydes to give the corresponding homoallylic alcohols in aqueous media. After the synthesis of the key compounds, the 4-bromo-2-enopyranoside and the 6-bromo-4-enopyranoside, we report a very convenient protocol for the preparation of 2-C- and 4-C-branched sugars and β(1->2)- and β(1->4)-C-disaccharides under indium promoted Barbier-type allylation in aqueous media
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Yip, Vivian Ling Yee. "Mechanistic investigation of family 4 glycosidases : a novel redox-elimination mechanism in the hydrolysis of glycosides." Thesis, University of British Columbia, 2007. http://hdl.handle.net/2429/31761.
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The chemical mechanisms of glycoside hydrolases, which catalyze the hydrolysis of glycosidic linkages, are some of the most extensively studied amongst enzymatic reactions. Decades of research have led to the widespread acceptance of the two general glycosidase mechanisms--both involving nucleophilic displacement steps and oxocarbenium ion-like transition states--first proposed by Koshland in 1953. Glycoside hydrolase family 4 is an anomaly within this large class of enzymes. Not only does this family uniquely contain both α- and β-glycosidases, but members of family 4 also require both a divalent metal (Mn²⁺, Co²⁺, Ni²⁺) and a NAD⁺ cofactor for activity. The unusual cofactor requirement, coupled with the observation of solvent deuterium incorporation into C2 of the reaction product prompted the proposal of a mechanism involving key NAD⁺ -mediated redox steps as well as elimination of the glycosidic oxygen. Mechanistic and structural analyses of BglT (a 6-phospho-β-glucosidase from Thermotoga maritima) and GlvA (a 6-phospho-α-glucosidase from Bacillus subtilis ) were performed, revealing a common mechanism for both the α- and β-glycosidases in this family. The key steps include: (1) C3 hydride abstraction by the NAD⁺ cofactor and consequent oxidation of the C3 hydroxyl; (2) abstraction of the C2 proton via general base catalysis; (3) α,β-elimination of the aglycone; (4) 1,4-Michael-like addition of water to the α,β-unsaturated intermediate; (5) reprotonation at C2; and finally (6) reduction of the C3 carbonyl via oxidation of the "on-board" NADH cofactor. Primary kinetic isotope effects and Brønsted relationships reveal that the C3 hydride and C2 proton abstractions are both partially rate-limiting and that the C1-O1 linkage is cleaved rapidly. The evidence suggests that both BgIT and GlvA utilize an E1 cb -type mechanism. Currently, only family 4 glycosidases are known to utilize an elimination mechanism proceeding via anionic transition state(s). Therefore, they stand in stark contrast to other glycoside hydrolases that use "classical" nucleophilic displacement mechanisms and oxocarbenium ion-like transition states. Structural analyses suggest that a tyrosine residue found in close proximity to the C2 proton of the substrate is oriented ideally to act as the catalytic base for C2 deprotonation. Consistent with this data, mutants in which this tyrosine residue have been replaced by phenylalanine or alanine have significantly lower activity than the wild type enzyme. Direct evidence for the role of NAD⁺ was obtained by reduction in situ using NaBH₄ leading to an inactive enzyme that could be reactivated by the addition of excess NAD⁺. This was accompanied by the expected UV-vis spectrophotometric changes. Furthermore, in the BgIT Y241A mutant, the deprotonation/elimination step is slowed sufficiently that steady state accumulation of the reduced nicotinamide cofactor NADH is observed during catalysis. Some clues as to the origins of this unusual class of enzymes come from their structural similarities to α-hydroxy organic acid dehydrogenases. Further, the proposed mechanism shows striking resemblances to those of NAD⁺-dependent sugar dehydratases and SAH-hydrolases.Science, Faculty of
Chemistry, Department of
Graduate
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Bercich, Mark David. "Asymmetric syntheses of anthraquinonyl C-glycosides." Thesis, University of Auckland, 1997. http://hdl.handle.net/2292/2007.
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Syntheses of C2-anthraquinone aldehydes from the commercially available anthrarufin 11 have been investigated. A synthesis of the ketoaldehyde 5 in nine steps and 73% overall yield was achieved. Syntheses of 5 exploiting selective oxidations of either a C-bound allyl group via Wacker oxidation to introduce the methyl ketone functionality, or of a C-bound prop-l-enyl moiety via dihydroxylation and oxidative cleavage to generate the C2 formyl group were also developed. The aldehyde 81 was synthesised in seven steps and 81% overall yield from ll, and syntheses of the phenolic aldehydes 82, 95, and 96, the Cl benzyloxyaldehyde 104, and the anthracene aldehyde 107 have been developed. Hetero Diels-Alder reactions of several anthraquinone aldehydes with the dienes 6,120, and 121 using catalysis by the complex (+)-VO(hfc)2 115 were studied. Reactions of the aldehydes 5 and 81 proceeded readily using catalytic amounts of 115 and dichloromethane, chloroform, or toluene as solvent to give the adducts 128 or 131 indicating an endo selective pericyclic reaction pathway. The enantioselectivites of these reactions were typically 20-50%, with a best ee of 56% for a reaction between 81 and 6 catalysed by 0.2 equivalents of 115 at -78°C. Reactions of the 1-silyloxydienes 120 and 121 with aldehyde 8l catalysed by 115 to give the enone 130 also proceeded readily with a best ee of 64% being obtained for a reaction between 81 and l2l in toluene at -78°C. Reactions of the phenolic aldehydes 95 and 96 and the diene 6, catalysed by 115, afforded good yields of cycloadducts, but with enantioselectivities identical to equivalent reactions of the aldehyde 81. However reactions of the Cl benzyloxyaldehyde 104 with the dienes 6 and 120, and 121 afforded cycloadducts with enantioselectivities lower than those from the equivalent reactions of the aldehyde 81. Elaboration of the cycloadduct 131 to the anthracene C-glycoside 149 established that the hetero Diels-Alder reaction had favoured the formation of the 2'R, 6'R enantiomer of 131. This enantiofacial selectivity was correlated with the sense of anisochrony observed in 1H NMR spectra of the ketone 129, derived from 131, in the presence of the chiral solvating agent (S)(+)-trifluoroanthrylethanol. The enone 130 was elaborated to the anthraquinone-olivose C-glycoside 154 demonstrating the utility of hetero Diels-Alder reactions involving silyloxydienes with Cl silyloxy and Cl methyl substituents for such syntheses. Attempts to use chiral acyloxyborane comploxes such as 168 and 169 as catalysts for hetero Diels-Alder reactions of the aldehydes 5, 81 and 107 with the dienes 6 and 120 were unsuccessful. However two equivalents of the chiral acyloxyborane complex 168a in dichloromethane at 30°C, mediated. a formal hetero Diels-Alder reaction between 81 and 120 affording the enone 13O in 45% yield, with a 79% ee in favour of the 6'R enantiomer. Reactions catalysed by the chiral acyloxyborane complex 169b between beenzaldehyde or o-anisaldehyde and the dienes 6,119, and 120 gave products resulting from a Mukaiyama aldol addition rather than a hetero Diels-Alder reaction. Hetero Diels-Alder reactions 81 and 120 employing the chiral titanium complexes Ti[(R)-BINOL]C12, Ti[(R)-BINOL]2, and Ti[R,R)-TADDOL]C12 were investigated. No reaction was observed when 0.5, 1.2 and 2 equivalents of Ti[(R)-BINOL]2 were used. However the complexes Ti[(R)-BINOL]C12 and Ti[(R,R)-TADDOL]C12 promoted the reaction between 81 and 120 at -30°C and -78°C, but induced low enantioselectivities (17-30%)
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Gremyachinskiy, Dmitriy Y. "Total Synthesis of Aminomethyl C-glycosides." Scholarly Commons, 2000. https://scholarlycommons.pacific.edu/uop_etds/3765.
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Prince-type cyclizations were performed with different Lewis acids to select optimal conditions, for the synthesis of a series of 4-chloro-2- phtalimidomethyl 6-methyl tetrahydropyrans and 4-chIoro-2.6- bis(phtalimido-methyl)-tetrahvdropyrans. The total yield for phtalimidomethyl products reached 92%, and for bis-phtalimido compounds 71%. An influence of reagent size and nucleophilicitv on the reaction outcome was observed, and was interpreted in terms of cationic mechanism and complex formation in the transition state. A cyclization step was also used to synthesize bicvclic compounds that can be used as precursors for the synthesis of C-oligosaccandes. Optimized eliminations of hydrogen halide by DBU in presence of LiCl yielded a mixture of 2.6-anhydro-1.3.4.5.7- penradeoxy-l-phtahmido-DA-erythrohepr-3-emto! 5b and 2.6-anhydrol, 3,4,5,7-pentadeoxy-l-phtalimido-D.L-erythrohept-4-enitoI 6b in 79°a yield for the isomeric mixture. Epoxidation of this alkene mixture by a newly developed method with urea-hydrogen peroxide complex and trifluoroaceric anhydride afforded a mixture of epoxy-2-methvl-6- phtalimidomethyl tetrahydropyrans in 92% total yield. Epoxides were cleaved by aq. CF3COOH to give a mixture of dihydroxy-2-methyi-6- phtalimi dome by 1 tetrahydropyrans with an overall yield of 74% from the mixture of 5b/6b. The regioisomers were separated and deprotected by a newly developed method, and were oxidized to produce partially functionalized racemic aminomethyl C-glycopyranosides. One of the isomers was characterized as an N-acetyl-di-O-acetyl derivative and as a NBoc di-O-acetyl derivative, because this isomer was very hygroscopic.
It was also found that transallylation occurred between acetal and homoallylic alcohol during the cyclization step. A new method for the synthesis of homoallylic alcohols from acetals was developed on the basis of this observation. Homoallylic alcohols, l-Benzyloxv-4-penten-2-ol 19. 1- Phenyl-4-pentene-2-ol 18 and BPhtalimido-4-pentene-2-ol 1β were synthesized by a new method with yields of 40%. 61 % and / i % respectively. The as yet unoptimized method allows to synthesize homoallylic alcohols from unstable aldehydes.
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Gremyachinskiy, Dmitriy. "Total synthesis of aminomethyl c-glycosides." Scholarly Commons, 2000. https://scholarlycommons.pacific.edu/uop_etds/544.
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Wong, Fred Tuck Khai. "Structure-activity relationships of cardiac glycosides." Thesis, The University of Sydney, 1989. https://hdl.handle.net/2123/26271.
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It is over 200 years since William Hithering published his famous treatise on the use of the foxglove. Since that time, digitalis has been in continuous use as a therapeutic agent, and, although its efficacy has often been challenged it continues to occupy a central role in the treatment of chronic congestive heart failure.
Interest in digitalis has been sustained by its therapeutic use and by the scientific interest in its mode of action. The cardiac glycosides, generally referred to by the generic name of digitalis, are unique inhibitors of the enzyme Na*, K*-ATPase. This enzyme is found in the plasma membrane of all eukaryotic cells where it acts as a transmembrane pump that couples the outward transport of Na+ with the inward transport of K*. As a result of this action, Na*, K*-ATPase plays an important role in cell homeostasis and makes a major contribution to the maintenance of the transmembrane resting potential. Such important cellular properties as excitability and conduction of electrical impulses depend very much on the action of Na*, K*-ATPase.
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MacManus, D. A. "Enzymatic synthesis of glycosides and oligosaccharides." Thesis, University of Warwick, 1991. http://wrap.warwick.ac.uk/110506/.
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The β-D-galactosidase of Escherichia coli catalysed galactosyl transfer to a variety of acceptor substrates. Transfers to simple alcohols were followed by transfers to chiral alcohols, chiral diols (bearing primary and secondary hydroxyl groups) and to a me so- diol. In particular, the regio- and stereoselective aspects of the reactions were investigated. In general, transfer to primary hydroxyl groups was favoured over transfer to secondary hydroxyl groups, but little or no preference for the transfer to specific enantiomers in a racemic mixture was observed. The results for propane-1,2-diol and butane- 1,3-diol are interpreted in terms of the possible conformations which might be adopted at the active site of the enzyme. Transfer to cii-cyclohexa-3,5-diene- 1,2-diol gave rise to two diastereoisomers. During the early stages of the reaction, a diastereoisomeric excess of ca. 80% was observed; this was reduced to ca. 20% as the yields of product reached their maximum values. Assignment of the structures of the products was based on a combination of the techniques of nuclear Overhauser enhancement and molecular modelling. α-Galactosyl transfers to lactose and cellobiose using Mortierella vinacea a-D-galactosidase were also studied. In both cases, a single trisaccharide was isolated. Spectroscopic evidence indicated that a (1-6) linkages had been formed in both cases. An acrylamide/acrylic acid polymer intended for use in enzymatic oligosaccharide synthesis was developed. The polymer was high swelling so as to allow permeation by the enzyme and could be easily stored. An attempt to introduce chiral cavities specific for certain monosaccharides was made by substituting part of the acrylamide for a boronate-containing acrylamide and carrying out the polymerisation in the presence of the monosaccharide. The success of the imprinting procedure was measured by the ability of the polymer to separate the components of a racemic mixture of the monosaccharide. The application of such "molecular imprinting" as an aid to oligosaccharide synthesis is discussed.
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McKay, Matthew Joseph. "Applications of cationic transition-metal-catalysis : the stereoselective synthesis of beta-O-aryl glycosides and alpha-urea glycosides." Diss., University of Iowa, 2014. https://ir.uiowa.edu/etd/4692.
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Having access to mild and operationally simple techniques for attaining carbohydrate targets will be necessary to facilitate advancement in biological, medicinal, and pharmacological research. Even with the abundance of elegant reports for generating glycosidic linkages, the stereoselective construction of alpha- and beta-oligosaccharides and glycoconjugates is by no means trivial. In an era when expanded awareness of the impact we are having on the environment drives the state-of-the-art, synthetic chemists are tasked with developing cleaner and more efficient reactions for achieving their transformations. This movement imparts the value that prevention of waste is always superior to its treatment or cleanup. Chapter 1 of this thesis will highlight recent advancement, in this regard, by examining strategies that employ transition metal catalysis in the synthesis of oligosaccharides and glycoconjugates. These methods are mild and effective for constructing glycosidic bonds with reduced levels of waste through utilization of sub-stoichiometric amounts of transition metals to promote the glycosylation.
The development of a general and practical method for the stereoselective synthesis of beta-O-aryl-glycosides that exploits the nature of a cationic palladium(II) catalyst, instead of a C(2)-ester directing group, to control the beta-selectivity is described in chapter 2. The beta-glycosylation protocol is highly diastereoselective and requires 2-3 mol % of Pd(CH3CN)4(BF4)2 to activate glycosyl trichloroacetimidate donors at room temperature. The method has been applied to D-glucose, D-galactose, and D-xylose donors with a non-directing group incorporated at the C(2)-position to provide the O-aryl glycosides with good to excellent beta-selectivity. In addition, its application is widespread to electron-donating, electron-withdrawing, and hindered phenols. The glycosylation is likely to proceed through a seven-member ring intermediate, wherein the palladium catalyst coordinates both the C(1)-trichloroacetimidate nitrogen and C(2)-ether oxygen, blocking the alpha-face. As a result, the phenol nucleophile preferentially approaches from the top face of the activated donor, leading to the formation of the beta-O-aryl glycoside.
The area of sugar urea derivatives has received considerable attention in recent years because of the unique structural properties and activities that these compounds display. The urea-linkage at the anomeric center is a robust alternative to the naturally occurring O- and N-glycosidic linkages of oligosaccharides and glycoconjugates, and the natural products that have been identified to contain these structures show remarkable biological activity. While methods for installing the beta-urea-linkage at the anomeric center have been around for decades, the first synthesis of alpha-urea glycosides has been much more recent. In either case, the selective synthesis of glycosyl ureas can be quite challenging, and a mixture of alph- and beta-isomers will often result. Chapter 3 provides a comprehensive review of the synthetic approaches to alpha- and beta-urea glycosides and examines the structure and activity of the natural products, and their analogues, that have been identified to contain them.
There are only a handful of reports for the construction of beta-urea glycosides, and even fewer that are able to attain the alpha-urea structures. Chapter 4 will cover two of these methods, where a transition metal catalyst is employed to facilitate the alpha-selective transformation. The 1st-generation process, covered in section 4.1, involves the cationic palladium(II)-catalyzed rearrangement of glycal trichloroacetimidate to alpha-glycal trichloroacetamide in its key step. The transformation is carried out with only 0.5 mol% Pd(CH3CN)4(BF4)2 catalyst and is both highly alpha-selective and tolerant to a diverse array of protecting groups. The glycal product of the rearrangement is functionalized to pyranoside, protected, and then converted to glycosyl urea in 3-steps. A diverse array of primary and hindered secondary nitrogen nucleophiles have been coupled with the alpha-acetamide products, generating alpha-urea glycosides with retention of stereochemical integrity at the anomeric center. This is the first synthesis of alpha-glycosyl urea to rely on the nature of the catalyst/ligand complex, rather than substrate, to control selectivity. This method, however, suffers from limitations in scope and a dependence on toxic osmium tetroxide to functionalize the glycal.
In section 4.2, the development and mechanistic investigation of a 2nd-generation process, able to overcome the limitations of the glycal methodology to provide an efficient and highly stereoselective access to alpha-urea glycosides, is decribed. This two-step procedure begins with a highly selective nickel-catalyzed conversion of alpha-glycosyl trichloroacetimidate to alpha-trichloroacetamide. The alpha-selectivity in the reaction is controlled with a cationic nickel(II) catalyst, Ni(dppe)(OTf)2. Mechanistic studies have identified a coordination of the nickel catalyst with equatorial C2-ether group of the glycosyl trichloroacetimidate to be paramount for achieving an á-selective transformation. A cross-over experiment has indicated that the reaction does not proceed in an exclusively-intramolecular fashion. The alpha-trichloroacetamide products are directly converted into alpha-urea glycosides by reacting them with a variety of nucleophilic amines in presence of cesium carbonate. Only alpha-urea products are observed, as the reaction retains stereochemical integrity at the anomeric center during the urea-forming step.
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Day, Andrea Jill. "Uptake and metabolism of dietary flavonoid glycosides." Thesis, University of East Anglia, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.327589.
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James, M. R. "Synthetic studies towards C-glycosides and spiroacetals." Thesis, University of Newcastle Upon Tyne, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.356787.
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Owler, David. "Uptake of cardiac glycosides by HeLa cells." Thesis, University of St Andrews, 1986. http://hdl.handle.net/10023/14072.
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Methods for the microcarrier culture of HeLa cells were developed and optimum culture conditions established. Methods were also established for the isolation of HeLa plasma membranes on beads, based on the principle of cell lysis followed by the shrearing away of the internal cell components, leaving the plasma membrane attached to the beads. The HeLa plasma membranes isolated on beads showed 5-8 fold enrichment of plasma membrane markers, while intracellular markers were depleted to the point of non-detection (except for some slight lysosomal contamination). The preparation time for isolation of HeLa plasma membranes on beads was about 1.5 hrs. The uptake of cardiac glycosides by HeLa cells was investigated. HeLa cells were labelled with [3H]-glycoside, the non-specific binding washed off and the cells returned to normal growth medium. At various time intervals the amount of [3H]-glycoside bound to HeLa plasma membranes and HeLa cells was determined. The rate of loss of ouabain and digoxin from HeLa plasma membranes was found to be about 10%hr-1. The excretion rates of ouabain and digoxin from HeLa cells were 4%hr-1 and 10%hr-1 respectively. The nature of the uptake and excretion processes were investigated using specific inhibitors of receptor-mediated endocytic processes. No inhibitor affected the rate of loss of cardiac glycoside from HeLa plasma membranes but monensin and chloroquine slowed the excretion rate of digoxin from HeLa cells. Modulation of sodium pump numbers by various chronic stress conditions - high serum concentration, low K medium and high K medium - were investigated. High concentrations of serum had no effect on the rate of loss ouabain from HeLa plasma membrane, but low K medium reduced the rate of loss of ouabain from membranes from 10%hr-1 to 4%hr-1. The low K medium also caused a x2 increase in sodium pump numbers in the plasma membrane. Increasing the serum concentration abolished the effects due to low K medium. High K medium also caused a reduction in the rate of loss of ouabain from plasma membranes from 10%hr-1 to 4%hr-1. The results obtained for low K medium were consistent with a model whereby sodium pumps in the plasma membrane are regulated by alteration of the sodium pump turnover rate (or internalisation rate).
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Chaguir, Brahim. "C-glycosides insaturés : synthèse et étude structurale." Lyon 1, 1992. http://www.theses.fr/1992LYO10266.
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Les composes a methylene active reagissent sur le 4,6-di-o-benzyl-2,3-dideoxy-d- erythro hex-2-enopyranoside et , en presence de quantite catalytique de palladium (0), pour donner les c-glycosides correspondants. Cette methodologie de formation de la liaison c-c est hautement stereoselective conduisant a des molecules fonctionnalisables soit sur la partie sucre, soit sur le substituant glycosidique. Si le seul anomere est obtenu a partir du phenylglycoside le phenylglycoside conduit, selon la nature du nucleophile, au seul anomere ou a un melange d'anomeres /. La raison de la perte de selectivite est due a l'intervention du proton restant dans le compose d'alkylation, via une reaction de type retro-michael. Pour mettre au point les modifications structurales ulterieures des c-glycosides, nous avons synthetise le 2-phenoxy (2h)-5-6-dihydropyrane comme substrat modele en grande quantite et nous avons montre que la reaction de couplage a l'aide d'un complexe de palladium (0) s'effectuait egalement sur ce phenylglycoside simple. Les bases puriques et pyrimidiques reagissent sur le phenylglycoside , en presence de palladium (0), pour conduire de facon tres stereoselective a des n-glycopyranosides insatures. L'etude comparative par diverses techniques spectrales des isomeres et montre que: 1) la rmn est une methode de choix pour l'attribution de la configuration au niveau du carbone anomere (constante de couplage j#4##,#5#, c-5, effet noe). Cependant la methode de choix est l'effet noe, surtout si on est en presence d'un seul anomere, 2) en spectrometrie de masse, la technique fab associee a la technique (ms/ms) mike et cad-mike en ionisation chimique ou en presence de metaux alcalins (li#+, k#+, na#+ et rb#+) permet de definir pour chaque anomere une empreinte digitale specifique, 3) en dichroisme circulaire, les anomeres presentent un effet cotton positif et les anomeres un effet cotton negatif
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Chandrasekaran, Appavu. "Microbial and human metabolism of cardiac glycosides /." The Ohio State University, 1986. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487265555441466.
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Sperandio-Leclercq, Claire. "Etudes sur de nouvelles synthèses de glycosides." Paris 11, 2001. http://www.theses.fr/2001PA112289.
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Les oligosaccharides sont responsables d'un grand nombre de phénomènes biologiques. Or,la synthèse chimique de ces composés a pris un grand retard par rapport aux oligopeptides et oligonucléotides. A l'heure actuelle, la stéréosélectivité des assemblages chimiques est contrôlée uniquement par le substrat :contrôle électronique ou contrôle par participation d'un groupement voisin. Le but de cette thèse est de s'appuyer sur une information chirale, venant d'un réactif externe du type acide de Lewis, pour contrôler la stéréosélectivité de la réaction de glycosylation. Dans un premier temps, des tests ont été effectués à partir de différents donneurs (notamment en série 2-désoxyglucose ) plus ou moins complexants pour notre système, et avec le triflate de titane (IV)(TiCl4-4 AgOTf). Puis l'ajout d'un ligand chiral, en particulier le binaphtol, a été testé pour étudier une possible induction. Les résultats obtenus lors de cette première partie d'étude nous ont permis de mettre en évidence la synthèse b-sélective d'un glycoside dérivé du 2-désoxyglucose et du cyclohexanol. .Oligosaccharides play important roles in many biological events. The chemical synthesis of these compounds is however way behind that of oligopeptides and oligonucleotides, mainly because the assembling step creates a new asymmetric center (a or b linkage). At the present time, the stereoselectivity of this crucial step is controlled by the substrate (glycosyl donor), using either the electronic control (anomeric effect ) or control by a stereodirecting neighboring group. The goal of this thesis work concerns the use of a chiral reagent such as a Lewis acid in order to control the stereoselectivity of the glycosylation reaction. Tests were first carried out using different glycosyl donors (especially from the 2-deoxyglucose series) with anomeric ester groups of different chelating abilities, and with "titanium triflate" (IV) (TiCl4-4AgOTf) as a promotor. The possible influence of a chiral promotor was studied by the addition of chiral ligands, particularly binaphtol. .
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Kadi, Nadia. "Synthèse enzymatique de glycosides de composés d'arôme." Montpellier 2, 2001. http://www.theses.fr/2001MON20193.
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Rousseau, Cyril. "Synthèse de C-aryl glycosides par voie intramoléculaire." Phd thesis, Université d'Orléans, 2002. http://tel.archives-ouvertes.fr/tel-00168483.
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De par leurs propriétés biologiques et leur structure remarquables, les C-aryl glycosidesont suscité l'intérêt de nombreuses équipes de recherche. La création de la liaison Cglycosidique
de façon régio- et stéréocontrôlée constitue la principale difficulté de la synthèse
de ces composés.
L'objectif de ce travail est la mise au point d'une synthèse de C-aryl glycosides par voie
intramoléculaire. Nous avons développé une méthode de C-arylation intramoléculaire efficace
et stéréocontrôlée basée sur l'activation d'un glycoside de pentényle. Cette méthode a été
appliquée à la synthèse de dérivés de la Bergénine et a conduit à des produits de cyclisation
inattendus en série mannopyranose.
Pour généraliser la méthode, nous avons exploré plusieurs liens temporaires entre
l'aglycone et la copule glucidique : les agrafes de type arylsilyle nous ont permis de mettre au
point la première méthode de synthèse d'αlpha-C-aryl glucosides avec un stéréocontrôle total et de
bons rendements.
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Jiao, Hailong. "Synthetic studies on 2-amino-2-deoxy glycosides." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape7/PQDD_0002/NQ39546.pdf.
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Godage, Himali Yasmin. "Novel approaches to the synthesis of C-glycosides." Thesis, University of Oxford, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.401067.
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Sinnott, Deborah. "Synthesis of biologically important O- and C- glycosides." Thesis, University of Liverpool, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.428239.
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Gremyachinskiy, Dmitriy. "Total synthesis of aminomethyl c-glycosides : a thesis." Scholarly Commons, 2001. https://scholarlycommons.pacific.edu/uop_etds/544.
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Xu, Bixue. "Synthèse de Mono- et gem-Difluoro-Carba-glycosides." Paris 6, 2012. http://www.theses.fr/2012PA066305.
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Les carbasucres sont des analogues stables de sucres dans lesquels l’oxygène endocyclique a été remplacé par un groupement méthylène. Ces composés ont suscité un grand intérêt parmi les chimistes et les biochimistes en raison de leurs propriétés biologiques potentielles, en particulier comme inhibiteurs de glycosidases ou glycosyltransférases. Toutefois, le remplacement de l’oxygène endocyclique par un groupe méthylène présente l’inconvénient intrinséque de supprimer toute liaison hydrogène possible ainsi que l’effet exo-anomere, un facteur important dans l’orientation de la position relative entre deux résidus monosaccharides. Une façon de surmonter ce problème est de remplacer l’atome d’oxygène endocyclique par un groupe gem-difluorométhylène (-CF2-) dont les effets stéréoélectroniques espérés induiraient des biais conformationnels qui rétabliraient partiellement l’effet exo-anomérique ainsi qu’une région d’interaction avec des récepteurs potentiels. Dans ce travail, nous avons réalisé avec succès les premières synthèses de monofluoro- et gem-difluoro- carbaglycoside analogues de mono- et di- saccharides. Notre stratégie est basée sur une carbacyclisation induite par des acides de Lewis sur des glycosides insaturés avec rétention du groupe anomère. Deux stratégies pour la synthèse de monofluoro et gem-difluoro-carbaglycosides ont été mises en place comme illustré dans le plan rétrosynthétique Figure 1. Elles se différencient par l’étape d’introduction d’un atome de fluor avant ou après l’étape de carbocyclisationCarbasugars, as hydrolytically stable carbohydrate mimetics in which endocyclic oxygen atom has been replaced by a methylene group, have attracted great interest among chemists and biochemists due to their potential biological properties, particularly as inhibitors of glycosidase or glycosyltransferases. However, the replacement of the endocyclic oxygen by a methylene group has the inherent disadvantage to suppress any possible hydrogen bonding as well as exo-anomeric effect, an important factor in directing the relative positioning between two monosaccharide residues. One way to overcome this problem is to replace the endocyclic oxygen atom by gem-difluoromethylene group (-CF2-) which would hopefully induce conformational bias through stereoelectronic effects to partially restore the exo-anomeric effect as well as provide key polar region for the interaction with potential receptors. In this work, we successfully realized the first syntheses of mono- and gem-difluoro- carba-glycoside analogues of mono- and disaccharides. Our strategy is based on a Lewis acid induced carbocyclization of glycosides of an enolether possessing an electron-donating group with retention of the anomeric group. Two strategies for the synthesis of mono- and gem-difluoro-carbaglycosides were established as illustrated in the retrosynthetic plan Figure 1. They differentiate by the stage of introduction of fluorine atom: before or after the carbocyclization step
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Barbaud, Christel. "C-glycosides aromatiques. Etudes synthetiques de la ravidomycine." Paris 11, 1993. http://www.theses.fr/1993PA112304.
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La ravidomycine est un c-arylglycoside d'origine bacteriologique et possede une activite antitumorale et antibiotique interessante. La structure est caracterisee comme etant une unite 4-(4-o-acetyl-3,6-didesoxy-3-dimethylamino)-alpha-altropyranosyle liee a un noyau benzonaphthopyranone. Seule la configuration absolue reste a etre definie. La synthese d'un analogue possedant la partie monosaccharidique complete a partir du d-glucose avec un noyau aromatique simplifie tel que le benzene est alors envisagee afin de comparer les spectres de dichroisme circulaire avec le produit naturel. Le d-glucose est converti en plusieurs etapes en un glycal phenylsulfone. L'introduction de l'amine en c-3 est accomplie soit par une reaction sn#2 intermoleculaire, soit intramoleculairement grace a l'assistance de l'hydroxyle en c-4. L'echange de la sulfone par le tributyletain suivie du couplage catalyse au palladium(0) avec un halogenure d'aryle conduit au c-glycoside correspondant avec de bons rendements. Malheureusement, les essais de fonctionnalisation du glycal par hydroboration ne fournissent pas le stereoisomere desire en c-1 et c-2
35
Baryal, Kedar N. "Stereoselective Synthesis of Digitoxin and S-Linked Glycosides." University of Toledo / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1438174529.
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Dubois, Eric. "Synthese de c-glycosides assistee par le palladium." Paris 11, 1991. http://www.theses.fr/1991PA112011.
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De nombreuses substances naturelles isolees de microorganismes et de plantes et douees d'activites biologiques variees possedent dans leur structure un motif c-aryl-glycosidique. Lors de ce travail, nous montrons qu'un couplage catalyse par le palladium entre un tri-n-butylstannyl-glucal et un halogenure aromatique permet d'obtenir le c-aryl-glucal correspondant. Sa fonctionnalisation regio- et stereoselective par hydroboration, epoxydation et reduction conduit aux c-beta-arylglucosides avec d'excellents rendements. Une extension au chlorures d'acides et aux halogenures de benzyle, d'allyle et de vinyle est decrite. Cette methodologie a ete appliquee a la synthese de squelette des papulacandines et de la chaetiacandine
37
Bouhajib, Mohammed. "Analyse des glycosides de Picea Mariana (Mill.) B.S.P." Thèse, Chicoutimi : Université du Québec à Chicoutimi, 1992. http://theses.uqac.ca.
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Cox, Jason M. "From C-glycosides to fused polycyclic ethernatural products." Diss., The University of Arizona, 2002. http://hdl.handle.net/10150/280019.
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A highly efficient and flexible approach to fused polycyclic ethers that couples the synthesis of C-glycosides with enol ether-olefin ring closing metathesis (RCM) and/or acid mediated cyclizations has been presented. We have developed a single flask, enol ether oxidation, carbon-carbon bond forming approach to the generation of C-glycosides. We have been successful in the formation of both alpha- (Table 1.11) and beta- (Table 1.10) C-glycosides from a single glycosyl donor (glycal anhydride). Both Schrock's Mo catalyst 123 and the 2nd generation Grubbs' Ru catalyst 124 have been used in enol ether-olefin RCM reactions to generate alpha-substituted enol ethers. PPTS, pyridine, and heat have been effective in generating alpha-unsubstituted enol ethers. Our ability to couple the formation of C-glycosides with RCM or acid mediated cyclizations directed our attention to the use of this strategy in the synthesis of fused polycyclic ether natural products. We initially targeted the synthesis of hemibrevetoxin B (2). We have completed a formal total synthesis of ±-hemibrevetoxin B to Mori intermediate 167 in 21 overall steps and in 3.9% yield from the Danishefsky-Kitahara diene 74. Our success in the formal total synthesis of hemibrevetoxin B gave us great confidence to pursue the synthesis of gambierol 6. We have synthesized the A-D ring system 283 in 20 steps and in 4.2% overall yield. The FG ring system 302 was synthesized in 9 steps and in 13% overall yield. We have been successful in the generation of C-glycosides and have been able to apply them in the formation of fused polycyclic ether natural products.
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Mensah, Enoch Akuamoah. "Palladium and nickel catalyzed stereoselective formation of glycosides." Diss., University of Iowa, 2011. https://ir.uiowa.edu/etd/2745.
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The development of new glycosylation methods for the stereoselective synthesis of β-glycosides in the absence of the traditional C(2)-ester participatory group on glycosyl donors using cationic palladium catalyst Pd(PhCN)2(OTF)2, as well as the formation of 1.2-cis-2-amino glycosides via cationic nickel catalyzed α-selective glycosylation using C(2)-N-substituted benzylidene D-glucosamine and galactosamine trichloroacetimidates is described. In the formation of β-glycosides, the process relies on the ability of the cationic palladium catalyst Pd(PhCN)2(OTF)2, generated in situ from Pd(PhCN)2Cl2 and AgOTf, to direct β-selectivity. The new glycosylation reaction is highly β-selective, and proceeds under mild conditions with 1-2 % of catalyst loading. This β-glycosylation protocol has been applied to a number of glucose donors with benzyl, allyl and p-methoxybenzyl groups incorporated at the C(2)-position, as well as xylose and quinovose donors to prepare various disaccharides and trisaccharides with good to excellent β-selectivity. Mechanistic studies suggest that the major operative pathway is likely a seven-membered ring intermediate, wherein the cationic palladium complex coordinates to both the C(1)-imidate nitrogen and the C(2)-oxygen of the trichloroacetimidate donor. Formation of this seven-membered ring complex directs the selectivity, leading to the formation of β-glycosides. In the formation of 1,2-cis-2-amino glycosides, the method relies on the nature of nickel-ligand complex to control α-selectivity. The reactive sites of the nucleophiles as well as the nature of the protecting groups have little effect on the alpha-selectivity. This protocol is mild, highly α-selective, and has been successfully applied towards the stereoselective synthesis heparin disaccharides, α-GluNAc/GalNAc glycoconjugates, and GPI anchor pseudodisaccharides. The nickel catalyzed glycosylation protocol has also been successfully applied to both disaccharide donors and acceptors to provide the corresponding oligosaccharides in high yields, and with excellent levels of α-selectivity. Mechanistic studies suggests that the presence of the substituted benzylidene functionality at the C(2)-amino position of glycosyl donors is crucial for the high α-selectivity observed in the coupling products.
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Berven, Leise Ann. "The carbonate catalyzed anomerization of protected 2, 4-dinitrophenyl glucopyranosides : a mechanistic study." Thesis, University of British Columbia, 1987. http://hdl.handle.net/2429/26167.
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The mechanism of the carbonate catalyzed conversion of 2,4-dinitrophenyl 2 ,3 ,4,6-tetra-0-acetyl-β-D-glucopyranoside in DMSO to an equilibrated
mixture of the α- and β-glycosides has been investigated using a variety of techniques. Pseudo-first-order rate constants (k) measured for the anomerization of the parent substrate and the 1-deuterio substrate
indicated a secondary deuterium isotope effect of kH/kD = 1.09 ± 0.06. Pseudo-first-order rate constants measured for several deoxy and deoxyfluoro derivatives of the parent sugar showed that the deoxyfluoro sugars react at least as fast as the parent sugar whereas the deoxy sugars reacted more slowly. In addition to the 2,4-dinitro-phenyl glucoside, 2,6-dinitrophenyl glucoside also was found to anomerize, yet attempts to exchange the 2,4-dinitrophenolate groups of the glucoside with added 2,6-dinitrophenolate anion and vice versa were unsuccessful. Exchange of the proton at the anomeric carbon with a deuteron also does not occur when the anomerization is performed in the presence of a deuteron source (and vice versa). Exchange of the glucosyl residue was observed, however, when the 1-deuterio substrate was anomerized in the presence of non-deuterated 2,3,4,6-tetra-O-acetyl-D-glucopyranose. ¹H-n.m.r. of the 2,4-dinitrophenyl α-glucoside isolated from this reaction indicated that the a-glucoside possessed only 50% of the deuterium label, at the anomeric center. These results along with the observation of a Meisenheimer intermediate indicate that the anomerization proceeds via nucleophilic aromatic substitution and as such is novel mechanism for glycoside anomerization.Science, Faculty of
Chemistry, Department of
Graduate
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Walker, Joel R. "Part 1. Synthesis of n-15 lab[e]led (R)-deuterioglycine. Part 2. Synthesis of carbon-Linked analogs of retinoid glycoside conjugates." Columbus, Ohio : Ohio State University, 2003. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1060698580.
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Thesis (Ph. D.)--Ohio State University, 2003.Title from first page of PDF file. Document formatted into pages; contains xxiii, 190 p.; also includes graphics. Includes abstract and vita. Advisor: Robert W. Curley, School of Pharmacy. Includes bibliographical references (p. 175-190).
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REKAI, EL DJOUHAR. "Synthese selective de c-glycosides par cyclisation radicalaire : preparation de c-glycosides cycliques complexes, de c-disaccharides et de trisaccharides mixtes." Paris 6, 1997. http://www.theses.fr/1997PA066525.
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Le travail effectue au cours de la these s'inscrit dans le cadre des activites de recherche du laboratoire du professeur pierre sinay. Il porte sur l'etablissement de nouvelles methodes de synthese de c-glycosides. Nos recherches, se sont en premier lieu, tournees vers la synthese de c-glycosides cycliques tres particuliers, obtenus par cyclisation radicalaire a l'aide de l'iodure de samarium ii. Au cours de cette recherche, des resultats inattendus lors de reactions de cyclisation radicalaires sur des cycles aromatiques, ainsi que des reactions de cyclisation de type 5-exo-trig, se sont reveles tres interessants. Il est en fait envisageable que cette generation de nouveaux c-glycosides cycliques complexes, donnent acces apres quelques modifications chimiques a de longues chaines carbonees hautement fonctionnalisees, pouvant etre incorporees notamment a la synthese de macrolides. Nous nous sommes egalement interesses a la synthese de c-disaccharides contenant du l-fucose et du d-galactose par emploi de deux types d'agrafes : - agrafe au silicium, - agrafe paramethoxybenzylacetalique. Apres comparaison des methodes, il semble que ces deux types d'agrafages se valent l'un l'autre. De plus, nous avons montre que la stereochimie des c-disaccharides contenant du l-fucose et du d-galactose, est fonction non seulement de la nature des sucres (galactose ou fucose), mais egalement de la nature des groupements protecteurs, du type d'agrafage employe et de la position d'agrafage utilisee. Des regles simples de cyclisation concernant le l-fucose et le d-galactose ont pu etre etablies. Dans un troisieme temps, nous avons applique ces regles a la synthese de l'analogue carbone du determinant antigenique h du groupe sanguin humain o. Cet analogue carbone a ete modifie puis teste dans des reactions de o-glycosylation afin d'analyser sa reactivite chimique et former des trisaccharides mixtes.
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Fontelle, Nathalie. "Mise au point d'une nouvelle voie d'accès aux iminosucres C-glycosides à six et sept chaînons dérivés du D-glucopyranose et de la N-acétyl-D-glucosamine." Thesis, Poitiers, 2013. http://www.theses.fr/2013POIT2334/document.
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Les iminosucres, analogues de sucres dont l'oxygène intracyclique a été remplacé par un azote, constituent une classe importante de mimes de sucres. Introduire une chaîne alkyle sur le carbone pseudo-anomérique donne accès à une classe importante d'iminosucres, les iminosucres C-glycosides, qui peuvent être des inhibiteurs de glycosidases puissants et sélectifs.Le principal défi associé à la synthèse d'iminosucres C-glycosides est la mise au point de voies de synthèse efficaces et applicables à tous types de sucres permettant ainsi d'accéder à une grande diversité de synthons et d'accélérer la découverte de molécules d'intérêt biologique.Ce travail de thèse a consisté dans un premier temps à élaborer une synthèse efficace et convergente d'iminosucres C-glycosides à six et sept chaînons, à partir d'un précurseur commun, le 6-azido-6-désoxy-2,3,4-tri-O-benzyl-D-glucopyranose. Cette nouvelle méthode implique une réaction tandem Staudinger/Aza-Wittig ainsi qu'une isomérisation de cycle d'azépanes stéréocontrolée.La deuxième partie de ce manuscrit traite de l'extension de cette méthodologie à la synthèse de nouveaux D- et L-iminosucres C-glycosides à six chainons mimes de la N-acétyle-D-glucosamine.La dernière partie de ce travail a été consacrée à la synthèse d'iminosucres-aza-couronnes, qui constituent un nouveau type de récepteur moléculaire. L'étude de leur capacité à complexer des métaux a été effectuée par des techniques de RMN ou fluorimétrie et a donné des résultats prometteursIminosugars, sugar analogs in which the endocyclic oxygen has been replaced by a nitrogen, constitute a major class of sugar mimetics. Introducing an alkyl chain at the pseudoanomeric carbon position leads to another class of important iminosugars, the iminosugars C-glycosides that can be potent and selective glycosidase inhibitors. The main challenge associated with iminosugars C-glycosides synthesis is currently the design of efficient and general routes applicable to any starting sugar and enabling introduction of structural diversity from advanced synthons to accelerate the discovery of biologically relevant molecules.The first part of this work focused on the development of an efficient and convergent synthesis of six and seven membered iminosugars C-glycosides from a common 6-azido-6-deoxy-2,3,4-tri-O-benzyl-D-glucopyranose precursor. This new methodology involves a highly diastereoselective tandem ring enlargement/alkylation and a stereocontrolled ring contraction.The second part of the thesis delt with the extension of the methodology to access six-membered D- and L-iminosugars C-glycosides derived from N-acetyl-D-glucosamine.The third part of this work was devoted to the synthesis of iminosugar-aza-crowns, which constitute a new type of molecular receptors, using the synthetic route developed in the first part. The ability of these compounds to complex metals was studied either by NMR or fluorimetric techniques and showed promising results
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Schuff, Brandon Patrick. "Palladium (II)-catalyzed stereoselective formation of [alpha]-O-glycosides." Thesis, Montana State University, 2007. http://etd.lib.montana.edu/etd/2007/schuff/SchuffB0507.pdf.
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Payne, Andrew Hele. "Stereoselective cyclisation reactions for the synthesis of c-glycosides." Thesis, Imperial College London, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.267487.
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Tsoukala, Georgia. "Design and Synthesis of Glycosides as Potential Anticancer Agents." Thesis, University College London (University of London), 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.509312.
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Meenune, Mutita. "Retention and release of flavour glycosides in extruded maize." Thesis, University of Nottingham, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.311766.
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Lu, Jun. "The total synthesis of C-glycosides by cycloaddition reactions." Scholarly Commons, 2002. https://scholarlycommons.pacific.edu/uop_etds/2709.
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C-glycosides play important roles in biological processes. Synthetic efforts to prepare carbohydrate mimetics—C-glycosides were undertaken. This thesis introduces the total syntheses of C-glycosides by starting with two cycloaddition reactions. The [4+2] reaction of 1,3-pentadiene with glyoxylic acid and subsequent reactions afforded five C-pyranosides. The [4+3] cycloaddition of furan and pentachloroacetone and subsequent reactions provided C-furanosides and C-pyranosides. A new type of C-disaccharide mimetic coupled by an amide bond was synthesized. This thesis describes how bromolactonization, stereoselective Beckmann rearrangement and stereoselective dechlorination were used in a new way to fulfill the research goal. This dissertation provides efficient ways to synthesize carborhydrate mimetics from cheap, easily available non-natural materials.
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Kometani, Takashi. "Studies on Biosynthesis of Novel Glycosides and Their Utilization." Kyoto University, 1994. http://hdl.handle.net/2433/160850.
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本文データは平成22年度国立国会図書館の学位論文(博士)のデジタル化実施により作成された画像ファイルを基にpdf変換したものであるKyoto University (京都大学)
0048
新制・論文博士
博士(農学)
乙第8742号
論農博第1954号
新制||農||692(附属図書館)
学位論文||H6||N2763(農学部図書室)
UT51-94-Z493
(主査)教授 佐々木 隆造, 教授 外村 辨一郎, 教授 伏木 亨
学位規則第4条第2項該当
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Dahl, Russell Scott. "Synthesis of aminoglycosides and amino-C-glycosides from glycals /." Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2004. http://wwwlib.umi.com/cr/ucsd/fullcit?p3158462.
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