Hiroyoshi Kuzuhara

A therapeutic agent with oriented carbohydrates for treatment of infections by Shiga toxin-producing Escherichia coli O157:H7

Infection with Shiga toxin (Stx)-producing Escherichia coli O157:H7, which causes diarrhea and hemorrhagic colitis in humans, often results in fatal systemic complications, such as neurological damage and hemolytic–uremic syndrome. Because Stx circulating in the blood is a major causative factor of these complications, the development of a Stx neutralizer that functions in the circulation holds promise as a viable therapy. Here we developed a series of carbosilane dendrimers, in which trisaccharides of globotriaosyl ceramide, a receptor for Stx, were variously oriented at their termini (referred to as SUPER TWIG), and identified a SUPER TWIG with six trisaccharides as a Stx neutralizer functioning in the circulation. This SUPER TWIG specifically bound to Stx with high affinity (Kd = 1.1 × 10−6 M) and inhibited the incorporation of the toxin into target cells. Intravenous administration of the SUPER TWIG along with Stx to mice substantially reduced the fatal brain damage and completely suppressed the lethal effect of Stx. Moreover, the SUPER TWIG protected mice from challenge with a fatal dose of E. coli O157:H7, even when administered after the establishment of the infection. The SUPER TWIG neutralized Stx in vivo by a mechanism in which the accumulation and immediate degradation of Stx by phagocytic macrophages present in the reticuloendothelial system were induced. Taken together, our findings indicate that this SUPER TWIG is therapeutic agent against infections by Stx-producing E. coli.

SYNTHETIC ASSEMBLY OF TRISACCHARIDE MOIETIES OF GLOBOTRIAOSYL CERAMIDE USING CARBOSILANE DENDRIMERS AS CORES. A NEW TYPE OF FUNCTIONAL GLYCO-MATERIAL

Abstract As a novel type of artificial receptor for Vero toxins, three pairs of carbosilane dendrimers uniformly carrying 12, 6, and 3 units of trisaccharide moieties of globotriaosyl ceramide were prepared through formation of the sulfide linkages in liquid NH3, which revealed unexpected differences among their biological responses.

Synthesis of amylostatin (XG), α-glucosidase inhibitor with basic pseudotrisaccharide structure

Abstract The basic pseudotrisaccharide ( 1 constituting the common and essential building block of several α-glucosidase inhibitors of microbial origin was synthesized by coupling two synthons: the chiral cyclohexyl halide ( 11 ) and the 4′-amino-4′-deoxy-disaccharide ( 14 ).

Synthesis of methyl glycoside derivatives of tri- and penta-saccharides related to the antithrombin III-binding sequence of heparin, employing cellobiose as a key starting-material

Two key synthons for the title pentasaccharide derivative, methyl O-(methyl 2-O-benzoyl-3-O-benzyl-alpha-L-idopyranosyluronate)-(1----4)-6-O-acetyl- 2-azido - 3-O- benzyl-2-deoxy-beta-D-glucopyranoside and O-(methyl 2,3-di-O-benzyl-4-O- chloroacetyl-beta-D-glucopyranosyluronate)-(1----4)-3,6-di-O-acetyl-2-az ido-2- deoxy-alpha-D- glucopyranosyl bromide, were prepared from a common starting material, cellobiose. They were coupled to give a tetrasaccharide derivative that underwent O-dechloroacetylation to the corresponding glycosyl acceptor. Its condensation with the known 6-O-acetyl-2-azido-3,4-di-O-benzyl-2-deoxy-alpha-D-glucopyranosyl bromide afforded a 77% yield of suitably protected pentasaccharide, methyl O-(6-O- acetyl-2-azido-3,4-di-O-benzyl-2-deoxy-alpha-D-glucopyranosyl)-(1----4)- O- (methyl 2,3- di-O-benzyl-beta-D-glucopyranosyluronate)-(1----4)-O-(3,6-di-O-acetyl-2- azido-2 - deoxy-alpha-D-glucopyranosyl)-(1----4)-O-(methyl 2-O-benzoyl-3-O-benzyl-alpha-L- idopyranosyluronate)- (1----4)-6-O-acetyl-2-azido-3-O-benzyl-2-deoxy-beta-D-glucopyranoside. Sequential deprotection and sulfation gave the decasodium salt of methyl O-(2- deoxy-2-sulfamido-6-O-sulfo-alpha-D-glucopyranosyl)-(1----4)-O-(be ta-D- glucopyranosyl-uronic acid)-(1----4)-O-(2-deoxy-2-sulfamido-3,6-di-O-sulfo-alpha-D-gluco pyranosyl)- (1----4)-O-(2-O-sulfo-alpha-L-idopyranosyluronic acid)-(1----4)-2-deoxy-2- sulfamido-6-O- sulfo-beta-D-glucopyranoside (3). In a similar way, the trisaccharide derivative, the hexasodium salt of methyl O-(2-deoxy-2-sulfamido-6-O-sulfo-alpha-D- glucopyranosyl)- (1----4)-O-(beta-D-glucopyranosyluronic acid)-(1----4)-2-deoxy-2-sulfamido-3,6- di-O- sulfo-alpha-D-glucopyranoside (4) was synthesized from methyl O-(6-O-acetyl-2- azido- 3,4-di-O-benzyl-2-deoxy-alpha-D-glucopyranosyl)-(1----4)-O-(methyl 2,3-di-O- benzyl-beta- D-glucopyranosyluronate)-3,6-di-O-acetyl-2-azido-2-deoxy-alpha-D- glucopyranoside. The pentasaccharide 3 binds strongly to antithrombin III with an association constant almost equivalent to that of high-affinity heparin, but the trisaccharide 4 appears not to bind.

Synthesis of a heparin pentasaccharide fragment with a high affinity for antithrombin III employing cellobiose as a key starting material

Abstract The methodology for regio- and stereoselective modifications and transformations of cellobiose was established, and applied to the total synthesis of a heparin pentasaccharide fragment having a high affinity for antithrombin III.

Peracetylated chitobiose: Preparation by specific degradations of chitin, and chemical manipulations

Abstract Chitobiose octaacetate (3) was preparable in moderate yield from chitin by microbial degradation followed by acetylation, or by modified chemical degradation. Compound 3 was chemically manipulated to give various compounds, including an oxazoline derivative, glycosides, and partially O-benzylated derivatives. The conformation of the oxazoline derivative is discussed.

Total synthesis of (-)-allosamidin, an insect chitinase inhibitor, employing chitin as a key starting material

Abstract (−)-Allosamidin ( 1 ), a novel insect chitinase inhibitor, was stereoselectively synthesized from di- and monosaccharidic constituens of chitin, N, N′-diacetylchitobiose ( 2 ) and D-glucosamine ( 3 ).

Introduction of monosaccharides having functional groups onto a carbosilane dendrimer: A broadly applicable one-pot reaction in liquid ammonia involving Birch reduction and subsequent Sn2 reaction ☆

Benzylthioalkyl glycosides of D-glucuronic acid, N-acetyl-D-glucosamine, and N-acetylneuraminic acid (common monosaccharide constituents of natural oligosaccharide chains) have been prepared as sulfide precursors for the carbohydrate coating of dendric carbosilane cores and used in a generally applicable one-pot reaction (Birch reduction in liquid ammonia and subsequent SN2 reaction) to generate a thioether linkage between the monosaccharide moieties and a carbosilane dendrimer. The dendrimers were uniformly functionalized with the monosaccharides in good yields.

Peracetylated laminaribiose: preparation by specific degradation of curdlan and its chemical conversion into N-acetylhyalobiuronic acid

beta-Laminaribiose octaacetate (2b) was prepared in greater than 50% yield from the microbial polysaccharide curdlan by specific degradation with a yeast cell-wall lytic enzyme preparation, Kitalase,and subsequent acetylation. Acetolysis of curdlan also gave alpha-laminaribiose octaacetate (2a) in 27% yield. The usefulness of these peracetates 2a and 2b as starting materials for organic synthesis was shown by converting 2b into N-acetylhyalobiuronic acid (23), the disaccharide repeating unit of hyaluronic acid. The conversion was carried out via a series of reactions, which included azidonitration of the glucal derivative and selective alkylidenation or direct tritylation to discriminate two primary hydroxyl groups existing in the disaccharide intermediates.

Discrimination between the 2,3- and the 2′,3′-hydroxyl groups of maltose and cellobiose through their specific protection☆

Abstract 1,6-Anhydro-4′,6′- O -benzylidene-maltose and -cellobiose were subjected to temporary O -protection with a tetraisopropyldisiloxane-1,3-diyl group at the 2′,3′- and the 2,3-positions, giving 1,6-anhydro-4′,6′- O -benzylidene-2′,3′- O -(tetraisopropyldisiloxane- 1,3-diyl)maltose ( 15 ) and 1,6-anhydro-4′,6′- O -benzylidene-2,3- O -(tetraisopropyldisiloxane-1,3-diyl)cellobiose ( 19 ), respectively, in 60–64% yield. These were then subjected to various types of O -protection fo the hydroxyl groups remaining. Treatment of 15 and 19 with acetic anhydride or phenyl isocyanate gave the corresponding diacetyl and dicarbamoyl derivatives in high yield. Benzylation of the maltose derivative 15 was rather difficult, but was finally achieved through a phase-transfer reaction, to give the 2,3-di- O -benzyl derivative ( 18 ) in moderate yield. In the cellobiose series, benzylation of 19 was conducted similarly, giving 22 , and also by employing a modification of the conventional procedure. The silyl groups of 18 and 22 were removed by treatment with tetrabutylammonium fluoride, to afford the corresponding diols in high yield.