Aggregate morphology and flow behaviour of micellar alkylglycoside solutions

Solutions of n-nonyl-β-D-glucoside (C₉G₁), n-decyl-β-D-glucoside (C₁₀G₁), n-dodecyl-β-D-maltoside (C₁₂G₂), n-tetradecyl-β-D-maltoside (C₁₄G₂) and C₉G₁/C₁₀G₁ mixtures have been characterised by capillary viscometry and rheology in H₂O and D₂O, in order to map the influence of surfactant characteristics on micellisation over a wide concentration range. For the maltosides, the micellar solutions are shear thinning with a zero-shear viscosity that scales with concentration according to a power law with an exponent of about 5.8. In contrast, solutions of the glucosides C₉G₁, C₁₀G₁ and their mixtures show Newtonian flow behaviour and a much lower scaling exponent (<2.4). In C₉G₁/C₁₀G₁ mixtures, the scaling exponent decreases monotonously with increasing C₁₀G₁ content. The flow behaviour correlates with the packing requirements of the various surfactants, and are compatible with the idea that the maltosides form worm-like micelles, whereas the glucosides form branched, interconnected micelles (C₉G₁) and space-filling micellar networks (C₁₀G₁).     

Lyotropic and thermotropic behavior of Alkylglucosides and related compounds

 The phase diagram of the binary system composed of octyl-β-D-glucopyranoside and water was investigated and the phase boundaries were determined. Polarising optical microscopy was used to define the different phases, proton and deuterium NMR experiments to define the region of existence of the different phases and to obtain information on axiality and head group solvation. DSC experiments were performed to determine the thermal transitions from solid to thermotropic liquid crystals for octyl-β-D-gluco-pyranoside, the related alkylglucosides or maltosides, and to gain information on the role played by sugar units in the thermodynamics of such phase transitions. Received: 15 May 1997 Accepted: 08 September 1997     

Synthesis of oligosaccharides related to the HNK-1 antigen. 5. Synthesis of a sulfo-mimetic of the HNK-1 antigenic trisaccharide

2-Aminoethyl 3,6-di-O-sulfo-β-D-glucopyranosyl-(1→3)-β-D-galactopyranosyl-(1→4)-2-acetamido-2-deoxy-β-D-glucopyranoside, which is the sulfo-mimetic of the antigenic trisaccharide HNK-1, and the corresponding monosulfates, viz., 2-aminoethyl 3-O-sulfo-and 2-aminoethyl 6-O-sulfo-β-D-glucopyranosyl-(1→3)-β-D-galactopyranosyl-(1→ 4)-2-acetamido-2-deoxy-β-D-glucopyranosides, were synthesized. 2-Azidoethyl 2,4-di-O-benzoyl-β-D-glucopyranosyl-(1→3)-2,4,6-tri-O-benzoyl-β-D-galactopyranosyl-(1→ 4)-2-acetamido-3,6-di-O-benzyl-2-deoxy-β-D-glucopyranoside served as the common precursor for the sulfated trisaccharides. This compound was synthesized according to the [2+1] pattern from monosaccharidic precursors: 3,6-di-O-acetyl-2,4-di-O-benzoyl-D-glucopyranosyl trichloroacetimidate, allyl 2-O-benzoyl-4,6-O-benzylidene-β-D-galactopyranoside, and 2-azidoethyl 2-acetamido-3,6-di-O-benzyl-2-deoxy-β-D-glucopyranoside. The structures of the glycosyl donors and glycosylation conditions were optimized for the efficient synthesis of the glucosyl-β-(1→3)-galactose disaccharide block and its subsequent transformation into the target trisaccharide sequence. Dedicated to Academician V. A. Tartakovsky on the occasion of his 75th birthday. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1593–1607, August, 2007.     

Stereospecific mannosylations of myo -inasitol: Synthesis of manno- myo -inositol fragment of Mycobacterium tuberculosis

Methyl iodide activated stereospecific α-mannosylations utilising 2-pyridyl-1-thiomannopyranoside derivatives (2,3,4) as donors and suitably protected myo-inositol derivatives (1,25,27,29) as acceptors to prepare 2-0-α-D-mannopyranosyl-6-[O-α-D-mannopyranosyl-(1–6)-O-α-D-mannopyranosyl-(l-6)-O-α-D-mannopyranosyl]-D-myo-inositol derivative (31) is described. IICT Commun. No. 3355     

Mild Pfitzner—Moffat oxidation of the (1→3)-β-D-glucan from Saccharomyces cerevisiae

The structure of the cell wall glucan isolated from the industrial strain of Saccharomyces cerevisiae was characterized as to be composed of a linear (1→3)-β-D-glucan chain with single β-D-glucopyranosyl residues attached to every ninth backbone unit by (1→6)-glycosidic linkages. Mild oxidation of this β-D-glucan with a dimethyl sulfoxide—acetic anhydride reagent yielded an “oxidized” glucan with aldehyde groups introduced at C-6 and carbonyl oxygens located at C-2 and C-4 of the glucopyranosyl rings. The conversion of the oxidized glucan into the polyoxime was used to study the progress of oxidation and to establish the carbonyl groups distribution in this new reactive polysaccharide derived from baker’s yeast cell wall.     

Polar steroidal compounds from the Far-Eastern starfish <Emphasis Type="Italic">Lethasterias fusca</Emphasis>

Nine steroidal compounds including three new steroidal glycosides, viz., sodium (24S)-3,24-di-O-(β-D-xylopyranosyl)-5α-cholestane-3β,6β,8,15α,24-pentol 15-sulfate (fuscaside A), (24S)-3,24-di-O-(β-D-xylopyranosyl)-5α-cholestane-3β,6β,8,15α,24-pentol (fuscaside B), and (22E,24R)-24-O-(β-D-xylopyranosyl)-5α-cholest-22-ene-3β,6α,8,15β,24-pentol (desulfated minutoside A); three previously known glycosides, viz., distolasterosides D₁ and D₂ and pycno-podioside A; two previously known polyhydroxysteroids, viz., 5α-cholestane-3β,6α,8,15β,16β,26-hexaol and 5α-cholestan-3β,4β,6α,7⇇8,15β,16β,26-octol; and the known sodium 24,25-dihydro-marthasterone 3-sulfate were isolated from the Far-Eastern starfish Lethasterias fusca. The structures of these compounds were elucidated by NMR spectroscopy and mass spectrometry. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 196–200, January, 2008.     

Synthesis of β-<Emphasis Type="SmallCaps">d</Emphasis>-galactopyranosylamine derivatives with the terminal amino group in the spacer as mono-, di-, and trivalent ligands of galectins

Glycoclusters were obtained by N-alkylation of N-glycyl-β-d-galactopyranosylamine with N-chloroacetyl derivatives of β-d-galactopyranosylamine and N,N″-iminodiacetyl-di-β-d-galactopyranosylamine. The glycoclusters with two and three galactopyranosylamine residues and the monovalent ligand N-diglycyl-β-d-galactopyranosylamine with an amino group in the spacer are suitable for subsequent conjugation with carboxyl-containing physiologically active compounds.     

Selection of protecting groups and synthesis of a β-1,4-GlcNAc-β-1,4-GlcN unit

Abstract  

The synthesis of the disaccharide tert-butyldimethylsilyl (4-O-acetyl-2-azido-3,6-di-O-benzyl-2-deoxy-β-d-glucopyranosyl)-3,6-di-O-benzyl-2-deoxy-2-phthalimido-β-d-glucopyranoside, designed as a repeating unit appearing in oligo- and polysaccharides, which exhibits a distinguished “obverse–reverse” property in β-1,4-glucan chain, was accomplished. This disaccharide was synthesized by glycosylation of a phthalimido sugar with an azido sugar. A selective removal of the two different protecting groups at C-2 for obtaining 2-acetamido-4-O-(2-amino-2-deoxy-β-d-glucopyranosyl)-2-deoxy-β-d-glucopyranose indicates that the selection and combination, using phthalimido and azido as protecting groups, are an excellent strategy for synthesizing such target disaccharides.     

Glycoconjugates of amino acids. Preparation throughN-alkylation of amino acids withN-chloroacetyl-β-glycopyranosylamines

Monoalkylation of amino acids of different structural types withN-chloroacetyl-glycosylamines was shown to be applicable for the preparation of glycoconjugates containing β-d-galactose,N-acetyl-β-d-glucosamine, β-d-mannose, and lactose residues. The glycoconjugates were synthesized from amino acids with secondary (sarcosine,l-proline) or primary (l-2- and 4-aminobutyric acids,l-tryptophan) amino groups as well as from various amino dicarboxylic acids (N-methyl-dl-aspartic,dl-aspartic,l-glutamic, anddl-2-aminoadipic acids). The derivatives obtained may be of interest for glycotargeting of physiologically active compounds of this series. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1377–1380, July, 1999.     

Synthesis of saccharide precursors for preparation of potential inhibitors of glycosyltranferases

Ethyl 6-O-tert-butyldimethylsilyl-3,4-di-O-acetyl-2-thio-α-D-fructofuranoside (Va), its β-analog (Vb); as well as benzyl 6-O-tert-butyldimethylsilyl-3,4-di-O-acetyl-2-thio-α-D-fructofuranoside (Xa) and its β-analog (Xb), having an unprotected OH group at C-1, were prepared by sequential synthesis starting from commercially available D-fructose. These compounds represent suitable nucleophiles for the preparation of model carbohydrate mimetics of a glycosyltransferase inhibitor type in transition state. The structures of all compounds were confirmed by NMR spectral data and elemental analyses.     

Comparison and characterization of polysaccharides from natural and cultured <Emphasis Type="Italic">Cordyceps</Emphasis> using saccharide mapping

Comparison and characterization of polysaccharides from natural and cultured Cordyceps on the basis of their chemical characteristics such as glycosidic linkages were performed for the first time using saccharide mapping. The results showed that polysaccharides from most of the natural and cultured Cordyceps had similar responses to enzymatic digestion. These polysaccharides mainly contained (1→4)-β-D-glucosidic linkages, and (1→4)-α-glucosidic, (1→6)-α-glucosidic, 1,4-β-D-mannosidic, as well as (1→4)-α-D-galactosiduronic linkages also existed in some polysaccharides. Especially, natural and cultured Cordyceps polysaccharides could be discriminated on the basis of high performance liquid chromatography profiles of pectinase hydrolysates, which is helpful to control the quality of polysaccharides from Cordyceps.     

New triterpenoid glycosides fromThalictrum minus L.

Two triterpenoid diglycosides of the cycloartane series were isolated from the terrestrial part ofThalictrum minus L. (Ranunculaceae). Genins of these glycosides are side-chain structural isomers—3-O-β-d-galactopyranosyl-29-O-β-d-glucopyranosyl-9β, 19-cyclo-20(S)-lanost-24(Z)-ene-3β, 16β, 22(S), 26, 29-pentaol and 3-O-β-d-galactopyranosyl-29-O-β-d-glucopyranosyl-9β, 19-cyclo-20(S)-lanost-25-ene-3β, 16β,22(S), 24ζ, 29-pentaol. The structures of these glycosides were established using 1D and 2D NMR spectroscopy and FAB mass spectrometry. For Part 9, see Ref. 1. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1434–1437, July, 1998.     

New polyhydroxysteroids and steroid glycosides from the far east starfishCeramaster patagonicus

Two new polyhydroxysteroids and five new glycosides were isolated from the starfishCeramaster patagonicus and their structures were elucidated: 5α-cholestane-3β,6α,15β,16β,26-pentol, (22E)-5α-cholest-22-ene-3β,6α,8,15α,24-pentol, (22E)-28-O-[O-(2-O-methyl-β-d-xylopyranosyl)-(1→2)-β-d-galactofuranosyl]-24-hydroxymethyl-5α-cholest-22-ene-3β,4β, 6α,8,15β,16β,28-heptol (ceramasteroside C₁), (22E)-28-O-[O-(2,4-di-O-methyl-β-d-xylopyranosyl)-(1→2)-β-d-galactofuranosyl]-24-hydroxymethyl-5α-cholest-22-ene-3β, 6α,8,15β,16β,28-hexol (ceramasteroside C₂), (22E)-28-O-[O-methyl-β-d-xylopyranosyl)-(1→2)-β-d-galactofuranosyl]-24-hydroxymethyl-5α-cholest-22-ene-3β,6α,8,15β,16β 28-hexol (eramasteroside C₃), (22E)-28-O-[O-(2-O-methyl-β-d-xylopyranosyl)-(1→2)-β-d-galactofuranosyl]-24-methyl-5α-cholest-22-ene-3β,4β,6α,8, 15β, 26-hexol (ceramasteroside C₄), and (22E)-28-O-[O-(2-O-methyl-β-d-xylopyranosyl)-(1→2)-β-d-xylopyranosyl]-5α-cholest-22-ene-3β,6α,8,15β,24-pentol (ceramasteroside C₅)). Three known polyhydroxysteroids (24-methylene-5α-cholestane-3β,6α,8,15β,16β,26-hexol, 5α-cholestane-3β,6α,8,15β,16β,26-hexol, and 5α-cholestane-3β,6β,15α,16β,26-pentol) were also isolated. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 190–195, January, 1997.     

Conjugates of polyhedral boron compounds with carbohydrates 6. Synthesis of glycoconjugates of closo-ortho-carborane with β-lactosylamine and β-d-galactopyranosylamine derivatives as galectin bi- and trivalent ligands

Five glycoconjugates were obtained from ortho-carboranylacetic acid and β-actosylamine or β-d-galactopyranosylamine derivatives with the terminal amino group in the spacer. The glycoconjugates have different lengths of the spacer (9 to 15 atoms) and contain two or three βlactosylamine residues or one, two, or three β-d-galactopyranosylamine residues.     

Synthesis of N 2-Arylisocytidines and N 2-Aryl-2′-deoxyisocytidines

2-(Arylamino)pyrimidin-4-ones were synthesized, silylated, and condensed with l,2,3,5-tetra-O-acetyl-β- d-ribofuranoside to afford the corresponding N ²-aryl protected isocytidines. Deprotection of the acetylated isocytidines using saturated NH₃ in MeOH solution gave 1-(β-d-ribofuranosyl)-2-(arylamino)-4-pyrimidinones. Methyl 2-deoxy-3,5-di-O-toluyl-α/β-d-ribofuranoside was prepared and condensed with the previously silylated bases to afford the anomeric mixture of protected nucleosides. The pure β-anomers were synthesized with better yield by treating the sodium salts of N ²-arylisocytosine derivatives with 2-deoxy-3,5-di-O-toluyl-α-d-ribofuranosyl chloride. Deprotection of the latter anomers afforded the corresponding free hydroxyl derivatives. The synthesized free nucleosides are under antiviral and oligonucleotide investigations.     

Synthesis of <Emphasis Type="Italic">N</Emphasis><Superscript>2</Superscript>-Arylisocytidines and <Emphasis Type="Italic">N</Emphasis><Superscript>2</Superscript>-Aryl-2′-deoxyisocytidines

Summary. 2-(Arylamino)pyrimidin-4-ones were synthesized, silylated, and condensed with l,2,3,5-tetra-O-acetyl-β- d-ribofuranoside to afford the corresponding N ²-aryl protected isocytidines. Deprotection of the acetylated isocytidines using saturated NH₃ in MeOH solution gave 1-(β-d-ribofuranosyl)-2-(arylamino)-4-pyrimidinones. Methyl 2-deoxy-3,5-di-O-toluyl-α/β-d-ribofuranoside was prepared and condensed with the previously silylated bases to afford the anomeric mixture of protected nucleosides. The pure β-anomers were synthesized with better yield by treating the sodium salts of N ²-arylisocytosine derivatives with 2-deoxy-3,5-di-O-toluyl-α-d-ribofuranosyl chloride. Deprotection of the latter anomers afforded the corresponding free hydroxyl derivatives. The synthesized free nucleosides are under antiviral and oligonucleotide investigations.     

Synthesis of bis(glycosylamino)alkanes and bis(glycosylamino)arenes

The condensation of D-mannose and D-galactose with aliphatic and aromatic diamines afforded a series of bis(glycosylamino)alkanes and-arenes. A possible mechanism was proposed for the formation of 1,2-bis(β-D-glycosylamino)benzenes. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2793–2801, December, 2005.     

Block co-oligomers of tri-O-methylated and unmodified cello-oligosaccharides as model compounds for methylcellulose and its dissolution/gelation behavior

A novel synthetic method for co-oligomers of tri-O-methylated and unmodified cello-oligosaccharides was designed. These oligomers are of importance as model compounds for investigations on the dissolution behavior of commercial methylcelluloses. In this connection, insights into the chemical structure of ‘cross linking loci’ in the thermo reversible gelation of aqueous solution of methylcellulose are of particular significance. The synthetic procedure consists of glycosylation using glycosyl fluoride and oligomerization of sugar orthoester. Thus, phenyl 2,3,6-tri-O-methyl-β-d-glucopyranosyl-(1→4)-2,3,6-tri-O-methyl-1-thio-β-d-glucopyranoside (1) as a glycosyl acceptor was glycosylated with 4-O-acetyl-2,3,6-tri-O-methyl-β-d-glucopyranosyl-(1→4)-2,3,6-tri-O-methyl-d-glucopyranosyl fluoride (2) as a glycosyl donor converted to give a cellotetraose derivative (3). Both reactants have been prepared from commercially available cellobiose. After deacetylation of 3, 3-O-benzyl-6-O-pivaloyl-α-d-glucopyranose 1,2,4-orthopivalate (5) was reacted with 4-hydroxyl group at non-reducing-end of cellotetraose derivative (4) to give the block co-oligomer (6). After the deprotection of compound 6, tri-O-methylated-block-unmodified cello-oligosaccharides (18 and 18′) (DP = 4 − 8, DS = 2.79 − 1.38) were obtained, monitored by MALDI-TOF MS spectra. Chloroform-soluble methylated cellotetraose derivatives (18 and 18′ (DP=4, n=0), DS=2.57, and 2.79, respectively) were also soluble in the water solution of tri-O-methylated-block-unmodified cello-oligosaccharides (DP=4−8, DS=2.79−1.50). This fact indicated that hydrophobic methylated cello-tetraose derivatives were encapsulated within a micelle of amphiphlic tri-O-methylated-block-unmodified cello-oligosaccharides. It was found that solubilities of 18 and 18′ (DP=4−8, DS=2.79−1.38) in water and chloroform were obviously different in the mixtures, depending on their DP and DS values. The substituent distribution of the tri-O-methylated-block-unmodified cello-oligosaccharides along one molecule and between molecules plays an important role in its solubility in water and chloroform.     

Structural modeling of glucanase–substrate complexes suggests a conserved tyrosine is involved in carbohydrate recognition in plant 1,3-1,4-β-<Emphasis Type="SmallCaps">d</Emphasis>-glucanases

Glycosyl hydrolase family 16 (GHF16) truncated Fibrobacter succinogenes (TFs) and GHF17 barley 1,3-1,4-β-d-glucanases (β-glucanases) possess different structural folds, β-jellyroll and (β/α)₈, although they both catalyze the specific hydrolysis of β-1,4 glycosidic bonds adjacent to β-1,3 linkages in mixed β-1,3 and β-1,4 β-d-glucans or lichenan. Differences in the active site region residues of TFs β-glucanase and barley β-glucanase create binding site topographies that require different substrate conformations. In contrast to barley β-glucanase, TFs β-glucanase possesses a unique and compact active site. The structural analysis results suggest that the tyrosine residue, which is conserved in all known 1,3-1,4-β-d-glucanases, is involved in the recognition of mixed β-1,3 and β-1,4 linked polysaccharide.     

Four new steroid glycosides from the Vietnamese starfish <Emphasis Type="Italic">Linckia laevigata</Emphasis>

Eighteen steroid compounds, including four new steroid glycosides, viz., linckosides L3–L6, along with the previously known nine glycosides and five free polyhydroxysteroids, were isolated from the starfish Linckia laevigata collected on the Vietnamese coast. New compounds contain the 2-O-methyl-β-D-xylopyranosyl unit at the C(3) atom of polyhydroxylated steroidal aglycone. Two of these compounds are monosides, and the other two belong to biosides and have an additional β-D-xylopyranosyl residue at C(26) in the side chain of the aglycone. The structures of the new compounds were determined by NMR spectroscopy, mainly by 2D NMR, and mass spectrometry. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 792–799, April, 2007.