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The synthesis of the hexasaccharide 2-(4-trifluoroacetamidophenyl)ethyl O-alpha-D-galactopyranosyl-(1-->3)-[O-alpha-D-galactopyranosyl-(1-->6)]- O-alpha-D-glucopyranosyl-(1-->3)-[O-L-glycero-alpha-D-manno-heptopyranos yl- (1-->7)]-O-L-glycero-alpha-D-manno-heptopyranosyl-(1-->3)-L-glycero-alph a-D- manno-heptopyranoside, corresponding to the heptose and part of the hexose region in the Salmonella Ra core, is described. Syntheses of the pentasaccharide 2-(4-trifluoroacetamidophenyl)ethyl O-alpha-D-galactopyranosyl-(1-->3)-O-alpha-D-glucopyranosyl-(1-->3)-[O-L - glycero-alpha-D-manno-heptopyranosyl-(1-->7)]-O-L-glycero-alpha-D-manno- heptopyranosyl-(1-->3)-L-glycero-alpha-D-manno-heptopyranoside and the tetrasaccharide 2-(4-trifluoroacetamidophenyl)ethyl O-alpha-D-glucopyranosyl-(1-->3)-[O-L-glycero-alpha-D-manno-heptopyranos yl- (1-->7)]-O-L-glycero-alpha-D-manno-heptopyranosyl-(1-->3)-L-glycero-alph a-D- manno-heptopyranoside are also described. Coupling of methyl 2,3,4,6-tetra-O-benzyl-1-thio-beta-D- glucopyranoside and methyl 2-O-benzyl-4,6-O-benzylidene-3-O-(2,3,4,6-tetra-O-benzyl-alpha-D- galactopyranosyl)-1-thio-beta-D-glucopyranoside to a triheptoside derivative with a free HO-3', using dimethyl(methylthio)sulfonium triflate and N-iodosuccinimide-silver triflate as promoters, gave the protected tetra- and penta-saccharide, respectively. Removal of the benzylidene group from the pentasaccharide followed by a regio- and stereo-selective coupling using halide-assisted conditions and 2,3,4,6-tetra-O-benzyl-alpha-D- galactopyranosyl bromide as donor gave the protected hexasaccharide. Deprotection then gave the target structures.
Acetylated 1-cyanoglycals (2,6-anhydro-3-deoxyhept/hex-2-enononitriles) were prepared by direct elimination of acetic acid from the appropriate acetylated 2,6-anhydrohept/hexononitriles with 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) in aprotic solvents. Heterocyclisation of the cyano group of acetylated 1-cyano-D-galactal with 2-aminothiophenol led to 2-(3,4,6-tri-O-acetyl-2-deoxy-D-lyxo-hex-1-enopyranosyl)benz othiazole. Several 2-(per-O-acetylhexo/pentopyranosyl)benzothiazoles also gave 2-(per-O-acetyl-2-deoxyhex/pent-1-enopyranosyl)benzothiazole s with DBU. 3-(Per-O-acetylhexo/pentopyranosyl)-[1,2,4]triazolo[4,3-a] pyrimidines rearranged with DBU to the corresponding acetylated 2-glycosyl-[1,2,4]triazolo[1,5-a]pyrimidines. By the reaction of 1-cyano-D-galactal with ammonium azide, 2-(3,4,6-tri-O-acetyl-2-deoxy-D-lyxo-hex-1-enopyranosyl)tetr azole was prepared and then transformed with carboxylic acid derivatives into 2-(3,4,6-tri-O-acetyl-2-deoxy-D-lyxo-hex-1-enopyranosyl)-5-s ubstituted-1,3,4- oxadiazoles.
The trisaccharides allyl O-(sodium 3-deoxy-alpha-D-manno-2-octulopyranosylonate)-(2-->6)-O-2-aceta mid o-2-deoxy- beta-D-glucopyranosyl-(1-->6)-2-acetamido-2-deoxy-alpha- and -beta-D-glucopyranoside (16a and 16b), the tetrasaccharides allyl O-(sodium 3-deoxy-alpha-D-manno-2-octulopyranosylonate)-(2-->4)-O-(sodium 3-deoxy-alpha-D-manno-2-octulopyranosylonate)-(2-->6)-O-2-aceta mid o-2-deoxy- beta-D-glucopyranosyl-(1-->6)-2-acetamido-2-deoxy-alpha- and -beta-D-glucopyranoside (19a and 19b), and the pentasaccharides allyl O-(sodium 3-deoxy-alpha-D-manno-2-octulopyranosylonate)-(2-->8)-O-(sodium 3-deoxy-alpha-D-manno-2-octulopyranosylonate)-(2-->4)-O-(sodium 3-deoxy-alpha-D-manno-2-octulopyranosylonate)-(2-->6)-O-2-aceta mid o-2-deoxy-bet a -D-glucopyranosyl-(1-->6)-2-acetamido-2-deoxy-alpha- and -beta-D-glucopyranoside (23a and 23b) were prepared. The glycosidic linkages were formed using 1,3,4,6-tetra-O-acetyl-2-chloroacetamido-2-deoxy-beta-D-glucopy ran ose (6) and FeCl3 as promoter as well as per-O-acetylated Kdo mono- and di-saccharide bromide derivatives (12 and 20) under Helferich conditions. The oligosaccharides, which correspond to dephosphorylated part-structures of enterobacterial and chlamydial lipopolysaccharides, were characterized by NMR spectroscopy as well as plasma desorption and matrix-assisted laser desorption mass spectrometry.
The diethyl dithioacetals of D-altrose, D-idose, and D-talose were used to synthesise the respective O-benzyl aldehydo-sugars as intermediates for the synthesis of 3-deoxy-D-glycero-D-gluco/manno-3-deoxy-D-glycero-L-gulo/ido -, and 3-deoxy-D-glycero-L-allo/altro-octonate derivatives, respectively. After reduction and deprotection, the respective 3-deoxyoctitols were obtained. For the synthesis of 3-deoxy-D-glycero-L-galacto/talo-octitol, 2,3:5,6-di-O-isopropylidene-D-gulono-1,4-lactone was transformed by reduction and selective oxidation at C-1 to the aldehydo-D-gulose, from which the 3-deoxy-D-glycero-L-galacto/talo-octonate was synthesised. Carboxyl- and carbonyl-reduction and deprotection gave the 3-deoxyoctitol. The 3-deoxyoctitols were characterised by GLC and GLC-MS in the acetylated and methylated form. The data presented here and the data published earlier [T. Krülle, O. Holst, H. Brade, and R.R. Schmidt, Carbohydr. Res., 247 (1993) 145-158] showed that methylated 3-deoxy-D-glycero-D-galacto/talo-octitol can be distinguished by GLC from the other 3-deoxy-D-octitols and thus allows the identification of the manno configuration of 3-deoxy-D-manno-octulosonic acid (Kdo) in natural products such as the lipopolysaccharides of different Gram-negative bacteria, where Kdo is a generally occurring constituent.
3-Ketosucrose (alpha-D-ribo-hexopyranosyl-3-ulose-beta-D-fructofuranoside), obtained from sucrose via microbial oxidation with Agrobacterium tumefaciens, was shown to be an appropriate and versatile synthon for regioselective syntheses. Condensation with hydroxylamine and its derivatives with allyl and benzyl groups leads to the oxime and the corresponding substituted products. By reductive amination 3-amino-3-deoxy-alpha-D-allopyranosyl-beta-D-fructofuranoside is obtained which can readily be submitted to further functionalization to methacryloyl and fatty acid derivatives. After silylation of 3-ketosucrose the 3-allyl and butylene-substituted as well as decyl- and dodecyl-substituted sucrose can be obtained via Grignard reaction, the side chains being C-C linked to the saccharide.
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The structures of two alpha-(1-->3)-alpha-D-xylo-mannans were determined. The different antiviral activity of the xylo-mannans from Nothogenia fastigiata was explained on the basis of a flexible backbone, molecular size, content and distribution of sulfate groups and of the single stubs of beta-(1-->2)-linked D-xylose.
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6I,6II-Diamino-6I,6II-dideoxy-cyclomaltoheptaose was prepared using the regioselective procedure described by Tabushi. The difunctionalized beta-cyclodextrin crystallizes as hexadecahydrate in the orthorhombic space group P2(1)2(1)2(1), with a = 11.395(3), b = 32.989(9), c = 17.560(5) A, V = 6601 A3, Z = 4. The structure was solved by molecular replacement techniques using the program PATSEE and was refined to a conventional final R = 0.058 for the 5031 observed reflections with I > or = 3 sigma(I). The beta-CD macrocycle presents only slight differences with respect to uncomplexed hydrated or methylated beta-CD. The macrocycle structure maintains an approximate seven-fold symmetry. The round shape of the cyclodextrin ring is stabilized by intramolecular O-H ... O H-bonds between the secondary hydroxyl groups of neighbouring glucose residues. Along the a axis, the beta-CD molecules are arranged in columns; the macrocycles form a herring-bone pattern, so that the cavity of each beta-CD molecule is closed at each end by neighbouring molecules. The macrocycles are directly linked to each other by H-bonds involving either primary and secondary hydroxyl or amino groups of symmetry-related molecules. The resulting layers are connected to each other by a dense intermolecular hydrogen-bond network, in which solvent molecules participate.
Phenyl 2,3,4-tri-O-acetyl-6-O-chloroacetyl-1-thio-alpha,beta-mannopyranoside (5) was condensed with benzyl O-(2,3,4-tri-O-benzyl-beta-D-mannopyranosyl)-(1-->6)-2,3,4-tri-O-benzyl- alpha-D- mannopyranoside (12) in the presence of NIS-triflic acid to give, after removal of the chloroacetyl group, the key intermediate, benzyl O-(2,3,4-tri-O-acetyl-alpha-D-mannopyranosyl)-(1-->6)-O-(2,3,4-tri-O-ben zyl- beta-D-mannopyranosyl)-(1-->6)-2,3,4-tri-O-benzyl-alpha-D-mannopyranosid e (14). A similar condensation of 6 and 7 with acceptor 14, followed by the removal of protecting groups, afforded 16 and 18, respectively. These compounds are expected to be useful in specificity studies of an antibody raised against a related, synthetic antigen that we are currently investigating.
Thermal treatment of anhydrous, acidified sucrose or inulin yields caramels containing monosaccharides and oligomers, predominantly dianhydrides and higher oligomers derived by the addition of glycosyl residues to dianhydrides. Fourteen dianhydrides, most of which comprise two fructose moieties, have been identified by mass spectroscopy of the per-O-trimethylsilyl ethers. Thirteen of these dianhydrides have been isolated and characterized; five of the dianhydrides are novel compounds and one of these is a glucose-fructose dianhydride. The dianhydrides and related oligomers are thought to have a prebiotic effect by stimulating the proliferation of bifidobacteria in the large intestine.
Two routes to a glucose-based mimic of the second messenger 1D-myo-inositol 1,4,5-trisphosphate related to adenophostin A are described. Fischer glycosidation of D-glucose with allyl alcohol in the presence of a strong cation-exchange resin gave a 7:3 alpha: beta-anomeric mixture of allyl glucopyranosides (5ab) from which the pure alpha anomer 5a was isolated by crystallisation. Treatment of 5ab with 1.05 equiv of dibutyltin oxide followed by 2.1 equiv of benzoyl chloride gave allyl 2,6-di-O-benzoyl-alpha-D-glucopyranoside, which was converted in 3 steps into allyl 2,6-di-O-benzyl-3,4-O-isopropylidene-alpha-D-glucopyranoside (4). Alternatively, treatment of 5a with 2.5 equiv of dibutyltin oxide followed by benzyl bromide gave allyl 2,6-di-O-benzyl-alpha-D-glucopyranoside (9) which was also converted into 4. Compound 4 was elaborated to the phosphorylation precursor 2-hydroxyethyl 2,6-di-O-benzyl-alpha-D-glucopyranoside (12) in a convenient one-pot reaction, and 12 was phosphorylated and deblocked to afford 2-hydroxyethyl alpha-D-glucopyranoside 2',3,4-trisphosphate. The 2,6-di-O-benzyl derivative 9 was converted in high yield into 2,6-di-O-benzyl-3,4-di-O-(p-methoxybenzyl)-D-glucopyranose, a useful intermediate for the synthesis of adenophostin A and related compounds.
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Hepatic glutathione (GSH) S-methyl transferase from rabbit, pig and dog demethylates dimethyl phosphate triesters. No stereospecificity towards racemic ethyl methyl 2-chloro-1-(2,4-dichlorophenyl)vinyl phosphate could be demonstrated but the enzyme exhibited some selectivity towards the (+) and (-) forms of O-methyl S-methyl 1-naphthyl phosphorothiolate. Pig liver enzyme, purified 30-fold, demethylated th prochiral substrate dimethyl 1-naphthyl phosphorothionate with 90% stero-selectivity.