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Добірка наукової літератури з теми "Anomeric position"

Автор: Grafiati

Опубліковано: 25 травня 2024

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Статті в журналах з теми "Anomeric position"

Filho, João Rufino de Freitas, Jucleiton José Rufino de Freitas, Pedro Ramos de Souza Neto, Fabrícia Aparecida Marques de Souza, Adiel Soares Ferreira, Anne Gabrielle Marques da Silva, Francisco Antonio Mabson Henrique Lopes, Marcilio Martins de Moraes, Clécio Souza Ramos, and Ronaldo Nascimentos de Oliveira. "Recent Advances Related to Anomeric and Exo-anomeric Effects in Carbohydrate Chemistry." International Research Journal of Pure and Applied Chemistry 24, no. 5 (September 22, 2023): 95–110. http://dx.doi.org/10.9734/irjpac/2023/v24i5830.

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The anomeric effect in carbohydrate chemistry is known as the interaction between the OHd substituent at the anomeric position to favor an axial orientation rather than an equatorial one, despite the increased 1,3-diaxial interactions. In the anomeric effect, a sugar ring is stabilized by an electronegative substituent at the C1 carbon, also known as the anomeric carbon. The stabilization is thought to result from interactions between lone electron pairs on oxygen and a C1 antibonding orbital. On the other hand, the anomeric effect can be of two types: endo-anomeric and exo-anomeric. The effect is called endo-anomeric when the lone pair comes from the oxygen atom in the sugar ring and exo-anomeric when the lone pair comes from oxygen in a substituent on C1. Several factors influence the anomeric effect. In this way, this review aims to describe the recent advances in main theories, observations, and advances achieved in the last decades related to the anomeric effect. GRAPHICAL ABSTRACT

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Jabbari, Hadi. "Selective Anomeric Deacetylation of Per-Acetylated Carbohydrates Using (i-Pr)3Sn(OEt) and Synthesis of New Derivatives." Journal of Molecular Biology Research 10, no. 1 (November 30, 2020): 166. http://dx.doi.org/10.5539/jmbr.v10n1p166.

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In this study natural carbohydrates such as glucose, galactose, xylose, fructose andlactose, are acetylated by acetic anhydride and sodium acetate catalyst. Anomeric configuration is deacetylated by (i-Pr)3Sn(OEt)as a catalyst, an easy synthetic regioselective deacetylation of full acetylated carbohydrates using (i--Pr)3Sn(OEt) is described. The acetylated carbohydrates reacted with HBr (solution in AcOH, 32 wt.%) for the bromination of anomeric position. The synthesis oxazaphosphorine, and bromo hexa alkyl Methylsulfonate derivatives from anomeric position of carbohydrates was reacted. FT IR, 1H, 13C NMR, 31PNMR spectroscopy techniques were employed to examine the synthesized compounds.

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Lee, Sang Jun, Dale E. A. Lewis, and Sankar Adhya. "Induction of the Galactose Enzymes in Escherichia coli Is Independent of the C-1-Hydroxyl Optical Configuration of the Inducer d-Galactose." Journal of Bacteriology 190, no. 24 (October 17, 2008): 7932–38. http://dx.doi.org/10.1128/jb.01008-08.

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ABSTRACT The two optical forms of aldohexose galactose differing at the C-1 position, α-d-galactose and β-d-galactose, are widespread in nature. The two anomers also occur in di- and polysaccharides, as well as in glycoconjugates. The anomeric form of d-galactose, when present in complex carbohydrates, e.g., cell wall, glycoproteins, and glycolipids, is specific. Their interconversion occurs as monomers and is effected by the enzyme mutarotase (aldose-1-epimerase). Mutarotase and other d-galactose-metabolizing enzymes are coded by genes that constitute an operon in Escherichia coli. The operon is repressed by the repressor GalR and induced by d-galactose. Since, depending on the carbon source during growth, the cell can make only one of the two anomers of d-galactose, the cell must also convert one anomer to the other for use in specific biosynthetic pathways. Thus, it is imperative that induction of the gal operon, specifically the mutarotase, be achievable by either anomer of d-galactose. Here we report in vivo and in vitro experiments showing that both α-d-galactose and β-d-galactose are capable of inducing transcription of the gal operon with equal efficiency and kinetics. Whereas all substitutions at the C-1 position in the α configuration inactivate the induction capacity of the sugar, the effect of substitutions in the β configuration varies depending upon the nature of the substitution; methyl and phenyl derivatives induce weakly, but the glucosyl derivative does not.

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Ölgen, Süreyya, and Chung K. Chu. "Synthesis And Antiviral Activity Of 2'-Deoxy-2'-Fluoro-L-Arabinofuranosyl 1,2,3-Triazole Derivatives." Zeitschrift für Naturforschung B 56, no. 8 (August 1, 2001): 804–11. http://dx.doi.org/10.1515/znb-2001-0814.

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The title compounds were prepared by building up the triazole ring at the anomeric position via the glycosyl azides 5 a,b. The anomeric configurations of these nucleosides were assigned by using 1H, 13C and NOESY NMR spectroscopy. The synthesized nucleosides were evaluated against HIV-1 and HBV

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Estevez, Juan C., Helen Ardron, Mark R. Wormald, David Brown, and George W. J. Fleet. "Spirocyclic peptides at the anomeric position of mannofuranose." Tetrahedron Letters 35, no. 47 (November 1994): 8889–90. http://dx.doi.org/10.1016/s0040-4039(00)78526-1.

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Tanzi, Lisa, Marina Simona Robescu, Sara Marzatico, Teresa Recca, Yongmin Zhang, Marco Terreni, and Teodora Bavaro. "Developing a Library of Mannose-Based Mono- and Disaccharides: A General Chemoenzymatic Approach to Monohydroxylated Building Blocks." Molecules 25, no. 23 (December 7, 2020): 5764. http://dx.doi.org/10.3390/molecules25235764.

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Regioselective deprotection of acetylated mannose-based mono- and disaccharides differently functionalized in anomeric position was achieved by enzymatic hydrolysis. Candida rugosa lipase (CRL) and Bacillus pumilus acetyl xylan esterase (AXE) were immobilized on octyl-Sepharose and glyoxyl-agarose, respectively. The regioselectivity of the biocatalysts was affected by the sugar structure and functionalization in anomeric position. Generally, CRL was able to catalyze regioselective deprotection of acetylated monosaccharides in C6 position. When acetylated disaccharides were used as substrates, AXE exhibited a marked preference for the C2, or C6 position when C2 was involved in the glycosidic bond. By selecting the best enzyme for each substrate in terms of activity and regioselectivity, we prepared a small library of differently monohydroxylated building blocks that could be used as intermediates for the synthesis of mannosylated glycoconjugate vaccines targeting mannose receptors of antigen presenting cells.

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Hain, Julia, Patrick Rollin, Werner Klaffke, and Thisbe K. Lindhorst. "Anomeric modification of carbohydrates using the Mitsunobu reaction." Beilstein Journal of Organic Chemistry 14 (June 29, 2018): 1619–36. http://dx.doi.org/10.3762/bjoc.14.138.

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The Mitsunobu reaction basically consists in the conversion of an alcohol into an ester under inversion of configuration, employing a carboxylic acid and a pair of two auxiliary reagents, mostly triphenylphosphine and a dialkyl azodicarboxylate. This reaction has been frequently used in carbohydrate chemistry for the modification of sugar hydroxy groups. Modification at the anomeric position, leading mainly to anomeric esters or glycosides, is of particular importance in the glycosciences. Therefore, this review focuses on the use of the Mitsunobu reaction for modifications of sugar hemiacetals. Strikingly, unprotected sugars can often be converted regioselectively at the anomeric center, whereas in other cases, the other hydroxy groups in reducing sugars have to be protected to achieve good results in the Mitsunobu procedure. We have reviewed on the one hand the literature on anomeric esterification, including glycosyl phosphates, and on the other hand glycoside synthesis, including S- and N-glycosides. The mechanistic details of the Mitsunobu reaction are discussed as well as this is important to explain and predict the stereoselectivity of anomeric modifications under Mitsunobu conditions. Though the Mitsunobu reaction is often not the first choice for the anomeric modification of carbohydrates, this review shows the high value of the reaction in many different circumstances.

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Wang, Ruibo, Kaimin Cai, Hua Wang, Chen Yin, and Jianjun Cheng. "A caged metabolic precursor for DT-diaphorase-responsive cell labeling." Chemical Communications 54, no. 38 (2018): 4878–81. http://dx.doi.org/10.1039/c8cc01715h.

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de Robichon, Morgane, Andrea Bordessa, Maciej Malinowski, Jacques Uziel, Nadège Lubin-Germain, and Angélique Ferry. "Access to C-aryl/alkenylglycosides by directed Pd-catalyzed C–H functionalisation of the anomeric position in glycal-type substrates." Chemical Communications 55, no. 78 (2019): 11806–8. http://dx.doi.org/10.1039/c9cc05993h.

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Sandoval, M., P. Hoyos, A. Cortés, T. Bavaro, M. Terreni та M. J. Hernáiz. "Development of regioselective deacylation of peracetylated β-d-monosaccharides using lipase from Pseudomonas stutzeri under sustainable conditions". RSC Adv. 4, № 98 (2014): 55495–502. http://dx.doi.org/10.1039/c4ra10401c.

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An efficient deacylation of peracetylated pyranosides has been developed in different biosolvents, catalyzed by Pseudomonas stutzeri lipase, which displayed regiospecific activity towards the anomeric position.

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Більше джерел

Дисертації з теми "Anomeric position"

Hammoud, Jana. "Evaluation des complexes dirhodium (II) tétraacétate-Carbène-N-Hétérocyclique pour la décomposition de diazoesters et applications en glycochimie Functionalization of GlucoPyranosides at position 5 by 1,5 C–H insertion of Rh(II)-Carbenes: Dramatic influence of the anomeric configuration." Thesis, Normandie, 2020. http://www.theses.fr/2020NORMIR03.

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Ces travaux de thèse ont concerné l’étude des propriétés catalytiques des complexes Rh₂L₄.NHC vis-à-vis des diazo esters, et leur application dans le domaine de la glycochimie. Nous avons tout d’abord développé une procédure expérimentale reproductible pour la préparation de ces complexes organométalliques. Par ailleurs, nous avons montré que le complexe Rh₂(OAc)₄.IMes était capable de décomposer de manière chimiosélective différentes familles de diazo esters, ouvrant ainsi la possibilité de la conception d’un système catalytique commutable. Dans le domaine de la glycochimie, les complexes Rh₂L₄.NHC ont permis d’amélioré les conditions expérimentales de la réaction de quaternarisation de la position anomèrique par fonctionnalisation de sa liaison C-H. Enfin, la quaternarisation de la position 5 de pyranosides par insertion 1,5 C-H d’un métallo-carbène de Rh(II) ancré sur la position primaire a été développée
This work deals with the study of the catalytic properties of Rh₂L₄.NHC complexes towards diazoesters, and their application in the field of glycochemistry. We first developed a reproducible synthetic procedure for the preparation of these organometallic complexes. Furthermore, we have shown that the Rh₂(OAC)₄.IMes complexe was inducing the chemoselective decomposition of diazo esters, depending on their electronic properties. This unprecedented property opened the way to a switchable catalytic system. In the field of glycochemistry, the Rh₂L₄.NHC complexes made possible to improve the experimental conditions for the quaternization reaction of the anomeric position by C-H bond functionalization. Finally, the quaternization of position 5 of pyranosides by 1,5 C-H insertion of a Rh (II) metallo-carbene anchored on the primary position was developed

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Gavel, Marine. "Nouveaux développements chimiques pour la conception d'inhibiteurs de glycosyltransférases Carbene-mediated quaternarization of the anomeric position of carbohydrates: synthesis of allylic ketopyranosides, access to the missing α-gluco and β-manno stereoisomers, and preparation of quaternary 2-deoxy 2-acetamido sugars Regio- and chemoselective deprotection of primary acetates by zirconium hydrides". Thesis, Normandie, 2019. http://www.theses.fr/2019NORMIR09.

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Ces travaux de thèse ont été consacrés au développement de voies de synthèses permettant l'obtention de structures cétopyranosidiques modulables en vue du développement d'outils chimiques dédiés à la glycobiologie. Nous avons tout d'abord travaillé au déploiement de séquences réactionnelles ouvrant l'accès à des glycophosphomimétiques possédant une unité triméthylène phosphonate. Par ailleurs, nous avons mis au point une nouvelle méthode de déprotection régiosélective de la position primaire de sucres peracétylés utilisant un mélange bimétallique de zirconium et d'aluminium permettant de faciliter l'accès à des (oligo)saccharides ayant des liens glycosidiques α-1,6. Enfin, en combinant ces développements chimiques, nous avons souhaité préparer des inhibiteurs potentiels de glycosyltransférases bi-substrats possédant à la fois un mime du groupe partant du donneur de glycosyle et de l'accepteur connectés à la position anomère quaternaire des cétopyranosides
The goal of this project is to challenge the hypothesis that a non-natural sugar with a quaternary anomeric position might be the central core of a powerful and selective inhibitor of glycosyltransferase. Our design is relying on a key quaternary anomeric centre that provide the unique opportunity to incorporate in a single innovative structure the acceptor, the donor and the leaving group released during the formation of the glycosidic linkage. The functionnalization of the ketopyranosides that will be at the centre of this new class of potent glycosyltransferases inhibitors rely on original synthetic methods allowing introduction of a trimethylene phosphonate and regioselective deprotection of primary position of acetylated sugars for building alpha-1,6 glycosidic linkages

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Частини книг з теми "Anomeric position"

Mébarki, K., M. Gavel, A. Joosten, T. Lecourt, and F. Heis. "Carbene-Mediated Quaternarization of the Anomeric Position of Carbohydrates." In Carbohydrate Chemistry, 75–86. Boca Raton : CRC Press, 2020. | Series: Proven synthetic methods ; volume 5: CRC Press, 2021. http://dx.doi.org/10.1201/9781351256087-11.

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Frey, Perry A., and Adrian D. Hegeman. "Glycosyl Group Transferases." In Enzymatic Reaction Mechanisms. Oxford University Press, 2007. http://dx.doi.org/10.1093/oso/9780195122589.003.0016.

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Glycosyl group transfer underlies the biosynthesis and breakdown of all nucleotides, polysaccharides, glycoproteins, glycolipids, and glycosylated nucleic acids, as well as certain DNA repair processes. Glycosyl transfer consists of the transfer of the anomeric carbon of a sugar derivative from one acceptor to another, as in, which describes the transfer of a generic pyranosyl ring between nucleophilic atoms :X and :Y of acceptor molecules. The stereochemistry at the anomeric carbon is not specified in eq. 12-1, but the leaving group occupies the axial position in an α-anomer or the equatorial position in a β-anomer. The overall transfer can proceed with either retention or inversion of configuration. In biochemistry, the acceptor atoms can be oxygen, nitrogen, sulfur, or in the biosynthesis of C-nucleosides even carbon. The great majority of biological glycosyl transfer reactions involve transfer between oxygen atoms of different acceptor molecules. Enzymes catalyzing glycosyl transfer are broadly grouped according to whether the acceptor :Y–R2 in is water or another molecule. In the actions of glycosidases, the acceptor is water, and glycosyl transfer results in hydrolysis of a glycoside, a practically irreversible process in dilute aqueous solutions. In the action of glycosyltransferases, the acceptors are molecules with hydroxyl, amide, amine, sulfhydryl, or phosphate groups. The simplest nonenzymatic glycosyl transfer reaction is the hydrolysis of a glycoside, and early studies revealed the fundamental fact that glycosides are much less reactive toward hydrolysis in basic solutions than in acidic solutions. This fact underlies much that is known about the mechanism of glycosyl transfer; that is, the anomeric carbon of a glycoside is remarkably unreactive toward direct nucleophilic attack, but it becomes reactive when one of the oxygens is protonated by an acid, as illustrated in fig. 12-1 for the acid-catalyzed hydrolysis of a generic glycoside. The reaction by both mechanisms in fig. 12-1 proceeds by pre-equilibrium protonation of the glycoside to form oxonium ion intermediates, which are subject to hydrolysis by water. The two mechanisms in fig. 12-1 are of interest. The mechanism proceeding through exocyclic cleavage of the glycoside has historically been regarded as the more likely, and for this reason, the route through endocyclic cleavage has received little consideration.

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Davis, Benjamin G., and Antony J. Fairbanks. "Chemical disaccharide formation." In Carbohydrate Chemistry. Oxford University Press, 2002. http://dx.doi.org/10.1093/hesc/9780198558330.003.0007.

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This chapter considers a crucial step in the synthesis of any oligosaccharide, namely the linking of two monosaccharide precursors by the construction of the glycosidic linkage. It talks about how glycosidic bond formation is achieved by the operation of the displacement of a leaving group at the anomeric position of one sugar, termed the glycosyl donor. It also defines the terms glycosylation reaction, glycosyl donor, and glycosyl acceptor. The chapter highlights the problems of regio- and stereochemistry inherent in the synthesis of di- and oligosaccharides. It explains how to synthesise and activate the most commonly used classes of glycosyl donors.

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David, Serge. "ABH and related blood group antigens." In The Molecular and Supramolecular Chemistry of Carbohydrates: Chemical Introduction to the Glycosciences, 265–76. Oxford University PressOxford, 1997. http://dx.doi.org/10.1093/oso/9780198500476.003.0016.

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Abstract Antigenic determinants are trisaccharide A, 16.1, trisaccharide B, 16.2, and disaccharide H, 16.3. The reader will recognize that trisaccharides A and B are glycosidation products of disaccharide H at position 3 of galactose by an N-acetylgalactosamine unit and a galactose unit, respectively, and in the two cases by an a-anomeric linkage. Thus the A and B determinants differ only by their substitution at position 2 on their D-galacto non-reducing terminal end, N-acetyl in the A substance, and hydroxyl in the B substance. Note as well the participation of the deoxygenated sugar fucose and finally the α-1,2-cis bonds, not as common as the β-1,2-trans bonds in glycoconjugates. These disaccharides and trisaccharides are located at the non-reducing terminal ends of the oligosaccharide chains of glycoproteins and glycolipids and possibly their branches. Blood group A individuals have the A determinant and a certain quantity of H, but not B, whereas those of blood group B have B and H but not A, in a symmetrical fashion. Blood group O individuals only have the H determinant. This immediately implies an incomplete biosynthesis due to the absence or the non-expression of genes which code for the A or B glycosyltransferases. Carrier molecules are found in the membrane of erythrocytes and determinants are exposed towards the outside. In blood group A individuals, the B molecule is recognized as a foreign substance and gives rise to the appearance of anti-B antibodies. For the same reason, anti-A antibodies are found in people with blood group B and and anti-A and anti-B antibodies in those with blood group 0. Problems observed during blood transfusions were due to the presence of these antibodies. Thus the donor of blood group A who has anti-B antibodies causes the agglutination of erythrocytes in a receiver of blood group B. ABH antigens are also present on cell surfaces in the majority of organs and in secretions. Their presence is one of the major causes of the failure of organ transplants between a donor and receiver of different blood groups. For this reason, they should also be named histo-blood group antigens.

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David, Serge. "Conformation of monosaccharides and their derivatives." In The Molecular and Supramolecular Chemistry of Carbohydrates: Chemical Introduction to the Glycosciences, 17–41. Oxford University PressOxford, 1997. http://dx.doi.org/10.1093/oso/9780198500476.003.0002.

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Abstract The conformations of the oxane ring (tetrahydropyran) of pyranoses are the same as those of cyclohexane. The carbons are numbered starting with the hemiacetal carbon, referred to as anomeric. This convention is not in keeping with the rule for numbering heterocycles where number one is assigned to the heteroatom (in this case, the oxygen). The oxane is represented with carbons 1, 3, and 5 in the horizontal plane, carbons l and 4 in the plane of the vertically positioned paper, and the cyclic oxygen behind the paper. To the viewer situated above the ring the numbers appear clockwise. In a pyranose sugar, all the carbons, or nearly all of them, are substituted, but for practical purposes, one only needs to introduce a substituent R to an arbitrary site. Equation (2.1) then represents the extension of the classic conformational equilibrium of cyclohexane to pyranoses.

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Michalski, Jean-Claude, and Catherine Alonso. "HPLC of oligosaccharides and glycopeptides." In HPLC of Macromolecules, 171–202. Oxford University PressOxford, 1998. http://dx.doi.org/10.1093/oso/9780199635719.003.0007.

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Abstract Protein glycosylation is a major modification which occurs after translation. Carbohydrate chains (glycans) may be found linked to proteins in different ways with respect to the kind of amino acids that are modified. Commonly, carbohydrate chains may be found 0-linked to serine or threonine residues, or N-linked to proteins at Asn-X-Ser (Thr) sequons (1, 2). Glycans present a great chemical diversity which results in the ability of monosaccharides to combine with each other in a variety of ways differing in sequence, anomery(o: or 13) position of linkages, branching points, and chain length. Additive substitution by sulfate. phosphate, acetyl, or methyl groups of the different monosaccharides considerably increase the structural diversity. There are four major classes of N-linked glycans: oligomannose type (high-mannose type), so-called N-acety1lactosaminic type (complex type), polylactosaminic type and hybrid type (3) (Figure I). O-glycans present a greater diversity and are generally subdivided into different classes according to common cores (4) (Figure 2).

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