Yoshiharu Ishido

Transglycosylation reaction of a chitinase purified from Nocardia orientalis

Chitinase from the culture filtrates of Nocardia orientalis IFO 12806 was purified to apparent homogeneity by precipitation with ammonium sulfate followed by successive chromatography on CM-Sephadex and Bio-Gel P-60, and finally by affinity chromatography on a phenyl-Sepharose CL-4B column. The enzyme, which is essentially a hydrolase, also catalyzed a transglycosylation reaction on tetra-N-acetyl-chitotetraose (GlcNAc)4 and penta-N-acetyl-chitopentaose (GlcNAc)5. The enzyme converted the tetrasaccharide into hexa-N-acetyl-chitohexaose (GlcNAc)6 (21%) and di-N-acetyl-chitobiose (GlcNAc)2 (63%) as the major products. The corresponding values for penta-N-acetyl-chitopentaose (GlcNAc)5 were hepta-N-acetyl-chitoheptaose (GlcNAc)7 23% and tri-N-acetyl-chitotriose (GlcNAc)3 59%. The rate of the transglycosylation depended on the temperature, the concentration of substrate and the pH.

A comparison of bis(tributyltin) oxide, potassium cyanide, and potassium hydroxide as reagents for the regioselective 1-O-deacetylation of fully acetylated sugars

Abstract Treatments of fully acetylated sugars with bis(tributyltin) oxide in toluene at reflux, and with potassium cyanide or potassium hydroxide, or both, in mixtures of tetrahydrofuran and 2-propanol were found to be effective for regioselective 1- O -deacetylation of fully acetylated sugars.

Stereoselective radical cyclization for the synthesis of bicyclic higher-carbon sugars. Synthesis of the sugar moiety of octosyl acids

The Bu3SnH - AIBN induced radical cyclization of 6-bromo-6-deoxy-3-O-[(E)-2-ethoxycarbonylethenyl]-1,2-O-isopropylidene-α-???-allofuranose (1) gave ethyl 3,7-anhydro-6,8-dideoxy-1,2-O-isopropylidene-α-???-glycero-???-allo-nonofuranuronate (2) in 80% yield. Similar cyclizations of furanose derivatives and a synthesis of the sugar moiety of octosyl acids were described.

Synthesis of C-glycosyl compounds by the addition of glycosyl radicals to olefins☆

The Bu3SnH - AIBN induced radical additions of 2,3,4,6-tetra-O-acetyl-D-glucopyranosyl derivatives, bearing α-Br (1), α-I (5) β-OCSSMe (7), and β-SePh (8) groups on the anomeric carbon, with olefins such as dimethyl maleate, methyl vinyl ketone, dimethyl acetylenedicarboxylate, butyl vinyl ether, and N-ethylmaleimide were examined for a synthesis of C-glycosyl compounds.

Highly stereoselective C-α-d-ribofuranosylation. Reactions of d-ribofuranosyl fluoride derivatives with enol trimethylsilyl ethers and with allyltrimethylsilane

Abstract 2,3,5-Tri-O-methyl- d -ribofuranosyl flouride (6), 2,3-di-O-benzyl-5-O-methyl- d -ribofuranosyl fluoride (7), and 5-O-benzyl-2,3-di-O-methyl- d -ribofuranosyl fluoride (8) were obtained in 57 (6α, 15; and 6β, 42), 87 (7α, 22; and 7β, 65), and 85.5 (8α, 35.5; and 8β, 50%) yields, respectively, from the corresponding OH-1 derivatives by the reaction with N,N-diethyl-1,1,2,3,3,3-hexafluoropropylamine, adduct of hexafluoropropene with diethylamine. These fluorides and 2,3,5-tri-O-benzyl- d -ribofuranosyl fluoride (5) reacted with isopropenyl trimethylsilyl ether, (Z)-1-ethyl-1-propenyl trimethylsilyl ether, and allyltrimethylsilane, in the presence of boron trifluoride·diethyl etherate to give the corresponding 1- d -ribofuranosyl-2-propanones, 2- d -ribofuranosyl-3-pentanones, and 3- d -ribofuranosyl-1-propenes in good yields. C-Acetonylation was confirmed to afford the α- d anomer as the initial product, and the α- d anomer was isomerized into the corresponding β- d anomer to give a mixture. The C-allylation reaction gave only the α- d anomer. C-Pentanonylation, however, gave a mixture of diastereoisomers that could not be isolated. All reactions afforded almost the same results starting with either α- or β- d -ribofuranosyl fluoride. No reaction of the β anomer of 5 with 1-isopropyl-2-methyl-1-propenyl trimethylsilyl ether took place.

Additions of a ribofuranosyl radical to olefins. A formal synthesis of showdomycin

Abstract The Bu3SnH - AIBN induced radical additions of 5- 0 -benzoyl-2,3- 0 -isopropylidene-1- 0 -methylthiothiocarbonyl-β-D-ribofuranose (1) to olefins such as dimethyl maleate, methyl vinyl ketone, methyl acrylate etc. gave corresponding C-ribofuranosyl compounds. And one of the adducts was converted to the key intermediate of a showdomycin synthesis.

Enzymatic synthesis of p-nitrophenylN,N′,N″,N′″,N′ ′″-pentaacetyl-β-chitopentaoside in water-methanol system; significance as a substrate for lysozyme assay

Transchitooligosylation from (GlcNAc)5 to the 4-position of PNP-GlcNAc was efficiently induced through lysozyme catalysis in an aqueous solution containing methanol with a high concentration. Use of the aqueous methanol system in this reaction not only guaranteed solubility of PNP-GlcNAc substrate, but also resulted in a remarkable increase in PNP-(GlcNAc)5 production. PNP-(GlcNAc)5 was substrate for lysozyme assay compared with PNP-(GlcNAc)4.

Synthesis of phenyl d-glucopyranosides; nucleophilic substitution of O-(2,3,4,6-tetra-O-benzyl-d-glucopyranosyl)-pseudoureas by phenols

Abstract A series of nucleophilic substitution-reactions of O -(2,3,4,6-tetra- O -benzyl- d -glucopyranosyl)pseudoureas by phenols was investigated as a novel procedure for the synthesis of phenyl d -glucopyranoside derivatives: these reactions were found to give the corresponding phenyl 2,3,4,6-tetra- O -benzyl- d -glucopyranosides in excellent yields. Reaction mechanisms were discussed on the basis of the results obtained.

Partial Protection of Carbohydrate Derivatives. Part 23.1 Simple, Efficient Procedure for the Preparation of 3′- and 2′-0-(Tetrahydropyran-2-YL)Ribonucleoside Derivatives Involving Highly Regioselective 2′,5′-DI-O-Acylation or that Followed by Acyl Migration on Silica Gel and Subsequent O-(Tetrahydropyran-2-YL)Ation

Abstract Acylation of ribonucleosides with an acyl chloride (1.2–1.5 and 2.2–3.0 mol. equiv. toward the D-ribofuranosyl moiety) in pyridine was induced with high regioselectivity to give the corresponding 2′-acylates and 2′,5′-diacylates, respectively, which were effectively converted into the corresponding 3′-acylates and 3′,5′-diacylates, respectively, by passage down a column of silica gel, followed by crystallization from a solvent. All of the 2′,5′- and 3′,5′-diacylates thus obtained were converted to the corresponding 3′- and 2′-0-(tetrahydropyran-2-yl) derivatives by the usual manner, i.e., (tetrahydropyran-2-yl)ation and subsequent O-deacylation.

Synthesis of Glycosyl Cyanides and C-Allyl Glycosides by the use of Glycosyl Fluoride Derivatives

Abstract A treatment of 2,3,5-tri-O-benzyl-B-D-ribofuranosyl fluoride (1) with cyanotrimethylsilane in the presence of boron trifluoride diethyl etherate gave 2,3,5-tri-O-benzyl-α- (2α) and -β-D-ribofuranosyl (2β) cyanide in 46.2% and 46.6% yields, respectively. Confirmation of the corresponding isocyano isomer (3) formation and its conversion into 2 under boron trifluoride catalysis at -78°C made it possible to deduce that both 2α and 2β were produced by way of 3 which was formed preponderantly in the initial stage of the reaction. On the other hand, the reaction of 2,3,4,6-tetra-O-benzyl-α-D-glucopyranosyl fluoride (4) with cyanotrimethylsilane in diethyl ether by the use of boron trifluoride diethyl etherate (0.05 mol. equiv.) gave 2,3,4,6-tetra-O-benzyl-α -D-glucopyranosyl cyanide (5α), 2,3,4,6-tetra-O-benzyl-α- (6α), and -β-D-glucopyranosyl isocyanide (6β) as a 30:61:9 mixture (94% yield) but that in dichloromethane by the use of the catalyst (1.0 mol. equiv.) gave 5α (85% yield) as a sole product. T...