Assignment of anomeric structure to carbohydrates through geminal13C-H coupling constants

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.

Application of high-resolution n.m.r. spectroscopy to the elucidation of the structure of the specific capsular polysaccharide of Streptococcus pneumoniae type 7F

The specific capsular polysaccharide of Streptococcus pneumoniae type 7F (American type 51) is a high-molecular-weight neutral polymer composed of 2-acetamido-2-deoxy-D-galactose, 2-acetamido-2-deoxy-D-glucose, D-glucose, D-galactose, L-rhamnose, and 2-O-acetyl-L-rhamnose residues. N.m.r. spectroscopy (1H and 13C), in conjunction with composition and methylation analyses, and periodate oxidation data, showed the polysaccharide to be a branched polymer with a repeating heptasaccharide unit having the following structure. (formula; see text)

[Synthesis of trisaccharide units from capsular polysaccharides of Streptococcus pneumoniae]

In the presence of silver silicate as promoter, the reaction of glycosyl bromide of 2-azido-2-deoxy-D-mannose with 1,6-anhydro-2,3-di-O-benzyl-beta-D- glucopyranose led to derivatives of the disaccharide beta-D-ManpNac-(1----4)-D- Glcp. The derivatives were activated into disaccharide halides and employed as glycosyl donors in block synthesis. By chain extension with L-rhamnose and D-glucose, four trisaccharides were synthesized. They represent components of capsular polysaccharide "repeating units" of various Streptococcus pneumoniae types, beta-D-Man-pNAc-(1----4)-alpha-D-Glcp-(1----2)-L-Rhap (type 19 F), beta-D-ManpNAc-(1----4)-alpha-D-Glcp-(1----3)-L-Rhap (type 19 A), beta-D-ManpNAc-(1----4)-alpha-D-Glcp-(1----4)-D-Glcp (type 9 A), and beta-D-ManpNAc-(1----4)-beta-D-Glcp-(1----4)-D-Glcp (type 9 V).

Structural studies of the Escherichia coli K93 and K53 capsular polysaccharides

The structures of the Escherichia coli K93 and K53 capsular polysaccharides have been investigated by chemical and spectroscopic methods. The repeating unit of both polymers was found to be----3)-beta-D-Galf-(1----f)-beta-D-GlcAp-(1. The O-5 and O-6 atoms of D-galactose are acetylated in the repeating unit of the K93 polymer, but only O-2 is acetylated in the K53 polymer. The K93 polysaccharide is cross-reactive with the Neisseria meningitidis Group A capsular polysaccharide (of known structure). The K53 polysaccharide, although structurally similar to that from K93 organisms, does not cross-react with the Group A polymer.

Synthesis of a trisaccharide component of the capsular polysaccharide of Streptococcus pneumoniae type 19F

2-O-[4-O-(2-Acetamido-2-deoxy-beta-D-mannopyranosyl)-alpha-D- glucopyranosyl]-alpha,beta-L-rhamnopyranose, a structural component of the capsular polysaccharide of Streptococcus pneumoniae type 19F, has been synthesized by sequential glycosylation reactions using the glycosyl acceptor 2,2,2-trichloroethyl 3,4-di-O-benzyl-alpha-L-rhamnopyranoside (prepared from the known 2-O-acetyl-3,4-di-O-benzyl-alpha-L-rhamnopyranosyl chloride), and the glycosyl donors 4-O-acetyl-2,3,6-tri-O-benzyl-alpha-D-glucopyranosyl chloride and 4,6-di-O-acetyl-2-azido-3-O-benzyl-2-deoxy-alpha-D-mannopyranosyl bromide (prepared in seven steps from the known methyl 2-azido-4,6-O-benzylidene-2-deoxy-alpha-D-altropyranoside). The corresponding 8-(methoxycarbonyl)octyl glycoside has also been synthesized, by coupling of 8-(methoxycarbonyl)octyl trifluoromethanesulfonate and the sodium salt of 2-O-[4-O-(2-acetamido-4,6-di-O-acetyl-3-O-benzyl-2-deoxy-beta-D- mannopyranosyl)-2,3,6-tri-O-benzyl-alpha-D-glucopyranosyl]-3,4-di-O- benzyl-alpha,beta-L-rhamnopyranose.

[Synthesis of modified tetrasaccharide sequences of N-glycoproteins]

The tetrasaccharides O-alpha-D-mannopyranosyl-(1----3)-O-[alpha-D- mannopyranosyl-(1----6)]-O-(4-deoxy-beta-D-lyxo-hexopyranosyl)-(1- ---4)-2- acetamido-2-deoxy-alpha, beta-D-glycopyranose (22) and O-alpha-D-mannopyranosyl-(1----3)-O-[alpha-D-mannopyranosyl-(1----6)]-O- beta-D-talopyranosyl-(1----4)-2-acetamido-2-deoxy-alpha, beta-D- glucopyranose (37), closely related to the tetrasaccharide core structure of N-glycoproteins, were synthesized. Starting with 1,6-anhydro-2,3-di-O-isopropylidene-beta-D-mannopyranose, the glycosyl donors 3,6-di-O-acetyl-2-O-benzyl-2,4-dideoxy-alpha-D-lyxo- hexopyranosyl bromide (10) and 3,6-di-O-acetyl-2,4-di-O-benzyl-alpha-D-talopyranosyl bromide (30), were obtained in good yield. Coupling of 10 or 30 with 1,6-anhydro-2-azido-3-O-benzyl-beta-D-glucopyranose to give, respectively, the disaccharides 1,6-anhydro-2-azido-3-O-benzyl-2-deoxy-4-O-(3,6-di-O-acetyl-2-O-benzyl-4 -deoxy- beta-D-lyxo-hexopyranosyl)-beta-D-glucopyranose and 1,6-anhydro-2-azido-3-O-benzyl-2-deoxy-4-O-(3,6-di-O-acetyl-2,4-di-O-ben zyl- beta-D-talopyranosyl)-beta-D-glucopyranose was achieved with good selectivity by catalysis with silver silicate. Simultaneous glycosylation of OH-3' and OH-6' of the respective disaccharides with 2-O-acetyl-3,4,6-tri-O-benzyl-alpha-D-mannopyranosyl chloride yielded tetrasaccharide derivatives, which were deblocked into the desired tetrasaccharides 22 and 37.

Synthesis of methyl 2-O- and 3-O-alpha-D-talopyranosyl-alpha-D-mannopyranoside

Methyl 3,4,6-tri-O-benzyl-2-O-[6-O-(tert-butyldiphenylsilyl)-alpha-D- mannopyranosyl]-alpha-D-mannopyranoside (2) was synthesized by treatment of methyl 3,4,6-tri-O-benzyl-2-O-alpha-D-mannopyranosyl-alpha-D-mannopyranoside with tert-butylchlorodiphenylsilane in the presence of imidazole. Isopropylidenation, followed by oxidation with pyridinium chlorochromate, and stereoselective reduction with sodium borohydride, converted 2 into methyl 3,4,6-tri-O-benzyl-2-O-[6-O-(tert-butyldiphenylsilyl)-2,3-O-isopro pylidene- alpha-D-talopyranosyl]-alpha-D-mannopyranoside (5). Treatment of 5 with a molar solution of tetrabutylammonium fluoride in dry oxolane produced a diol which, on O-de-isopropylidenation followed by catalytic hydrogenolysis, afforded the disaccharide glycoside methyl 2-O-alpha-D-talopyranosyl-alpha-D-mannopyranoside. Synthesis of methyl 3-O-alpha-D-talopyranosyl-alpha-D-mannopyranoside was accomplished by a similar reaction-sequence. The structures of the final disaccharides, and of various other intermediates, were established by 1H- and 13C-n.m.r. spectroscopy.

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.

Structure of a rhamnan from the surface-layer glycoprotein of Bacillus stearothermophilus strain NRS 2004/3a

The structure of a glycan from the surface-layer glycoprotein of Bacillus stearothermophilus strain NRS 2004/3a has been studied by 1H- and 13C-n.m.r. spectroscopy. The results indicate the glycan to be a polymer of the trisaccharide repeating-unit ----2)-alpha-L-Rhap-(1----2)-alpha-L-Rhap-(1----3)-beta-L-++ +Rhap-(1----.

[Synthesis of a branched pentasaccharide sequence of "bisected" structure of N-glycoproteins]

For the synthesis of the threefold-branched pentasaccharide, O-alpha-D-mannopyranosyl-(1----3)-O-[(2-acetamido-2-deoxy-beta-D- glucopyranosyl)-(1----4)]-O-[alpha-D-mannopyranosyl-(1----6)]-O-beta-D- mannopyranosyl-(1----4)-2-acetamido-2-deoxy-D-glucopyranose (20), which is a part of the structure of the N-glycoproteins, the disaccharide 4-O-(4-O-acetyl-3,6-di-O-allyl-2-O-benzyl-beta-D-mannopyranosyl) -1,6-anhydro-2-azido-3-O-benzyl-2-deoxy-beta-D-glucopyranose was synthesized as a key compound by use of the silver silicate-catalyst procedure. After elimination of the 4-O-acetyl group, a 2-acetamido-2-deoxy-beta-D-glucopyranosyl group was attached according to the phthalimido method. Further elimination of the allyl groups allowed the linkage of two alpha-D-mannopyranosyl groups in the presence of mercury salt. A deblocking sequence consisting of four steps gave 20.

Antigenic S-type lipopolysaccharide of Brucella abortus 1119-3

Antigenic phenol-phase soluble lipopolysaccharide isolated from Brucella abortus 1119-3 by hot phenol-water extraction was shown by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, controlled hydrolysis, periodate oxidation, methylation, and 1H and 13C nuclear magnetic resonance studies to be an S-type lipopolysaccharide which could be cleaved to yield a lipid A and an O-chain polysaccharide identified as an unbranched linear homopolymer of 1,2-linked 4,6-dideoxy-4-formamido-alpha-D-mannopyranosyl residues. The serological reactivity of bovine antiserum to B. abortus 1119-3 with the lipopolysaccharides of Yersinia enterocolitica serotype O:9 and Vibrio cholerae species has now been related to the occurrence of 1,2-linked N-acylated 4-amino-4,6-dideoxy-alpha-D-mannopyranosyl units in the O-chain polysaccharides of their lipopolysaccharides.

Structure of the O-chain of the phenol-phase soluble cellular lipopolysaccharide of Yersinia enterocolitica serotype O:9

The phenol-phase soluble cellular lipopolysaccharide isolated by the phenol/water extraction method from Yersinia enterocolitica serotype O:9 cells was shown by hydrolytic, periodate oxidation, methylation and nuclear magnetic resonance studies to be an S-type lipopolysaccharide with a linear O-antigenic polysaccharide of 1,2-linked 4,6-dideoxy-4-formamido-alpha-D-mannopyranosyl units. The serological cross-reactivity between Y. enterocolitica serotype O:9 and the lipopolysaccharides of Vibrio cholerae and Brucella species can now be related to the presence of N-acylated 4-amino-4,6-dideoxy-alpha-D-mannopyranosyl residues in their respective O-antigenic chains.

Somatic antigens of Shigella: the structure of the polysaccharide chain of Shigella boydii type 2 lipopolysaccharide

The structure of the polysaccharide chain of Shigella boydii type 2 lipopolysaccharide was established using mainly 13C-n.m.r. spectroscopy, partial hydrolysis, Smith degradation, and methylation analysis. The repeating unit of the polysaccharide was concluded to be a branched hexasaccharide, as follows: (formula in text). Acetaldehyde was detected in the hyrolysate of the lipopolysaccharide, but no evidence was obtained to indicate that acetaldehyde is located in the polysaccharide moiety.