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Considering the importance of bacterial glycoconjugates on virulence and host mimicry, there is a need to better understand the biosynthetic pathways of these unusual sugars to identify critical targets involved in bacterial pathogenesis. In this report, we describe the cloning, overexpression, purification, and biochemical characterization of the four central enzymes in the biosynthesis pathway for UDP-2-acetamido-4-formamido-2,4,6-trideoxy-hexose, WekG, WekE, WekF, and WekD. Product peaks from enzyme-substrate reactions were detected by using a combination of capillary electrophoresis (CE) and electrospray ionization-mass spectrometry (ESI-MS). Putative enzyme assignments were provided by protein sequence analysis. Combined with the mass spectrometric characterization of pathway intermediates, we propose a biosynthetic pathway for UDP-2-acetamido-4-formamido-2,4,6-trideoxy-hexose. This process involves C-4, C-6 dehydration, C-4 amination, and formylation. CID-ESI-MSn result confirmed that the final product is a 4 formamido derivative too rather than the 3 formamido derivatives as reported earlier.

O-Polysaccharide was isolated from the lipopolysaccharide of an entomopathogenic bacterium Photorhabdus temperata subsp. temperata XlNach(T). Sugar analysis after full acid hydrolysis of the polysaccharide revealed D-glucose, D-mannose, D-galactose, D-GalNAc, and a branched monosaccharide, 3,6-dideoxy-4-C-[(S)-1',2'-dihydroxyethyl]-D-xylo-hexose (Sug), which was isolated as a 1,2'-anhydro furanose derivative. The following structure of the polysaccharide was established by 1D and 2D 1H and 13C NMR spectroscopy

The O-polysaccharide isolated by mild acid hydrolysis of the lipopolysaccharide of Pseudomonas mandelii CYar1 was studied by sugar analysis and 1D and 2D 1 H and 13 C NMR spectroscopies. The following structure of the O-polysaccharide was established

Reduction of ribono-1,4-lactones and gulono-1,4-lactone as well as ribono-1,5-lactone and glucono-1,5-lactones with LTBH (1.2 equiv.) in CH2Cl2 at 0 °C for 30 min. provided the corresponding pentose or hexose hemiacetals in high yields. Commonly used in carbohydrate chemistry protecting groups such as trityl, benzyl, silyl, acetals and to some extent acyls are compatible with this reduction.

The O-specific polysaccharide was isolated by mild acid degradation of the lipopolysaccharide of Yersinia pseudotuberculosis O:4a and studied by NMR spectroscopy, including 2D ROESY and (1)H, (13)C HMBC experiments. The following structure of the pentasaccharide repeating unit of the polysaccharide was established, which differs from the structure reported earlier [Gorshkova, R. P. et al., Bioorg. Khim. 1983, 9, 1401-1407] in the linkage modes between the monosaccharides: [carbohydrate sequence see in text] where Tyv stands for 3,6-dideoxy-D-arabino-hexose (tyvelose). The structure of the Y. pseudotuberculosis O:4a antigen resembles that of Y. pseudotuberculosis O:2c, which differs in the presence of abequose (3,6-dideoxy-D-xylo-hexose) in place of tyvelose only.

The O-polysaccharide was isolated by mild acid degradation of the lipopolysaccharide of Providencia alcalifaciens O6 and studied by sugar and methylation analysis, selective hydrolytic removal of 3,6-dideoxy- l - xylo -hexose (colitose, Col), 1 H and 13 C NMR spectroscopy, including 2D 1 H, 1 H COSY, TOCSY, ROESY and H-detected 1 H, 13 C HSQC and HMBC experiments. The polysaccharide was found to have a branched pentasaccharide repeating unit with the following structure: Download full-size image Remarkably, the trisaccharide side chain of the O6-polysaccharide represents a colitose (‘3-deoxy- l -fucose’) analogue of the H type 1 (precursor) antigenic determinant.

Four derivatives of 2 II -deoxycellobiose were synthesized from d -glucal and acceptor sugars ( d -glucose, d -xylose, d -mannose, and 2-deoxy- d - arabino -hexose) using a cellobiose phosphorylase from Cellvibrio gilvus . The enzyme was found to be an effective catalyst to synthesize the β-(1→4) linkage of 2-deoxy- d - arabino -hexopyranoside. The acceptor specificity for the d -glucal reaction was identical to that for the α- d -glucose 1-phosphate reaction, but the activity of d -glucal was approximately 500 times less than that of α- d -glucose 1-phosphate, using 10 mM substrates.

The O-chain polysaccharide of the lipopolysaccharide from the halophilic marine bacterium Pseudoalteromonas carrageenovora IAM 12662T was characterized. The structure was studied by means of chemical analysis and 2D NMR spectroscopy of the de-O-acylated lipopolysaccharide and shown to be the following: Col is colitose, 3,6-di-deoxy- l -xylo-hexose.

The acidic polysaccharide from Serratiamarcescens serogroup O14:K12 was analyzed by means of chemical studies and NMR spectroscopy and its repeating unit structure found to be Download : Download full-size image O-Acetyl groups are proposed to be present in non-stoichiometric amounts on O-6 on one of the hexose residues in the main chain.

Five diastereomeric trideoxy-1,6-iminohexitols were synthesised, and their inhibitory activities were determined against selected glycosidases. For comparison, 1,4,5-trideoxy-1,5-imino- d - lyxo -hexitol, the 4-deoxy derivative of 1-deoxymannojirimicin, was prepared by enzymatic isomerisation of 6-azido-3,6-dideoxy- d - ribo -hexose into the corresponding 2-ulose and subsequent hydrogenation accompanied by intramolecular reductive amination.

Immobilised glucose isomerase (EC 5.3.1.5) accepted various (2 R ,3 R ,4 R )-configured hexoses such as 5-deoxy- d - ribo -hexose, 5-azido-5-deoxy- d -allose, as well as the corresponding epimer at C-5, 5-azido-5-deoxy- l -talose, as substrates. From the resulting azidodeoxyketoses, 5-azido-5-deoxy- d -psico- and - l -tagatopyranose, the powerful d -galactosidase inhibitors 2,5-dideoxy-2,5-imino- d -galactitol and - d -altritol were obtained in one additional step.

The kinetics of Pd(II) catalysed oxidation of Ara, Xyl and Gal by N-bromosuccinimide (NBS) in acidic medium has been studied using Hg(OAc)2 as a scavenger for the Br− ion. The reaction data show that first-order kinetics in each pentose and hexose at low concentrations tend to zero-order at high concentrations. First-order kinetics with respect to NBS and Pd(II) and inverse fractional order, i.e., decreasing effect of [H+] and [Cl−], were observed, whereas ionic strength, Hg(OAc)2 and succinimide did not influence the oxidation rate. Various activation parameters have been calculated and recorded. The corresponding acids, arabonic, xylonic and galactonic, were identified as the main oxidation products of the reactions. On the basis of the experimental findings, a suitable mechanism has been proposed.

The kinetic behaviour and relative reactivities of some carbohydrates (aldoses, amino sugars and methylated sugars) towards platinum(IV) in alkaline medium have been investigated. The reactions are first order with respect to [substrate] and Pt IV . The rates increase with the increase in OH − . The reactions show pseudo-first-order dependence on OH − . The oxidation rates in alkaline medium follow the order triose>tetrose>pentose>hexose. Activation parameters of the reactions have been calculated. Mechanisms have been proposed for the reactions.

Succinct syntheses for l -galactose, 3-deoxy- l - xylo -hexose (3-deoxy- l -galactose), 6-deoxy- l -galactopyranose ( l -fucose) and 3,6-dideoxy- l - xylo -hexose (3,6-dideoxy- l -galactose) have been developed starting from commercially available l -galactono-1,4-lactone. l -Galactose and variants were then converted to the guanosine diphosphate derivatives, via the formation of the anomeric phosphates and coupling to guanosine monophosphate morpholidate.

Acetylation of d -mannose phenylhydrazone gives acetylated d - arabino -1-phenyl-azo-1-( E )-hexene. Subsequent reduction with sodium borohydride produces 2-deoxy- d - arabino -hexose phenylhydrazone which, on hydrolysis, gives 2-deoxy- d - arabino -hexose. By a similar procedure 2-deoxy- d - lyxo -hexose, 2,6-dideoxy- l - arabino -hexose, and 2-deoxy- d - erythropentose can be prepared from d -galactose, l -rhamnose, and d -arabinose, respectively.

Two novel saccharinic acids, 2- C -(2-hydroxyethyl)erythronic and 2- C -(2-hydroxyethyl)threonic acids, were identified as their per(trimethylsilyl) derivatives by GLC-MS after alkaline degradation of leucrose (5- O - α -d-glucopyranosyl-d-fructopyranose). The identifications were supported by converting the acids into two different types of 1,4-lactones, that is, 3-(1,2-dihydroxyethyl)-3-hydroxydihydro-2(3 H )-furanone and 3,4-dihydroxy-3-(2-hydroxyethyl)dihydro-2(3 H )-furanone. The novel acids appear to be highly characteristic alkaline degradation products of (1 → 5)-linked hexose disaccharides, although several other hydroxy acids were formed and identified as well.

The dielectric relaxation behaviour of glucose, maltose, and their mixtures with water up to a concentration of 12.0 and 23.0% w/w, respectively, were examined in the frequency range 10 2 to 10 5 Hz. A primary relaation was observed at temperatures above the glass transition temperature, T g , and a secondary relaxation at sub- T g temperatures. The addition of water shifted the primary relaxations to lower temperatures. For the glucose mixtures, water increased the strength of the secondary relaxation and resulted in a merging of the primary and secondary relaxations. The increase in strength of the secondary relaxation was much more marked for the maltose-water mixtures and, in this case, the relaxations remained separate over the range of frequency and water contents studied. For the maltose-water mixtures, the dependence of the strength of the secondary relaxation on the water content was bilinear with a change in gradient at ∼ 10.0% w/w water. The sub- T g relaxations were thought to arise from motions of pendant hydroxymethyl groups attached to the hexose rings and from the reorientation of water molecules. The difference in the secondary relaxation behaviour of glucose and maltose indicates that structural factors, in addition to the presence of hydroxymethyl groups, are also important.

Starting from pentaerythritol, photolabile mono-, di-, and tri-dentate galactose derivatives as well as their 3H-labelled isotopomers were synthesised. The hydrophilic chains linking the 6 position of D-galactose to pentaerythritol consist of 13 atoms in line. The mono-, di- and tri-dentate compounds, although themselves not transported, inhibit in increasing order 14C-D-galactose transport into erythrocytes. On irradiating whole cells in the presence of ligand with 350-nm UV light, these compounds also in increasing order, could irreversibly block the hexose transport system. Irradiation without ligand has no effect. By using the 3H-labelled tridentate galactose compound the hexose transporter (zone 4.5) is specifically radiolabelled, as could be shown in an SDS-PAGE of membrane proteins from erythrocytes previously photoaffinity labelled. Radiolabelling is significantly suppressed in the presence of D-glucose.

The methyl β-glycopyranoside of l -vancosamine (1, 3-amino-2,3,6-trideoxy-3 -C- methyl- l -lyxo- hexose ), a constituent of vancomycin and related glycopeptide antibiotics, was synthesized stereoselectively from methyl 2,6-dideoxy-β- l -lyxo- hexopyranoside (2) in eight steps. Compound 2 was subjected in sequence to regioselective 3-O-p-methoxybenzylation, 4-O-tert-butyldimethylsilylation, oxidative 3-O-deprotection, and pyridinium dichromate oxidation to give methyl 4-O-tert- butyldimethylsilyl-2,6-dideoxy-β- l -threo- hexopyranosid-3-ulose (8). O-Benzyloximation of 8 and removal of the tert-butyldimethylsilyl protective group furnished methyl 2,6-dideoxy-β- l -threo- hexopyranosid-3-ulose O- benzyloxime (12). Addition of a methylcerium reagent to 12 provided the branched-chain hydroxyamino sugar methyl 3-benzyloxyamino-2,3,6-trideoxy-3 -C- methyl-β- l -lyxo- hexopyranoside (14) which was easily converted into the title compound by hydrogenolysis. On the other hand, reaction of the 4-benzyl ether 11 with the organocerium reagent gave only traces of the 3-epi-analogue of 14, methyl 4-O- benzyl-3-benzyloxyamino-2,3,6-trideoxy-3 -C- methyl-β- l -xylo- hexopyranoside .

We discovered an inverting maltose phosphorylase (Bsel2056) belonging to glycoside hydrolase family 65 from Bacillus selenitireducens MLS10, which possesses synthetic ability for α- d -glucosyl disaccharides and trisaccharides through the reverse phosphorolysis with β- d -glucose 1-phosphate as the donor. Bsel2056 showed the flexibility for monosaccharide acceptors with alternative C2 substituent (2-amino-2-deoxy- d -glucose, 2-deoxy- d - arabino -hexose, 2-acetamido-2-deoxy- d -glucose, d -mannose), resulting in production of 1,4-α- d -glucosyl disaccharides with strict regioselectivity. In addition, Bsel2056 synthesized two maltose derivatives possessing additional d -glucosyl residue bound to C2 position of the d -glucose residue at the reducing end, 1,4-α- d -glucopyranosyl-[1,2-α- d -glucopyranosyl]- d -glucose and 1,4-α- d -glucopyranosyl-[1,2-β- d -glucopyranosyl]- d -glucose, from 1,2-α- d -glucopyranosyl- d -glucose (kojibiose) and 1,2-β- d -glucopyranosyl- d -glucose (sophorose), respectively, as the acceptors. These results suggested that Bsel2056 possessed a binding space to accommodate the bulky C2 substituent of d -glucose.

The following structure of the O-specific polysaccharide (O-antigen) of Budvicia aquatica 20186 was elucidated by sugar analysis along with 1D and 2D 1 H and 13 C NMR spectroscopy: →4)-α- l -Rha p -(1→3)-α- d -Gal p -(1→2)-α-Yer p -(1→3)-β- d -Gal p NAc-(1→ where Yer stands for 3,6-dideoxy-4- C -[( S )-1-hydroxyethyl]- d - xylo -hexose (yersiniose A).

A fucoidan from the brown alga Fucus evanescens was effectively depolymerized by autohydrolysis. Negative-ion electrospray ionization mass spectrometry (ESIMS) revealed that the mixture contained sulfated mono- and oligosaccharides with polymerization degree (DP) up to 6, having from 1 to 4 sulfate groups per molecule. The prevalence of oligosaccharides with even DP was observed. It could be explained by the tendency of the 3-linked α- l -fucopyranose residues to hydrolyze faster than 4-linked ones. The intermolecular sulfate transfer during autohydrolysis was detected by ESIMS, when equimolar quantities of d -Rib and d -Glc were added as acceptors. The products were singly-sulfated and hexose was about four times more effective as an acceptor, than pentose. It was impossible to record MS/MS spectra of the sulfate transfer products, since intensities of their ions were too low.

The syntheses of d -mannose 6-phosphate ( 4 ), several d -mannopyranoside 6-phosphates, and methyl α- d -glucopyranoside 6-phosphate are de Compound 2 was obtained in 67% yield, from methyl 2,3,4,6-tetra- O -(trimethylsilyl)-α- d -mannopyranoside, by selective hydrolysis with a sa Butyl and hexadecyl α- d -mannopyranosides were prepared by glycosidation of the respective alcohols with tetra- O -benzoyl-α- d -mannopyrano

Mannitol dehydrogenase ( d -mannitol:NADP+ 2-oxidoreductase, EC 1.1.1.138), isolated from the sporocarps of Agaricus bisporus, has been purified 120-fold following fractionation with protamine sulphate, followed by hydrophobic and affinity chromatography. d -Mannitol and d -fructose appear to be the only substrate and products involved in the reaction, having Km values of 7.5 and 9.8m m , respectively. The purified enzyme has been used for the determination of d -mannitol and also the d -mannose content of glycoproteins and polysaccharides following the liberation of that hexose and reduction to d -mannitol.

Macoma birmanica agglutinin (MBA) that seems to play crucial roles in the innate immunity of marine bivalve, M. birmanica has been earlier defined as GlcNAc/Man specific. However, most complementary carbohydrate structures to its binding domain and ligand clustering in its recognition profile have not been established. In this study, the complete recognition profile of MBA was examined by enzyme-linked lectin-sorbent assay and inhibition assay. Among the monosaccharides tested, GlcNAc was more reactive followed by Man and Glc, others were non-reactive; revealing the importance of equatorial -NAc group at C-2, -OH group at C-4 and C-6, and pyranose conformation of hexose. Moreover, beta-glycosides of GlcNAc and Glc were more potent whereas for Man it was alpha-glycoside. MBA recognized both exposed and internal alpha-Man and beta-GlcNAc/Glc residues well with most linkages except (beta1-4). This binding pattern was further extended and confirmed by polyvalent glycoside clusters of GlcNAc(beta1-2)Man(alpha1-, which was a better inhibitor than Man(alpha1-2/3/6)Man(alpha1- or Man(alpha1-3/6)Man(beta1- present in well-defined naturally occurring glycoproteins. This broad range specificity explains the importance of MBA as an important pattern recognition molecule that provides more realistic picture of carbohydrate-based immune response triggering.

An efficient and stereoselective synthesis of d,l-gulose was described. The key step of the synthetic route is represented by a multicomponent enyne cross metathesis—hetero Diels–Alder reaction which allows the formation of the pyran ring from cheap and commercially available substrates in a single synthetic step. The synthesis of d,l-gulose was accomplished without the use of protecting groups making this approach highly desirable also in terms of atom economy.

The lipopolysaccharide of Citrobacter freundii O22 (strain PCM 1555) was degraded under mild acidic conditions and the O-polysaccharide released was isolated by gel chromatography. Sugar and methylation analyses along with (1)H and (13)C NMR spectroscopy, including two-dimensional (1)H,(1)H ROESY and (1)H,(13)C HMBC experiments, showed that the repeating unit of the O-polysaccharide has the following structure: alpha-Abep 1 --3 --2)-alpha-D-Manp-(1--4)-alpha-L-Rhap-(1--3)-alpha-D-Galp-(1--where Abe is abequose (3,6-dideoxy-D-xylo-hexose). SDS-PAGE and immunoblotting revealed that the O-antigen of C. freundii O22 is serologically indistinguishable from those of Salmonella group B serovars (Typhimurium, Brandenburg, Sandiego, Paratyphi B) but not related to other abequose-containing O-antigens tested (Citrobacter werkmanii O38 and Salmonella Kentucky) or colitose (l enantiomer of abequose)-containing O-antigen of Escherichia coli O111.

The sensitivity of detection and extent of information on structure obtainable by liquid-secondary-ion mass spectrometry (l.s.i.-m.s.) of neoglycolipids on the conventional target probe and directly from the surface of silica plates following t.l.c. has been assessed. Neoglycolipids were derived from malto-oligosaccharides, chitin oligosaccharides, and a range of deoxyhexose-, hexose-, 2-acetamido-2-deoxyhexose-, and sialic acid-containing mammalian oligosaccharides by reductive amination using phosphatidylethanolamine dipalmitoate (PPEADP). Sub-pmol amounts of the maltopentaose-PPEADP derivative applied directly to the target probe provided information on molecular weight, whereas approximately 1 pmol was required when analysed on the silica gel t.l.c. plate. With a biantennary octasaccharide derivative, the sensitivity of detection was 20-50 times lower and the other oligosaccharides had intermediate sensitivities. Information on composition and sequence was obtained readily from fragment ions, using 5 pmol of the maltopentaose derivative and 50 pmol of the octasaccharide derivative on the target probe, and 50 and 200 pmol, respectively, on the silica gel chromatogram. The optimised conditions formed the basis for characterising the structures of the components of mixtures of oligosaccharides generated from glycoproteins.

3-Deoxy-3- C -methylene- d - ribo -hexose-6-phosphate and 3-deoxy-3- C -methylene- d - erythro -pentose-5-phosphate were prepared from a common intermediate 3-deoxy-3- C -methylene-1,2- O -isopropylidene-α- d - ribo -hexofuranose. The preparation of the phosphorylated unsaturated sugars employed di- tert -butyl diethylphosphoramidite as the phosphitylating reagent. The removal of all the protecting groups was done under acidic conditions in the ultimate step. The unsaturated sugar phosphates were competitive inhibitors but neither substrates nor inactivators of glucose-6-phosphate and ribose-5-phosphate isomerases.

1-Deoxy- d -erythro-hexo-2,3-diulose (1-DG) was prepared by the reaction of ethoxyvinyllithium with an erythronolactone derivative. Characterization by 1H and 13C NMR spectroscopy and NOE difference experiments revealed the 2C5-chair β-pyranose as the major isomer in solution. Experiments assessing browning and polymerization reactivity proved 1-DG to be a much more potent protein modifier than 3-deoxy- d -erythro-hexos-2-ulose.

2,6-Dideoxy-D-lyxo-hexose was prepared efficiently from D-galactose in eight steps (25% overall yield). The synthesis is amenable to multigram scale-up.

The concentrations of methyl glycosides, oligosaccharides, glycopeptides, and glycoproteins can be accurately determined by using calibration curves composed of the appropriate monosaccharide(s) obtained with a modified version of the colorimetric phenol-sulfuric acid method. Calibration curves of micrograms sugar vs. 490 nm for Man, Glc, or Gal are shown to provide reliable determinations (typically +/- 3-4%) of corresponding methyl glycosides and linear and branched-chain oligosaccharides containing the corresponding reactive hexose residue. For complex oligosaccharides containing a known mixture of reactive hexose units, the appropriate mixture of monosaccharides are shown to provide equally accurate calibration curves for concentration determinations. In the case of the soybean agglutinin, which is a tetramer possessing one Man9 oligomannose-type chain per subunit, the protein concentration was determined from the Man calibration curve which agreed with that obtained from the molar extinction coefficient of the protein.

Bovine beta-(1-->4)-galactosyltransferase (GalT) transfers galactose from UDP-galactose to beta-D-GlcpNAc-terminating oligosaccharides to produce N-acetyllactosamine sequences. We report here the chemical synthesis, structural characterization and enzymatic evaluation of the very labile UDP-2-deoxy-D-lyxo-hexose ("UDP-2-deoxy-galactose," 2) as an alternate donor for GalT. Donor 2 had kinetic parameters, including a Km value of 51 microM, almost identical to those for the natural substrate UDP-galactose when beta-D-GlcpNAc-O(CH2)8COOMe was used as the acceptor. The product of the enzymatic transfer was isolated and confirmed to have the expected 2'-deoxy-N-acetyllactosamine sequence.

The disaccharide L-glycero-D-manno-heptosyl-D-glucose was isolated from the lipopolysaccharide (LPS) of Escherichia coli K-12 strain W3100 after partial hydrolysis with acid, and the structure was determined by methylation analysis, n.m.r. spectroscopy, and comparison with a synthetic standard. In addition, the oligosaccharides L,D-Hep-D-Glc-D-Glc and L,D-Hep-D-Glc-D-Glc-D-Glc were isolated, and their structures were established by g.l.c.-m.s. and methylation analysis. The results indicated that L-glycero-D-manno-heptose, a characteristic constituent of the inner core region, may also occur in the outer core region which, in E. coli, is generally composed of hexoses. A revised structure of the carbohydrate backbone of the hexose/heptose region of the LPS is given.

A procedure has been developed by which less than micrograms quantities of hexoses in glycoproteins can be determined by g.l.c.-m.s. with selected-ion monitoring of the alditol acetates derived from the sugars released by acid hydrolysis. The effectiveness of the method was demonstrated by determination of the hexose and hexosamine composition of 5-micrograms samples of antithrombin III and von Willebrand factor, respectively.

Trifluoroacetolysis of d -glucuronic acid and methyl α- d -glucopyranosiduronic acid resulted in an initial phase of degradation followed by stabilisation of the compounds as their 6,3-lactones. The methyl ester of methyl 4-O-methyl-α- d -glucopyranosiduronic acid was largely stable towards trifluoroacetolysis. Aldonic acids substituted at O-3 or O-6 were stable towards trifluoroacetolysis because of the formation of γ-lactones. Aldonic acids substituted at O-4, and incapable of forming γ-lactones, were converted into the trifluoroacetylated enol of 3-deoxy-2-hexulosonic acid. Treatment of the 3-deoxy-2-hexulosonic acid with mild base eliminated the substituent at O-4.

The reduction of 2,6-dibromo-2,6-dideoxy- D -mannono- and 2,6-dibromo-2,6-dideoxy- D -glucono-1,4-lactone with sodium borohydride affords 2,6-dibromo-2,6-dideoxy- D -mannose and 2,6-dibromo-2,6-dideoxy- D -glucose, respectively, which may be isolated as their acetates. Similarly, 2-bromo-2,6-dideoxy- L- -glucono-1,4-lactone yields 2-bromo-2,6-dideoxy- L -glucose. Hydrogenolysis of 2,6-dibromo-2,6-dideoxy- D -mannono-1,4-lactone gives 6-bromo-2,6-dideoxy- D - arabino -hexono-1,4-lactone and, subsequently, 2,6-dideoxy- D - arabino -hexono-1,4-lactone. Reduction of the latter with bis(1,2-dimethylpropyl)borane leads to 2,6-dideoxy- D - arabino -hexose, which may be converted into methyl 2,6-dideoxy-3,4-di- O - p -nitrobenzoyl- D - arabino -hexopyranoside.

Study of the molecular-weight distribution of the raw gum exuded from Acacia baileyana F. Muell., of partially hydrolysed material, and of products of successive Smith-degradations of the gum suggests the occurrence of sub-units having a molecular weight of ∼4000. These sub-units consist of β-(1→3)-linked d -galacto-pyranose residues, to most of which are attached residues of l -arabinofuranose or d -galactopyranose; the bulk of the pendant groups are removed by a single Smith-degradation to give a monodisperse fragment of molecular weight 2500. Further, successive degradations by the oxidation-reduction-hydrolysis procedure yielded a galactan which contains about ten hexose residues and which is essentially linear.

5,6-Dideoxy-6-phosphono- d - arabino -hexose, an isosteric phosphonate analogue of d -arabinose 5-phosphate, was synthesized in six steps from the known methyl 5- O -triphenylmethyl-α- d -arabinofuranoside. The key step involves pyridinium chlorochromate oxidation of methyl 2,3-di- O -acetyl-α- d -arabinofuranoside to the 5- aldelhydo derivative, and Wittig synthesis with (diphenyl phosphonomethylene)triphenylphosphorane. 5,6-Dideoxy-6-phosphono- d - arabino -hexose, a compound of interest for the study of Gram-negative lipopolysaccharide biosynthesis, is converted by 3-deoxyoctulosonate 8-phosphate synthetase from Escherichia coli K 235 into a material yielding a thiobarbituric acid chromophore with 2 max 550 nm, probably 9-phosphono-3,8,9-trideoxy- d -manno-nonulosonate, an isosteric phosphonate analog of 3-deoxyoctulosonate 8-phosphate (KDO 8-phosphate).

The intramolecular cyclization of O -tosyl derivatives of dithioacetals of d -ribose, d -arabinose, and d -glucose was investigated. p -Toluenesulfonylation of d -glucose diethyl dithioacetal gave 3,6-anhydro- d -glucose diethyl dithioacetal. Variously substituted 5- O -tosyl- d -glucose dibenzyl dithioacetals gave derivatives of either 2,5-anhydro- l -idose dibenzyl dithioacetal, benzyl 1,5-dithio- l -idopyranoside, or l -idose dibenzyl dithioacetal. Likewise, 4- O -tosyl- d -glucose dibenzyl dithioacetal derivatives gave benzyl 1,4-dithio- d -galactofuranoside derivatives.

Escherichia coli C is an R-strain, and hence its lipopolysaccharide consists only of lipid A joined to a basal core. Intact core-polysaccharides have been prepared from this strain, and from mutants of the same strain defective in various stages of core biosynthesis. Using sugar and methylation analyses, and chemical and enzymic degradations, the hexose region of the core of the parent strain has been shown to be a pentasaccharide for which the following structure is proposed