Osamu Kanie

Acceptor-substrate recognition by N-acetylglucosaminyltransferase-V: Critical role of the 4″-hydroxyl group in β-d-GlcpNAc-(1 → 2)-α-d-Manp(1 → 6)-β-d-Glcp-OR

The enzyme N-acetylglucosaminyltransferase-V (GlcNAcT-V) transfers GlcNAc from UDP-GlcNAc to the OH-6′ group of oligosaccharides terminating in the sequence β-d-GlcpNAc-(1 → 2)-α-d-Manp(1 → 6)-β-d-Glcp (or Manp)-OR (5, R  (CH2)7CH3) to yield the sequence β-d-GlcpNAc-(1 → 2)-[β-d-GlcpNAc-(1 → 6)]-α-d-Manp-(1 → 6)-β-d-Glcp (or Manp)-OR. Biosynthetically, if β-(1 → 4)-galactosyltransferase acts first on 5, the product β-d-Galp-(1 → 4)-β-d-GlcpNAc-(1 → 2)-α-d-Manp-(1 → 6)-β-d-Glcp (or Manp)-OR (7) is no longer a substrate for GlcNAcT-V even though it retains the active OH-6′ group. The reason for this loss in activity is examined in this paper. Six analogues of the acceptor trisaccharide 5, all with the reducing-end d-gluco configuration, were chemically synthesized. A key feature of the synthetic scheme is the use of 1,2-diaminoethane for the efficient removal of N-phthalimdo protecting groups. In these analogues OH-4 of the terminal sugar unit, the site of galactosylation by GalT in the normal GlcNAc-terminating trisaccharide 5, was systematically replaced by OMe, F, NH2, NHAc, and H, as well as inverted to the galacto configuration. The interactions of the resulting trisaccharide analogues with GlcNAcT-V from hamster kidney were then evaluated kinetically. All six compounds were found to be essentially inactive either as acceptors or as inhibitors of GlcNAcT-V. The conclusion is reached that galactosylation of natural acceptors for GlcNAcT-V destroys acceptor activity, not by introduction of the steric bulk of an added sugar residue, but by destroying an important hydrogen-bonding interaction of terminal OH-4 of the GlcNAc residues with the enzyme. This OH-4 group is therefore designated as a key polar group for GlcNAcT-V.

Glycosylation Using Methylthioglycosides of N-Acetylneuraminic Acid and Dimethyl(Methylthio)Sulfonium Triflate

Abstract Recently, great interest has been focussed on the synthesis of oligosaccharides containing N-acetylneuraminic acid (Neu5Ac) because of its important roles in a variety of biological recognitions.2 However, many difficulties in the synthesis of naturally occurring α-glycosides still remained.3 We have recently reported the stereo-selective synthesis of a series of α- and β-2-thio-neuraminyl glycosides.1-4 In the meantime, the utility of thioglycosides in oligosaccharide synthesis has been widely developed.5 Particularly noteworthy is the dimethyl(methylthio)sulfonium triflate (DMTST) promoted glyco-sylation method5k.1 because excellent yields are achieved due to the high thiophilicity of this reagent.

A Lysoganglioside/Poly-L-glutamic Acid Conjugate as a Picomolar Inhibitor of Influenza Hemagglutinin

Based on the principle of a multivalent interaction, the amphiphilic polymer 1, present in solution as an aggregate (see below right), is able to inhibit infection with the influenza virus. After recognition of a specific sialyllactose epitope through hemaglutinin (HA) on the virus surface, the sphingosine residues and the fluorescent tag form a stable complex with HA through hydrophobic interactions. Polymer 1 shows in vitro inhibitory activity 106 -fold greater than that of sialyllactose. PGA=polyglutamic acid.

Syntheses of C-3-Modified Sialylglycosides as Selective Inhibitors of Influenza Hemagglutinin and Neuraminidase

In an effort to develop new structures as inhibitors of both influenza virus proteins hemagglutinin and neuraminidase, a series of sialic acid derivatives, including those with one of the hydrogen atoms at the C-3 position replaced by either OH or F, were synthesized. The sialic acid derivative with a 3-eq-OH group was first synthesized by means of a new process and used as the key intermediate for further derivatization at the C-3 position. The stability of these compounds under acid- and sialidase-catalyzed hydrolysis conditions was studied, and the results showed that these compounds exhibit stronger resistance towards both conditions than their parent p-nitrophenyl α-sialoside. Further inhibition assay indicated that the 3-ax-OH or F derivatives 4, 5, and 24, the 4-epimer of 4, are effective specific inhibitors of the sialidases from Clostridium perfringens, among other bacterial sialidases tested. The 3-eq-OH derivative 3, however, showed little inhibition. The same tendency was observed for the inhibition of human influenza sialidases N1 and N2. Compounds 3−5 and sialic acid were then converted into the distealoylphosphatidylethanolamine conjugates. Of these liposome-like compounds, the ones from 4 and 5 showed potent and selective inhibitory activities against the hemagglutinin H3 subtype, but displayed resistance to the influenza virus neuraminidases N1 and N2.

Solid phase synthesis of polylactosamine oligosaccharide

Abstract Solid phase synthesis of polylactosamine oligosaccharide was performed starting from resin supported lactose 1a,b . Glycosylation of 1a with the lactosamine unit 6 followed by delevulinoylation afforded tetrasaccharides, which were further converted into hexa- and octasaccharide and was cleaved from resin by TrBF 4 in CH 2 Cl 2 to afford 7 . Ester linked 1b was converted in a similar manner into hexasaccharide that was liberated under basic conditions to give 8 . Subsequent deprotection into 9 was performed in three steps.

ORTHOGONAL GLYCOSYLATION STRATEGY IN SYNTHESIS OF EXTENDED BLOOD GROUP B DETERMINANT

Abstract The orthogonal glycosylation strategy was applied for the synthesis of extended blood type B determinant ( 2 ) of a novel glycolipid 1 . Key features in the synthesis are 1) four monosaccharide units were synthesized as either glycosyl fluoride or thioglycoside to be engaged to the orthogonal glycosylation strategy and 2) all necessary manipulations were completed at the monosaccharide level, therefore, manipulations during the elongation of sugar chain were minimized.

Synthesis of oligosaccharides, glycolipids and glycopeptides

Abstract Several new strategies have been introduced into the realm of synthetic carbohydrate chemistry during the period covered by this review. Regioselective glycosylation of lightly protected glycosyl acceptors has been applied successfully to the synthesis of molecules which are related to cell adhesion. Intramolecular reactions are becoming promising methods of obtaining the β-mannosides found in the core region of N-linked glycoproteins.

Quantitative Monitoring of Solid‐Phase Synthesis Using Gated Decoupling 13C NMR Spectroscopy with a 13C‐Enriched Protecting Group and an Internal Standard in the Synthesis of Sialyl LewisX Tetrasaccharide

Just tagging along. For the nondestructive quantitative monitoring of solid-phase oligosaccharide synthesis a 13 C-enriched tag (*) was incorporated in the linker and a 13 C-enriched protecting group (⧫) was included in the growing molecule. By integration of the signals in a gated decoupling 13 C NMR experiment the reaction progress can be monitored. This method was demonstrated with the synthesis of sialyl Lewisx tetrasaccharide on a Tentagel support ((P)). Bn=benzyl, PEG=poly(ethylene glycol).

Synthesis and enzymatic evaluation of five-membered iminocyclitols and a pseudodisaccharide

Described here are the synthesis of five-membered iminocyclitols with galacto-configuration and a pseudodisaccharide, and their inhibitory activities against beta-galactosyltransferase, beta-galactosidase and alpha-mannosidase.

Recent Developments in Oligosaccharide Synthesis: Tactics, Solid-Phase Synthesis and Library Synthesis

Oligosaccharides, commonly found on the cell surfaces, are deeply involved in a variety of important biological functions, yet demanding difficulties synthesizing such structures limit the investigation of their functions. Technologies to chemically synthesize these oligosaccharides have dramatically advanced during the last two decades mainly due to the introduction of good anomeric leaving groups. In addition, tactical analyses have been addressed to enhance the overall efficiency of oligosaccharide synthesis. Based on the advancement of solution-phase chemistry, solid-phase technologies are being investigated in connection with the current trend of combinatorial chemistry and high throughput screening. This review summarizes the necessary solution-phase methodologies, the status of solid-phase synthesis of oligosaccharides, and combinatorial synthesis of oligosaccharide libraries.