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

Structure of a muramic acid containing capsular polysaccharide from the pathogenic strain of Vibrio vulnificus ATCC 27562

Vibrio vulnificus strains isolated from septicemia cases and from the environment show a wide variety of capsular types. In an attempt to find common structural features which can be correlated with pathogenicity and toxicity, we have determined structures of the capsular polysaccharides (CPS) from several pathogenic strains. We report the complete structure of the polysaccharide from the pathogenic V. vulnificus strain ATCC 27562 using a combination of homonuclear and heteronuclear one-dimensional and two dimensional NMR experiments. The 13C and 1H NMR spectra, including the exchangeable amide proton resonances, have been completely assigned. The amide linkage between Ser and C6 of GalA has been unambiguously determined by water-suppressed 2D NOESY. To verify the structure established by NMR, we have fragmented the polymer employing the Smith degradation procedure. The Smith product identified by NMR and matrix-assisted laser desorption mass spectrometry is consistent with the proposed structure for the CPS, which is composed of D-GlcNAc, MurNAc, D-GalA, L-Rha and is serine-linked as shown: [formula: see text]

Architecture of the yeast cell wall. Beta(1-->6)-glucan interconnects mannoprotein, beta(1-->)3-glucan, and chitin

In a previous study (Kollár, R., Petráková, E., Ashwell, G., Robbins, P. W., and Cabib, E. (1995) J. Biol. Chem. 270, 1170-1178), the linkage region between chitin and beta(1-->3)-glucan was solubilized and isolated in the form of oligosaccharides, after digestion of yeast cell walls with beta(1-->3)-glucanase, reduction with borotritide, and subsequent incubation with chitinase. In addition to the oligosaccharides, the solubilized fraction contained tritium-labeled high molecular weight material. We have now investigated the nature of this material and found that it represents areas in which all four structural components of the cell wall, beta(1-->3)-glucan, beta(1-->6)-glucan, chitin, and mannoprotein are linked together. Mannoprotein, with a protein moiety about 100 kDa in apparent size, is attached to beta(1-->6)-glucan through a remnant of a glycosylphosphatidylinositol anchor containing five alpha-linked mannosyl residues. The beta(1-->6)-glucan has some beta(1-->3)-linked branches, and it is to these branches that the reducing terminus of chitin chains appears to be attached in a beta(1-->4) or beta(1-->2) linkage. Finally, the reducing end of beta(1-->6)-glucan is connected to the nonreducing terminal glucose of beta(1-->3)-glucan through a linkage that remains to be established. A fraction of the isolated material has three of the main components but lacks mannoprotein. From these results and previous findings on the linkage between mannoproteins and beta(1-->6)-glucan, it is concluded that the latter polysaccharide has a central role in the organization of the yeast cell wall. The possible mechanism of synthesis and physiological significance of the cross-links is discussed.

Complete NMR structural elucidation of the capsular polysaccharide adjuvant from Klebsiella I-714

The capsular polysaccharide (CPS) produced by the non-pathogenic Klebsiella strain I-714, selected for its immunomodulating activity, has been purified and almost completely detoxified in a previous study [Adam, O., Vercellone, A., Paul, F., Monsan, P. F. & Puzo, G. (1995) Anal. Biochem. 225, 321-327]. The present report concerns the structural elucidation of this CPS by several one-dimensional and two-dimensional 1H-NMR and 13C-NMR experiments performed on the native molecule. It was found to be a high molecular-mass branched polymer constituted by a hexasaccharide repeating unit of following structure: 4)-alpha-L-Rhap-(1-->3)-beta-D-Galp-(1-->2)-alpha-L-Rhap-(1- ->4)-beta-D- GlcpA-(1-->3)-¿alpha-L-Rhap-(1-->2)-¿-alpha-D-Galp-(1. The presence of two glycosidic substitutions on the Galp residue resulted in a strong overlapping of its proton signals, preventing direct assignment of both proton and carbon resonances. However, assignment could be achieved using the two-bond and three-bond 1H-13C heteronuclear coupling observed in the 1H-13C heteronuclear multiple-bond correlation (HMBC) spectrum.

An N-[(R)-(-)-2-hydroxypropionyl]-alpha-L-perosamine homopolymer constitutes the O polysaccharide chain of the lipopolysaccharide from Vibrio cholerae O144 which has antigenic factor(s) in common with V. cholerae O76

Chemical and serological studies were performed with the lipopolysaccharide (LPS) from Vibrio cholerae O144 (O144). The LPS of O144 contained D-glucose, D-galactose, L-glycero-D-manno-heptose, D-fructose, D-quinovosamine (2-amino-2,6-dideoxy-D-gluco-pyranose) and L-perosamine (4-amino-4,6-dideoxy-L-manno-pyranose). The perosamine, a major component sugar of the LPS from O144, was in an L-configuration, as is also the case in the LPS from V. cholerae O76 (O76), in contrast to the D-configuration of the perosamine in the LPS of V. cholerae O1. A structural analysis revealed that the O polysaccharide chain of the LPS from O144 is an alpha(1-->2)-linked homopolymer of (R)-(-)-2-hydroxypropionyl-L-perosamine. The serological cross-reactivity between O144 and O76 was clearly revealed by cross-agglutination and cross-agglutinin absorption tests with whole cells, as well as by passive hemolysis tests with sheep red-blood cells that had been sensitized with the LPS from O144 and O76. In contrast, in passive hemolysis tests, the LPS of O144 did not cross-react serologically with the LPSs from other strains such as V. cholerae O1 (Ogawa and Inaba), V. cholerae O140, Vibrio bio-serogroup 1875 (Original and Variant) and Yersinia enterocolitica O9. The LPSs from these strains consist of O polysaccharide chains composed of alpha(1-->2)-linked homopolymers of D-perosamine with various N-acyl groups, and they share the Inaba antigen factor C of V. cholerae O1 in common. The results obtained in this study demonstrate that the absolute configuration of the perosamine residue in homopolymers plays a very important role in the expression of the serological specificity of the Inaba antigen factor C of V. cholerae O1.

Versatile intermediates in the selective modification of the amino function of 2-amino-2-deoxy-D-mannopyranose and the 3-position of 2-acetamido-2-deoxy-D-mannose: potential membrane modifiers in neoplastic control

A general method has been developed to selectively modify the amino group of 2-amino-2-deoxy-D-mannopyranose (D-mannosamine), a precursor of the terminal membrane sugar, sialic acid. 1,3,4,6-Tetra-O-acetyl-2-amino-2-deoxy-alpha-D-mannopyranose oxalate was prepared via two routes that allowed introduction of various acyl groups onto the amino function. These compounds were evaluated for their antineoplastic properties. The most significant preclinical therapeutic finding was the antileukemic activity found in mice for tetra-O-acetyl-2-epi-streptozotocin (the acetylated alpha-mannosamine epimer of streptozotocin). Administration of 50 mg/kg/day x 5 to leukemia L1210-bearing DBA/2Ha mice resulted in 5/5 35-day survivors. Neutralization of 1,3,4,6-tetra-O-acetyl-2-amino-2-deoxy-alpha-D-mannopyranose oxalate under aqueous conditions led to 2-acetamido-1,4,6-tri-O-acetyl-2-deoxy-alpha-D-mannopyranose, the oxidation of which gave 2-acetamido-4,6-di-O-acetyl-1,5-anhydro-2-deoxy-D-erythro-hex-1-en-3- ulose. This agent demonstrated an IC50(2) of 25 microM with a murine L1210 cell culture. Administration of 100 mg/kg/day x 5 resulted in 42% ILS3 in DBA/2 mice with ip L1210 leukemia. Several other nonacetylated derivatives were also prepared by direct N-acylation, producing, for example, fluorescently tagged N-dansylmannosamine.

Synthesis of pentasaccharide analogues of the N-glycan substrates of N-acetylglucosaminyltransferases III, IV and V using tetrasaccharide precursors and recombinant beta-(1-->2)-N-acetylglucosaminyltransferase II

Recombinant human UDP-GlcNAc: alpha-Man-(1-->6)R beta-(1-->2)-N-acetylglucosaminyltransferase II (EC 2.4.1.143, GlcNAc-T II) was produced in the Sf9 insect cell/baculovirus expression system as a fusion protein with a (His)6 tag and partially purified by affinity chromatography on a metal chelating column. The partially purified enzyme was used to catalyze the transfer of GlcNAc from UDP-GlcNAc to R-alpha-Man(1-->6)(beta-GlcNAc(1-->2)alpha-Man(1-->3))beta-Man-O-octyl to form beta-GlcNAc(1-->2)R-alpha-Man(1-->6)(beta-GlcNAc(1-->2)alpha- Man(1-->3))beta-Man-O-octyl where there is either no modification of the alpha-Man(1-->6) residue (7), or where R is 3-deoxy (8), 4-deoxy (9) or 6-deoxy (10). The yields ranged from 64-80%. Products were characterized by 1H and 13C nuclear magnetic resonance spectroscopy and fast atom bombardment mass spectrometry. Compounds 7-10 are pentasaccharide analogues of the biantennary N-glycan substrates of N-acetylglucosaminyltransferases III, IV and V.

The structure of the acidic exopolysaccharide produced by Pseudomonas "gingeri" strain Pf9

The structure of the acidic exopolysaccharide produced by the mushroom pathogen Pseudomonas "gingeri" strain Pf9, a bacterium which causes ginger blotch, was investigated by chemical analysis, mass spectrometry and 1D and 2D NMR spectroscopy. The polysaccharide consists of the linear trisaccharide repeating unit [formula: see text] where the cyclic pyruvic acetal groups at O-4 and O-6 of the mannopyranosyl residues have the S-configuration. Methylation analysis under neutral conditions and NMR data showed that the mannose residues are acetylated at O-2. This exopolysaccharide has the same structure as the E. coli K55 capsular polysaccharide and differs from the Klebsiella K5 capsular polysaccharide only in the position of acetylation (C-2 of the glucopyranose residue).

Stereoselective synthesis of O-serinyl/threoninyl-2-acetamido-2-deoxy-alpha- or beta-glycosides

General glycosidation methodology has been developed which can selectively provide 2-acetamido-2-deoxy-alpha- or beta-glycosides of beta-hydroxy-alpha-amino acid derivatives [glucopyranoside-(8, 43), galactopyranoside- (9, 13), mannopyranoside- (10), lactoside analogs (11, 38) and 3-O-beta-galactopyranosyl-mannopyranoside (12)] stereoselectively in excellent yield from the highly nucleophilic alpha-imino esters (Schiff bases) of L-serine and L-threonine. Various glycosides were converted via their amino and acetamido derivatives to Fmoc-protected serinyl- or threoninyl-glycosides (24-28, 37, 41, 46) which are all suitable building blocks for the solid-phase synthesis of O-glycopeptides. Complete 1H- and 13C-NMR data are provided for all compounds.

Immunochemistry of group A and Inaba C antigen factors constituting the O antigen of O1 Vibrio cholerae

Serological cross-reactivity among intact lipopolysaccharides (LPS) from O1 Vibrio cholerae Inaba O-form (Inaba), Yersinia enterocolitica O9 (O9), non-O1 V. cholerae serogroup Hakata (Hakata) and Vibrio bio-serogroup 1875 Variant (1875 Variant) (all of which share Inaba antigen factor C), as well as a total of six kinds of chemically modified LPS (three from O9 and three from Inaba) was demonstrated by passive hemolysis and passive hemolysis inhibition by using these LPS as antigen for sensitizing sheep red blood cells and as inhibitor. These intact as well as chemically modified LPS contained, in their O polysaccharide chain, alpha(1-->2)-linked linear perosamine (4-amino-4,6-dideoxy-D-manno-pyranose) homopolymers with different N-acyl groups: their acyl groups comprise 3-deoxy-L-glycero-tetronyl (Inaba LPS), formyl (O9 LPS), 3-hydroxypropionyl (1875 Variant LPS), acetyl (Hakata LPS and artificially introduced into Inaba and O9 LPS), propionyl and butyryl (both artificially introduced into Inaba and O9 LPS) groups. N-Deacylation of the alpha(1-->2)-linked N-(3-deoxy-L-glycero-tetronyl)perosamine homopolymer of Inaba and the N-formyl one of O9 LPS resulted in virtual elimination of their serological reactivity with both homologous and heterologous antisera. Furthermore, when the resultant NH2 groups of the N-deacylated perosamine homopolymers of both LPS were N-acylated with acetyl, propionyl or butyryl groups, they markedly recovered both of their serological reactivities. These results are compatible with the interpretation that the Inaba antigen factor C possessed by the four bacteria is substantially related to the common presence of N-acyl groups, regardless of their identity, residing in the perosamine residues constituting the O polysaccharide chain of their LPS. It was also indicated that the group antigen factor A of O1 V. cholerae is substantially related to the 3-deoxy-L-glycero-tetronyl groups residing in the perosamine homopolymer of Inaba LPS.

Glycan structure of the S-layer glycoprotein of Bacillus sp. L420-91

Preliminary taxonomic characterization of isolate L420-91 has revealed that this organism is closely related to the species Bacillus aneurinolyticus. The bacterium is covered by a squarely arranged crystalline surface layer composed of identical glycoprotein subunits with an apparent molecular mass in the range of 109 kDa. A total carbohydrate content of approximately 3.5% (wt/wt) was determined in the purified surface layer glycoprotein. Glycopeptides were obtained after exhaustive Pronase digestion and purification including gel filtration, ion exchange chromatography and HPLC. From the combined evidence of composition analysis. Smith degradation and nuclear magnetic resonance spectroscopy experiments we propose the following structure for the glycan chain of the surface layer glycoprotein: [formula: see text]

Structure elucidation of an acetylated saponin of Blighia welwitschii by NMR spectroscopy

A new glycosylated triterpene has been isolated from the fruit of Blighia welwitschii. The structural analysis of its peracetylated derivative (1) was performed by 2D homonuclear and heteronuclear NMR spectroscopy. The saponin was shown to contain hederagenin and five sugar residues forming two glycosyl chains. The complete structure of the saponin was established to be 3-O-[beta-D-Glc p-(1-->3)-alpha-L-Rha p-(1-->2)-alpha- L-Ara p]-28-O-[beta-D-Glc p-(1-->6)-beta-D-Glc p]hederagenin.

Composition of the coagulant polysaccharide fraction from Strychnos potatorum seeds

The composition of the coagulant polysaccharide fraction from Strychnos potatorum seeds is described. This fraction comprises a 1:1.7 mixture of a galactomannan and a galactan. The structure of these polysaccharides is also discussed. In addition, the coagulant properties of the polysaccharide fractions of two other Strychnos species, innocua and nux-vomica, have been assayed.

A plasmid-encoded rfbO:54 gene cluster is required for biosynthesis of the O:54 antigen in Salmonella enterica serovar Borreze

Previous studies demonstrated that the presence of a 7-8 kb plasmid is correlated with expression of the lipopolysaccharide (LPS) O:54 antigen in several Salmonella enterica serovars. In this study, a 6.7 kb plasmid from a field isolate of S. enterica serovar Borreze was shown to encode enzymes responsible for the synthesis of the O:54 polysaccharide. Curing the plasmid results in simultaneous loss of smooth O-polysaccharide-substituted LPS molecules and O:54 serotype. SDS-PAGE analysis of other O:54 isolates indicated that the O:54 O-polysaccharide can be co-expressed with an additional O-polysaccharide, likely encoded by chromosomal genes. The structure of the O:54 polysaccharide was determined by a combination of chemical and nuclear magnetic resonance (NMR) methods and was found to be an unusual homopolymer of N-acetylmannosamine (D-ManNAc) residues. The polysaccharide contained a disaccharide repeating unit with the structure:-->4)-beta-D-ManpNAc-(1-->3)-beta-D-ManpNAc-(1--> This structure does not resemble other O-polysaccharides in S. enterica. To examine the role played by plasmid functions in synthesis of the O:54 polysaccharide, the 6.7 kb plasmid was cloned to produce a hybrid plasmid (pWQ800) in pGEM-7Zf(+). In Escherichia coli K-12 delta rfb, pWQ800 directed the synthesis of authentic O:54 polysaccharide. Polymerized O:54 polysaccharide was also produced in S. enterica serovar Typhimurium rfb and rfc mutants. From these data, we conclude that pWQ800 carries the rfbO:54 gene cluster and synthesis of the O:54 polysaccharides does not require host chromosomal rfb functions. However, synthesis of the O:54 polysaccharide requires the function of the rfe and rffE genes which are part of the gene cluster encoding enzymes involved in biosynthesis of enterobacterial common antigen. The rffE gene product synthesizes the O:54 precursor, uridine diphospho-N-acetylmannosamine. This is the first description of a plasmid-encoded rfb gene cluster in Salmonella.

Structural determination of the capsular polysaccharide produced by Klebsiella pneumoniae serotype K40. NMR studies of the oligosaccharide obtained upon depolymerisation of the polysaccharide with a bacteriophage-associated endoglycanase

The Klebsiella pneumoniae K40 capsular polysaccharide has been isolated and investigated by use of methylation analysis, specific degradations and NMR spectroscopy. The polysaccharide was depolymerised by a bacteriophage-associated endogalactosidase, and the resulting oligosaccharide was characterised by one-dimensional and two-dimensional NMR spectroscopy and direct chemical ionisation MS. The repeating unit of the K40 capsular polysaccharide was shown to be a linear hexasaccharide with the composition-->3)- alpha-L-Rhap-(1-->2)-alpha-L-Rhap-(1-->4)-alpha-D-GlcpA++ +-(1-->2-)- alpha-D-Manp-(1-->2)-alpha-D-Manp-(1-->3)-alpha-D-Galp-(1--> (Rha, rhamnose).

Structure of the repeating unit of the O-specific polysaccharide of the lipopolysaccharide of Yersinia kristensenii strain 490 (O:12,25)

The O-specific polysaccharide isolated by mild acid degradation of the lipopolysaccharide of Y. kristensenii strain 490 (O:12,25) contained D-glucose, 2-acetamido-2-deoxy-D-glucose, 2-acetamido-2-deoxy-D-galactose, 2-acetamido-2,6-dideoxy-L-galactose, glycerol, and phosphate in the ratios 2:2:1:1:1:1. On the basis of 31P- and 13C-n.m.r. data, methylation analysis, dephosphorylation, solvolysis with anhydrous hydrogen fluoride, and Smith degradation, it was concluded that the repeating unit of the polysaccharide was a branched hexaosylglycerol phosphate with the following structure. [formula: see text]

Synthesis of an octasaccharide fragment of high-mannose-type glycans of glycoproteins

O-(alpha-D-Mannopyranosyl)-(1----2)-O-(alpha-D-mannopyranosyl)-(1----3)- O- [(alpha-D-mannopyranosyl)-(1----2)-O-(alpha-D-mannopyranosyl)-(1----6)]- O- (alpha-D-mannopyranosyl)-(1----6)-O-(beta-D-mannopyranosyl)-(1----4)-O-( 2- acetamido-2-deoxy-beta-D-glucopyranosyl)-(1----4)-2-acetamido-2-deoxy- glucopyranose, an octasaccharide fragment of high-mannose type glycan of glycoproteins, was synthesized. Crucial glycosylation of trisaccharide intermediate, benzyl O-(2,4-di-O-benzyl-beta-D-mannopyranosyl)-(1----4)-O-(2-acetamido-3,6-di -O- benzyl-2-deoxy-beta-D-glucopyranosyl)-(1----4)-2-acetamido-3,6-di-O-benz yl-2- deoxy-beta-D-glucopyranoside, was successful only with a di-O-acetyltetradeca-O-benzyl-D-mannopentaosyl chloride. The use of the corresponding hexadeca-O-acetyl-D-mannopentaosyl bromide did not give the desired product.

Structure and antitumor activity of a branched (1----3)-beta-D-glucan from the alkaline extract of Amanita muscaria

A beta-(1----6)-branched (1----3)-beta-D-glucan(AM-ASN) was isolated from the alkaline extract of the fruiting bodies of Amanita muscaria. AM-ASN had [alpha]D - 11 degrees in 0.5 M sodium hydroxide. Its estimated molecular weight was 95,000 in this alkaline solution and 260,000 in a neutral solution. The branches in the glucan were primarily single, (1----6)-linked D-glucopyranosyl groups, two for every seven residues in the (1----3)-linked main chain. AM-ASN exhibited significant antitumor activity against Sarcoma 180 in mice, and a mixture of AM-ASN with mitomycin C was more effective against the tumor than mitomycin C only.

One-bond carbon-proton coupling constants: angular dependence in alpha-linked oligosaccharides

An investigation is presented of the angular dependence of 1JC,H in model compounds related to alpha-linked oligosaccharides. Values calculated by FPT formulation in the semi-empirical INDO method for models of (1----1)-, (1----2)-, (1----3)-, and (1----4)-linked disaccharides were compared, and the effect of the orientation of HO-2 was elucidated. The angular dependence of 1JC,H on the glycosidic dihedral angles phi H and psi H was characterised in the form 1JC,H = A cos 2 phi + B cos phi + C sin 2 phi + D sin phi + E. The 1JC,H values, measured by DEPT methods for C-1-H-1 and C-X'-H-X' in various rigid carbohydrates, were used to adjust the calculated angular dependences and to determine solvent effects. Based on the abundance of the conformers for maltose and isomaltose, the thermodynamically averaged 1JC,H values have been calculated. The results obtained (less than 1JC-1,H-1 greater than 169.9, less than 1JC-4',H-4' greater than 147.7 Hz for methyl beta-maltoside and less than 1JC-1,H-1 greater than 169.8 Hz for methyl beta-isomaltoside) agree with the experimental values of 172.4, 147.7, and 170.3 Hz, respectively.

Structure of the capsular polysaccharide from Actinobacillus pleuropneumoniae serotype 10

The capsular polysaccharide of A. pleuropneumoniae serotype 10 was found to be composed of a linear disaccharide repeating unit. By use of methylation analysis, partial hydrolysis, g.l.c.--and f.a.b.- m.s., and 1D and 2D n.m.r. studies, the polysaccharide was determined to be a polymer of a repeating disaccharide unit composed of D-mannose and 3-deoxy-D-manno-octulosonic acid (Kdo) having the structure: [formula; see text]

Structure of pescaproside E, a fatty acid glycoside from Ipomoea pescaprae

Three fatty acid glycosides, designated pescaprosides A, B, and E, have been isolated from Ipomoea pescaprae (family Convolvulaceae). Chemical studies on pescaproside E, the major product, led to its characterisation as a pentaglycoside of 11-hydroxyhexadecanoic acid. Its sugar chain was esterified with 2-methylbutanoic and lauric acids. The structure of the pentaglycoside has been established as O-alpha-L-rhamnopyranosyl-(1----3)-O-[alpha-L-rhamnopyranosyl- (1----4)]-O-alpha-L-rhamnopyranosyl-(1----4)-O-beta-D-fucopyranosyl-(1-- --2)- O-alpha-L-rhamnopyranosyl-(1----11)-oxyhexadecanoic acid.

Synthesis of a spacer-containing repeating unit of the capsular polysaccharide of Streptococcus pneumoniae type 23F

The synthesis is reported of 3-aminopropyl 4-O-(4-O-beta-D-glucopyranosyl-2-O-alpha-L-rhamnopyranosyl-beta-D- galactopyranosyl)-beta-L-rhamnopyranoside 3'-(glycer-2-yl sodium phosphate) (25 beta), which represents the repeating unit of the capsular polysaccharide of Streptococcus pneumoniae type 23F (American type 23) [(----4)-beta-D-Glcp-(1----4)-[Glycerol-(2-P----3)] [alpha-L- Rhap-(1----2)]-beta-D-Galp-(1----4)-beta-L-Rhap-(1----)n). 2,4,6-Tri-O-acetyl-3-O-allyl-alpha-D-galactopyranosyl trichloroacetimidate (5) was coupled with ethyl 2,3-di-O-benzyl-1-thio-alpha-L-rhamnopyranoside (6). Deacetylation of the resulting disaccharide derivative, followed by benzylidenation, and condensation with 2,3,4-trio-O-acetyl-alpha-L-rhamnopyranosyl trichloroacetimidate (10) afforded ethyl 4-O-[3-O-allyl-4,6-O-benzylidene-2-O-(2,3,4-trio-O-acetyl- alpha-L-rhamnopyranosyl)-beta-D-galactopyranosyl]-2,3-di-O-benzyl-1-thio - alpha-L-rhamnopyranoside (11). Deacetylation of 11, followed by benzylation, selective benzylidene ring-opening, and coupling with 2,3,4,6-tetra-O-acetyl-alpha-D-glucopyranosyl trichloroacetimidate (15) gave ethyl 4-O-[3-O-allyl-6-O-benzyl-4-O-(2,3,4,6- tetra-O-acetyl-beta-D-glucopyranosyl)-2-O-(2,3,4-tri-O-benzyl-alpha-L- rhamnopyranosyl)-beta-D-galactopyranosyl]-2,3-di-O-benzyl-1-thio-alpha-L - rhamnopyranoside (16). Deacetylation of 16 followed by benzylation, deallylation, and acetylation yielded ethyl 4-O-[3-O-acetyl-6-O-benzyl-4-O-(2,3,4,6-tetra-O-benzyl-beta-D-glucopy ran osyl)- 2-O-(2,3,4-tri-O-benzyl-alpha-L-rhamnopyranosyl)-beta-D-galactopyranosyl ]-2,3- di-O-benzyl-1-thio-alpha-L-rhamnopyranoside (20). The glycosyl bromide derived from 20, when coupled with 3-benzyloxycarbonylamino-1-propanol, gave the beta-glycoside (21 beta) as the major product. Deacetylation of 21 beta followed by condensation with 1,3-di-O-benzylglycerol 2-(triethylammonium phosphonate) (27), oxidation, and deprotection, afforded 25 beta.

Structure of the O-antigen of Actinobacillus pleuropneumoniae serotype 7 lipopolysaccharide

The structure of the O-antigen polysaccharide of A. pleuropneumoniae serotype 7 was investigated by methylation analysis, partial acid hydrolysis, periodate oxidation, and 1H- and 13C-n.m.r. spectroscopy. The polysaccharide repeating-unit consists of a branched tetrasaccharide having the following structure. [formula: see text]

The occurrence of alpha (1----2) linked N-acetylperosamine--homopolymer in lipopolysaccharides of non-O1 Vibrio cholerae possessing an antigenic factor in common with O1 V. cholerae

Chemical analysis was carried out on lipopolysaccharides from Vibrio cholerae bio-serogroup Hakata 487-85. The O-specific chain of the phenol-soluble lipopolysaccharides was demonstrated by 13C-NMR spectroscopy and methylation analysis to contain a linear homopolymer of alpha(1----2) linked N-acetylperosamine (4-acetamido-4,6-dideoxy-D-mannopyranose), which was closely similar to but not identical to a linear alpha(1----2) linked N-3-deoxy-L-glycerotetronyl (S-2,4-dihydroxybutyryl) perosamine-homopolymer constituting that of O1 Vibrio cholerae lipopolysaccharides.

13C-substituted pentos-2-uloses: synthesis and analysis by 1H- and 13C-n.m.r. spectroscopy

D-erythro-Pentos-2-ulose and D-threo-pentos-2-ulose and their 1-13C- and 2-13C-substituted derivatives have been prepared by oxidizing the corresponding natural and 13C-substituted D-aldopentoses (D-arabinose, D-xylose) with cupric acetate, and purifying the products by chromatography on a cation-exchange resin in the calcium or barium form. The equilibrium compositions of the pentos-2-uloses in 2H2O were determined by 13C-n.m.r. spectroscopy (75 MHz) at 25 degrees and 80 degrees. Among the eighteen possible monomeric acyclic, cyclic, and bicyclic forms, the anomeric pairs of the unhydrated aldopyranoses, aldopyranose endocyclic hydrates, aldofuranose endocyclic hydrates, and ketofuranose exocyclic hydrates were identified on the basis of 13C chemical shifts and 13C-1H and 13C-13C spin-coupling constants. 1H-N.m.r. (300, 500, and 620 MHz) and 13C-n.m.r. (75 MHz) spectroscopic data in one and two dimensions (DQF-COSY, homonuclear 2D-J) were used to evaluate the conformational properties of the cyclic structures. The unhydrated pyranoses are highly conformationally homogeneous; the erythro and threo isomers prefer 1C4 and 4C1 conformations, respectively. D-threo-Pentos-2-ulopyranose hydrate prefers the 4C1 conformation whereas the erythro isomers exists in both the 4C1 and 1C4 conformations. The furanoid forms favor structures having quasi-axial anomeric hydroxyl groups and quasi-equatorial exocyclic hydroxymethyl or dihydroxymethyl groups.

Stereoselective total synthesis of dodecagalacturonic acid, a phytoalexin elicitor of soybean

O-(alpha-D-Galactopyranosyluronic acid)-[(1----4)-O-(alpha-D-galactopyranosyluronic acid)]10-D-galactopyranuronic acid (1), an endogenous elicitor of the phytoalexin of soybean, was synthesized by way of highly stereoselective glycosylations that involved glycosyl fluorides as the donors and oxidation of the twelve primary hydroxyl groups in the alpha-(1----4)-linked galactododecaoside derivative.

Synthesis of an appropriately protected core glycotetraoside, a key intermediate for the synthesis of "bisected" complex-type glycans of a glycoprotein

A stereocontrolled synthetic route to a glycotetraoside, allyl O-(3,4,6-tri-O-benzyl-2-deoxy-2-phthalimido-beta-D-glucopyranosyl)-(1--- -4)-O- (3,6-di-O-allyl-2-O-benzyl-beta-D-mannopyranosyl)-(1----4)-O-3, 6-di-O-benzyl-2-deoxy-2-phthalimido-beta-D-glucopyranosyl)-(1----4)-3-O- benzyl- 2-deoxy-6-O-p-methoxy-phenyl-2-phthalimido-beta-D-glucopyranoside, an important intermediate for the synthesis of "bisected" complex type glycans of glycoproteins has been established by employing two glycosyl donors, 3,4,6-tri-O-benzyl-2-deoxy-2-phthalimido-beta-D-glucopyranosyl trichloroacetimidate and 4-O-acetyl-3,6-di-O-allyl-2-O-benzyl-alpha-D-mannopyranosyl bromide, and a glycosyl acceptor, allyl O-(3,6-di-O-benzyl-2-deoxy-2-phthalimido-beta-D-glucopyranosyl)-(1----4) -3-O- benzyl-2-deoxy-6-O-p-methoxyphenyl-2-phthalimido-beta-D-glucopyranoside.

Characterization of the surface layer glycoprotein of Clostridium symbiosum HB25

The cell surface of Clostridium symbiosum HB25 is covered by a squarely arranged surface layer (S-layer) glycoprotein. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the sodium dodecyl sulfate-soluble whole-cell extract showed the presence of several high-molecular-weight protein bands in a narrow range (approximate Mr, 140,000) which, upon periodic acid-Schiff staining, gave a positive reaction. After proteolytic degradation of the purified S-layer glycoprotein, a single glycopeptide fraction was obtained by gel permeation chromatography. Hydrolysis, treatment with aqueous hydrofluoric acid, and 1H and 13C nuclear magnetic resonance studies showed that the glycoprotein glycan is a high-molecular-weight polymer (approximate Mr, 15,000) of tetrasaccharide repeating units with the component sugars N-acetylgalactosamine (GalNAc), N-acetylmannosamine (ManNAc), and N-acetylbacillosamine (BacNAc; 2-N-acetyl-4-amino-2,4,6-trideoxy glucose) linked by monophosphate diesters. The following structure is proposed: [----6)-alpha-D-ManpNAc-(1----4)-beta-D-GalpNAc-(1----3)-alpha-D-+ ++BacpNAc- (1----4)-alpha-D-GalpNAc-(1----PO3)----]n. The nuclear magnetic resonance data provided evidence for a charge interaction between the free amino group of BacNAc and the phosphate group of adjacent glycan chains. Since polycationic ferritin did not label the cell surface of intact cells, an electrostatic interaction can also be expected in vivo, leading to a charge-neutral outer surface, which is characteristic of all other S layers from members of the family Bacillaceae studied so far.

[Synthesis of a highly branched nonasaccharide sequence of the "bisected"structure of N-glycoproteins]

A highly branched nonasaccharide, beta-D-Galp-(1----4)-beta-D-GlcpNAc-(1----2)-alpha-D-Manp-(1----3) -[beta-D- Glcp-NAc-(1----4)-[beta-D-Galp-(1----4)-beta-D-GlcpNAc-(1----2)-alpha-D- Manp- (1----6)]-beta-D-Manp-(1----4)-D-GlcNAc, that represents the carbohydrate chain of the "bisected" structure of lactosamine-type N-glycoproteins was synthesized by a block synthesis approach. The activated trisaccharide block beta-D-Galp-(1----4)-beta-D-GlcpNAc-(1----2)-D-Man was coupled first with the low reactive OH-3 group and, in a second step, with the reactive OH-6 group of the central beta-D-mannopyranosyl residue within the suitably protected trisaccharide block beta-D-GlcpNAc-(1----4)-beta-D-Manp-(1----4)-D-GlcNAc. During these coupling steps, the alpha-glycosidic linkages of D-mannopyranosyl residues were formed without neighboring-group participation, which is only successful by use of the imidate procedure.

Synthesis of (1----4)-linked galacturonic acid trisaccharides, a proposed plant wound-hormone and a stereoisomer

Syntheses of alpha-GalA-(1----4)-alpha-GalA-(1----4)-GalA, a proposed plant wound-hormone, and its stereoisomer beta-GalA-(1----4)-alpha-GalA-(1----4)-GalA are described. The key intermediates, tert-butyldiphenylsilyl O-(6-O-acetyl-2,3,4-tri-O-benzyl-alpha-D-galactopyranosyl)-(1----4)-O-(6 -O- acetyl-2,3-di-O-benzyl-alpha-D-galactopyranosyl)-(1----4)-6-O-acetyl-2,3 -di-O- benzyl-beta-D-galactopyranoside and tert-butyldiphenylsilyl O-(6-O-acetyl-2,3,4-tri-O-benzyl-beta-D-galactopyranosyl)-(1----4)-O-(6- O- acetyl-2,3-di-O-benzyl-alpha-D-galactopyranosyl)-(1----4)-6-O-acetyl-2,3 -di-O- benzyl-beta-D-galactopyranoside, were prepared by stereoselective alpha-glycosylation of tert-butyldiphenylsilyl 6-O-acetyl-2,3-di-O-benzyl-beta-D-galactopyranoside with O-(6-O-acetyl-2,3,4-tri-O-benzyl-alpha-D-galactopyranosyl)-(1----4)-6-O- acetyl-2,3-di-O-benzyl-D-galactopyranosyl fluoride and O-(6-O-acetyl-2,3,4-tri-O-benzyl-beta-D-galactopyranosyl)-(1----4)-6-O-a cetyl- 2,3-di-O-benzyl-D-galactopyranosyl fluoride, respectively. The corresponding beta isomers were minor products. Characteristic features in the n.m.r. data of the key intermediates are discussed.

Proof of the structure of ristotetraose: synthesis of propyl alpha-ristotetraoside

A definitive synthesis of the propyl glycoside (1) of ristotetraose, the heterotetrasaccharide component of the antibiotic ristomycin A (ristocetin A) is described.

Total synthesis of the mollu-series glycosyl ceramides alpha-D-Manp-(1----3)-beta-D-Manp-(1----4)-beta-D-Glcp-(1----1)-Cer and alpha-D-Manp-(1----3)-[beta-D-Xylp-(1----2)]-beta-D-Manp-(1----4)-beta- D-Glcp-(1----1)-Cer

The mollu-series glycosphingolipids, O-alpha-D-mannopyranosyl-(1----3)-O-beta-D-mannopyranosyl-(1----4)-O-bet a-D-glucopyranosyl-(1----1)-2-N-tetracosanoyl-(4E)-sphingeni ne and O-alpha-D-mannopyranosyl-(1----3)-O-[beta-D-xylopyranosyl-(1----2])-O- beta-D-mannopyranosyl-(1----4)-O-beta-D-glucopyranosyl-(1----1)-2-N- tetracosanoyl-(4E)-sphingenine, were synthesized for the first time by using 2,3,4-tri-O-acetyl-D-xylopyranosyl trichloroacetimidate, methyl 2,3,4,6-tetra-O-acetyl-1-thio-alpha-D-mannopyranoside, benzyl O-(4,6-di-O-benzyl-beta-D-mannopyranosyl)-(1----4)-2,3,6-tri-O-benzyl-be ta-D- glucopyranoside 9, and (2S,3R,4E)-2-azido-3-O-(tert-butyldiphenylsilyl)-4-octade cene-1,3-diol 6 as the key intermediates. The hexa-O-benzyl disaccharide 9 was prepared by coupling two monosaccharide synthons, namely, 2,3-di-O-allyl-4,6-di-O-benzyl-alpha-D-mannopyranosyl bromide and benzyl 2,3,6-tri-O-benzyl-beta-D-glucopyranoside. It was demonstrated that azide 6 was highly efficient as a synthon for the ceramide part in the coupling with both glycotriaosyl and glycotetraosyl donors, particularly in the presence of trimethylsilyl triflate.