Glycosyl

About: Glycosyl is a research topic. Over the lifetime, 4915 publications have been published within this topic receiving 100087 citations. The topic is also known as: glycosyl & glycosyl groups.

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

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.

Structure and function of the primary cell walls of plants.

Abstract: 1 Abbreviations and conventions used: AceA, aceric acid (3-C-carboxy-5-deoxy-L-xylose); Api, apiose; Ara, arabinose; Fuc, fucose; Gal, galactose; GalVA, galacturonic acid; Glc, glucose; GlcA, glucuronic acid; Rha, rhamnose; Xyl, xylose; PGA lyase, endo-IX-I,4polygalacturonic acid lyase; and PIIF, Proteinase Inhibitor Inducing Factor. All glycosyl residues are in the pyranoid ring form unless the furanoid form is indicated, e.g. Ara! Standard D and L notations are used when the absolute configuration of a particular glycosyl residue has been experimentally determined. When the absolute configuration has not been experiment­ ally determined, we omit the D or L notation, although in all cases studied the glycosyl residues Gal, Glc, Xyl, GalA, and GlcA have been found in the D configuration, and the glycosyl residues Fuc, Ara, and Rha in the L configuration. We use in this review a simplified linkage notation. All glycosyl residues (except the residue at the reducing end of an oligosaccharide, which is called a glycose residue) are glycosidically linked at C-l. This fact is assumed in the notation used, and, thus, C-\ is not mentioned. For example, a glycosyl residue designated as "terminal" (T) is glycosidically linked to another glycosyl or glycose residue only through C-J and contains no glycosyl residues linked to it. A glycosyl residue designated as 2-linked is glycosidicaUy linked to another glycosyl or glycose residue through C-J and has another glycosyl residue linked to it at 0-2. A glycosyl residue designated as 3,6-linked is glycosidically linked to another sugar through C-l and has glycosyl residues linked to it at 0-3 and 0-6; therefore, such a residue represents a branch point in a complex carbohydrate. The linkage from C l is also assumed in the notation for oligosac­ charides. Thus, L-Fuc � 2-D-Gal is a disaccharide in which an L-fucosyl residue is attached by an ()(-glycosidic bond from its C-l to 0-2 of a D-galactose residue. 2 Present address: Department of Bot

RHAMNOGALACTURONAN II: Structure and Function of a Borate Cross-Linked Cell Wall Pectic Polysaccharide

Abstract: ▪ Abstract Rhamnogalacturonan II (RG-II) is a structurally complex pectic polysaccharide that was first identified in 1978 as a quantitatively minor component of suspension-cultured sycamore cell walls. Subsequent studies have shown that RG-II is present in the primary walls of angiosperms, gymnosperms, lycophytes, and pteridophytes and that its glycosyl sequence is conserved in all vascular plants examined to date. This is remarkable because RG-II is composed of at least 12 different glycosyl residues linked together by more than 20 different glycosidic linkages. However, only a few of the genes and proteins required for RG-II biosynthesis have been identified. The demonstration that RG-II exists in primary walls as a dimer that is covalently cross-linked by a borate diester was a major advance in our understanding of the structure and function of this pectic polysaccharide. Dimer formation results in the cross-linking of the two homogalacturonan chains upon which the RG-II molecules are constructed and ...