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Journal ArticleDOI

New Methods for the Synthesis of Glycosides and Oligosaccharides—Are There Alternatives to the Koenigs‐Knorr Method? [New Synthetic Methods (56)]

01 Mar 1986-Angewandte Chemie (Hüthig & Wepf Verlag)-Vol. 25, Iss: 3, pp 212-235
TL;DR: Emphasis is placed on glycoside and saccharide formation by 1-O-alkylation, on the trichloroacetimidate method, and on activation through the formation of glycosylsulfonium salts and Glycosyl fluorides.
Abstract: Glycoproteins, glycolipids, and glycophospholipids (glycoconjugates) are components of membranes. The oligosaccharide residue is responsible for intercellular recognition and interaction; it acts as a receptor for proteins, hormones, and viruses and governs immune reactions. These significant activities have stimulated interest in oligosaccharides and glycoconjugates. With their help it should be possible to clarify the molecular basis of these phenomena and to derive new principles of physiological activity. Major advances in the synthesis of oligosaccharides have been made by the use of the Koenigs-Knorr method, in which glycosyl halides in the presence of heavy-metal salts are employed to transfer the glycosyl group to nucleophiles. The disadvantages of this procedure have led to an intensive search for new methods. Such methods will be discussed in this article. Emphasis is placed on glycoside and saccharide formation by 1-O-alkylation, on the trichloroacetimidate method, and on activation through the formation of glycosylsulfonium salts and glycosyl fluorides.
Citations
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Journal ArticleDOI
TL;DR: New principles for the formation of glycoside bonds are discussed and developments, mainly in the last ten years, that have led to significant advances in oligosaccharide and glycoconjugate synthesis have been compiled and are evaluated.
Abstract: Increased understanding of the important roles that oligosaccharides and glycoconjugates play in biological processes has led to a demand for significant amounts of these materials for biological, medicinal, and pharmacological studies. Therefore, tremendous effort has been made to develop new procedures for the synthesis of glycosides, whereby the main focus is often the formation of the glycosidic bonds. Accordingly, quite a few review articles have been published over the past few years on glycoside synthesis; however, most are confined to either a specific type of glycoside or a specific strategy for glycoside synthesis. In this Review, new principles for the formation of glycoside bonds are discussed. Developments, mainly in the last ten years, that have led to significant advances in oligosaccharide and glycoconjugate synthesis have been compiled and are evaluated.

741 citations

Journal ArticleDOI
TL;DR: The synthesis of ionic liquids and their applications in various chemical and biochemical transformations, in ecofriendly-milder conditions have been reviewed in this paper, with metal and enzyme catalyzed as well as non-catalyzed reactions in ionic liquid reactions covered with 354 refs.

679 citations

Journal ArticleDOI
TL;DR: The enzymatic polymerizations allowed the first in vitro synthesis of natural polysaccharides having complicated structures like cellulose, amylose, xylan, chitin, hyaluronan, and chondroitin, and producing minimal byproducts.
Abstract: The present article comprehensively reviews the macromolecular synthesis using enzymes as catalysts. Among the six main classes of enzymes, the three classes, oxidoreductases, transferases, and hydrolases, have been employed as catalysts for the in vitro macromolecular synthesis and modification reactions. Appropriate design of reaction including monomer and enzyme catalyst produces macromolecules with precisely controlled structure, similarly as in vivo enzymatic reactions. The reaction controls the product structure with respect to substrate selectivity, chemo-selectivity, regio-selectivity, stereoselectivity, and choro-selectivity. Oxidoreductases catalyze various oxidation polymerizations of aromatic compounds as well as vinyl polymerizations. Transferases are effective catalysts for producing polysaccharide having a variety of structure and polyesters. Hydrolases catalyzing the bond-cleaving of macromolecules in vivo, catalyze the reverse reaction for bond forming in vitro to give various polysacchar...

374 citations

References
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Journal ArticleDOI
TL;DR: In this article, a reagent formed by combining diethyl azodicarboxylate (DEAD) and triphenylphosphine (TPP) could be utilized in the intermolecular dehydration between an alcohol and various acidic components such as carboxylic acids, phosphoric diesters, imides, and active methylene compounds.
Abstract: The reagent formed by combining diethyl azodicarboxylate (DEAD) and triphenylphosphine (TPP) could be utilized in the intermolecular dehydration between an alcohol and various acidic components such as carboxylic acids, phosphoric diesters, imides, and active methylene compounds. By the use of DEAD and TPP, diols and hydroxy acids gave cyclic ethers and lactones, respectively. The reaction of nucleosides with DEAD and TPP afforded triphenylphosphoranylnucleosides. Alcohols reacted with 2,6-di-t-butyl-4-nitrophenol in the presence of DEAD and TPP to give aci-nitroesters which converted into the corresponding carbonyl compounds.

3,209 citations

Journal ArticleDOI
TL;DR: The majority of neutral glycolipids present in plasma membranes are cryptic, and further extensive studies of the organization of glycolIPid in other eukaryotic cell membranes are necessary.
Abstract: The idea that glycosphingolipids (or, briefly, glycolipids) are ubiquitous components of plasma membrane and display cell type-specific patterns perhaps stemmed from the classical studies on glycolipids of erythrocyte membranes.(1,2) Subsequently, plasma membranes of various animal cells were successfully isolated and analyzed; all were characterized by their much higher content of glycolipid than was found in intracellular membranes.(3–8) It is generally assumed that glycolipids are present at the outer leaflet of the plasma membrane bilayer, although this assumption is based only on experiments with surface-labeling by galactose oxidase-NaB[3H]4 of intact and lysed erythrocyte membranes and inside-out vesicles.(9,10) Obviously, further extensive studies of the organization of glycolipid in other eukaryotic cell membranes are necessary. Interestingly, the majority of neutral glycolipids present in plasma membranes are cryptic (see Section 4.2.1).

1,637 citations

Journal ArticleDOI
01 Mar 1985-Nature
TL;DR: These findings either may reflect limitations in the methods of selection of hybridoma antibodies or point to important roles for the diverse carbohydrate structures as receptors for regulators of cell growth and differentiation.
Abstract: The hope that hybridoma antibodies would reveal unique cell surface antigens during embryogenesis, differentiation and oncogenesis has been replaced by the realization that such antigens are mainly carbohydrate structures of glycoproteins and glycolipids occurring in many cell types. These findings either may reflect limitations in the methods of selection of hybridoma antibodies or may point to important roles for the diverse carbohydrate structures as receptors for regulators of cell growth and differentiation.

1,156 citations

Journal ArticleDOI
TL;DR: A wide variety of complex oligosaccharides has now been made accessible as a result of methodological improvements in the sphere of chemical synthesis, which can be used for the study of conformations and interactions with protein-receptor molecules.
Abstract: A wide variety of complex oligosaccharides has now been made accessible as a result of methodological improvements in the sphere of chemical synthesis, which can be used for the study of conformations and interactions with protein-receptor molecules. Such work is of particular importance because the oligosaccharide chains of glycoproteins and glycolipids anchored to the plasma membrane are important in cell-cell interactions and are receptors for enzymes, hormones, proteins, and viruses; furthermore, they determine the antigen properties of cells. The methods of synthesis available for the production of selective linkages in oligosaccharides are dealt with, particular attention being paid to conversion of saccharides into oligosaccharides, which are important from the biological point of view.

885 citations