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.     

Entwicklung eines syntheseblocks der 3-O-β-d-galactopyranosyl-d-galactopyranose

In the presence of trimethylsilyl triflate, 1,2,3,4,6-penta-O-acetyl-β-d-galactopyranose reacted with benzyl 4-O-acetyl-2,6-di-O-benzyl-β-d-galactopyranoside to give benzyl 2,6-di-O-benzyl-3-O-β-d-galactopyranosyl-β-d-galactopyranoside further converted into the synthetic block 1,2,4,6-tetra-O-acetyl-3-O-(2,3,4,6-tetra-O-acetyl-β-d-galactopyranosyl)-β-d-galactopyranose. This, in the presence of a Lewis acid catalyst and with the corresponding glycosyl acceptors, gave 8-methoxycarbonyloctyl 3-O-β-d-galactopyranosyl-β-d-galactopyranoside and 8-methoxycarbonyloctyl O-β-d-galactopyranosyl-(1→3)-O-β-d-galactopyranosyl-(1→3)-2-acetamido-2-deoxy-α-d-galactopyranoside.     

The synthesis of O-(2-acetamido-2-deoxy-β-d-glucopyranosyl)-(1→4)-N-acetylnormuramoyl-l-α-aminobutanoyl-d-isoglutamine

Benzyl 2-acetamido-3-O-allyl-6-O-benzyl-2-deoxy-4-O-(3,4,6-tri-O-acetyl-2-deoxy-2-phthalimido-β-d-glucopyranosyl)- α-d-glucopyranoside (4) was obtained in high yield on using the silver triflate method in the absence of base. Compound 4 was converted in six steps into benzyl 2-acetamido-4-O-(2-acetamido-3,4,6-tri-O-benzyl-2-deoxy-β-d-glucopyranosyl)-6-O-benzyl-3-O-(carboxymethyl)-2-deoxy-α-d- glucopyranoside, which was coupled with the benzyl ester of l-α-aminobutanoyl-d-isoglutamine and the product hydrogenolyzed to afford the title compound. O-Benzylation of benzyl 2-acetamido-4-O-(2-acetamido-2-deoxy-β-d-glucopyranosyl)-3-O-allyl-6-O-benzyl-2-deoxy-α-d-glucopyranoside with benzyl bromide and barium hydroxide in N,N-dimethylformamide is strongly exhanced by sonication of the reaction mixture.     

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.     

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 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.     

Echinocystic acid 3,16-O-bisglycosides from Albizia procera

Three triterpene glycosides and two known ones were isolated from the bark of Albizia procera by using chromatographic techniques. The structures of the compounds were determined to be 3-O-β-d-xylopyranosyl-(1 → 2)-β-d-galactopyranosyl-(1 → 6)-2-acetamido-2-deoxy-β-d-glucopyranosyl echinocystic acid 16-O-β-d-glucopyranoside, 3-O-β-d-xylopyranosyl-(1 → 2)-α-l-arabinopyranosyl-(1 → 6)-2-acetamido-2-deoxy-β-d-glucopyranosyl echinocystic acid 16-O-β-d-glucopyranoside and 3-O-α-l-arabinopyranosyl-(1 → 2)-α-l-arabinopyranosyl-(1 → 6)-2-acetamido-2-deoxy-β-d-glucopyranosyl echinocystic acid 16-O-β-d-glucopyranoside. Their structures were determined by NMR techniques including HOHAHA, ¹H-¹H COSY, ROE, HMQC and HMBC experiments together with FABMS as well as acid hydrolysis. To the best of our knowledge, the new compounds are considered the first examples of echinocystic acid 3,16-O-bisglycosides. In contrast to other cytotoxic echinocystic acid glycosides with N-acetyl glucosamine unit, the new glycosides were found inactive when assayed by MTT method for their cytotoxicities against the human tumor cell lines HEPG2, A549, HT29 and MCF7. The results showed the importance of the free hydroxyl group at the aglycone C-16 for exhibiting cytotoxic properties.     

The synthesis of P1-2-acetamido-4-O-(2-acetamido-2-deoxy-β-d-glucopyranosyl)-2-deoxy-α-d-glucopyranosyl P2-dolichyl pyrophosphate, (P1-di-N-acetyl-α-chitobiosyl P2-dolichyl pyrophosphate)

2-Acetamido-4-O-(2-acetamido-2-deoxy-β-d-glucopyranosyl)-2-deoxy-α-d-glucopyranosyl phosphate, pure according to thin-layer and gas—liquid chromatography, optical rotation, and treatment with alkaline phosphatase and 2-acetamido-2-deoxy-β-d-glucosidase, was prepared by treatment of 2-methyl-[4-O-(2-acetamido-3,4,6-tri-O-acetyl-2-deoxy-β-d-glucopyranosyl)-3,6-di-O-acetyl-1,2-dideoxy-α-d-glucopyrano]-[2,1-d]-2-oxazoline with dibenzyl phosphate, followed by the removal of the benzyl groups by catalytic hydrogenolysis, and O-deacetylation. In contrast, a sample prepared by the phosphoric acid procedure was shown to consist mainly of the β anomer. 2-Acetamido-4-O-(2-acetamido-3,4,6-tri-O-acetyl-2-deoxy-β-d-glucopyranosyl)-3,6-di-O-acetyl-2-deoxy-α-d-glucopyranosyl phosphate was treated wit P¹-diphenyl P²-dolichyl pyrophosphate to give a fully acetylated pyrophosphoric diester, which was O-deacetylated to give P¹-2-acetamido-4-O-(2-acetamido-2-deoxy-β-d-glucopyranosyl)-2-deoxy-α-d-glucopyranosyl P²-dolichyl pyrophosphate. This compound could be separated from the β anomer by t.l.c., and its behavior under dilute acid and alkaline conditions was investigated.     

A 13c-n.m.r. study of a di- and a tri-saccharide containing the α-d-galactopyranosyl group

The ¹³C-n.m.r. spectra of methyl 4-O-α-d-galactopyranosyl-α-d-galactopyranoside (1) and methyl 4-O-[4-O-(α-d-galactopyranosyl)-β-d-galactopyranosyl]-β-d-glucopyranoside (2) in D₂O were recorded. Comparison of these spectra with the spectra of methyl α-d-galactopyranoside (4) and methyl β-lactoside (5) provided substantial confirmation of the structures of 1 and 2.     

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.     

The synthesis of oligosaccharide-asparagine compounds. V. O- -D-mannopyranosyl-(1 leads to 6)-O-(2-acetamido-2-deoxy- -D-glucopyranosyl)-(1 leads to 4)-2-acetamido-N-(L-aspart-4-oyl)-2-deoxy- -D-glucopyranosylamine

O-α-d-Mannopyranosyl-(1→6)-O-(2-acetamido-2-deoxy-β-d-glucopyranosyl)-(1→4)-2-acetamido-N-(l-aspart-4-oyl)-2-deoxy-β-d-glucopyranosylamine (12), used in the synthesis of glycopeptides and as a reference compound in the structure elucidation of glycoproteins, was synthesized via condensation of 2,3,4,6-tetra-O-acetyl-α-d-mannopyranosyl bromide with 2-acetamido-4-O-(2-acetamido-3-O-acetyl-2-deoxy-β-d-glucopyranosyl)-3,6-di-O-acetyl-2-deoxy-β-d-glucopyranosyl azide (5) to give the intermediate, trisaccharide azide 7. [Compound 5 was obtained from the known 2-acetamido-4-O-(2-acetamido-3,4,6-tri-O-acetyl-2-deoxy-β-d-glucopyranosyl)-3,6-di-O-acetyl-2-deoxy-β-d-glucopyranosyl azide by de-O-acetylation, condensation with benzaldehyde, acetylation, and removal of the benzylidene group.] The trisaccharide azide 6 was then acetylated, and the acetate reduced in the presence of Adams' catalyst. The resulting amine was condensed with 1-benzyl N-(benzyloxycarbonyl)-l-aspartate, and the O-acetyl, N-(benzyloxycarbonyl), and benzyl protective groups were removed, to give the title compound.     

An improved method for the syntheses of p-aminophenyl 1-thio-β-d-glycosides

The condensation of the appropriate acetylglycosyl bromides with p-amino-benzenethiol in the presence of sodium methoxide afforded p-aminophenyl 1-thio-β-d-glucopyranoside, 1-thio-β-d-galactopyranoside, 1-thio-β-d-xylopyranoside, and 2-acetamido-2-deoxy-1-thio-β-d-glucopyranoside. p-Aminophenyl 1-thio-β-d-glucopyranosiduronic acid was synthesized by condensation of methyl (2,3,4-tri-o-acetyl-β-d-glucopyranosyl bromide)uronate with p-aminobenzenethiol, followed by saponification with sodium hydroxide.     

Stereoselectivity of glycosylation with derivatives of 2-azido-2-deoxy-d-galactopyranose. The synthesis of a determinant oligosaccharide related to blood-group a (type 1)

The stereoselective glycosylation of a model alcohol (cyclohexanol) by derivatives of 2-azido-2-deoxy-d-galactopyranose was studied under various conditions. 2-Azido-3,4,6-tri-O-benzyl-2-deoxy-β-d-galactopyranosyl chloride (9) was found to be the most efficient glycosylating agent for the synthesis of oligosaccharides containing 2-acetamido-2-deoxy-α-d-galactopyranose residues, and gave a tetrasaccharide, which is a determinant of the blood-group A (Type 1), i.e., O-α-l-fucopyranosyl-(1→2)-[O-2-acetamido-2-deoxy-α-d- galactopyranosyl-(1→3)]-O-β-d-galactopyranosyl-(1→3)-2-acetamido-2-deoxy-d-glucose, and its trisaccharide fragment, O-2-acetamido-2-deoxy-α-d-galactopyranosyl-(1→3)-O-β-d-galactopyranosyl-(1→3)-2-acetamido-2-deoxy-d-glucose. In the course of this synthesis, the determinant trisaccharide related to the H blood-group, i.e., O-α-l-fucopyranosyl-(1→2)-O-β-d-galactopyranosyl-(1→3)-2-acetamido-2- deoxy-d-glucose, was also obtained.     

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).     

Synthesis of the pentasaccharide repeating unit of Escherichia coli O128 antigen

A pentasaccharide, 4-methoxyphenyl 2-acetamido-2-deoxy-β-d-galactopyranosyl-(1→4)-α-d-galactopyranosyl-(1→3)-2-acetamido-2-deoxy-β-d-galactopyranosyl-(1→6)-[α-l-fucopyranosyl-(1→2)]-β-d-galactopyranoside (1), representing the repeating unit of Escherichia coli O128 antigen, was successfully prepared in 23% overall yield via a convergent ‘2+3’ glycosylation strategy.     

A convenient synthesis of p-nitrophenyl 2-deoxy-2-(thio-acetamido)-β-d-glucopyranoside, -galactopyranoside,and their 1-thio analogs as inhibitors of 2-acetamido-2-deoxy-β-d-glucosidase

The acetamido group of p-nitrophenyl 2-acetamido-2-deoxy-β-d-glucopyranoside, -β-d-galactopyranoside, and their 1-thio analogs was modified by replacement of the amide-carbonyl oxygen atom with sulfur by treatment of their fully acetylated derivatives with phosphorus pentasulfide in pyridine. The resulting p-nitrophenyl 2-deoxy-2-thioacetamido-β-d-hexopyranoside triacetates were O-deacetylated with catalytic amounts of sodium methoxide in methanol to obtain p-nitrophenyl 2-deoxy-2-thioacetamido-β-d-glucopyranoside, -β-d-galactopyranoside, and their 1-thio analogs. These derivatives inhibited 2-acetamido-2-deoxy-β-d-glucosidase from Turbatrix aceti to various extents. Also obtained in significant yields in the aforementioned reaction with phosphorus pentasulfide in pyridine were the two hitherto unreported thiazolines, namely, 2-methyl(2-acetamido-3,4,6-tri-O-acetyl-α-d-glucopyrano)[2′,1′:4,5]-2-thiazoline and 2-methyl(2-acetamido-3,4,6-tri-O-acetyl-α-d-galactopyrano)[2′,1′:4,5]-2-thiazoline.     

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.     

Synthese von O-(3-desoxy-α-d-manno-2-octulopyranosylonsäure)-(2→4)-O-(3-desoxy-α-d-manno-2-octulopyranosylonsäure)- (2→6)-O-(2-amino-2-desoxy-β-d-glucopyranosyl)-(1→6)-2-amino-2-desoxy-d-glucopyranose

Benzyl-3-O-benzyl-2-benzyloxycarbonylamino-6-O-[2-benzyloxycarbonyl-amino-2-deoxy-3,4-O-(tetraisopropyldisiloxane-1,3-diyl)- β-d-glucopyranosyl]-2-deoxy-α-d-glucopyranoside was coupled with methyl (4,5,7,8-tetra-O-acetyl-3-deoxy-α-d-manno-2-octulopyranosyl bromide)onate (13) to yield the α-glycosidically linked trisaccharide. After deacetylation and selective introduction of a second 7′,8′-O-tetraisopropyldisiloxane group, a further glycosidation reaction with 13 led regioselectively to the tetrasaccharide benzyl O-[methyl (4,5,7,8-tetra-O-acetyl-3-deoxy-α-d-manno-2-octulopyranosyl)onate]-(2→4)-O-{methyl [3-deoxy-7,8-O-(tetraisopropyldisiloxane-1,3-diyl)-α-d-manno-2-octulopyranosyl]-onate}-(2→6)-O- [2-benzyloxycarbonylamino-2-deoxy-3,4-O-(tetraisopropyldisiloxane-1,3-diyl)-β-d-glucopyranosyl]- (1→6)-3-O-benzyl-2-benzyloxycarbonyl-amino-2-deoxy-α-d-glucopyranoside. A series of deblocking steps gave O-(3-deoxy-α-d-manno-2-octulopyranosylonic acid)-(2→4)-O-(3-deoxy-α-d-manno-2-octulopyranosylonic acid)- (2→6)-O-(2-amino-2-deoxy-β-d-glucopyranosyl)-(1→6)-2-amino-2-deoxy-d-glucopyranose which was identical with a tetrasaccharide that had been isolated by hydrazinolysis of the lipopolysaccharide from Salmonella minnesota R 595. Hence, synthetic proof is provided for the linkages in this part of the inner core region of lipopolysaccharides.     

Synthesis of p-nitrophenyl 6-O-(2-acetamido-2-deoxy-β-d-glucopyranosyl)-α-d-mannopyranoside

The reaction of p-nitrophenyl 2,3-O-isopropylidene-α-d-mannopyranoside and 2-methyl-(3,4,6-tri-O-acetyl-1,2-dideoxy-α-d-glucopyrano)-[2,1-d]-2-oxazoline gave a crystalline, 6-O-substituted disaccharide derivative which, on de-isopropylidenation followed by saponification, produced the disaccharide p-nitrophenyl 6-O-(2-acetamido-2-deoxy-β-d-glucopyranosyl)-α-d-mannopyranoside. Synthesis of methyl 6-O-(2-acetamido-2-deoxy-β-d-glucopyranosyl)-α-d-mannopyranoside was also accomplished by a similar reaction-sequence. The structures of these disaccharides have been established by ¹³C-n.m.r. spectroscopy.