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PubMed1987

Synthesis of methyl 2-O-alpha-D-mannopyranosyl-alpha-D-talopyranoside and methyl 2-O-alpha-D-talopyranosyl-alpha-D-talopyranoside.

Treatment of methyl 3-O-benzyl-2-O-(2,3,4,6-tetra-O-acetyl-alpha-D-mannopyranosyl)-alpha-D- mannopyranoside (1) with tert-butyldiphenylsilyl chloride in N,N-dimethylformamide afforded methyl 3-O-benzyl-6-O-tert-butyldiphenylsilyl-2-O-(2,3,4,6-tetra-O-acetyl -alpha-D- mannopyranosyl)-alpha-D-mannopyranoside (2). Oxidation of 2 with pyridinium chlorochromate, followed by reduction of the carbonyl group, and subsequent O-deacetylation afforded methyl 3-O-benzyl-6-O-tert-butyldiphenylsilyl-2-O-alpha-D-mannopyranosyl- alpha-D- talopyranoside (5). Cleavage of the tert-butyldiphenylsilyl group of 5 with tetrabutylammonium fluoride in oxolane, followed by hydrogenolysis, gave methyl 2-O-alpha-D-mannopyranosyl-alpha-D-talopyranoside (7). O-Deacetylation of 1 gave methyl 3-O-benzyl-2-O-alpha-D-mannopyranosyl-alpha-D-mannopyranoside (8). Treatment of 8 with tert-butyldiphenylsilyl chloride afforded a 6,6'-disilyl derivative, which was converted into a 2',3'-O-isopropylidene derivative, and then further oxidized with pyridinium chlorochromate. The resulting diketone was reduced and removal of the protecting groups gave methyl 2-O-alpha-D-talopyranosyl-alpha-D-talopyranoside (15). The structures of both 7 and 15 were established by 13C-n.m.r. spectroscopy.

Indicators and Reagents↗
PubMed1987

Synthetic mucin fragments. Methyl 6-O-(2-acetamido-2-deoxy-beta-D- glucopyranosyl)-beta-D-galactopyranoside, methyl 3,4-di-O-(2-acetamido-2-deoxy- beta-D-glucopyranosyl)-beta-D-galactopyranoside, and methyl O-(2-acetamido-2- deoxy-beta-D-glucopyranosyl)-(1----3)-O-beta-D-galactopyranosyl-(1---- 3)-O-(2- acetamido-2-deoxy-beta-D-glucopyranosyl)-(1----3)-beta-D-galactopyr ano side.

Condensation of methyl 2,6-di-O-benzyl-beta-D-galactopyranoside with 2-methyl-(3,4,6-tri-O-acetyl-1,2-dideoxy-alpha-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-beta-D-glucopyranosyl)-2,6-di-O-benzyl-bet a-D- galactopyranoside (5). Hydrogenolysis of the benzyl groups of 5 furnished the title trisaccharide (6). A similar condensation of methyl 2,3-di-O-benzyl-beta-D-galactopyranoside with 1 produced a partially-protected disaccharide derivative, which, on O-deacetylation followed by hydrogenolysis, gave methyl 6-O-(2-acetamido-2-deoxy-beta-D-glucopyranosyl)-beta-D-galactopyranoside (10). Condensation of methyl 3-O-(2-acetamido-4,6-O-benzylidene-2-deoxy-beta-D- glucopyranosyl)-2,4,6-tri-O-benzyl-beta-D-galactopyranoside with 3-O-(2-acetamido-3,4,6-tri-O-acetyl-2-deoxy-beta-D-glucopyranosyl)-2,4,6 -tri-O-acetyl-alpha-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-beta-D-glucopyranosyl)-(1----3)-O-beta- D-galactopyranosyl-(1----3)-O-(2-acetamido-2-deoxy-beta-D-glucopyranosyl )- (1----3)-beta-D-galactopyranoside (15). The structures of 6, 10, and 15 were established by 13C-n.m.r. spectroscopy.

Carbohydrate Conformation↗
PubMed1987

Synthesis of 7'-(3-hydroxypropyl)fortimicin A and 6'-epifortimicin A.

1,10-Di-0-acetyl-2,3,4,6,7,8,9-heptadeoxy-2,6-bis(2, 4-dinitrophenylamino)-L-lyxo-decopyranose (7) and -D-ribo-decopyranose (8) have been prepared from methyl 2-acetamido-2,3,4,6-tetradeoxy-6-nitro-alpha-D-erythro-hexopyranoside via a nitro aldol reaction with 4-[(tetrahydropyranyl)oxy]butanal in the presence of cesium fluoride, and their configurations at C-6 have been established by conversion of the precursor of 8, namely, methyl 2,6-diacetamido-10-O-acetyl-2,3,4,6,7,8,9-heptadeoxy-alpha-D - ribo-decopyranoside, into the known methyl 2,6-diacetamido-2,3,4,6,7,8,9,10-octadeoxy-alpha-D-ribo-d ecopyranoside. The title fortimicin A derivatives, 7'-(3-hydroxypropyl)fortimicin A and 6'-epifortimicin A, have been synthesized by condensation of compound 7 and 8, respectively, with 2,5-di-O-benzoyl-1,4-bis[N-(methoxycarbonyl)]fortamine B, followed by deprotection and introduction of a glycyl group. Their antimicrobial activities have been found to be weak compared to that of fortimicin A.

Aminoglycosides↗
PubMed1988

Synthesis of uridine 5'-(2-acetamido-2,4-dideoxy-4-fluoro-alpha-D-galactopyranosyl) diphosphate and uridine 5'-(2-acetamido-2,6-dideoxy-6-fluoro-alpha-D-glucopyranosyl) diphosphate.

Benzyl 2-acetamido-3,6-di-O-benzyl-2-deoxy-alpha-D-glucopyranoside was converted into its 4-O-(methylsulfonyl) derivative (2) by treatment with methanesulfonyl chloride in pyridine. Displacement of the methylsulfonyloxy group of 2 with fluoride ion afforded benzyl 2-acetamido-3,6-di-O-benzyl-2,4-dideoxy-4-fluoro-alpha-D-galactopyranosi de, which on hydrogenolysis, followed by acetylation, furnished 2-acetamido-1,3,6-tri-O-acetyl-2,4-dideoxy-4-fluoro-D-galactopyranose. Treatment of this and of 2-acetamido-1,3,4-tri-O-acetyl-2,6-dideoxy-6-fluoro-D-glucopyranose with trimethylsilyl trifluoromethanesulfonate in 1,2-dichloroethane at approximately 50 degrees afforded the 4-deoxy-4-fluoro- or the 6-deoxy-6-fluoro-oxazolines (5) and (11), respectively. Reaction of 5 and 11 with dibenzyl phosphate in 1,2-dichloroethane produced the alpha-linked dibenzyl phosphate derivatives 6 and 12, respectively. Catalytic hydrogenation of 6 provided 2-acetamido-3,6-di-O-acetyl-2,4-dideoxy-4-fluoro-alpha-D-galactopyranosy l phosphate (7), and that of 12 gave 2-acetamido-3,4-di-O-acetyl-2,6-dideoxy-6-fluoro-alpha-D-glucopyranosyl phosphate (13). Coupling of 7 and 13 with uridine 5'-monophosphomorpholidate in dry pyridine at approximately 37 degrees, followed by O-deacetylation, furnished the title compounds, respectively, isolated and characterized as their respective dilithium salts.

Carbohydrate Conformation↗
PubMed1988

Systematic chemical synthesis and n.m.r. spectra of methyl alpha-glycosides of isomalto-oligosaccharides and related compounds.

Acid-catalyzed thiophenolysis of 1,6-anhydro-2,3,4-tri-O-benzyl-beta-D-glucopyranose and acetylation of the resulting phenyl 2,3,4-tri-O-benzyl-1-thio-alpha-D-glucopyranoside (4) gave phenyl 6-O-acetyl-2,3,4-tri-O-benzyl-1-thio-alpha-D-glucopyranoside (5). Reaction of 5 with chlorine gave, stereospecifically, the corresponding beta-glycosyl chloride, which was treated with 4 in the presence of silver perchlorate and 2,4,6-trimethylpyridine to afford phenyl O-(6-O-acetyl-2,3,4-tri-O-benzyl-alpha-D-glucopyranosyl)-(1----6)-2,3,4- tri-O- benzyl-1-thio-alpha-D-glucopyranoside (17). Crystalline O-(6-O-acetyl-2,3,4-tri-O-benzyl-alpha-D-glucopyranosyl)-(1----6)-2,3,4- tri- O-benzyl-beta-D-glucopyranosyl chloride, readily obtainable in a stereo-specific manner from 17 by treatment with chlorine, was used as the key glycosyl (isomaltosyl) donor in the blockwise synthesis of methyl glycosides of isomalto-oligosaccharides, up to and including the octasaccharide. The methyl alpha-glycoside of isomaltotetraose fluorinated at C-6 of the terminal D-glucopyranosyl group was prepared by using SnCl2-activated 2,3,4-tri-O-benzyl-6-deoxy-6-fluoro-alpha,beta-D-glucopyranosyl fluoride as the glycosyl donor, a suitably protected methyl alpha-isomaltotrioside as the nucleophile, and silver perchlorate as the promoter. The n.m.r. spectra (1H- and 13C-) of numerous synthetic intermediates were analyzed and completely assigned by a variety of two-dimensional homo- and hetero-nuclear n.m.r.-spectroscopic techniques, and the final deprotected title oligosaccharides were characterized by 13C-n.m.r. data. Silver perchlorate-mediated glycosylation reactions involving beta-glycosyl chlorides were high-yielding and showed high stereo-selectivity for the formation of an alpha-(cis)-glycosidic linkage. The practical limitation of obtaining high isomalto-oligosaccharides in this way appears to lie solely in the separation technique applied for the resolution of the crude products formed.

Carbohydrate Conformation↗
PubMed1988

Malto-oligosaccharide homologues of 3,7-anhydro-2-azi-1,2-dideoxy-D-glycero-D-gulo-octitol+ ++: improved photoaffinity reagents for labelling the malto-oligosaccharide-binding protein of Escherichia coli.

3,7-Anhydro-2-azi-1,2-dideoxy-D-glycero-D-gulo-octitol (2) was synthesized as a beta-D-glucopyranosyl analogue, which could be converted into a series of malto-oligosaccharide derivatives (3-7) by cyclodextrinase-catalyzed glucosyl transfer from alpha-cyclodextrin (cyclomaltohexaose). The pure analogues 3-7 containing 1-5 (1----4)-linked alpha-D-glucose residues inhibited the uptake of maltose via the maltose-binding protein-dependent transport system in Escherichia coli. The concentration of half-maximal inhibition of maltose transport at 60nM decreases with increasing chain-length of the analogue, reaching a minimum at 0.02 mM for 6 (4 glucose residues). 3H-Labelled alpha-cyclodextrin was prepared by partial oxidation and reduction of the aldehyde groups with NaB3H4. Radiolabelled 5a was used to photolabel the binding site of the maltose-binding protein.

ATP-Binding Cassette Transporters↗
PubMed1988

Carbohydrate components for modified anthracyclines: synthesis of derivatives of 3-amino-3,4,6-trideoxy-L-lyxo- and -L-xylo-hexose, and attempts at fluorination of C-2.

Two new trideoxyglycosides, methyl 3,4,6-trideoxy-3-nitro-alpha-L-lyxo-hexopyranoside (7) and its alpha-L-arabino isomer, as well as the known alpha-L-xylo isomer (15), were synthesized from methyl 3,6-dideoxy-3-nitro-alpha-L-glucopyranoside (1) by methods involving elimination and reduction processes in mesylates prepared from 1. Catalytic hydrogenation of 7 and 15 gave the new and the known aminodeoxyglycosides, respectively, both of which were N-(trifluoroacetyl)ated and sub-subsequently O-(trifluoromethylsulfonyl)ated. Various attempts to effect displacement by fluoride ion in the N-protected 2-triflates so obtained, and also in a related 3-azido-2-triflate, were unsuccessful as far as fluorination at C-2 was concerned. Among other products, two new 2-enopyranosides resulting from elimination of triflic acid were obtained.

Deoxy Sugars↗
PubMed1988

Stereoselective syntheses of C-(D-glucopyranosyl)alkenes.

alpha-D-Glucopyranose pentaacetate (1) was found to undergo stereoselective conversion in good yield into 3-(tetra-O-acetyl-alpha-D-glucopyranosyl)-1-propene (4) by treatment with allyltrimethylsilane and boron trifluoride etherate in acetonitrile. Similar treatment of methyl tetra-O-acetyl-alpha-D-glucopyranoside or tetra-O-acetyl-alpha-D-glucopyranosyl bromide also gave 4 in preference to its beta anomer, but net yields were lower. Similar reaction of 1 with (E)-penta-2,4-dienyltrimethylsilane afforded the readily polymerizable 5-(tetra-O-acetyl-alpha-D-glucopyranosyl)-(E)-1,3-pentadiene, accompanied by a minor proportion of its beta anomer.

Alkenes↗
PubMed1988

An azidoaryl thioglycoside of sialic acid. A potential photoaffinity probe of sialidases and sialic acid-binding proteins.

An azidoaryl thioglycoside of sialic acid was prepared, as a potential photoaffinity probe reagent for the analysis of sialidases and sialic acid-binding proteins, by treatment of the glycosyl chloride of N-acetylneuraminic acid methyl ester with potassium thioacetate to give, in 70% yield, methyl 5-acetamido-4,7,8,9-tetra-O-acetyl-2-S-acetyl-2,3,5-trideoxy-2-thio-alph a-D- glycero-D-galacto-2-nonulopyranosonate. Selective hydrolysis of the thioacetate ester, followed by condensation with 4-fluoro-3-nitrophenyl azide, O-deacetylation, and hydrolysis gave (4-azido-2-nitrophenyl)- 5-acetamido-2,3,5-trideoxy-2-thio-alpha-D-glycero-D-galacto-2- nonulopyranosidonic acid.

Affinity Labels↗
PubMed1988

Synthetic receptor analogues: preparation and calculated conformations of the 2-deoxy, 6-O-methyl, 6-deoxy, and 6-deoxy-6-fluoro derivatives of methyl 4-O-alpha-D-galactopyranosyl-beta-D-galactopyranoside (methyl beta-D-galabioside).

The 2-deoxy (7), 6-O-methyl (15), 6-deoxy (22), and 6-deoxy-6-fluoro (31) derivatives of methyl beta-D-galabioside (1) have been synthesised. Thus, 7 was prepared by xanthate reduction using tributyltin hydride, whereas 22 was obtained by catalytic hydrogenation of a 6-deoxy-6-iodogalabioside. Regioselective monofluorination of methyl 2,3-di-O-benzoyl-beta-D-galactopyranoside with Et2NSF3 and subsequent alpha-D-galactosylation provided 31. Molecular mechanics calculations yielded similar conformations for 1, 7, 15, 22, and 31 with differences in phi H and psi H of less than 5 degrees. No indications of intramolecular hydrogen bonds, as displayed by 1 in the crystal, were found for 7, 15, 22, or 31.

Carbohydrate Conformation↗
PubMed1988

General methods for modification of sialic acid at C-9. Synthesis of N-acetyl-9-deoxy-9-fluoroneuraminic acid.

Methyl 5-acetamido-3,5-dideoxy-2-O-methyl-D-glycero-D-galacto-2-nonulopyrano sate was converted into the 9-O-trityl derivative and the remaining hydroxyl groups were protected as benzyl ethers. Removal of the trityl group, followed by treatment with diethylaminosulfur trifluoride gave the 9-deoxy-9-fluoro derivative, and deprotection N-acetyl-9-deoxy-9-fluoroneuraminic acid (8). In another procedure, coupling of 2-acetamido-2,6-dideoxy-6-fluoro-D-glucopyranose with potassium di(tert-butyl) oxaloacetate, followed by hydrolysis and decarboxylation gave 8. Some of the derivatives were active as inhibitors of growth of mouse mammary adenocarcinoma (TA3) and L1210 cells in culture.

Indicators and Reagents↗