Synthesis and characterization of propyl O-β-d-galactopyranosyl-(1→4)-O-β-d-galactopyranosyl-(1→4)-α-d-galactopyranoside

Allyl 4-O-(4-O-acetyl-2-O-benzoyl-3,6-di-O-benzyl-β-d-galactopyranosyl)-2-O-benzoyl-3,6-di-O-benzyl-α-d- galactopyranoside was O-deallylated to give the 1-hydroxy derivative, and this was converted into the corresponding 1-O-(N-phenylcarbamoyl) derivative, treatment of which with dry HCl produced the α-d-galactopyranosyl chloride. This was converted into the corresponding 2,2,2-trifluoroethanesulfonate, which was coupled to allyl 2-O-benzoyl-3,6-di-O-benzyl-α-d-galactopyranoside, to give crystalline allyl 4-O-[4-O-(4-O-acetyl-2-O-benzoyl-3,6-di-O-benzyl-β-d-galactopyranosyl)-2-O-benzoyl-3,6-di- O-benzyl-β-d-galactopyranosyl]-2-O-benzoyl-3,6-di-O-benzyl-α-d-galactopyranoside (15) in 85% yield, no trace of the α anomer being found. The trisaccharide derivative 15 was de-esterified with 2% KCN in 95% ethanol, and the product O-debenzylated with H₂-Pd, to give the unprotected trisaccharide. Alternative sequences are discussed.     

Synthesis of a tetrasaccharide donor corresponding to the O-specific polysaccharide of Shigella dysenteriae type 1

O-(2,4-Di-O-chloroacetyl-α-l-rhamnopyranosyl)-(1 → 2)-O-(3,4,6-tri-O-benzoyl-α-d-galactopyranosyl)-(1 → 3)-O-(2-acetamido-4,6-di-O-acetyl-2-deoxy-α-d-glycopyranosyl)-(1 → 3)-2,4-di-O-benzoyl-α-l-rhamnopyranosyl trichloroacetimidate (1) was synthesized in a stepwise manner, using the following monosaccharide units: 2-(trimethylsilyl)ethyl 2,4-di-O-benzoyl-α-l-rhamnopyranoside, 2-azido-4,6-O-benzylidene-3-O-chloroacetyl-2-deoxy-β-d-glycopyranosyl chloride, methyl 3,4,6-tri-O-benzoyl-2-O-(4-methoxybenzyl)-1-thio-β-d-galactopyranoside, and 2,4-di-O-benzoyl-3-O-chloroacetyl-α-l-rhamnopyranosyl chloride. Compound 1 corresponds to a complete tetrasaccharide repeating unit of the O-specific polysaccharide of the lipopolysaccharide of Shigella dysenteriae type 1.     

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.     

The synthesis and properties of benzylated oxazolines derived from 2-acetamido-2-deoxy-D-glucose

2-Methyl-(2-acetamido-3,4,6-tri-O-benzyl-1,2-dideoxy-α-D-glucopyrano)-[2,1-d]-2-oxazoline,2-methyl-(2-acetamido-6-O-acetyl-3,4-di-O-benzyl-1,2-dideoxy-α-D-glucopyrano)-[2,1-d]-2-oxazoline,and 2-methyl-(2-acetamido-4-O-acetyl-3,6-di-O-benzyl-1,2-dideoxy-α-D-glucopyrano)-[2,1-d]-2-oxazoline were synthesized from the allyl 2-acetamido-3,4,6-tri-O-benzyl-2-deoxy-D-glucopyranosides, and from the 3,4-di-O-benzyl or 3,6-di-O-benzyl analogs, respectively, both the α and β anomer being used in each case. The preparation of allyl 2-acetamido-3,4,6-tri-O-benzyl- and 3,6-di-O-benzyl-2-deoxy-β-D-glucopyranoside is also described. Treatment of the tri-O-benzyl oxazoline with dibenzyl phosphate gave a pentabenzylglycosyl phosphate, from which all the benzyl groups were removed by catalytic hydrogenation, giving 2-acetamido-2-deoxy-α-D-glucopyranosyl phosphate. The corresponding β anomer was not detectable. Treatment of the 3,4-, or 3,6-, di-O-benzyl oxazoline with allyl 2-acetamido-3,4-di-O-benzyl-α-D-glucopyranoside readily gave disaccharide products from which the protecting groups were removed, to give the (1→6)-linked isomer of di-N-acetylchitobiose. Under both acidic and basic conditions, this isomer was less stable than the (1→4)-linked compound.Attempts to employ the 3,6-di-O-benzyl oxazoline for the formation of (1→4)-linked disaccharides, by treatment with either anomer of allyl 2-acetamido-3,6-di-O-benzyl-2-deoxy-D-glucopyranoside, were not very successful, presumably owing to hindrance by the bulky benzyl groups.     

Conversion of allyl 2-acetamido-2-deoxy-β-d-glucopyranoside into 2-methyl-(3,4,6-tri-O-benzoyl-1,2-dideoxy-α-d- galactopyrano)-[2′,1′:4,5]-2-oxazoline

2-Methyl-(3,4,6-tri-O-benzoyl-1,2-dideoxy-α-d-galactopyrano)-[2′,1′:4,5]-2-oxazoline (7) was prepared from 1-propenyl 2-acetamido-3,4,6-tri-O-benzoyl-2- deoxy-β-d-galactopyranoside (6). The latter was prepared from allyl 2-acetamido-2-deoxy-β-d-glucopyranoside (1) through selective benzoylation at O-3 and O-6, conversion into the 4-p-bromobenzenesulfonate 4, inversion of configuration at C-4 to afford allyl 2-acetamido-3,4,6-tri-O-benzoyl-β-d-galactopyranoside (5), and subsequent isomerization with palladium-charcoal to give 6.     

Synthesis of three oligosaccharides that form part of the complex type of carbohydrate moiety of glycoproteins

Silver trifluoromethanesulfonate-promoted condensation of 3,4,6-tri-O-acetyl-2-deoxy-phthalimido-β-d-glucopyranosyl bromide with benzyl 3,6-di-O-benzyl-α-d-mannopyranoside and benzyl 3,4-di-O-benzyl-α-d-mannopyranoside gave the protected 2,4- and 2,6-linked trisaccharides in yields of 54 and 32%, respectively. After exchanging the 2-deoxy-2-phthalimido groups for 2-acetamido-2-deoxy groups and de-blocking, the trisaccharides 2,4-di-O-(2-acetamido-2-deoxy-β-d-glucopyranosyl)-d-mannose and 2,6-di-O-(2-acetamido-2-deoxy-β-d-glucopyranosyl)-d-mannose were obtained. Similar condensation of 3,6-di-O-acetyl-2-deoxy-2-phthalimido-4-O-(2,3,4,6-tetra-O-acetyl-β-d-galactopyranosyl)-β-d-glucopyranosyl bromide with benzyl 3,4-di-O-benzyl-α-d-mannopyranoside gave a pentasaccharide derivative in 52% yield. After transformations analogous to those applied to the trisaccharides, 2,6-di-O-[β-d-galactopyranosyl-(1→4)-O-(2-acetamido-2-deoxy-β-d-glucopyranosyl)]-d-mannose was obtained.     

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.     

Syntheses of 3-O-(2-acetamido-2-deoxy-β-d-glucopyranosyl)-α-d-galactopyranose (“lacto-N-biose II”) and 3,4-di-O-(2-acetamido-2-deoxy-β-d-glucopyranosyl)-d-galactopyranose

3- O-(2-Acetamido-2-deoxy-β-d-glucopyranosyl)-α-d-galactopyranose (10, “Lacto-N-biose II”) was synthesized by treatment of benzyl 6-O-allyl-2,4-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 (5), followed by selective O-deallylation, O-deacetylation, and catalytic hydrogenolysis. Condensation of 5 with benzyl 6-O-allyl-2-O-benzyl-α-d-galactopyranoside, followed by removal of the protecting groups, gave 10 and a new, branched trisaccharide, 3,4-di-O-(2-acetamido-2-deoxy-β-d-glucopyranosyl)-d-galactopyranose (27).     

First synthesis of the immunodominant beta-galactofuranose-containing tetrasaccharide present in the cell wall of Aspergillus fumigatus

β-Galf-(1→5)-β-Galf-(1→6)-α-Manp-(1→6)-α-Manp, the immunodominant epitope in the cell-wall galactomannan of Aspergillus fumigatus, was synthesized for the first time as its allyl glycoside. The key disaccharide glycosyl donor, 2,3,5,6-tetra-O-benzoyl-β-d-galactofuranosyl-(1→5)-2-O-acetyl-3,6-di-O-benzoyl-β-d-galactofuranosyl trichloroacetimidate (10), was constructed by 5-O-glycosylation of 1,2-O-isopropylidene-3,6-di-O-benzoyl-α-d-galactofuranose (4) with 2,3,5,6-tetra-O-benzoyl-β-d-galactofuranosyl trichloroacetimidate (5), followed by 1,2-O-deacetonation, acetylation, selective 1-O-deacetylation, and trichloroacetimidation. The target tetrasaccharide 16 was obtained by the condensation of allyl 2,3,4-tri-O-benzoyl-α-d-mannopyranosyl-(1→6)-2,3,4-tri-O-benzoyl-α-d-mannopyranoside (14) as glycosyl acceptor with the disaccharide glycosyl donor 10, followed by deprotection.     

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.     

Further immunochemical studies on the combining sites of Lotus tetragonolobus and Ulex europaeus I and II lectins

A series of 2-O-benzoyl-4,6-di-O-benzyl-α-d-galactopyranosyl halides carrying either a second benzoyl group (8a, 12a) or a selectively removable, temporary protecting group (8b–d, 12b) at position 3 was synthesized from allyl α-d-galactopyranoside (1). The key intermediate was 1-propenyl 4,6-di-O-benzyl-α-d-galactopyranoside (5), prepared from 1 via the 4,6-O-benzylidene-2,3-di-O-crotyl derivative 2. The successive incorporation of the 2-O-benzoyl group, by selective acylation at low temperature, and of various 3-substituents gave fully substituted 1-propenyl α-d-galactopyranosides 6a–d. These were converted into the glycosyl halides by published methods. An improved preparation of allyl 2,6-di-O-benzyl-(15) and 2,4,6-tri-O-benzyl-(19) α-d-galactopyranoside was achieved. The direct acetonation of 1 to the 3,4-O-isopropylidene derivative 13, followed by benzylation and mild acid hydrolysis, gave 15 in 56% yield. The transient protection of O-3 in 15 was accomplished by the alkylation of the dibutylstannylene derivative 16 with (2-methoxyethoxy)methyl chloride. Successive benzylation and mild acid hydrolysis of the product 17 efficiently furnished 19.     

Synthesis of the tetrasaccharide repeating-unit of the O-specific polysaccharide from Salmonella senftenberg

The oligosaccharide β-d-Man-(1 → 4)-α-l-Rha (1 → 3)-d-Gal-(6 ← 1)-α-d-Glc, which is the repeating unit of the O-specific polysaccharide chain of the lipopolysaccharide from Salmonella senftenberg, was obtained by glycosylation of benzyl 2,4-di-O-benzyl-6-O-(2,3,4-tri-O-benzyl-6-O-p-nitrobenzoyl-α-d-glucopyranosyl)-β-d-galactopyranoside or benzyl 2-O-acetyl-6-O-(2,3,4-tri-O-benzyl-6-O-p-nitrobenzoyl-α-d-glucopyranosyl)-β-d-galactopyranoside with 3-O-acetyl-4-O-(2,3,4,6-tetra-O-acetyl-β-d-mannopyranosyl)-β-l-rhamnopyranose 1,2-(methyl orthoacetate) followed by removal of protecting groups.     

Synthesis of phenyl 2-acetamido-2-deoxy-3-O-α-l-fucopyranosyl-β-d-glucopyranoside and related compounds

The reaction of phenyl 2-acetamido-2-deoxy-4,6- O-(p-methoxybenzylidene)-β-d-glucopyranoside with 2,3,4-tri-O-benzyl-α-l-fucopyranosyl bromide under halide ion-catalyzed conditions proceeded readily, to give phenyl 2-acetamido-2-deoxy-4,6-O-(p-methoxybenzylidene)-3-O-(2,3,4-tri-O-benzyl-α-l-fucopyranosyl)-β-d-glucopyranoside (8). Mild treatment of 8 with acid, followed by hydrogenolysis, provided the disaccharide phenyl 2-acetamido-2-deoxy-3-O-α-l-fucopyranosyl-β-d-glucopyranoside. Starting from 6-(trifluoroacetamido)hexyl 2-acetamido-3,4,6-tri-O-acetyl-2-deoxy-β-d-glucopyranoside, the synthesis of 6-(trifluoroacetamido)hexyl 2-acetamido-2-deoxy-3-O-β-l-fucopyranosyl-β-d-glucopyranoside has been accomplished by a similar reaction-sequence. On acetolysis, methyl 2-acetamido-2-deoxy-3-O-α-l-fucopyranosyl-α-d-glucopyranoside gave 2-methyl-[4,6-di-O-acetyl-1,2-dideoxy-3-O-(2,3,4-tri-O-acetyl-α-l-fucopyranosyl)-α-d-glucopyrano]-[2, 1-d]-2-oxazoline as the major product.     

Synthesis of benzyl and allyl ethers of D-glucopyranose

Starting from allyl 3-O-benzyl-4,6-O-benzylidene-α-D-glucopyranoside as a key intermediate, the following crystalline compounds were prepared: 2-O-allyl-3,4,6-tri-O-benzyl-D-glucopyranose (11) and its p-nitrobenzoate; 2,3,5-tri-O-benzyl-D-arabinofuranose (12) and the corresponding arabinitol; allyl 3,4,6-tri-O-benzyl-α-D-glucopyranoside (7); 3,4,6-tri-O-benzyl-D-glucopyranose (8); 2-O-allyl-3,4-di-O-benzyl-D-glucopyranose (17) and its bis(p-nitrobenzoate); and 3,4-di-O-benzyl-D-glucopyranose (19). The p-nitrobenzoates of compounds 11 and 17 are potential intermediates for the synthesis of the glycolipids of the cytoplasmic membranes of Streptococci.     

Synthesis of 3-O Substituted D-Mannoses

1,2,4,6-Tetra-O-acetyl-3-O-benzyl-α-D-mannopyranose (7) was obtained in good yield from 3,4,6-tri-O-benzyl-1,2-O-(1-methoxyethylidene)-β-D-mannopyranose (1) by acetolysis. Hydrogenolysis of 7 afforded 1,2,4,6-tetra-O-acetyl-α-D-mannopyranose which is a versatile intermediate for the preparation of other 3-O-substituted D-mannoses, such as 3-O-methyl-D-mannose and 3-O-α-D-mannopyranosyl-D-mannose. 3,4-Di-O-methyl-D-mannose was readily prepared from 1,2,6-tri-O-acetyl-3,4-di-O-benzyl-α-D-mannopyranose, which was also obtained from 1 by controlled acetolysis.     

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.     

Unusual properties of glycuronans [poly(glycosyluronic) compounds]

2-Methyl-[3,6-di-O-acetyl-2-deoxy-4-O-(2,3,4,6-tetra-O-acetyl-β-d-galactopyranosyl)-α-d-glucopyrano]-[2,1-d]-2-oxazoline (4) was prepared from 2-acetamido-3,6-di-O-acetyl-2-deoxy-4-O-(2,3,4,6-tetra-O-acetyl-β-d-galactopyranosyl)-α-d- glucopyranosyl chloride. Condensation of 3,4:5,6-di-O-isopropylidene-d-mannose dimethyl acetal with 4 in the presence of a catalytic amount of p-toluenesulfonic acid afforded O-(2,3,4,6-tetra-O-acetyl-β-d-galactopyranosyl)-(1 → 4)-O-(2-acetamido-3,6-di-O-acetyl-2-deoxy-β-d-glucopyranosyl)-(1 → 2)-3,4:5,6-di-O-isopropylidene-d-mannose dimethyl acetal (6) in 8.6% yield. Catalytic deacetylation of 6 with sodium methoxide, followed by hydrolysis with dilute sulfuric acid, gave O-β-d-galactopyranosyl-(1 → 4)-O-(2-acetamido-2-deoxy-β-d-glucopyranosyl)-(1 → 2)-d-mannose (7). The inhibitory activities of 7 and related sugars against the hemagglutinating activities of various lectins were assayed, and 7 was found to be a good inhibitor against Phaseolus vulgaris hemagglutinin.     

A new synthesis of 4-O-α-d-galactopyranosyl-d-galactopyranose

The bromide-catalyzed condensation of 2,3,4,6-tetra-O-benzyl-d-galactopyranosyl bromide (11) with methyl 2,3,6-tri-O-benzoyl-α-d-galactopyranoside (3) gave methyl 2,3,6-tri-O-benzoyl-4-O-(2,3,4,6-tetra-O-benzyl-α-d-galactopyranosyl)-α-d-galactopyranoside (12) in 83% yield. The yield of this glycosidation reaction was high, despite the axial orientation of the 4-hydroxyl group of 3. Stepwise deprotection of 12 afforded methyl 4-O-α-d-galactopyranosyl-α-d-galactopyranoside (15). Acetylation of 15, followed by acetolysis, gave the known α-octaacetate 17. This scheme constituted a total synthesis of 4-O-α-d-galactopyranosyl-d-galactopyranose (2) in 25% yield from 3. The disaccharide 2 is the terminal disaccharide of the ceramide trisaccharide related to Fabry's disease.     

Syntheses of 2-acetamido-2-deoxy-4-O-α-D-glucopyranosyl-α-d-glucopyranose (n-acetylmaltosamine) and 2-acetamido-2-deoxy-4-O-β-d-glucopyranosyl-α-d-glucopyranose

Condensation of benzyl 2-acetamido-3,6-di-O-benzyl-2-deoxy-α-D-glucopyranoside with 2,3,4,6-tetra-O-benzyl-1-O-(N-methyl)acetimidoyl-β-D-glucopyranose gave benzyl 2-acetamido-3,6-di-O-benzyl-2-deoxy-4-O-(2,3,4,6-tetra-O-benzyl-α-D-glucopyranosyl)-α-D-glucopyranoside which was catalytically hydrogenolysed to crystalline 2-acetamido-2-deoxy-4-O-α-D-glucopyranosyl-α-D-glucopyranose (N-acetylmaltosamine). In an alternative route, the aforementioned imidate was condensed with 2-acetamido-3-O-acetyl-1,6-anhydro-2-deoxy-β-D-glucopyranose, and the resulting disaccharide was catalytically hydrogenolysed, acetylated, and acetolysed to give 2-acetamido-1,3,6-tri-O-acetyl-2-deoxy-4-O-(2,3,4,6-tetra-O-acetyl-α-D-glucopyranosyl)-α-D-glucopyranose Deacetylation gave N-acetylmaltosamine. The synthesis of 2-acetamido-2-deoxy-4-O-β-D-glucopyranosyl-α-D-glucopyranose involved condensation of benzyl 2-acetamido-3,6-di-O-benzyl-2-deoxy-α-D-glucopyranoside with 2,3,4,6-tetra-O-acetyl-α-D-glucopyranosyl bromide in the presence of mercuric bromide, followed by deacetylation and catalytic hydrogenolysis of the condensation product.     

Synthesis of a model of an inner chain of cell-wall proteoheteroglycan isolated from Piricularia oryzae: Branched d-mannopentaosides

Efficient syntheses are described of the branched d-mannopentaosides methyl 2,6-di-O-(2-O-α-d-mannopyranosyl-α-d-mannopyranosyl)α-d-mannopyranoside and methyl 2,4-di-O-(2-O-α-d-mannopyranosyl-α-d-mannopyranosyl)-α-d-mannopyranoside, starting from the glycosyl acceptors methyl 3,4-di-O-benzyl-α-d-mannopyranoside and methyl 3,6-di-O-benzyl-α-d-mannopyranoside, and employing the protected d-mannotriosides methyl 3,4-di-O-benzyl-2,6-di-O-(3,4,6-tri-O-benzyl-α-d-mannopyranosyl)-α-d-mannopyranoside, and methyl 3,6-di-O-benzyl-2,4-di-O-(3,4,6-tri-O-benzyl-α-d-mannopyranosyl)-α-d-mannopyranoside as key intermediates.