Photochemical addition of 2-propanol and of acetone to 2-acetoxy-3,4,6-tri-O-acetyl-D-glucal

Irradiation of a solution of 2-acetoxy-3,4,6-tri-O-acetyl-D-glucal (1) in 1:200 acetone-2-propanol with a high-pressure mercury-lamp gave 4,5,6,8-tetra-O-acetyl-3,7-anhydro-1-deoxy-2-C-methyl-D-glycero-D-gulo-octitol (2) (51.2%), -D-glycero-D-ido-octitol (3) (16.2%), and-D-glycero-D- galacto-octitol (4) (21.0%). The irradiation of 1 in 1:1 acetone-2-propanol gave 5,6,8-tri-O-acetyl-3,7-anhydro-1-deoxy-4-C-(1-hydroxy-1-methylethyl)-2-C-methyl-D-glycero-D-(gluco or manno, etc.)-octitol 2,4,4¹-orthoacetate (17%) and a 2:1:1 mixture of 2, 3, and 4 (64%). Moreover, the irradiation of 1 in 1:9 acetone-tert-butyl alcohol gave 2 (15%), 3 (9%), 4 (7%), and (4S)-4,5,6,8-tetra-O-acetyl-2,4:3,7-dianhydro-1-deoxy-2-C-methyl-D-gluco-octos-4-ulose (14%).     

Synthesis of methyl O-(3-deoxy-3-fluoro-β-d-galactopyranosyl)-(1→6)-β-d-galactopyranoside and methyl O-(3-deoxy-3-fluoro-β-d-galactopyranosyl)-(1→6)-O-β-d-galactopyranosyl-(1→6)-β-d-galactopyranoside

Condensation of 2,4,6-tri-O-acetyl-3-deoxy-3-fluoro-α-d-galactopyranosyl bromide (3) with methyl 2,3,4-tri-O-acetyl-β-d-galactopyranoside (4) gave a fully acetylated (1→6)-β-d-galactobiose fluorinated at the 3′-position which was deacetylated to give the title disaccharide. The corresponding trisaccharide was obtained by reaction of 4 with 2,3,4-tri-O-acetyl-6-O-chloroacetyl-α-d-galactopyranosyl bromide (5), dechloroacetylation of the formed methyl O-(2,3,4-tri-O-acetyl-6-O-chloroacetyl-β-d-galactopyranosyl)-(1→6)- 2,3,4-tri-O-acetyl-β-d-galactopyranoside to give methyl O-(2,3,4-tri-O-acetyl-β-d-galactopyranosyl)-(1→6)-2,3,4-tri-O-acetyl-β-d-galactopyranoside (14), condensation with 3, and deacetylation. Dechloroacetylation of methyl O-(2,3,4-tri-O-acetyl-6-O-chloroacetyl-β-d-galactopyranosyl)-(1→6)-O-(2,3,4-tri-O-acetyl- β-d-galactopyranosyl)-(1→6)-2,3,4-tri-O-acetyl-β-d-galactopyranoside, obtained by condensation of disaccharide 14 with bromide 5, was accompanied by extensive acetyl migration giving a mixture of products. These were deacetylated to give, crystalline for the first time, the methyl β-glycoside of (1→6)-β-d-galactotriose in high yield. The structures of the target compounds were confirmed by 500-MHz, 2D, ¹H- and conventional ¹³C- and ¹⁹F-n.m.r. spectroscopy.     

Ring-opening reactions of sucrose epoxides: Synthesis of 4′-derivatives of sucrose

The 2,1′-O-isopropylidene derivative (1) of 3-O-acetyl-4,6-O-isopropylidene-α-d-glucopyranosyl 6-O-acetyl-3,4-anhydro-β-d-lyxo-hexulofuranoside and 2,3,4-tri-O-acetyl-6-O-trityl-α-d-glucopyranosyl 3,4-anhydro-1,6-di-O-trityl-β-d-lyxo-hexulofuranoside have been synthesised and 1 has been converted into 2,3,4,6-tetra-O-acetyl-α-d-glucopyranosyl 1,6-di-O-acetyl-3,4-anhydro-β-d-lyxo-hexulofuranoside (2). The S_N2 reactions of 2 with azide and chloride nucleophiles gave the corresponding 2,3,4,6-tetra-O-acetyl-α-d-glucopyranosyl 1,3,6-tri-O-acetyl-4-azido-4-deoxy-β-d-fructofuranoside (6) and 2,3,4,6-tetra-O-acetyl-α-d-glucopyranosyl 1,3,6-tri-O-acetyl-4-chloro-4-deoxy-β-d-fructofuranoside (8), respectively. The azide 6 was catalytically hydrogenated and the resulting amine was isolated as 2,3,4,6-tetra-O-acetyl-α-d-glucopyranosyl 4-acetamido-1,3,6-tri-O-acetyl-4-deoxy-β-d-fructofuranoside. Treatment of 5 with hydrogen bromide in glacial acetic acid followed by conventional acetylation gave 2,3,4,6-tetra-O-acetyl-α-d-glucopyranosyl 1,3,6-tri-O-acetyl-4-bromo-4-deoxy-β-d-fructofuranoside. Similar S_N2 reactions with 2,3,4,6-tetra-O-acetyl-α-d-glucopyranosyl 1,6-di-O-acetyl-3,4-anhydro-β-d-ribo-hexulofuranoside (12) resulted in a number of 4′-derivatives of α-d-glucopyranosyl β-d-sorbofuranoside. The regiospecific nucleophilic substitution at position 4′ in 2 and 12 has been explained on the basis of steric and polar factors.     

Photochemical addition of 1,3-dioxolane and of 2-propanol to 1,2,4,6-tetra-O-acetyl-3-deoxy-α- and -β-D-erythro-hex-2-enopyranose

Photoirradiation of a solution of 1,2,4,6-tetra-O-acetyl-3-deoxy-β-D-erythro-hex-2-enopyranose (1) in 1:50 acetone-1,3-dioxolane with a high-pressure mercury-lamp, followed by chromatographic separation, gave 1,2,4,6-tetra-O-acetyl-3-deoxy-3-C-(1,3-dioxolan-2-yl)-β-D-glucopyranose (3) (44%) and-mannopyranose (4) (35%). Similar treatment of the α anomer (2) of 1 afforded 1,2,4,6-tetra-O-acetyl-3-deoxy-3-C-(1,3-dioxolan-2-yl)-α-D-glucopyranose (5) (38%), -mannopyranose (6) (31%), and -allopyranose (7) (21%).On the other hand, irradiation of 2 in 1:100 acetone-2-propanol gave 1,2,4,6-tetra-O-acetyl-3-deoxy-3-C-(1-hydroxy-1-methylethyl)-α-D-mannopyranose (8) (76%). Moreover, irradiation of 2 in 1:1 acetone-2-propanol yielded 1,4,6-tri-O-acetyl-3-deoxy-2,3-di-C-(1-hydroxy-1-methylethyl)-α-D-gluco- or -manno-pyranose 2,2¹,3¹-orthoacetate (10) (15%), in addition to 8 (44%).     

The relationship of molecular weight, and sulfate content and distribution to anticoagulant activity of heparin preparations

The crystalline intermediate 2-acetamido-6-O-(2-acetamido-3,4,6-tri-O-acetyl-2-deoxy-β-D-glucopyranosyl)-3,4-di-O-acetyl-2-deoxy-β-D-glucopyranosyl azide (5), obtained by condensation of 2-acetamido-3,4,6-tri-O-acetyl-2-deoxy-β-D-glucopyranosyl bromide with either 2-acetamido-3,4-di-O-acetyl-2-deoxy-β-D-glucopyranosyl azide or its 6-O-triphenylmethyl derivative, was reduced in the presence of Adams' catalyst to give a disaccharide amine. Condensation with 1-benzyl N-(benzyloxycarbonyl)-L-aspartate afforded crystalline 2-acetamido-6-O-(2-acetamido-3,4 6-tri-O-acetyl-2-deoxy-β-D-glucopyranosyl)-3,4-di-O-acetyl-1-N-[1-benzyl N-(benzyloxycarbonyl)-L-aspart-4-oyl]-2-deoxy-β-D-glucopyranosylamine (9). Catalytic hydrogenation in the presence of palladium-on-charcoal was followed by saponification to give 2-acetamido-6-O-(2-acetamido-2-deoxy-β-D-glucopyranosyl)-1-N-(L-aspart-4-oyl)-2-deoxy-β-D-glucopyranosylamine (11) in crystalline form. From the mother liquors of the reduction of 5, a further crystalline product was isolated, to which was assigned a bisglycosylamine structure (12).     

Synthèse des 2-acé-tamido-2-désoxy-6-O-α-et β-D-xylopyranosyl-α-D-glucopyranose

2-Acetamido-2- deoxy-6-O-, -xylopyranosyl-O-D-glucopyranose has been synthesized in crystalline form by condensation of 2,3,4-tri-O-acetyl-α-D-xylopyranosyl chloride (1) with benzyl 2-acetamido-3,4-di-O-acetyl-2-deoxy-β-D-glucopyranoside (2), followed by O-deacetylation and catalytic hydrogenation. Condensation of 2 with 2,3,4-tri-O-chlorosulfonyl-β-D-xylopyranosyl chloride, followed by dechlorosulfonylation and acetylation, gave benzyl 2-acetamido-3,4-di-O-acetyl-2-deoxy-6-O-(2,3,4-tri-O-acetyl-α-D-xylopyranosyl)β-D-glucopyranoside in crystalline form. O-Deacetylation, followed by catalytic hydrogenation, gave 2-acetamido-2-deoxy-6-O-α-D-xylopyranosyl-α-D-glucopyranose in crystalline form.     

Use of 3-O-(2-acetamido-3,4,6-tri-O-acetyl-2-deoxy-β-d-glucopyranosyl)-2,4,6-tri-O-acetyl-α-d-galactopyranosyl bromide as a glycosyl donor: Synthesis of p-nitrophenyl 3-O-(2-acetamido-2-deoxy-β-d-glucopyranosyl)-β-d-galactopyranoside

Acetolysis of methyl 3-O-(2-acetamido-3,4,6-tri-O-acetyl-2-deoxy-β-d-glucopyranosyl)-2,4,6-tri-O-acetyl-α-d-galactopyranoside afforded 3-O-(2-acetamido-3,4,6-tri-O-acetyl-2-deoxy-β-d-glucopyranosyl)-1,2,4,6-tetra-O-acetyl-d-galactopyranose (2). Treatment of 2 in dichloromethane with hydrogen bromide in glacial acetic acid gave 3-O-(2-acetamido-3,4,6-tri-O-acetyl-2-deoxy-β-d-glucopyranosyl)- 2,4,6-tri-O-acetyl-α-d-galactopyranosyl bromide (3). The α configuration of 3 was indicated by its high, positive, specific rotation, and supported by its ¹H-n.m.r. spectrum. Reaction of 3 with Amberlyst A-26-p-nitrophenoxide resin in 1:4 dichloromethane-2-propanol furnished p-nitrophenyl 3-O-(2-acetamido-3,4,6- tri-O-acetyl-2-deoxy-β-d-glucopyranosyl)-2,4,6-tri-O-acetyl-β-d-galactopyranoside (7). Compound 7 was also obtained by the condensation (catalyzed by silver trifluoromethanesulfonate-2,4,6-trimethylpyridine) of 3,4,6-tri-O-acetyl-2-deoxy-2-phthalimido-β-d-glucopyranosyl bromide with p-nitrophenyl 2,4,6-tri-O-acetyl-β-d-galactopyranoside, followed by the usual deacylation-peracetylation procedure. O-Deacetylation of 7 in methanolic sodium methoxide furnished the title disaccharide (8). The structure of 8 was established by ¹³C-n.m.r. spectroscopy.     

Chemical modification of aminocyclitol antibiotics

The aminocyclitol antibiotic neamine has been chemically modified at the hydroxyl group on C-6 of the 2-deoxystreptamine moiety. The partially acetylated neamine derivatives, 6,3′,4′-tri-O-acetyl- (3) and 5,3′,4′-tri-O-acetyl-1,3,2′,6′-tetra-N-(ethoxycarbonyl)neamine (4), were prepared by random hydrolysis of the 5,6-O-ethoxyethylidene derivative (2), followed by chromatographic purification. Condensation of 4 and 2,3,5-tri-O-benzoyl-d-ribofuranosyl chloride led to 6-O-(β-d-ribofuranosyl)neamine (7). Analogous condensation of 4 with 2,3,4,6-tetra-O-acetyl-α-d-glucopyranosyl bromide or 2,3,4,6-tetra-O-acetyl-α-d-galactopyranosyl bromide afforded the corresponding 6-O-(d-hexopyranosyl)neamines.     

The attachment of poly(ribitol phosphate) to lipoteichoic acid carrier

2-Acetamido-3,4,6-tri-O-acetyl-1-N-[N-(benzyloxycarbonyl)-L-aspart-1-oyl-(L-leucyl-L-threonyl-N²-tosyl-L-lysine p-nitrobenzyl ester)-4-oyl]-2-deoxy-β-D-glucopyranosylamine (21) and 2-acetamido-3,4,6-tri-O-acetyl-1-N-[N-(benzyloxycarbonyl)-L-aspart-1-oyl-(L-leucyl-L-threonyl-N²-tosyl-L-lysine p-nitrobenzyl ester)-4-oyl]-2-deoxy-β-D-glucopyranosylamine (22), 2-acetamido-3,4,6-tri-O-acetyl-1-N-[N-(benzyloxycarbonyl)-L-aspart-1-oyl-(glycine ethyl ester)-4-oyl]-2-deoxy-β-D-glucopyranosylamine, and 2-acetamido-3,4,6-tri-O-acetyl-1-N-[N-(benzyloxycarbonyl)-L-aspart-1-oyl-(phenylalanine methyl ester)-4-oyl]-2-deoxy-β-D-glucopyranosylamine were synthesized by condensation of 2-acetamido-3,4,6-tri-O-acetyl-1-N-[N-(benzyloxycarbonyl)-L-aspart-4-oyl]-2-deoxy-β-D-glucopyranosylamine with the appropriate protected amino acids and tri- and tetra-peptides. The amino acid sequences of 21 and 22 correspond to the protected amino acid sequences 34–37 and 34–38 of ribonuclease B that are adjacent to the carbohydrate-protein linkage.     

The stepwise synthesis of a methyl β-xylotetraoside related to branched xylans

3,4-Di-O-acetyl-2-O-benzyl-α-d-xylopyranosyl bromide (1) reacts with methyl 2,3-anhydro-α-d-ribopyranoside (2) to afford, in high yield, methyl 2,3-anhydro-4-O- (3,4-di-O-acetyl-2-O-benzyl-β-d-xylopyranosyl)-β-d-ribopyranoside (3). Deacetylation of 3 gave 4, which reacted with 2,3,4-tri-O-acetyl-α-d-xylopyranosyl bromide to give the branched tetrasaccharide derivative 5, which, in turn, was converted by a series or conventional reactions into methyl 4-O-[3,4-di-O-(β-d-xylopyranosyl)-β-d- xylopyranosyl]-β-d-xylopyranoside. The reaction of 1 with its hydrolysis product gave 3,4-di-O-acetyl-2-O-benzyl-α-d-xylopyranosyl 3,4-di-O-acetyl-2-O-benzyl-β-d-xylopyranoside, which was also isolated after the reaction of 1 with 2.     

Synthesis of two purple-membrane glycolipids and the glycolipid sulfate O-(β-d-glucopyranosyl 3-sulfate)-(1→6)-O-α-d-mannopyranosyl-(1→2)-O-α-d-glucopyranosyl-(1→1)-2, 3-di-O-phytanyl-sn-glycerol

The two purple-membrane glycolipids O-β-d-glucopyranosyl- and O-β-d-galactopyranosyl-(1→6)-O-α-d-mannopyranosyl-(1→2)-O-α-d-glucopyranosyl-(1→1)-2, 3-di-O-phytanyl-sn-glycerol were prepared by coupling O-(2,3,4-tri-O-acetyl-α-d-mannopyranosyl)-(1→2)-O-(3,4,6-tri-O-acetyl-α-d-glucopyranosyl)-(1→1)-2, 3-di-O-phytanyl-sn-glycerol (9) with 2,3,4,6-tetra-O-acetyl-α-d-glucopyranosyl bromide or 2,3,4,6-tetra-O-acetyl-α-d-mannopyranosyl bromide, respectively, followed by deacetylation. The glycolipid sulfate O-(β-d-glucopyranosyl 3-sulfate)-(1→6)-O-α-d-mannopyranosyl-(1→2)-O-α-d-glucopyranosyl-(1→1)-2,3-di-O-phytanyl-sn-glycerol was prepared by coupling of 9 with 2,4,6-tri-O-acetyl-3-O-trichloroethyloxycarbonyl-α-d-glucopyranosyl bromide in the presence of Hg(CN)₂/HgBr₂ followed by selective removal of the 3?-trichloroethyloxycarbonyl group, sulfation of HO-3?, and deacetylation. The suitably protected key-intermediate 9 could be prepared by two distinct approaches.     

Synthesis of benzyl 2-acetamido-2-deoxy-3-O-β-d-fucopyranosyl-α-d-galactopyranoside and benzyl 2-acetamido-6-O-(2-acetamido-2-deoxy-β-d-glucopyranosyl)-2-deoxy-3-O-β-d-fucopyranosyl-α-d-galactopyranoside

Condensation of benzyl 2-acetamido-4,6-O-benzylidene-2-deoxy-α-d-galactopyranoside with 2,3,4-tri-O-acetyl-α-d-fucopyranosyl bromide in 1:1 nitromethane-benzene, in the presence of powdered mercuric cyanide, afforded benzyl 2-acetamido-4,6-O-benzylidene-2-deoxy-3-O-(2,3,4-tri-O-acetyl-β-d-fucopyranosyl)-α-d-galactopyranoside (3). Cleavage of the benzylidene group of 3 with hot, 60% aqueous acetic acid afforded diol 4, which, on deacetylation, furnished the disaccharide 5. Condensation of diol 4 with 2-methyl-(3,4,6-tri-O-acetyl-1,2-di-deoxy-α-d-glucopyrano)-[2,1-d]-2-oxazoline in 1,2-dichloroethane afforded the trisaccharide derivative (7). Deacetylation of 7 with Amberlyst A-26 (OH^?) anion-exchange resin in methanol gave the title trisaccharide (8). The structures of 5 and 8 were confirmed by ¹³C-n.m.r. spectroscopy.     

Addition of halogenoazides to glycals

Addition of chloroazide to 3,4,6-tri-O-acetyl-1,5-anhydro-2-deoxy-d-lyxo- (1) and -d-arabino-hex-1-enitol (2) under u.v. irradiation proceeds regio- and stereo-selectively yielding mainly O-acetyl derivatives of 2-azido-2-deoxy-d-galactopyranose and -d-glucopyranose, respectively. 3,4,6-Tri-O-acetyl-2-chloro-2-deoxy-α-d-galactopyranosyl azide and 3,4,6-tri-O-acetyl-2-azido-2-deoxy-α-d-talopyranose (from 1), and 1,3,4,6-tetra-O-acetyl-2-chloro-2-deoxy-α-d-glucopyranosyl azide and 1,3,4,6-tetra-O-acetyl-2-azido-2-deoxy-α-d-mannopyranose (from 2) are byproducts. 1,5-Anhydro-3,4,6-tri-O-benzyl-2-deoxy-d-lyxo- and -d-arabino-hex-1-enitol reacted more rapidly with chloroazide, to give, under irradiation, derivatives of 2-azido-2-deoxy-d-galactose and -d-glucose, respectively. However, reaction in the dark gave mainly O-benzyl derivatives of 2-chloro-2-deoxy-α-d-galacto- and -α-d-glucopyranosyl azide. The difference between the products obtained may depend on the existence of two parallel processes, one radical (under irradiation), and the other ionic (reaction in the dark).     

The synthesis of 5-O-(2-acetamido-2-deoxy-α-D-glucopyranosyl)-β-D-glucofuranose

Condensation of dimeric 3,4,6-tri-O-acetyl-2-deoxy-2-nitroso-α-D-glucopyranosyl chloride (1) with 1,2-O-isopropylidene-α-D-glucofuranurono-6,3-lactone (2) gave 1,2-O-isopropylidene-5-O-(3,4,6-tri-O-acetyl-2-deoxy-2-hydroxyimino-α-D-arabino-hexopyranosyl)-α-D-glucofuranurono-6,3-lactone (3). Benzoylation of the hydroxyimino group with benzoyl cyanide in acetonitrile gave 1,2-O-isopropylidene-5-O-(3,4,6-tri-O-acetyl-2-benzoyloxyimino-2-deoxy-α-D-arabino-hexopyranosyl)-α-D-glucofuranurono-6,3-lactone (4). Compound 4 was reduced with borane in tetrahydrofuran, yielding 5-O-(2-amino-2-deoxy-α-D-glucopyranosyl)-1,2-O-isopropylidene-α-D-glucofuranose (5), which was isolated as the crystalline N-acetyl derivative (6). After removal of the isopropylidene acetal, the pure, crystalline title compound (10) was obtained.     

Conversion of a 2-(N-nitroso)acetamido hexose into a five-carbon, acetylenic sugar derivative

Dinitrogen tetraoxide was used to convert 2-acetamido-1,3,4,6-tetra-O-acetyl-2-deoxy-β-D-glucopyranose (1) in high yield into the syrupy N-nitroso derivative 2, and benzyl 2-acetamido-3,4,6-tri-O-acetyl-2-deoxy-β-D-glucopyranose (6) into the crystalline N-nitroso analog 7. The N-nitroso derivative 2 in acetonitrile underwent photolysis by pyrex-filtered, u.v. light to regenerate the starting acetamide 1 in high yield; spontaneous decomposition of 2 afforded β-D-glucopyranose pentaacetate (3) and other products. In ethereal solution, compound 2 reacted with potassium hydroxide in isopropyl alcohol with loss of the 2-substituent and C-1, to give a C₅ acetylene, 1,2-dideoxy-D-erythro-pent-1-ynitol, isolated in high yield as its triacetate 4 and characterized by conversion into the known, crystalline 1,2-dideoxy-3-O-(3,5- dinitrobenzoyl)-4,5-O-isopropylidene-D-erythro-pent-1-ynitol (5).     

Synthesis of 2-acetamido-2-deoxy-3-O-β-d-mannopyranosyl-d-glucose

Condensation of 4,6-di-O-acetyl-2,3-O-carbonyl-α-d-mannopyranosyl bromide with benzyl 2-acetamido-4,6-O-benzylidene-2-deoxy-α-d-glucopyranoside (2) gave an α-d-linked disaccharide, further transformed by removal of the carbonyl and benzylidene groups and acetylation into the previously reported benzyl 2-acetamido-4,6-O-benzylidene-2-deoxy-3-O-(2,3,4,6-tetra-O-acetyl-α-d-mannopyranosyl)-α-d-glucopyranoside. Condensation of 3,4,6-tri-O-benzyl-1,2-O-(1-ethoxyethylidene)-α-d-glucopyranose or 2-O-acetyl-3,4,6-tri-O-benzyl-α-d-glucopyranosyl bromide with 2 gave benzyl 2-acetamido-3-O-(2-O-acetyl-3,4,6-tri-O-benzyl-β-d-glucopyranosyl)-4,6-O-benzylidene-2-deoxy-α-d-glucopyranoside. Removal of the acetyl group at O-2, followed by oxidation with acetic anhydride-dimethyl sulfoxide, gave the β-d-arabino-hexosid-2-ulose 14. Reduction with sodium borohydride, and removal of the protective groups, gave 2-acetamido-2-deoxy-3-O-β-d-mannopyranosyl-d-glucose, which was characterized as the heptaacetate. The anomeric configuration of the glycosidic linkage was ascertained by comparison with the α-d-linked analog.     

Synthesis of 1,3,4,6-tetra-O-acetyl-2-[3-alkyl-(aryl)-thioreido]-2-deoxy-α-d-glucopyranoses and their transformation into 2-alkyl(aryl)amino-(1,2-dideoxy-α-d-glucopyrano)[2,1-d]-2-thiazolines

1,3,4,6-Tetra-O-acetyl-2-deoxy-2-isothiocyanato-α-d-glucopyranose, produced from 1,3,4,6-tetra-O-acetyl-2-amino-2-deoxy-α-d-glucopyranose hydrochloride, thiophosgene, and calcium carbonate, was condensed with alkyl- and aryl-amines in ether to afford the crystalline 1,3,4,6-tetra-O-acetyl-2-[3-alkyl(aryl)-thioureido]-2-deoxy-α-d-glucopyranoses (2). Compounds 2 and the β anomers 3 were converted in high yield into 2-alkyl(aryl)amino-(3,4,6-tri-O-acetyl-1,2-dideoxy-α-d-glucopyrano)[2,1-d]-2-thiazoline hydrobromides (4) by hydrogen bromide-promoted cyclisation. The O-deacetylated thiazoline hydrobromide 5 was also isolated and converted into 2-[N-(4-methoxyphenyl)acetamido]-(3,4,6-tri-O-acetyl-1,2-dideoxy-α-d-glucopyrano)[2,1-d]-2-thiazoline (8). Conformational studies of 4 and 8 were made by ¹H-n.m.r. spectroscopy.     

Changes in the hemicellulosic polysaccharides of rye-grass with increasing maturity

Reaction of the C-2 mercurated methyl hexopyranoside acetates 1–3 with an excess of iodine resulted in nearly quantitative replacement of mercury by iodine with retention and inversion of configuration at C-2. Similar replacement was observed with 2-acetoxymercuri-3,4,6-tri-O-acetyl-2-deoxy-α-d-glucopyranose (4). In the iodinolysis of 2-acetoxymercuri-1,3,4,6-tetra-O-acetyl-2-deoxy-α-d-glucopyranose (5) in methanol, however, replacement at C-2 was accompanied to a considerable extent by solvolysis of the 1-acetoxyl group, and a mixture of 1,2-trans isomers of methyl 3,4,6-tri-O-acetyl-2-deoxy-2-iodo-hexopyranosides having the d-gluco and d-manno configurations was obtained, together with 1,3,4,6-tetra-O-acetyl-2-deoxy-2-iodo-α-d-mannopyranose.     

Synthetic mucin fragments. Methyl 6-O-(2-acetamido-2-deoxy-β-D-glycopyranosyl)-β-D-galactopyranoside,methyl 3,4-di-O-(2-acetamido-2-deoxy-β-D-glycopyranosyl)-β-D-galactopyranoside,and methyl O-(2-acetamido-2-deoxy-β-D-glucopyranosyl)-(1 å 3)-O-β-D-galactopyranosyl-(1 å 3)-O-(2-acetamido-2-deoxy-β- D-glucopyranosyl)-(1 å 3)-β-D-galactopyranoside

Condensation of methyl 2,6-di-O-benzyl-β-d-galactopyranoside with 2-methyl-(3,4,6-tri-O-acetyl-1,2-dideoxy-α-d-glucopyrano)-[2,1,-d]-2-oxazoline (1) in 1,2-dichloroethane, in the presence of p-toluenesulfonic acid, afforded a trisaccharide derivative which, on deacetylation, gave methyl 3,4-di-O-(2-acetamido-2-deoxy-β-d-glucopyranosyl)-2,6-di-O-benzyl-β-d- glactopyranoside (5). Hydrogenolysis of the benzyl groups of 5 furnished the title trisaccharide (6). A similar condensation of methyl 2,3-di-O-benzyl-β-d-galactopyranoside with 1 produced a partially-protected disacchraide derivative, which, on O-deacetylation followed by hydrogenolysis, gave methyl 6-O-(2-acetamido-2-deoxy-β-d-glucopyranosyl)-β-d-glactopyranoside (10). Condensation of methyl 3-O-(2-acetamido-4,6-O-benzylidene-2-deoxy-β-d-glucopyranosyl)-2,4,6-tri-O-benzyl-β-d- galactopyranoside with 3-O-(2-acetamido-3,4,6-tri-O-acetyl-2-deoxy-β-d-glucopyranosyl)-2,4,6-tri-O-acetyl-α-d-galactopyranosyl bromide in 1:1 benzene-nitromethane in the presence of powdered mercuric cyanide gave a fully-protected tetrasaccharide derivative, which was O-deacetylated and then subjected to catalytic hydrogenation to furnish methyl O-(2-acetamido-2-deoxy-β-d-glucopyranosyl)-(1→3)-O-β-d-galactopyranosyl-(1å3)-O-(2-acetamido-2-deoxy- β-d-glucopyranosyl)-(1å3)-β-d-galactopyranoside (15). The structures of 6, 10, and 15 were established by ¹³C-n.m.r. spectroscopy.     

Synthesis of methyl O-(3-deoxy-3-fluoro-β- -galactopyranosyl)-(1→6)-β- -galactopyranoside and methyl O-(3-deoxy-3-fluoro-β- -galactopyranosyl)-(1→6)-O-β- -galactopyranosyl-(1→6)-β- -galactopyranoside

Condensation of 2,4,6-tri-O-acetyl-3-deoxy-3-fluoro-α- -galactopyranosyl bromide (3) with methyl 2,3,4-tri-O-acetyl-β- -galactopyranoside (4) gave a fully acetylated (1→6)-β- -galactobiose fluorinated at the 3′-position which was deacetylated to give the title disaccharide. The corresponding trisaccharide was obtained by reaction of 4 with 2,3,4-tri-O-acetyl-6-O-chloroacetyl-α- -galactopyranosyl bromide (5), dechloroacetylation of the formed methyl O-(2,3,4-tri-O-acetyl-6-O-chloroacetyl-β- -galactopyranosyl)-(1→6)- 2,3,4-tri-O-acetyl-β- -galactopyranoside to give methyl O-(2,3,4-tri-O-acetyl-β- -galactopyranosyl)-(1→6)-2,3,4-tri-O-acetyl-β- -galactopyranoside (14), condensation with 3, and deacetylation. Dechloroacetylation of methyl O-(2,3,4-tri-O-acetyl-6-O-chloroacetyl-β- -galactopyranosyl)-(1→6)-O-(2,3,4-tri-O-acetyl- β- -galactopyranosyl)-(1→6)-2,3,4-tri-O-acetyl-β- -galactopyranoside, obtained by condensation of disaccharide 14 with bromide 5, was accompanied by extensive acetyl migration giving a mixture of products. These were deacetylated to give, crystalline for the first time, the methyl β-glycoside of (1→6)-β- -galactotriose in high yield. The structures of the target compounds were confirmed by 500-MHz, 2D, ¹H- and conventional ¹³C- and ¹⁹F-n.m.r. spectroscopy.