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Glycosyl Donor (glycosyl + donor)
Selected AbstractsRelevance of the Glycosyl Donor to the Regioselectivity of Glycosidation of Primary-Secondary Diol Acceptors and Application of These Ideas to in situ Three-Component Double Differential Glycosidation.CHEMINFORM, Issue 4 2006Clara Uriel No abstract is available for this article. [source] Going to Extremes: "Super" Armed Glycosyl Donors in Glycosylation ChemistryCHEMISTRY - A EUROPEAN JOURNAL, Issue 27 2007Henrik Abstract This concept article gives an overview of stereoelectronic effects in monosaccharide systems and how these can be used to dramatically enhance the reactivity of glycosyl donors in oligosaccharide synthesis. [source] Synthesis, NMR, and Conformational Studies of Cyclic Oligo-(1,6)-,- D -Glucosamines,EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 13 2010Marina L. Gening Abstract The first synthesis of a series of homologous cyclic oligo-(1,6)-,- D -glucosamines consisting of two to seven residues and representing a new type of functionalized cyclic oligosaccharides is reported. Remarkably high yields of the studied macrocyclization reaction irrespective of the length of the acyclic precursors were observed. In the case of compounds constituted of four to seven glucosamine units ,-stereoisomers formed as side products despite the presence of a strongly participating 2- N -phthaloyl group to control ,-glycosylation. Both phenomena may be accounted for by conformational features of the linear bifunctional precursors. According to computer modeling and NMR conformational studies, the described linear (1,6)-,-linked oligoglucosamines exist in a right-handed helix-like conformation, in which the glycosyl donor and acceptor moieties are prearranged in a way that facilitates intramolecular glycosylation from the ,-side. Prepared cyclo-oligoglucosamines differ in their conformational flexibilities, as illustrated by their spectral characteristics and calculated asphericity distributions. Moreover, the obtained compounds do not possess a distinct hydrophobic cavity, which is in contrast to the well-known cyclodextrins. All these characteristics provide an excellent basis for the use of these novel cyclic oligosaccharides as scaffolds for the construction of biomolecular conjugates. [source] Efficient synthesis of a long carbohydrate chain alkyl glycoside catalyzed by cyclodextrin glycosyltransferase (CGTase)BIOTECHNOLOGY & BIOENGINEERING, Issue 5 2009David Svensson Abstract Alkyl glycosides with long carbohydrate groups are surfactants with attractive properties but they are very difficult to synthesize. Here, a method for extension of the carbohydrate group of commercially available dodecyl-,- d -maltoside (DDM) is presented. DDM was converted to dodecyl-,- d -maltooctaoside (DDMO) in a single step by using a CGTase as catalyst and ,-cyclodextrin (,-CD) as glycosyl donor. The coupling reaction is under kinetic control and the maximum yield depends on the selectivity of the enzyme. The Bacillus macerans CGTase favored the coupling reaction while the Thermoanaerobacter enzyme also catalyzed disproportionation reactions leading to a broader product range. A high ratio ,-CD/DDM favored a high yield of DDMO and yields up to 80% were obtained using the B. macerans enzyme as catalyst. Biotechnol. Bioeng. 2009; 104: 854,861. © 2009 Wiley Periodicals, Inc. [source] Glycosyltransferases and their AssaysCHEMBIOCHEM, Issue 14 2010Dr. Gerd K. Wagner Abstract Glycosyltransferases (GTs) are a large family of enzymes that are essential in all domains of life for the biosynthesis of complex carbohydrates and glycoconjugates. GTs catalyse the transfer of a sugar from a glycosyl donor to a variety of acceptor molecules, for example, oligosaccharides, peptides, lipids or small molecules. Such glycosylation reactions are central to many fundamental biological processes, including cellular adhesion, cell signalling and bacterial- and plant-cell-wall biosynthesis. GTs are therefore of significant interest as molecular targets in chemical biology and drug discovery. In addition, GTs have found wide application as synthetic tools for the preparation of complex carbohydrates and glycoconjugates. In order to exploit the potential of GTs both as molecular targets and synthetic tools, robust and operationally simple bioassays are essential, especially as more and more protein sequences with putative GT activity but unknown biochemical function are being identified. In this minireview, we give a brief introduction to GT biochemistry and biology. We outline the relevance of GTs for medicinal chemistry and chemical biology, and describe selected examples for recently developed GT bioassays, with a particular emphasis on fluorescence-based formats. [source] FRET-Based Direct and Continuous Monitoring of Human Fucosyltransferases Activity: An Efficient synthesis of Versatile GDP- L -Fucose Derivatives from Abundant d- Galactose,CHEMISTRY - A EUROPEAN JOURNAL, Issue 2 2008Takahiro Maeda Abstract We have developed a facile and versatile protocol for the continuous monitoring of human fucosyltransferases activity by using fluorescence energy resonance transfer (FRET), and have explored the feasibility of its use in an inhibitor screening assay. A convenient sugar nucleotide with a fluorogenic probe, 6-deoxy-6- N -(2-naphalene-2-yl-acetamide)-,- L -galactopyranos-1-yl-guanosine 5,-diphosphate disodium salt (1), was efficiently synthesized from naturally abundant D -galactopyranose via a key intermediate, 6-azide-1,2,3,4-tetra- O -benzoyl-6-deoxy-,- L -galactopyranose (10). It was demonstrated that the combined use of the glycosyl donor 1 and a dansylated acceptor substrate, sialyl-,2,3-LacNAc derivative (2) allowed us to carry out highly sensitive, direct, and continuous in vitro monitoring of the generation of sialyl Lewis,X (SLex), which is catalyzed by human ,-1,3-fucosyltransferase,VI (FUT-VI). A kinetic analysis revealed that compound 1 was an excellent donor substrate (KM=0.94,,M and Vmax=0.14,,M,min,1) for detecting human FUT-VI activity. To the best of our knowledge, this synthetic fluorogenic probe is the most sensitive and selective donor substrate for FUT-VI among all of the known GDP-Fuc analogues, including the parent GDP-Fuc. When a dansylated asparagine-linked glycopeptide 20, which is derived from egg yolk was employed as an alternate acceptor substrate, a FRET-based assay with compound 1 could be used to directly monitor the ,1,6-fucosylation at the reducing terminal GlcNAc residue by human FUT-VIII (KM=175,,M and Vmax=0.06,,M/,min); this indicates that the present method might become a general protocol for the characterization of various mammalian fucosyltransferases in the presence of designated fluorogenic acceptor substrates. The present protocol revealed that compound 23, which was obtained by a 1,3-dipolar cycloaddition between the disodium salt 16 and 1-ethynyl-naphthalene exhibits highly potent inhibitory effects against the FUT-VI-mediated sialyl Lewis,X synthesis (IC50=5.4,,M). [source] A Study on the Influence of the Structure of the Glycosyl Acceptors on the Stereochemistry of the Glycosylation Reactions with 2-Azido-2-Deoxy-Hexopyranosyl TrichloroacetimidatesCHEMISTRY - A EUROPEAN JOURNAL, Issue 3 2005M. Belén Cid Dr. Abstract The stereochemical outcome of glycosylations with 2-azido-2-deoxy- D -gluco- and D -galactopyranosyl trichloroacetimidates as glycosyl donors has been investigated by using a series of chiro -inositol derivatives as glycosyl acceptors. The influence of the absolute configuration, the conformation and the conformational flexibility of the glycosyl acceptor has been studied by using different glycosyl donors under similar pre-established experimental conditions. Although the structure of the acceptor may play a role in governing the stereochemistry of these glycosylations, the results show that, in general terms, the relative influence of these factors is difficult to evaluate. For a given set of experimental conditions, the stereochemical course of these glycosylations depends on structural features of both glycosyl donor and glycosyl acceptor. It is a balance of these factors, where the structure of the glycosyl donor always plays a major role, which determines the stereochemistry of the coupling reaction. Therefore, the examples reported in the literature in which the structure of the glycosyl acceptor appears to be crucial in determining the stereochemistry of the reaction constitute particularly favorable cases which do not presently allow any further generalization. [source] Donor-Bound Glycosylation for Various Glycosyl Acceptors: Bidirectional Solid-Phase Semisynthesis of Vancomycin and Its DerivativesCHEMISTRY - AN ASIAN JOURNAL, Issue 1 2007Takayuki Doi Prof. Abstract The glycosidation of a polymer-supported glycosyl donor, N -phenyltrifluoroacetimidate, with various glycosyl acceptors is reported. The application of the polymer-supported N -phenyltrifluoroacetimidate is demonstrated in the synthesis of vancomycin derivatives. 2- O -[2-(azidomethyl)benzoyl]glycosyl imidate was attached to a polymer support at the 6-position by a phenylsulfonate linked with a C13 alkyl spacer. Solid-phase glycosidation with a vancomycin aglycon, selective deprotection of the 2-(azidomethyl)benzoyl group, and glycosylation of the resulting 2-hydroxy group with a vancosamine unit were performed. Nucleophilic cleavage from the polymer support with acetate, chloride, azido, and thioacetate ions provided vancomycin derivatives in pure form after simple purification. The semisynthesis of vancomycin was achieved by deprotection of the acetate derivative. [source] Highly Concise Synthesis of 3'-"Up"-ethynyl-5'-methylbicyclo- [3.1.0]hexyl Purine and Pyrimidine Nucleoside Derivatives Using Rhodium(II) Carbenoid Cycloaddition and Highly Diastereoselective Grignard ReactionCHINESE JOURNAL OF CHEMISTRY, Issue 12 2009Zunhua Yang Abstract Synthesis of north -5'-methylbicyclo[3.1.0]hexyl purine and pyrimidine nucleosides with an ethynyl group at C-3' position has been successfully accomplished by a facile method. Methylbicyclo[3.1.0]hexanone (±)- 5 having three contiguous chiral centers was remarkably simply constructed only by four steps containing a carbenoid insertion reaction in the presence of rhodium(II) acetate dimer and CuSO4, giving a correct relative stereochemistry of the generated three chiral centers. Upon Grignard reaction of (±)- 5 with ethynylmagnesium bromide, exclusive diastereoselectivity was observed. Condensation of glycosyl donor (±)- 9 with purine nucleobase afforded only the desired N9 -alkylated nucleoside, while condensation with pyrimidine, N3 -benzoylated uracil gave the desired N1 -alkylated nucleoside (±)- 13 with the undesired O2 -alkylated nucleoside (±)- 14. Probably, (±)- 14 would be formed due to steric hindrance caused upon approaching for N1 -alkylation. [source] Glycosylations Directed by the Armed-Disarmed Effect with Acceptors Containing a Single Ester GroupEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 23 2007Thomas H. Schmidt Abstract A selective glycosylation reaction controlled by the armed-disarmed effect is described by the use of phenyl thioglycosides. The donor thioglycoside is fully protected with benzyl ethers while the acceptor thioglycoside contains benzyl ethers at position 2 and 3 and a strongly electron-withdrawing pentafluorobenzoate ester group at position 6. The coupling can be performed with galactose, glucose, mannose, and phthalimide-protected glucosamine to afford the corresponding 1,4-linked disaccharides in good yield. These disaccharides can act as glycosyl donors for an additional coupling reaction in the same pot if another acceptor and more promoter are added. In this way, two consecutiveglycosylations can be achieved to afford trisaccharides in one operation. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] Simultaneous Regio- and Enantiodifferentiation in Carbohydrate Coupling,EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 17 2006M. Belén Cid Abstract The glycosylation of 1,2- trans -diequatorial diols derived from tetrabenzoylated and tetrabenzylated D - and L - chiro -inositol with several glycosyl donors has been investigated. An unprecedented dependence of the regioselectivity on the absolute configuration of the acceptor has been found. However this trend is also modulated by the nature of the protecting groups on both the donor and acceptor, with benzoylated acceptors affording higher levels of regioselectivity. Most of the results have been rationalized by DFT calculations which indicate that stereoelectronic factors and hydrogen bonding between the donor and acceptor govern their relative orientation and determine the regiochemical outcome of the process. These studies also highlight the role of the acyl group adjacent to the OH to be glycosylated in facilitating the glycosylation reaction. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source] Endohexosaminidase M: Exploring and Exploiting Enzyme Substrate SpecificityCHEMBIOCHEM, Issue 8 2006Thomas W. D. F. Rising Oxazoline saccharides have been synthesised and tested as glycosyl donors for endohexosaminidase M (Endo M)-catalysed glycosylation of a GlcNAcAsn glycosyl amino acid. Endo M-catalysed glycosylation is not limited to donors containing the Man,(1-4)GlcNAc linkage, and replacement of the core mannose unit by glucose promotes irreversible glycosylation. In this case, use of a modified oxazoline donor as a transition-state mimic allows enzyme-catalysed synthesis, but precludes product hydrolysis. [source] Synthesis of 2-C-Branched Oligo(glyco,amino acid)s (OGAAs) by Ring Opening of 1,2-Cyclopropanecarboxylated Sugar DonorsCHEMISTRY - A EUROPEAN JOURNAL, Issue 31 2009Perali, Ramu Sridhar Dr. Hybrid theory: 1,2-Cyclopropanecarboxylated sugars were used as glycosyl donors for the first time in the synthesis of 2-C-branched oligo(glyco,amino acid)s (OGAAs; see scheme) decorated with ,-amino acids. The method was applied to an acceptor-reactivity-based stereo- and regioselective glycosylation reaction towards the preparation of several disaccharide-derived glyco,amino acid derivatives. [source] Going to Extremes: "Super" Armed Glycosyl Donors in Glycosylation ChemistryCHEMISTRY - A EUROPEAN JOURNAL, Issue 27 2007Henrik Abstract This concept article gives an overview of stereoelectronic effects in monosaccharide systems and how these can be used to dramatically enhance the reactivity of glycosyl donors in oligosaccharide synthesis. [source] A Study on the Influence of the Structure of the Glycosyl Acceptors on the Stereochemistry of the Glycosylation Reactions with 2-Azido-2-Deoxy-Hexopyranosyl TrichloroacetimidatesCHEMISTRY - A EUROPEAN JOURNAL, Issue 3 2005M. Belén Cid Dr. Abstract The stereochemical outcome of glycosylations with 2-azido-2-deoxy- D -gluco- and D -galactopyranosyl trichloroacetimidates as glycosyl donors has been investigated by using a series of chiro -inositol derivatives as glycosyl acceptors. The influence of the absolute configuration, the conformation and the conformational flexibility of the glycosyl acceptor has been studied by using different glycosyl donors under similar pre-established experimental conditions. Although the structure of the acceptor may play a role in governing the stereochemistry of these glycosylations, the results show that, in general terms, the relative influence of these factors is difficult to evaluate. For a given set of experimental conditions, the stereochemical course of these glycosylations depends on structural features of both glycosyl donor and glycosyl acceptor. It is a balance of these factors, where the structure of the glycosyl donor always plays a major role, which determines the stereochemistry of the coupling reaction. Therefore, the examples reported in the literature in which the structure of the glycosyl acceptor appears to be crucial in determining the stereochemistry of the reaction constitute particularly favorable cases which do not presently allow any further generalization. [source] | ||||||||||||||||||||||