Izumi Takai

Reactions of methyl 4,6-O-benzylidene-2,3-dideoxy-2-C-p-tolylsulfonyl-β-D-erythro-hex-2-enopyranoside and its phenyl analog with several nucleophiles ; stereoselective preparation of 3-O-acyl-D-arabino- and -D-ribo-hex-1-enitol derivatives

Abstract Reactions of methyl 2- C - p -tolylsulfonyl-2-enopyranoside ( 6 ) with nucleophiles (methoxide, nitromethane, 2,4-pentanedione, and ammonia) afforded the β- d - gluco adducts with high stereoselectivity. However, similar treatment of the phenyl analog 11 with sodium borodeuteride, nitromethane, methoxide, and lithium hydroxide led mainly to an S n 2′ process to give 1-enitol derivatives having the arabino configuration. Conversely, treatment of 11 with carboxylic acids in pyridine gave the 1-enitol derivatives having the ribo configuration as the major product.

Preparation of 4,6-O-benzylidene-2-C- and -3-C-p-tolylsulfonylhex-2-enopyranoside derivatives and a 2-C-p-tolylsulfonylhex-2-enitol derivative

Abstract 4,6- O -Benzylidenehex-2-enopyranoside derivatives having a 2- C - or 3- C-p -tolylsulfonyl group were synthesized from appropriate nitro sugars by the addition of p -toluenesulfinic acid followed by elimination of nitrous acid. 1,5-Anhydro-4,6- O -benzylidene-2,3-dideoxy-2- C-p -tolylsulfonyl- d - erythro -hex-2-enitol was similarly prepared. Methyl 4,6- O -benzylidene-2,3-dideoxy-2- C - and -3- C-p -tolylsulfonyl-α- d - erythro -hex-2-enopyranosides were alternatively ynthesized from methyl 2,3-anhydro-α- d -allo- and -mannopyranosides, respectively, by cleavage of the oxirane ring with sodium p -toluenethiolate, followed by oxidation.

A novel method for determination of α1,6fucosyltransferase activity using a reducing oligosaccharide from egg yolk as a specific acceptor

A new method for determination of α1,6fucosyltransferase activity has been described. Recently, the disialyl-biantennary undecasaccharide was prepared in high yield from egg yolk [(1996), Carbohydr Lett 2: 137–42]. By treatment of this oligosaccharide with neuraminidase and β-galactosidase, we readily obtained an asialo-agalacto-biantennary heptasaccharide (GlcNAcβ 1,2Manα1,6[GlcNAcβ1,2Manα1,3]Manβ1,4GlcNAcβ1,4GlcNAc). Using this asialo-agalacto-oligosaccharide as an acceptor, fucosyltransferases from human plasma and extracts of various human hepatoma cell lines were assayed in the presence of GDP-[3H]fucose. The reaction mixture was applied to a column of GlcNAc-binding, Psathyrella velutina lectin coupled gel. All the fucosylated acceptor were bound to the column which was eluted with 50 mM GlcNAc. Structural analyses revealed that only the innermost GlcNAc residue of the acceptor was fucosylated through an α1,6-linkage, and the oligosaccharide prepared could be used as a specific acceptor for α1,6fucosyltransferase. The present method was used to screen plasma α1,6fucosyltransferase in several patient groups, and significantly elevated activities were found in samples from patients with liver diseases, including chronic hepatitis, liver cirrhosis, and hepatocellular carcinoma.

Efficient catalysis by pyridinium sulfonate in glycosylation involving an oxazoline intermediate derived from per-O-acetyl-N-acetyllactosamine andN,N′-diacetylchitobiose

New and facileN-acetyllactosaminidation andN,N′-diacetylchitobiosylation with various alcohols, thiols, and sugar derivatives through the 1,2-oxazoline intermediates catalyzed by pyridiniump-toluenesulfonate were achieved.

p-Nitrophenyl Glycosides of Chitooligosaccharides; Their Syntheses Through the Autocatalytic Fusion Reaction of Chitooligosaccharides Acetates with p-Nitrophenol

Abstract Fusion reactions of p-nitrophenol with acetates of chito-biose, chitotriose, chitotetraose, and chitopentaose under autocatalytic conditions gave the corresponding p-nitrophenyl chitooligosides acetates in acceptable yields. Complete O-deacetylation of these acetates was attained by treatment with sodium methoxide in methanol under reflux in the case of the latter two, and at room temperature with the former two.

Preparation of nitroalkenes from the corresponding nitroalkanes

Phenylselenenyl bromide reacts with nitro-alkanes to give nitro(phenylseleno)alkanes and oxidative elimination provided nitroalkenes.