A convergent synthesis of trisaccharides with alpha-Neu5Ac-(2 --> 3)-beta-D-gal-(1 --> 4)-beta-D-GlcNAc and alpha-Neu5Ac-(2 --> 3)-beta-D-gal-(1 --> 3)-alpha-D-GalNAc sequences

The syntheses of three trisaccharides: alpha-Neu5Ac-(2 --> 3)-beta-D-Gal-(1 --> 4)-beta-D-GlcNAc --> OMe, alpha-Neu5Ac-(2 --> 3)-beta-D-Gal6SO3Na-(1 --> 4)-beta-D-GlcNAc --> OMe, and alpha-Neu5Ac-(2 --> 3)-beta-D-Gal-(1 --> 3)-alpha-D-GalNAc --> OBn were accomplished by using either methyl (phenyl 5-acetamido-4,7,8,9-tetra-O-acetyl-3,5-dideoxy-2-thio-beta-D-glycero-D-g alacto-2-nonulopyranoside)onate or methyl (phenyl N-acetyl-5-acetamido-4,7,8,9-tetra-O-acetyl-3,5-dideoxy-2-thio-beta-D-gl ycero-D-galacto-2-nonulopyranoside)onate as the sialyl donor. The N,N-diacetylamino sialyl donor appears to be more reactive than its parent acetamido sugar when allowed to react with an disaccharide acceptor under the same glycosylation conditions. The trisaccharides, as well as the intermediate products, were fully characterized by 2D DQF 1H-1H COSY and 2D ROESY spectroscopy.     

Facile syntheses of the hexasaccharide repeating unit of the exopolysaccharide from Cryptococcus neoformans serovar A

Two hexasaccharides, beta-D-Xylp-(1-->2)-alpha-D-Manp-(1-->3)-[beta-D-Xylp-(1-->2)-]alpha-D-Manp-(1-->3)-[beta-D-GlcpA-(1-->2)-]alpha-D-Manp and beta-D-GlcpA-(1-->2)-alpha-D-Manp-(1-->3)-[beta-D-Xylp-(1-->2)-]alpha-D-Manp-(1-->3)-[beta-D-Xylp-(1-->2)-]alpha-D-Manp, the repeating unit of the exopolysaccharide from Cryptococcus neoformans serovar A, were synthesized as their methyl glycosides in a regio- and stereoselective manner.     

Facile synthesis of the heptasaccharide repeating unit of O-deacetylated GXM of C. neoformans serotype B

A heptasaccharide, beta-D-Xylp-(1-->2)-alpha-D-Manp-(1-->3)-[beta-D-Xylp-(1-->2)]-alpha-D-Manp-(1-->3)-[beta-D-GlcpA-(1-->2)][beta-D-Xylp-(1-->4)]-alpha-D-Manp, the repeating unit of the exopolysaccharide from Cryptococcus neoformans serovar B, was synthesized as its methyl glycoside. Thus 2,3,4-tri-O-benzoyl-beta-D-xylopyranosyl-(1-->2)-3,4,6-tri-O-benzoyl-alpha-d-mannopyranosyl trichloroacetimidate (7) and allyl 2,3,4-tri-O-benzoyl-beta-D-xylopyranosyl-(1-->2)-4,6-di-O-benzoyl-alpha-D-mannopyranoside (8), readily obtained from the corresponding monosaccharide derivatives via simple transformation, were coupled to give a (1-->3)-linked tetrasaccharide 9. Deallylation of 9 followed by trichloroacetimidate formation produced the tetrasaccharide donor 11. Condensation of methyl 2,3,4-tri-O-benzoyl-beta-d-xylopyranosyl-(1-->4)-2-O-acetyl-6-O-benzoyl-alpha-D-mannopyranoside (18) with 11 followed by selective deacetylation yielded hexasaccharide acceptor 20. Coupling of 20 with methyl 2,3,4-tri-O-acetyl-alpha-D-glucopyranosyluronate bromide (21) and subsequent deprotection furnished the target heptaoside. A hexasaccharide fragment, alpha-D-Manp-(1-->3)-[beta-D-Xylp-(1-->2)]-alpha-D-Manp-(1-->3)-[beta-D-GlcpA-(1-->2)][beta-D-Xylp-(1-->4)]-alpha-D-Manp, was also similarly synthesized as its methyl glycoside.     

Synthesis of alpha-D-Manp-(1----3)-[beta-D-GlcpNAc-(1----4)]-[alpha-D-Manp+ ++-(1----6)] - beta-D-Manp-(1----4)-beta-D-GlcpNAc-(1----4)-[alpha-L-Fucp- (1----6)]-D- GlcpNAc, a core glycoheptaose of a "bisected" complex-type glycan of glycoproteins

A synthesis of alpha-D-Manp-(1----3)-[beta-D-GlcpNAc-(1----4)]-[alpha-D-Manp++ +-(1----6)]- beta-D-Manp-(1----4)-beta-D-GlcpNAc-(1----4)-[alpha-L-Fucp-( 1----6)]-D- GlcpNAc was achieved by employing benzyl O-(3,4,6-tri-O-benzyl-2-deoxy-2-phthalimido-beta-D-glucopyranosyl)-(1--- -4)-O- (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- methoxyphenyl-2-phthalimido-beta-D-glucopyranoside as a key glycosyl acceptor. Highly stereoselective mannosylation was performed by taking advantage of the 2-O-acetyl group in the mannosyl donors. The alpha-L-fucopyranosyl residue was also stereoselectively introduced by copper(II)-mediated activation of methyl 2,3,4-tri-O-benzyl-1-thio-beta-L-fucopyranoside.     

Efficient synthesis of a 3,6-branched mannose hepta- and octasaccharide

Alpha-D-Manp-(1-->3)-[alpha-D-Manp-(1-->2)-alpha-D-Manp-(1-->6)]-alpha-D-Manp-(1-->3)-[alpha-D-Manp-(1-->2)-alpha-D-Manp-(1-->6)]-D-Manp and alpha-D-Manp-(1-->2)-alpha-D-Manp-(1-->3)-[alpha-D-Manp-(1-->2)-alpha-D-Manp-(1-->6)]-alpha-D-Manp-(1-->3)-[alpha-D-Manp-(1-->2)-alpha-D-Manp-(1-->6)]-D-Manp, were synthesized as their methyl glycosides in a regio- and stereoselective way.     

Structure of the O-polysaccharide from the lipopolysaccharide of Providencia stuartii O43 containing an amide of D-galacturonic acid with L-serine

The O-polysaccharide was obtained by mild acid degradation of the lipopolysaccharide of Providencia stuartii O43:H28 and studied by sugar and methylation analyses, Smith degradation and 1H and 13C NMR spectroscopy, including 2D ROESY, and H-detected 1H, 13C HSQC and HMBC experiments, as well as a NOESY experiment in a 9:1 H2O/D2O mixture to reveal correlations for NH protons. It was found that the polysaccharide is built up of linear tetrasaccharide repeating units containing an amide of D-galacturonic acid with L-serine [D-GalA6(L-Ser)] and has the following structure:[3)-beta-D-GalpA6(L-Ser)-(1-->3)-beta-D-GlcpNAc-(1-->2)-alpha-D-Rhap4NAc-(1-->4)-beta-D-GlcpA-(1-->]n.     

The structures of oligosaccharides excreted by sheep with swainsonine toxicosis

Eleven oligosaccharides were purified form the urine of sheep with swainsonine toxicosis induced by the feeding of Astragalus lentiginosus. Oligosaccharides were extracted by charcoal adsorption, chromatographed on Bio-Gel P-2, and partially fractionated by preparative-layer chromatography. Separation into individual compounds was completed by semi-preparative high pressure liquid chromatography. Structures were determined by a combination of high pressure liquid chromatography and exo- and endo- glycosidase action, methanolysis followed by gas-liquid chromatography, methylation analysis, and high resolution nuclear magnetic resonance spectroscopy. Two homologous series of oligosaccharides were identified: (a) alpha-D-Manp-(1----6)-beta-D-Manp-(1----4)-D-GlcpNAc, alpha-D-Manp(1----3)-[alpha-D-Manp-(1----6)]-beta-D-Manp+ ++-(1----4)-D-GlcpNAc, alpha-D-Manp-(1----2)-alpha-D-Manp(1----3)-[alpha-D-Manp+ ++-(1----6)]-beta-D-Manp-(1----4)-D-GlcpNAc, and alpha-D-Manp-(1----2)-alpha-D-Manp-(1----2)-alpha-D-Manp+ ++-(1----3)-[alpha- D-Manp-(1----6)]-beta-D-Manp-(1----4)-D-GlcpNAc (minor series); (b) alpha-D-Manp-(1----6)-beta-D-Manp-(1----4)-beta-D-GlcpNAc- (1----4)-D-GlcpNAc, alpha-D-Manp-(1----3)-[alpha-D-Manp-(1----6)]-beta-D-Manp -(1----4)-beta-D-GlcpNAc-(1----4)-D-GlcpNAc, alpha-D-Manp(1----3)-alpha-D-Manp-(1----6)-beta-D-Manp -(1----4)-beta-D-GlcpNAc- (1----4)-D-GlcpNAc, alpha-D-Manp-(1----6)-alpha-D-Manp-(1----6)-beta-D-Manp++ +-(1----4)-beta-D-GlcpNAc - (1----4)-D-GlcpNAc, alpha-D-Manp-(1----3)-alpha-D-Manp-(1----6)-[alpha-D-Manp -(1----3)]-beta-D- Manp-(1----4)-beta-D-GlcpNAc-(1----4)-D-GlcpNAc, alpha-D-Manp-(1----3)-[alpha-D-Manp-(1----6)]-alpha-D-Man p-(1----6)-beta-D- Manp-(1----4)-beta-D-GlcpNAc-(1----4)-D-GlcpNAc, and alpha-D-Manp-(1----3)-[alpha-D-Manp-(1----6)]-alpha-D-Man p-(1----6)- [alpha-D-Manp-(1----3)]-beta-D-Manp-(1----4)-beta-D-GlcpNAc- (1----4)-D- GlcpNAc (major series).     

Synthesis of four structural elements of xylose-containing carbohydrate chains from N-glycoproteins

The synthesis of the oligosaccharides beta-D-Xylp-(1----2)-beta-D-Manp-OMe (12), beta-D-Xylp-(1----2)-[alpha-D-Manp-(1----6)]-beta-D-Manp+ ++-OMe (17), beta-D-Xylp-(1----2)-[alpha-D-Manp-(1----3)]-beta-D-Manp+ ++-OMe (21), and beta-D-Xylp-(1----2)-[alpha-D-Manp-(1----3)] [alpha-D-Manp-(1----6)]-beta-D-Manp-OMe (25) is described. Methyl 3-O-benzyl-4,6-O-isopropylidene-beta-D-mannopyranoside (6) was prepared from the corresponding glucoepimer (4) by oxidation, followed by stereoselective reduction. Condensation of 6 with 2,3,4-tri-O-acetyl-alpha-D-xylopyranosyl bromide in the presence of mercuric cyanide gave a 1:9 mixture of methyl 3-O-benzyl-4,6-O-isopropylidene-2-O-(2,3,4- tri-O-acetyl-alpha- (7a) and -beta-D-xylopyranosyl)-beta-D-mannopyranoside (7), and then 7 was converted into the acetylated disaccharide-glycoside 11. Regioselective mannosylation, with 2,3,4,6-tetra-O-acetyl-alpha-D-mannopyranosyl bromide, at position 6 of deisopropylidenated 7 (8), using mercuric bromide as a promoter, afforded the trisaccharide-glycoside derivative 13, which was transformed into the acetylated trisaccharide-glycoside 16. The disaccharide derivative 10, obtained from 8, and the trisaccharide derivative 15, obtained from 13, were glycosylated at position 3 with O-(2,3,4,6-tetra-O-acetyl-alpha-D-mannopyranosyl)trichloroacetimidate (19), using trimethylsilyl triflate as a promoter, giving rise to acetylated tri- (20) and tetra-saccharide (24) derivatives, respectively. O-Deacetylation of 11, 16, 20, and 24 gave 12, 17, 21, and 25, respectively.     

Chemical synthesis of sulfated oligosaccharides with a beta-D-Gal-(1-->3)

The syntheses of two sulfated pentasaccharides: beta-D-Gal6SO3Na-(1-->3)-[beta-D-Gal-(1-->4)-alpha-L-Fuc-(1-->3)-beta-D-Glc-NAc-(1-->6)]-alpha-D-GalNAc-->OMe (1) and beta-D-Gal6SO3Na-(1-->3)-[beta-D-Gal-(1-->4)-alpha-L-Fuc-(1-->3)-beta-D-Glc-NAc6SO3Na-(1-->6)]-alpha-D-GalNAc-->OMe (2) by using Lewisx trisaccharides 12 and 16 as glycosyl donors are described. Sulfated oligosaccharides 1-2 and intermediate compounds are fully characterized by 2D 1H-1H DQF-COSY and 2D ROESY experiments.     

The structure of the asparagine-linked sugar chains of bovine brain ribonuclease

The asparagine-linked sugar chains of bovine brain ribonuclease were quantitatively released as oligosaccharides from the polypeptide backbone by hydrazinolysis. After N-acetylation, they were converted into radioactively-labeled oligosaccharides by NaB3H4 reduction. The radioactive oligosaccharide mixture was fractionated by ion-exchange chromatography, and the acidic oligosaccharides were converted into neutral oligosaccharides by sialidase digestion. The neutral oligosaccharides were then fractionated by Bio-Gel P-4 column chromatography. Structural studies of each oligosaccharide by sequential exoglycosidase digestion in combination with methylation analysis revealed that bovine brain ribonuclease showed extensive heterogeneity. It contains bi- and tri-antennary, complex-type oligosaccharides having alpha-D-Manp-(1----3)-[alpha-D-Manp-(1----6)]-beta-D-Manp -(1----4)-beta-D- GlcpNAc-(1----4)-[alpha-L-Fucp-(1----6)]-D-GlcNAc as their common core. Four different outside oligosaccharide chains, i.e., beta-D-Galp-(1----4)-beta-D-GlcpNAc-(1----, alpha-Neu5Ac-(2----6)-beta-D- Galp-(1----4)-beta-D-GlcpNAc-(1----, alpha-Neu5Ac-(2----3)-beta-D-Galp-(1----4)- beta-D-GlcpNAc-(1----, and alpha-D-Galp-(1----3)-beta-D-Galp-(1----4)-beta-D-GlcpNAc-(1----, were found. The preferential distribution of the alpha-D-Galp-(1----3)-beta-D-Galp-(1----4)-beta-D-GlcpNAc group on the alpha-D-Manp-(1----6) arm is a characteristic feature of the sugar chains of this enzyme.     

Structure of xylogalacturonan fragments from watermelon cell-wall pectin. Endopolygalacturonase can accommodate a xylosyl residue on the galacturonic acid just following the hydrolysis site

A combination of xylogalacturonan (XGA), homogalacturonan, and rhamnogalacturonan was extracted from watermelon fruit cell walls with 0.1 M NaOH. In contrast to the resistance of xylogalacturonans from most other sources to endopolygalacturonase (EPG), about 50% of the extracted XGA could be converted into oligosaccharides by EPG digestion with a commercial EPG from Megazyme International. The oligosaccharides were fractionated by ion-exchange chromatography, and their structures were investigated by mass spectrometry and NMR spectroscopy. The smallest oligosaccharide was beta-D-Xylp-(1-->3)-alpha-D-GalAp-(1-->4)-alpha-D-GalAp-(1-->4)-alpha-D-GalAp-(1-->4)-GalAp. The most abundant was beta-D-Xylp-(1-->3)-alpha-D-GalAp-(1-->4)-alpha-D-GalAp-(1-->4)(beta-D-Xylp-(1-->3)-alpha-D-GalAp-(1-->4))-alpha-D-GalAp-(1-->4)-alpha-D-GalAp-(1-->4)-GalAp. Given that the nonreducing ends of the oligosaccharides often were xylosylated GalA residues, and that fungal EPG digests homogalacturonans between the third and fourth GalA bound to the enzyme, it appears that EPG can accommodate a xylosylated GalA in the site that binds the fourth GalA. Since all of the oligosaccharides characterized had three unsubstituted GalA residues at their reducing ends, the enzyme appears not to accommodate xylosylated residues in the first three sugar-binding sites. Thus, XGA regions with fewer than three unsubstituted residues between branch points will be resistant to EPG. The EPG-susceptible XGA was not recovered from cell walls prepared using phosphate buffer for the homogenization of the watermelon tissue, probably because it was degraded by endogenous watermelon EPG and lost during isolation of the walls. Use of Tris-buffered phenol during wall isolation to prevent enzyme action caused some amidation of GalA residues with Tris.     

Structure of the O-specific polysaccharide of Hafnia alvei PCM 1196

An acidic O-specific polysaccharide was isolated from Hafnia alvei PCM 1196 lipopolysaccharide and studied by sugar and methylation analyses along with one- and two-dimensional 1H and 13C NMR spectroscopy, including NOESY and HMBC experiments. The following structure of the pentasaccharide repeating unit was established: -->4)-alpha-D-GalpA-(1-->3)-beta-D-GlcpNAc-(1-->2)-beta-D-Galp-(1-->6)-alpha-D-Glcp-(1-->6)-alpha-D-GlcpNAc-(1-->.     

Structure of the O-specific polysaccharide of Proteus vulgaris O45 containing 3-acetamido-3,6-dideoxy-D-galactose

An O-specific polysaccharide was isolated by mild acid degradation of the lipopolysaccharide of Proteus vulgaris O45 and studied by sugar and methylation analyses along with 1H and 13C NMR spectroscopy, including 2D COSY, TOCSY, ROESY, H-detected 1H,13C HSQC and HMBC experiments. The following structure of the pentasaccharide repeating unit of the polysaccharide was established:-->6)-alpha-D-GlcpNAc-(1-->4)-alpha-D-GalpNAc-(1-->4)-alpha-D-GalpA-(1-->3)-beta-D-GlcpNAc-(1-->2)-beta-D-Fucp3NAc4Ac-(1-->where Fuc3NAc4Ac is 3-acetamido-4-O-acetyl-3,6-dideoxygalactose. A cross-reactivity of anti-P. vulgaris O45 serum was observed with several other Proteus lipopolysaccharides, which contains Fuc3N derivatives.     

Biosynthesis of dolichyl pentasaccharide diphosphate in calf pancreas microsomes

Incubation of synthetic dolichyl pyrophosphate tetrasaccharide and GDP-[14C]mannose with calf pancreas microsomes gave three lipid-linked oligosaccharides, which could be extracted with chloroform/methanol (2:1) and separated on silica gel plates. The fastest migrating product was characterized as dolichyl pyrophosphate pentasaccharide based on gel filtration and high pressure liquid chromatography. The formation of the pentasaccharide-lipid was greatly stimulated by addition of synthetic tetrasaccharide-lipid and required the presence of Triton X-100. Dolichyl phosphate mannose could not replace GDP-mannose as a sugar donor. The structure of the pentasaccharide was determined by degradation with endo-beta-N-acetylglucosaminidase D, acetolysis, alpha-D-mannosidase, and concanavalin A-Sepharose chromatography, showing that the following reaction was taking place: alpha-D-Manp-(1 leads to 3)-beta-D-Manp-(1 leads to 4)-beta-D-GlcpNAc-(1 leads to 4)-alpha-D-GlcpNAcPPDol + GDPMan leads to GDP + alpha-D-Manp-(1 leads to 3)-[alpha-D-Manp-(1 leads to 6)]-beta-D-Manp-(1 leads to 4)-beta-D-GlcpNAc-(1 leads to 4)-alpha-D-GlcpNAcPPDol. The mannosyltransferase was partially characterized.     

Efficient synthesis of a heptasaccharide,the repeating unit of the O-chain lipopolysaccharide produced by Xanthomonas campestris strain 642

alpha-L-Rhap-(1-->3)-alpha-L-Rhap-(1-->2)-alpha-L-Rhap-(1-->3)-[beta-D-Xylp-(1-->2)-][beta-D-Xylp-(1-->4)-]alpha-L-Rhap-(1-->3)-alpha-L-Rhap, the repeating unit of the O-chain lipopolysaccharide produced by Xanthomonas campestris strain 642 was synthesized as its methyl glycoside via 3-O-selective glycosylation of methyl alpha-L-rhamnopyranosyl-(1-->3)-2,4-di-O-benzoyl-alpha-L-rhamnopyranoside (9) with 2,3,4-tri-O-benzoyl-alpha-L-rhamnopyranosyl-(1-->3)-2,4-di-O-benzoyl-alpha-L-rhamnopyranosyl-(1-->2)-3,4-di-O-benzoyl-alpha-L-rhamnopyranosyl trichloroacetimidate (8), followed by dixylosylation with 2,3,4-tri-O-benzoyl-alpha,beta-D-xylopyranosyl trichloroacetimidate (12) and subsequent deacylation.     

Structure of the O-specific polysaccharide of Proteus vulgaris O15 containing a novel regioisomer of N-acetylmuramic acid, 2-acetamido-4-O-[(R)-1-carboxyethyl]-2-deoxy-D-glucose

An acidic O-specific polysaccharide was obtained by mild acid degradation of the lipopolysaccharide of Proteus vulgaris O15 and studied by sugar and methylation analyses along with 1H and 13C NMR spectroscopy, including 2D COSY, TOCSY, ROESY, and H-detected 1H,(13)C HMQC experiments. The polysaccharide was found to contain an ether of GlcNAc with lactic acid, and the following structure of the repeating unit was established:-->3)-alpha-D-GlcpNAc4(R-Lac)6Ac-(1-->2)-beta-D-GlcpA-(1-->3)-alpha-L-6dTalp2Ac-(1-->3)-beta-D-GlcpNAc-(1-->where L-6dTal and D-GlcNAc4(R-Lac) are 6-deoxy-L-talose and 2-acetamido-4-O-[(R)-1-carboxyethyl]-2-deoxy-D-glucose, respectively. The latter sugar, which to our knowledge has not been hitherto found in nature, was isolated from the polysaccharide by solvolysis with anhydrous triflic acid and identified by comparison with the authentic synthetic compound. Serological studies with the Smith-degraded polysaccharide showed an importance of 2-substituted GlcA for manifesting of the immunospecificity of P. vulgaris O15.     

Synthesis of a hexasaccharide fragment of the O-deacetylated GXM of C. neoformans serotype B

beta-D-Xylp-(1-->4)-alpha-D-Manp-(1-->3)-[beta-D-Xylp-(1-->2)]-alpha-D-Manp-(1-->3)-[beta-D-Xylp-(1-->2)]-alpha-D-Manp, the fragment of the exopolysaccharide from Cryptococcus neoformans serovar B, was synthesized as its methyl glycoside. Thus, acetylation of allyl 3-O-benzoyl-4,6-O-benzylidene-alpha-D-mannopyranoside (1) followed by debenzylidenation and selective 6-O-benzoylation afforded allyl 2-O-acetyl-3,6-di-O-benzoyl-alpha-D-mannopyranoside (4). Glycosylation of 4 with 2,3,4-tri-O-benzoyl-D-xylopyranosyl trichloroacetimidate (5) furnished the beta-(1-->4)-linked disaccharide 6. Deallylation followed by trichloroacetimidate formation gave the disaccharide donor 8, and subsequent coupling with allyl 2,3,4-tri-O-benzoyl-beta-D-xylopyranosyl-(1-->2)-4,6-di-O-benzoyl-alpha-D-mannopyranoside (9), produced the tetrasaccharide 10. Reiteration of deallylation and trichloroacetimidate formation from 10 yielded the tetrasaccharide donor 12. The downstream disaccharide acceptor 18 was obtained by condensation of 5 with methyl 3-O-acetyl-4,6-O-benzylidene-alpha-D-mannopyranoside, followed by debenzylidenation, benzoylation, and selective 3-O-deacetylation. Coupling of 18 with 12 afforded the hexasaccharide 19, and subsequent deprotection gave the hexasaccharide glycoside 20. Selective 2"-O-deacetylation of 19 gave the hexasaccharide acceptor 21. Condensation of 21 with glucopyranosyluronate imidate 22 did not produce the expected heptasaccharide glycoside; instead, a transacetylation product 19 was obtained. Meanwhile, there was no reaction between 21 and the bromide donor 23.     

Synthesis of two oligosaccharides, the GPI anchor glycans from S. cerevesiae and A. fumigatus

Two oligosaccharides, alpha-D-Manp-(1-->2)-alpha-D-Manp-(1-->2)-alpha-D-Manp-(1-->6)-alpha-D-Manp-(1-->4)-alpha-D-GlcpNAc (I) and alpha-D-Manp-(1-->3)-alpha-D-Manp-(1-->2)-alpha-D-Manp-(1-->2)-alpha-D-Manp-(1-->6)-alpha-D-Manp-(1-->4)-alpha-D-GlcpNAc (II), the glycosylphosphatidylinositol (GPI) anchor glycans from S. cerevesiae and A. fumigatus were synthesized as their methyl glycosides in a regio- and stereoselective manner. The pentasaccharide I was obtained from 6-O-selective glycosylation of methyl 2,3-di-O-benzoyl-alpha-D-mannopyranosyl-(1-->4)-2-acetamido-3,6-di-O-benzoyl-2-deoxy-alpha-D-glucopyranoside (8) with 2-O-acetyl-3,4,6-tri-O-benzoyl-alpha-D-mannopyranosyl-(1-->2)-3,4,6-tri-O-benzoyl-alpha-D-mannopyranosyl trichloroacetimidate (9), followed by benzoylation, deacetylation, and mannosylation, and then by deprotection. The hexasaccharide (II) was obtained via condensation of allyl 3,4,6-tri-O-benzoyl-alpha-D-mannopyranosyl-(1-->2)-3,4,6-tri-O-benzoyl-alpha-D-mannopyranoside (17) with 2,3,4,6-tetra-O-benzoyl-alpha-D-mannopyranosyl-(1-->3)-2,4,6-tri-O-acetyl-alpha-D-mannopyranosyl trichloroacetimidate (16), followed by deallylation, trichloroacetimidation, and coupling with acceptor (8), and finally by deprotection.     

Structure of a lactic acid ether-containing and glycerol phosphate-containing O-polysaccharide from Proteus mirabilis O40

An O-polysaccharide was isolated by mild acid hydrolysis from the lipopolysaccharide of Proteus mirabilis O40 and studied by NMR spectroscopy, including 2D 1H, 1H COSY, TOCSY, ROESY, and 1H, 13C HMQC experiments, along with chemical methods. The polysaccharide was found to contain an ether of GlcNAc with lactic acid and glycerol phosphate in the main chain and to have the following structure: --> 3)-beta-D-GlcpNAc4(R-Lac)-(1 --> 3)-alpha-D-Galp-(1 --> 3)-D-Gro-1-P-(O --> 3)-beta-D-GlcpNAc-(1 --> where D-GlcpNAc4(R-Lac) stands for 2-acetamido-4-O-[(R)-1-carboxyethyl]-2-deoxy-D-glucose. This structure is unique among the known structures of the Proteus O-polysaccharides, which is in agreement with the classification of the strain studied into a separate O-serogroup. A serological relatedness of P. mirabilis O40 with some other Proteus strains was revealed and discussed in view of the O-polysaccharide structures.     

Structure determination of the O-antigenic polysaccharide from the enteroinvasive Escherichia coli O136.

The structure of the O-antigen polysaccharide of the lipopolysaccharide from the enteroinvasive Escherichia coli O136 has been elucidated. The composition of the repeating unit was established by sugar and methylation analysis together with 1H and 13C NMR spectroscopy. Two-dimensional nuclear Overhauser effect spectroscopy (NOESY) and heteronuclear multiple-bond correlation experiments were used to deduce the sequence. The absolute configuration for the nonulosonic acid (NonA) could be determined using spin-spin coupling constants, 13C chemical shifts and NOESY. The anomeric configuration of the NonA was determined via vicinal and geminal 13C,1H coupling constants. The structure of the repeating unit of the polysaccharide from E. coli O136 is as follows, in which beta-NonpA is 5,7-diacetamido-3,5,7, 9-tetradeoxy-Lglycero-beta-Lmanno-nonulosonic acid: -->4)-beta-NonpA-(2-->4)-beta-D-Galp-(1-->4)-beta-D-GlcpNAc-(1-->