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PubMed1985

p-Trifluoroacetamidophenyl O-alpha-D-mannopyranosyl-(1----3)-O-[alpha-D-mannopyranosyl- (1----6)]-beta-D-mannopyranoside.

p-Nitrophenyl 2-O-benzyl-4,5-O-cyclohexylidene-beta-D-mannopyranoside (4) was condensed with tetra-O-benzoyl-alpha-D-mannopyranosyl bromide. The resulting, protected disaccharide was converted into p-nitrophenyl O-(2,3,4-tri-O-benzoyl-alpha-D-mannopyranosyl)-(1----3)-4-O-benzoyl-2-O- benzyl-beta-D-mannopyranoside (8), which was condensed with tetra-O-benzoyl-alpha-D-mannopyranosyl bromide to give p-nitrophenyl O-(2,3,4-tri-O-benzoyl-alpha-D-mannopyranosyl)-(1----3)-O -[2,3,4-tri-O-benzoyl-alpha-D-mannopyranosyl-(1----6)]-4-O-benzoyl-2-O -benzyl-beta-D-mannopyranoside (9) in 75% yield. Conversion of the p-nitrophenyl group followed by deprotection then yielded the title compound, whose structure was confirmed by 1H- and 13C-n.m.r. spectroscopy.

Hydrogen-Ion Concentration↗
PubMed1985

2-Substituted methyl alpha-D-galactopyranosides: synthesis and binding affinity for the A and B subunits of the Griffonia simplicifolia I isolectins.

The binding affinities of the N-acetyl, N-trifluoroacetyl, N-propionyl, N-formyl, N-benzoyl, N-p-nitrobenzoyl, N-p-aminobenzoyl, and N-methyl derivatives of methyl 2-amino-2-deoxy-alpha-D-galactopyranoside and the 2-O-acetyl, -benzoyl, -benzyl, and -methyl derivatives of methyl alpha-D-galactopyranoside for the A and B subunits of the Griffonia simplicifolia I isolectins have been determined by hapten inhibition analysis of a galactomannan-isolectin precipitation system. Models for these carbohydrate-protein interactions are presented together with an interpretation of the results on the basis of electronic and steric effects.

Haptens↗
PubMed1985

4-O-beta-D-Galactopyranosyl-3-O-methyl-D-glucose: a new synthesis and application to the evaluation of intestinal lactase.

4-O-beta-D-Galactopyranosyl-3-O-methyl-D-glucose (1, 3-O-methyl-lactose) has been prepared from benzyl 2,6-di-O-benzyl-4-O-(2,6-di-O-benzyl-3, 4-O-isopropylidene-beta-D-galactopyranosyl)-beta-D-glucopyranoside (5) and from benzyl 2,6-di-O-benzyl-4-O-(2,3,4,6-tetra-O-benzyl-beta-D-galactopyranosyl)-bet a-D-glucopyranoside (15). Partial benzylation of benzyl 3',4'-O-isopropylidene-beta-lactoside (4) gave 5 and partial benzylation of either benzyl beta-lactoside (13) or benzyl hepta-O-acetyl-beta-lactoside (24) gave 15. All other products from the partial benzylation of 4, 13, and 24 were also isolated and characterised. The hydrolysis of 1 in vitro by intestinal lactase was linear during 20 h; the Vmax was 5% of that with lactose and the Km was 120mM (cf. 30mM for lactose). Oral administration of 1 to suckling rats led to urinary excretion of 3-O-methyl-D-glucose.

Aging↗
PubMed1985

Structural studies of the capsular polysaccharide from Streptococcus pneumoniae type 5.

The structure of the capsular polysaccharide (S5) elaborated by Streptococcus pneumoniae type 5 has been investigated by using n.m.r. spectroscopy, methylation analysis, and various specific degradations. It is concluded that the polysaccharide is composed of pentasaccharide repeating-units having the following structure: (Formula: see text) In this structure, L-PneNAc stands for 2-acetamido-2,6-dideoxy-L-talose (pneumosamine) and D-Sug for 2-acetamido-2,6-dideoxy-D-xylo-hexos-4-ulose. The latter sugar accounts for the lability of S5 towards alkali. N.m.r. spectra indicate heterogeneity in S5, most probably associated with the hexosyl-4-ulose residue.

Carbohydrate Conformation↗
PubMed1985

Synthesis of (S)-2-fluoro-L-daunosamine and (S)-2-fluoro-D-ristosamine.

Derivatives of (S)-2-fluoro-L-daunosamine and (S)-2-fluoro-D-ristosamine were synthesized, starting ultimately from 2-amino-2-deoxy-D-glucose which was converted, according to the literature, into methyl 2-benzamido-4, 6-O-benzylidene-2-deoxy-3-O-(methylsulfonyl)-alpha-D-glucopyranoside (2). Treatment of 2 with tetrabutylammonium fluoride gave a 63% yield of (known) methyl 3-benzamido-4,6-O-benzylidene-2,3-dideoxy-2-fluoro-alpha-D-altropyran oside (4), together with a 6% yield of its 2-benzamido-2,3-dideoxy-3-fluoro-alpha-D-gluco isomer. From 4, the corresponding 6-bromo-2,3,6-trideoxyglycoside 4-benzoate (6) was obtained by Hanessian-Hullar reaction. Dehydrobromination of 6, followed by catalytic hydrogenation of the resulting 5-enoside, and subsequent debenzoylation and N-trifluoroacetylation, afforded the fluorodaunosaminide, methyl 2,3,6-trideoxy-2-fluoro-3-trifluoroacetamido-beta-L-galactopyranos ide. Reductive debromination of 6, followed by debenzoylation and N-trifluoroacetylation, gave the fluororistosaminide, methyl 2,3,6-trideoxy-2-fluoro-3-trifluoroacetamido-alpha-D-altropyran oside. The 1H-n.m.r. spectra of the new aminofluoro sugars are discussed with respect to the effects of neighboring amino and acylamido substituents on geminal and vicinal 1H-19F coupling constants, in comparison with the reported effects of oxygen substituents.

Antineoplastic Agents↗
PubMed1985

A structural investigation of the capsular polysaccharide of Klebsiella K14.

The structure of the capsular polysaccharide isolated from Klebsiella serotype K14 has been investigated employing a combination of chemical and spectroscopic methods. The repeating structure is shown to be of the "4 + 1 + 1" type, and it carries a 1-carboxyethylidene acetal substituent at positions 4 and 6 of a terminal glucose residue. The polysaccharide is one of a group of only three Klebsiella polysaccharides that have been found to contain a galactofuranose residue in the repeating unit. The repeating unit has the following structure: (Formula: see text).

Carbohydrate Conformation↗
PubMed1985

Synthesis of methyl glycosides of beta-(1----6)-linked D-galactobiose, galactotriose, and galactotetraose having a 3-deoxy-3-fluoro-beta-D-galactopyranoside end-residue.

Methyl 2,4-di-O-acetyl-3-deoxy-3-fluoro-beta-D-galactopyranoside was synthesized by sequential tritylation, acetylation, and detritylation of methyl 3-deoxy-3-fluoro-beta-D-galactopyranoside, and used as the initial nucleophile in the synthesis of methyl beta-glycosides of (1----6)-beta-D-galacto-biose, -triose (20), and -tetraose (22) having a 3-deoxy-3-fluoro-beta-D-galactopyranoside end-residue. The extension of the oligosaccharide chains, to form the internal units in 20 and 22, was achieved by use of 2,3,4-tri-O-acetyl-6-O-bromoacetyl-alpha-D-galactopyranosyl bromide as a glycosyl donor, and mercuric cyanide or silver triflate as the promotor. While fewer by-products were formed in the reactions involving mercuric cyanide, the reactions catalyzed by silver triflate were stereospecific and yielded only the desired beta (trans) products.

Carbohydrate Conformation↗
PubMed1985

Synthesis of methyl O-(3-deoxy-3-fluoro-beta-D-galactopyranosyl)-(1----6)-O-beta-D- galactopyranosyl-(1----6)-3-deoxy-3-fluoro-beta-D-galactopyranoside and related N.M.R. studies.

Sequential tritylation, benzoylation, and detritylation of methyl 3-deoxy-3-fluoro-beta-D-galactopyranoside gave crystalline methyl 2,4-di-O-benzoyl-3-deoxy-3-fluoro-beta-D-galactopyranoside (9), which was used as the initial nucleophile in the synthesis of the target oligosaccharide (16). Treatment of 9 with 2,3,4-tri-O-benzoyl-6-O-bromoacetyl-alpha-D-galactopyranosyl bromide gave the corresponding disaccharide derivative 13, having a selectively removable blocking group at O-6'. Debromoacetylation of 13 afforded the disaccharide nucleophile 14 which, when treated with 2,4,6-tri-O-benzoyl-3-deoxy-3-fluoro-alpha-D-galactopyranosyl bromide, gave the fully protected trisaccharide 15. Debenzoylation of 15 gave the title glycoside 16. Condensation reactions were performed with silver trifluoromethane-sulfonate as a promoter in the presence of sym-collidine under base-deficient conditions, and gave excellent yields of the desired beta(trans)-products. Analyses of the 1H- and 13C-n.m.r. spectra, as well as determination of the JCF and JHF coupling constants, were made by using various one- and two-dimensional n.m.r. techniques.

Carbohydrate Conformation↗
PubMed1985

Synthesis of a tri- and a hepta-saccharide which contain alpha-L-fucopyranosyl groups and are part of the complex type of carbohydrate moiety of glycoproteins.

Reaction of a thioglycoside with methyl trifluoromethanesulfonate (methyl triflate) in the presence of a hydroxyl compound is an efficient glycosylation method. Thus, methyl triflate-promoted condensation of ethyl 4,6-O-benzylidene-2-deoxy-2-phthalimido-1-thio-3-O-(2,3,4-tri-O-benzyl-a lpha-L- fucopyranosyl)-beta-D-glucopyranoside with benzyl 3,4,6-tri-O-benzyl-alpha-D-mannopyranoside and with benzyl 2,4-di-O-benzyl-3,6-di-O-(3,4,6-tri-O-benzyl-alpha-D-mannopyranosyl)-alp ha-D- mannopyranoside gave a trisaccharide and a heptasaccharide derivative, respectively. The trisaccharide 1 and the heptasaccharide 2, which are parts of the complex type of glycoproteins, were obtained by removal of the protecting groups and N-acetylation. (formula: see text).

Carbohydrate Conformation↗
PubMed1985

Synthesis of a tetra- and a nona-saccharide which contain alpha-L-fucopyranosyl groups and are part of the complex type of carbohydrate moiety of glycoproteins.

Methyl trifluoromethanesulfonate-promoted condensation of ethyl 6-O-benzyl-2-deoxy-2-phthalimido-4-O-(2,3,4,6-tetra-O-acetyl-beta-D- galactopyranosyl)-1-thio-3-O-(2,3,4-tri-O-benzyl-alpha-L-fucopyranosyl)- beta-D- glucopyranoside with benzyl 3,4,6-tri-O-benzyl-alpha-D-mannopyranoside and benzyl 2,4-di-O-benzyl-3,6-di-O-(3,4,6-tri-O-benzyl-alpha-D-mannopyranosyl)-alp ha-D- mannopyranoside gave a tetrasaccharide and a nonasaccharide derivative, respectively. The tetrasaccharide 1 and the nonasaccharide 2 were obtained after removal of the protecting groups and N-acetylation. (formula: see text).

Carbohydrate Conformation↗
PubMed1985

An unusual reaction of 1,6-anhydroaldohexopyranose derivatives leading to glycals.

Treatment of a solution of the 2-O-(N,N-dimethylsulfamoyl) derivative 3 of the levoglucosenone-derived carbocycle 1 in liquid ammonia at -40 to -50 degrees with sodium metal gave 73% of the glycal derivative 4 instead of the expected 2-deoxy derivative (2) of 1. Under the same conditions, the 2-O-(N,N-dimethylsulfamoyl) derivatives of 1,6-anhydro-3,4-dideoxy-4-C-methyl-beta-D-ribo- and -arabino-hexopyranoses gave, after acetylation, 70% of 6-O-acetyl-1,5-anhydro-2,3,4-trideoxy-4-C-methyl-D-erythro-hex-1-enit ol. In contrast, the 2-(N,N-dimethyl-sulfamates) obtained from 1,6-anhydro-3,4-O-isopropylidene-beta-D-galacto- and -talo-pyranose gave 6-O-acetyl-1,5-anhydro-2-deoxy-3,4-O-isopropylidene-D-lyxo-hex-1-enit ol in only low yields; the oxy substituent at C-3 may interfere with the reaction leading to the glycal.

Aldehydes↗
PubMed1986

Stereocontrolled routes to cis-hydroxyamino sugars, Part VII: Synthesis of daunosamine and ristosamine.

The nitrogen of an allylic amine can serve as the fulcrum for stereocontrolled delivery of oxygen to an adjacent trigonal site, and cis-hydroxyamino sugars can thus be prepared. Methods for achieving the complementary procedure, namely, control of the delivery of nitrogen to an adjacent site by an allylic oxygen, are described. For example, treatment of methyl 2,3,6-trideoxy-alpha-L-erythro-hex-2-enopyranoside with trichloroacetonitrile gave an imidate ester which reacted with iodonium dicollidine perchlorate to give 2-trichloromethyl-(methyl 2,3,4,6-tetradeoxy-2-iodo-alpha-L-altropyranosido)-[3,4-d]-2-oxazo line. Exhaustive reductive dehalogenation of this product followed by hydrolysis led to methyl N-acetyl-alpha-L-ristosaminide. An analogous series of reactions was used to prepare the corresponding daunosaminide.

Hexosamines↗
PubMed1986

Synthesis of some derivatives of 6-amino-1,5-anhydro-6-deoxy-D-glucitol and 2-amino-1,5-anhydro-2-deoxy-D-glucitol.

6-Amino-1,5-anhydro-6-deoxy-D-glucitol (11) was prepared from 2,3,4,6-tetra-O-acetyl-alpha-D-glucopyranosyl bromide (1) in six steps. Reduction of 1 with tributyltin hydride, followed by deacetylation, monomolar tosylation, and reacetylation, afforded 2,3,4-tri-O-acetyl-1,5-anhydro-6-O-toluene-p-sulfonyl-D-glucitol (9). Alternatively, tritylation of 1,5-anhydro-D-glucitol, followed by acetylation, detritylation, and tosylation, gave 9. Mesylation gave 8. Treatment of 8 or 9 with azide anion afforded the azide 10, reduction of which with tributyltin hydride gave 11, which was mesylated or tosylated, and then deacetylated to give the 6-methane-sulfonamido or 6-toluene-p-sulfonamido derivative. Similarly, mesylation or tosylation of 3,4,6-tri-O-acetyl-2-amino-1,5-anhydro-2-deoxy-D-glucitol (20) gave the 2-methanesulfonamido or 2-toluene-p-sulfonamido derivatives. Treatment of 11 and 20 with sulfur trioxide-pyridine afforded the sulfoamino derivatives, deacetylation of which gave sugar analogs of cyclamate-like compounds.

Glucosamine↗
PubMed1986

Synthesis of tetrasaccharides related to the antigenic determinants from the glycopeptidolipid antigens of serovars 9 and 25 in the Mycobacterium avium-M. intracellulare-M. scrofulaceum serocomplex.

The synthesis of the tetrasaccharides O-(2,3-di-O-methyl-alpha-L-fucopyranosyl)-(1----4)-O-(2,3- di-O-methyl-alpha-L-fucopyranosyl)-(1----3)-O-alpha-L-rhamnopyranosyl -(1----2)-6-deoxyl-L-talose (36) and O-(2-O-methyl-alpha-L-fucopyranosyl)-(1----4)-O-(2-O-methyl-alpha-L- fucopyranosyl)-(1----3)-O-alpha-L-rhamnopyranosyl-(1----2)-6-deoxy-L- talose (41) is described. The former and the latter structures, respectively, have been proposed as the carbohydrate chains in the polar glycopeptidolipid antigens of serovars 9 and 25 in the Mycobacterium avium-M. intracellulare-M. scrofulaceum serocomplex. Glycosylation of allyl 2,3-di-O-methyl-alpha-L-fucopyranoside with 4-O-benzoyl-2,3-di-O-methyl-alpha-L-fucopyranosyl chloride gave the alpha-linked disaccharide derivative, which was O-deallylated and converted into the corresponding disaccharide alpha-chloride. This was coupled with benzyl 3,4-di-O-benzyl-6-deoxy-2-O-(2,4-di-O-benzoyl-alpha-L-rhamnopyranosyl)- alpha-L-talopyranoside (32) to give a fully protected tetrasaccharide derivative, which was deprotected to furnish 36. Likewise, 3-O-benzyl-4-O-(3,4-di-O-acetyl-2-O-methyl-alpha-L- fucopyranosyl)-2-O-methyl-alpha-L-fucopyranosyl chloride, prepared by way of condensation of allyl 3-O-benzoyl-2-O-methyl-alpha-L-fucopyranoside with 2-O-methyl-3,4-di-O-(p-nitrobenzoyl)-alpha-L-fucopyranosyl bromide, reacted with 32, to provide, after removal of blocking groups, 41.

Epitopes↗
PubMed1986

The assembly of oligosaccharides from "standardized intermediates": beta-(1----3)-linked oligomers of D-galactose.

Several 2-O-benzoyl-4,6-di-O-benzyl-3-O-R-alpha-D-galactopyranosyl chlorides, designed as general precursors of beta-linked, interior D-galactopyranosyl residues in oligosaccharides, were tested in a sequential synthesis of the galactotriose beta-D-Galp-(1----3)-beta-D-Galp-(1----3)-D-Gal (19). The chlorides having R = tetrahydro-2-pyranyl and tert-butyldimethylsilyl gave excellent results, whereas those having R = 3-benzoylpropionyl and chloroacetyl were unsatisfactory. An activated disaccharide block (17), having R = 2,3-di-O-benzoyl-4,6-di-O-benzyl-beta-D-galactopyranosyl, was also prepared and tested as a glycosyl donor. The coupling of 17 to 1-propenyl 2-O-benzoyl-4,6-di-O-benzyl-alpha-D-galactopyranoside (14), in the molar ratio 1.13:1, gave 64% of a trisaccharide derivative (18) that could be converted into 19. This latter synthesis of 19 is efficient because all three galactose units are derived from 14 or its immediate precursor.

Carbohydrate Conformation↗
PubMed1986

Structural studies of the O-antigen from Vibrio cholerae O:21.

The O-antigen from Vibrio cholerae O:21 has been investigated, using n.m.r. spectroscopy, methylation analysis, and Smith degradation as the main methods. It is concluded that the O-antigen is composed of tetrasaccharide repeating-units having the following structure (in which Hep = D-glycero-D-manno-heptose). (Formula: see text).

Antigens, Bacterial↗