Glycosidation at C-4 of 2-acetamido-2-deoxy-D-glucopyranose derivatives by koenigs-knorr type condensations

The condensation of 2,3,4,6-tetra-O-benzyl-D-glucopyranosyl bromide and 2,3,4,6-tetra-O-benzyl-D-mannopyranosyl chloride with benzyl 2-acetamido-3,6-di-O-benzyl-2-deoxy-α-D-glucopyranoside (1), under Koenigs-Knorr conditions, gave the fully benzylated derivatives of benzyl 2-acetamido-2-deoxy-4-O-α-D-glucopyranosyl-α-D-glucopyranoside, benzyl 2-acetamido-2-deoxy-4-O-β-D-glucopyranosyl-α-D-glucopyranoside, and benzyl 2-acetamido-2-deoxy-4-O-α-D-mannopyranosyl-α-D-glucopyranoside. Three further compounds, namely, benzyl 2-acetamido-3-O-benzyl-2-deoxy-6-O-(2,3,4,6-tetra-O-benzyl-D-glucopyranosyl)-α-D-glucopyranoside, benzyl 2-acetamido-3-O-benzyl-2-deoxy-6-O-(2,3,4,6-tetra-O-benzyl-D)-mannopyranosyl)-α-D-glucopyranoside, and benzyl 2-acetamido-3-O-benzyl-2-deoxy-4,6-di-O-(2,3,4,6-tetra-O-benzyl-D-mannopyranosyl)-α-D-glucopyranoside, were formed by reaction of the respective glycosyl halide with benzyl 2-acetamido-3-O-benzyl-2-deoxy-α-D-glucopyranoside present as contaminant in 1.     

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.     

Neighbouring acetamido-group participation in reactions of derivatives of 2-acetamido-2-deoxy-D-glucose

Kinetic measurements suggest that neighbouring acetamido-group participation occurs in the spontaneous hydrolysis and methanolysis of o-carboxyphenyl 2-acetamido-2-deoxy-β-D-glucopyranoside and in the spontaneous hydrolysis of 2,4-dinitrophenyl 2-acetamido-2-deoxy-β-D-glucopyranoside and 2-acetamido-2-deoxy-β-D-glucopyranosyl fluoride. The methanolyses of these compounds proceed with predominant retention of configuration which is also consistent with neighbouring acetamido-group participation. The oxazoline intermediate which would arise from such a process was detected during methanolysis of 2-acetamido-2-deoxy-β-D-glucopyranosyl fluoride in the presence of bases by n.m.r., i.r., and u.v. spectroscopy. Attempts to isolate the oxazoline were unsuccessful.     

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.     

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.     

Preparation of some acylated D-arabino-hexopyranosuloses and 4-deoxy-D-glycero-hex-3-enopyranosuloses

Oxidation of 1,3,4,6-tetra-O-benzoyl-α- and β-D-glucopyranose gave the tetra-O-benzoyl-α- and -β-D-arabino-hexopyranosuloses (3α and β), from which benzoic acid was readily eliminated to give the anomeric tri-O-benzoyl-4-deoxy-D-glycero-hex-3-enopyranosuloses (4α and β). The anomeric 1-O-acetyl-tri-O-benzoyl-D-arabino-hexopyranosuloses (7α and β) were obtained as very unstable syrups which readily lost benzoic acid. Treatment of tetra-O-benzoyl-2-O-benzyl-D-glucopyranose (1) with hydrogen bromide gave 3,4,6-tri-O-benzoyl-α-D-glucopyranosyl bromide (5) in one step.     

Synthesis of glycopeptide derivatives containing the 2-acetamido-N-(L-aspart-4-oyl)-2-deoxy-β-D-glucopyranosylamine linkage and having the amino acid sequences 32–34, 33–35,33–37, and 33–38 of bovine ribonuclease

The synthesis is described of the glycotripeptide derivatives 2-acetamido-3,4,6-tri-O-acetyl-N-[N-(benzyloxycarbonyl)-L--seryl-L-nitroarginyl-L-aspart-4-oyl]-2-deoxy-β-D-glucopyranosylamine, 2-acetamido-3,4,6-tri-O-acetyl-N-[N-(benzyloxycarbonyl)-L-seryl-L-nitroarginyl-L-aspart-1-oyl-(1-p-nitrobenzyl ester)-4-oyl]-2-deoxy-β-D-glucopyranosylamine, and 2-acetamido-3,4,6-tri-O-acetyl-N-[N-(benzyloxycarbonyl)-L-nitroarginyl-L-aspart-1-oyl-(L-leucine methyl ester)-4-oyl]-2-deoxy-β-D-glucopyranosylamine, and of the glycopentapeptide and glycohexapeptide derivatives 2-acetamido-3,4,6-tri-O-acetyl-N-[N-(benzyloxycarbonyl)-L-nitroarginyl-L-aspart-1-oyl-(L-leucyl-L-threonyl-threonyl-N^ε-tosyl-L-lysine-(p-nitrobenzyl ester)-4-oyl]-2-deoxy-β-D-glycopyranosylamine and 2-acetamido-3,4,6-tri-O-acetyl-N-[N-(benzyloxycarbonyl)-L-nitroarginyl-L-aspart-1-oyl-(L-leucyl-L-threonyl-N^ε-tosyl-L-lysyl-L-aspartic 1,4-di-p-nitrobenzyl ester)-4-oyl]-2-deoxy-β-D-glucopyranosylamine.     

Preparation of 2-amino-2-deoxy-α-D-glucopyranosyl phosphate from uridine 5'-(2-acetamido-2-deoxy-α-D-glucopyranosyl pyrophosphate)

Hydrazine treatment of uridine 5'-(2-acetamido-2-deoxy-α-D-glucopyranosyl pyrophosphate) for 1 h resulted in N-deacetylation and cleavage of the pyrophosphate bond to give 2-amino-2-deoxy-α-D-glucopyranosyl phosphate as the main compound. It was separated from other degradation products by paper electrophoresis and isolated in a yield of 50–60%.     

Enamine and pyrrole formation from 2-amino-2-deoxy-D-glucose and dimethyl acetylenedicarboxylate

Addition of 2-amino-2-deoxy-β-D-glucopyranose to dimethyl acetylenedicarboxylate afforded an almost quantitative yield of amorphous 2-deoxy-2-(1,2-dimethoxycarbonylvinyl)amino-D-glucose (5). Acetylation of this adduct gave crystalline 1,3,4,6-tetra-O-acetyl-2-deoxy-2-[(Z)-1,2-dimethoxycarbonylvinyl]amino-α-D-glucopyranose (6a); the corresponding β-D anomer (6b) was obtained by addition of 1,3,4,6-tetra-O-acetyl-2-amino-2-deoxy-β-Dglucopyranose to dimethyl acetylenedicarboxylate. O-Deacetylation of tetra-acetate 6a with barium methoxide in methanol occurred selectively at C-1, yielding enamine 6c derived from 3,4,6-tri-O-acetyl-2-amino-2-deoxy-α-D-glucopyranose. Conversion of the crude adduct 5 into 3-methoxycarbonyl-5-(D-arabino-tetrahydroxybutyl)-2-pyrrolecarboxylic acid (7) took place by heating in water or in slightly basic media in yields up to 83%. Acetylation of 7 gave the tricyclic derivative 8, and its periodate oxidation afforded 5-formyl-3-methoxycarbonyl-2-pyrrolecarboxylic acid (9). Oxidation of 9 with alkaline silver oxide yielded 3-methoxy-carbonyl-2,5-pyrroledicarboxylic acid (10).     

Synthesis of 2,4-diacetamido-2,4,6-trideoxy-D-Galactose

Treatment of benzyl 2-acetamido-3-O-benzyl-2,6-dideoxy-4-O-(methylsulfonyl)-α-D-glucopyranoside (1) with sodium azide in hexamethylphosphoric triamide gave the 4-azido-α-D-galacto derivative (2), which was converted into benzyl 2,4-di-acetamido-3-O-benzyl-2,3,6-trideoxy-α-D-galactopyranoside (3) by hydrogenation and subsequent acetylation. Hydrogenolysis of 3 at atmospheric pressure afforded benzyl 2,4-diacetamido-2,4,6-tridcoxy-α-D-galactopyranoside (4), which was acetylated to give the 3-O-acetyl derivative (5). The n.m.r. spectrum of 5 was in agreement with the assigned structure and different from that of benzyl 2,4-di-acetamido-3-O-acetyl-α-D-glucopyranoside (9), which was prepared from the known benzyl 2,4-diacetamido-3-O-benzyl-2,4,6-trideoxy-α-D-glucopyranoside. Catalytic hydrogenolysis of 4 gave 2,4-diacetamido-2,4,6-trideoxy-D-galactose (6).     

Synthesis of 3-amino-2,3,6-trideoxy-d-ribo- and -l-lyxo-hexofuranoses suitable for nucleoside synthesis

N-Acetylepidaunosamine (3-acetamido-2,3,6-trideoxy-d-ribo-hexopyranose) was converted into the diethyl dithioacetal and this was cyclized with HgCi₂, HgO, and MeOH, to give methyl 3-acetamido-2,3,6-trideoxy-α- and -β-d-ribo-hexofuranoside (4 and 5). These anomers were acetylated or (p-nitrobenzoyl)ated, and the esters were subjected to acetolysis, to afford 3-acetamido-1,5-di-O-acetyl-2,3,6-trideoxy-d-ribo-hexofuranose and 3-acetamido-1-O-acetyl-2,3,6-trideoxy-5-O-(p-nitrobenzoyl)-d-ribo-hexofuranose, respectively. Alternatively, compounds 4 and 5 were hydrolyzed to the free bases with barium hydroxide, and these were converted into the trifluoroacetamido derivatives which, on (p-nitrobenzoyl)ation and acetolysis, afforded 1-O-acetyl-2,3,6-trideoxy-5-O-(p-nitrobenzoyl)-3-(trifluoroacetamido)-d-ribo-hexofuranose. To prepare the corresponding daunosamine derivative, 2,3,6-trideoxy-3-(trifluoroacetamido)-l-lyxo-hexopyranose was converted into the diethyl dithioacetal, and this was cyclized in the same way, to afford methyl 2,3,6-trideoxy-3-(trifluoroacetamido)-α- and -β-l-lyxo-hexofuranoside. On (p-nitrobenzoyl)ation and acetolysis, both afforded 1-O-acetyl-2,3,6-trideoxy-5-O-(p-nitrobenzoyl)-3-(trifluoroacetamido)-l-lyxo-hexofuranose.     

Structure of l-arabino-d-galactan-containing glycoproteins from radish leaves

Two l-arabino-d-galactan-containing glycoproteins having a potent inhibitory activity against eel anti-H agglutinin were isolated from the hot saline extracts of mature radish leaves and characterized to have a similar monosaccharide composition that consists of l-arabinose, d-galactose, l-fucose, 4-O-methyl-d-glucuronic acid, and d-glucuronic acid residues. The chemical structure features of the carbohydrate components were investigated by carboxyl group reduction, methylation, periodate oxidation, partial acid hydrolysis, and digestion with exo- and endo-glycosidases, which indicated a backbone chain of (1→3)-linked β-d-galactosyl residues, to which side chains consisting of α-(1→6)-linked d-galactosyl residues were attached. The α-l-arabinofuranosyl residues were attached as single nonreducing groups and as O-2- or O-3-linked residues to O-3 of the β-d-galactosyl residues of the side chains. Single α-l-fucopyranosyl end groups were linked to O-2 of the l-arabinofuranosyl residues, and the 4-O-methyl-β-d-glucopyranosyluronic acid end groups were linked to d-galactosyl residues. The O-α-l-fucopyranosyl-(1→2)-α-l-arabinofuranosyl end-groups were shown to be responsible for the serological, H-like activity of the l-arabino-d-galactan glycoproteins. Reductive alkaline degradation of the glycoconjugates showed that a large proportion of the polysaccharide chains is conjugated with the polypeptide backbone through a 3-O-d-galactosylserine linkage.     

The action of thiols on derivatives of D-xylose

The action of thiols on 1,2,3,4-tetra-O-acetyl-β-D-xylopyranose gave 2- and 5-alkylthiopentose dithioacetals and alkyl 1-thio-D-xylopyranosides. On treatment with thiols and trifluoroacetic acid- 3-O-acetyl-1,2-O-isopropylidene-α-D-xylofuranose derivatives rapidly formed 4-O-acetyl-2,3-dialkylthio-D-ribose dithioacetal derivatives, which were in turn converted into 4-O-acetel-3-S-benzyl-2,5-epithio-3-thio-D-ribose (or D-arabinose) dithioacetal.     

Untersuchungen zur modifikation der cellobiose und synthese von methyl-2,6-didesoxy-4-O-(6-desoxy-β-D-glucopyranosyl)-α-D-arabino-hexopyranosid (methyl-4-O-β-D-chinovosyl-α-D-olivosid)

Starting with cellobiosides, several different procedures were employed to prepare 6,6′-dichloro-6,6′-dideoxy, 6,6′-dibromo-6,6′-dideoxy, and 6,6′-dideoxy-6,6′-diiodo derivatives. Reduction with lithium aluminum hydride or nickel boride afforded peracetyl derivatives of methyl, phenyl, and benzyl 6-deoxy-4-O-(6-deoxy-β-D-glucopyranosyl)-β-D-glucopyranoside. Following acetolysis or hydrogenolysis, the glycosyl halide and the corresponding-glycal 40 were prepared. Iodomethoxylation of 40 and subsequent reduction gave the title compound. Alternatively, the halomethoxylation products of cellobial hexaacetate gave, by various procedures, the 2,6,6′-trideoxy-2,6,6′-trihalo derivatives, which, in turn, could be reduced to the title compound. The structures of the derivatives prepared were unequivocally assigned by n.m.r. spectroscopy. The various reaction sequences were compared with respect to the number of steps and the yields obtained.     

Characterization of structurally similar neutral and acidic tetrasaccharides obtained from the enzymic hydrolyzate of a 4-O-methyl-D-glucurono-D-xylan

Two similar tetrasaccharides, one neutral and one acidic, were isolated from the products released by the attack of a xylanase on the in situ reduced 4-O-methyl-D-glucurono-D-xylan from aspen (Populus tremuloides). Paper chromatography, gel filtration behavior, methylation followed by reduction, and mass spectrometry showed that the oligosaccharides were O-(4-O-methyl-α-D-glucopyranosyluronic acid)-(1→2)-D-xylotriose and-O-(4-O-methyl-α-D-glucopyranosyluronic acid)-(1→2)-D-xylotriose. Independent of the acidic or neutral substituent on the present xylan chain, the enzymic cleavage led preferentially to oligosaccharides substituted at the nonreducing end. The existence, in wood, of a few uronic acid substituents of the D-xylan in the esterified form was confirmed, and their linkage to lignin postulated.     

Distribution of D-galactosyl groups in guaran and locust-bean gum

Distribution of α-d-galactopyranosyl side-chain groups in two galactomannans, guaran and locust-bean gum, was determined by measurement of the O-acetyl-O-methyl-d-mannitol derivatives obtained from the corresponding primary C-p-tolylsulfonyl polysaccharide derivatives. The O-acetyl-O-methyl-d-mannitol derivatives were produced by β-elimination and methylation, with sodium (methylsulfinyl)methide and methyl iodide, of the primary C-p-toluenesulfinylated galactomannans, followed by sequential acid hydrolysis, reduction, and acetylation of the partially degraded p-tolyl sulfones. The results indicated that side-chain units of guaran are alternately disposed along the d-mannan backbone, whereas those of locust-bean gum are disposed in uniform blocks along the backbone.     

Selenium derivatives of L-arabinose, D-ribose,and D-xylose

Attempted cyclization of 2,3,4-tri-O-methyl-5-seleno-L-arabinose dimethyl acetal in acidic solution gave the corresponding diselenide. Intramolecular attack by the selenobenzyl group at C-5 of 5-O-p-tolylsulfonyl-L-arabinose dibenzyl diseleno-acetal resulted in the formation of benzyl 1,5-diseleno-L-arabinopyranoside. Similarly, 2,3,5-tri-O-methyl-4-O-p-tolylsulfonyl-D-xylose dibenzyl diselenoacetal gave benzyl 2,3,5-tri-O-methyl-1,4-diseleno-L-arabinofuranoside, and 2,3,4-tri-O-acetyl-5-O-p-tolylsulfonyl-D-xylose (or ribose) dibenzyl diselenoacetal gave benzyl 2,3,4-tri-O-acetyl-1,5-diseleno-D-xylo- (or ribo-)pyranoside. The glycosylic benzylseleno group was removed from the pyranoside with mercuric acetate, but attempted deacetylation of the product led to decomposition and not to the expected 5-seleno-D-xylopyranose.     

Synthesis of methyl 4,6-O-methylene-D-glycopyranosides

Methyl 4,6-O-methylene-D-glycopyranosides having the α-D-altro, α- and β-D-gluco, α-D-manno, and α-D-galacto configurations were prepared in 3.4 to 27.4% yields by condensing formaldehyde from 1,3,5-trioxane with the methyl glucosides in anhydrous 1,4-dioxane at 95° with boron trifluoride as the catalyst. A crystalline methyl 2,3:4,6-di-O-methylene-α-D-mannopyranoside was also isolated. Crystalline methyl 4,6-O-methylene 2,3-di-O-p-tolylsulfonyl-α-D-galacto- and α-D-glucopyranosides were prepared in 78 and 54.4% yields. N.m.r. coupling constants of the 2,3-di-O-acetyl derivatives of the 4,6-O-methylene glycosides were used to establish the Cl(D) conformation for each derivative.     

Syntheses of methyl 2,6-diacetamido-2,3,6-trideoxy-α-d-ribo-hexopyranoside (methyl di-N-acetyl-α-d-tobrosaminide) and methyl 2-acetamido-2,3,6-trideoxy-β-l-lyxo-hexopyranoside

The title glycosides were synthesised from d-glucose, via the common intermediate methyl 2-acetamido-4-O-benzoyl-6-bromo-2,3,6-trideoxy-α-d-ribo-hexopyranoside.     

Synthesis of 2-acetamido-3,4,6-tri-O-acetyl-2-deoxy-β-d-glucopyranosylamine and dimer formation

the synthesis of 2-acetamido-3,4,6-tri-O-acetyl-2-deoxy-β-d-glucopyranosylamine (2), the key intermediate in glycopeptide synthesis, has been improved. The dimerization of 2 has been studied as a model for its activity in biological systems. The formation of β,? and α,β dimers from 2 and their interconversions could be readily followed by ₁₃C-n.m.r. spectroscopy, and a probable mechanism of their formation involving an acyclic immonium ion intermediate has been proposed.