Crystal structure of 2-deoxy-β-d-lyxo-hexose (2-deoxy-β-d-galactose)

2-Deoxy-β-d-lyxo-hexose (2-deoxy-β-d-galactose, C₆H₁₂O₅), M_r = 164.16, is monoclinic, P2₁ with a = 9.811(1), b = 6.953(1), c = 5.315(1) Å, β = 91.58(2)°, V = 362.5(1) ų, Z = 2, and D_x = 1.504 g.cm^?3. The structure was solved by direct methods (MULTAN 79) and refined to R = 0.032 for 800 observed reflections. Each hydroxyl oxygen, acting both as donor and acceptor, is involved in a hydrogen-bonding system, which consists of infinite helical chains around the crystallographic screw axes. Moreover, weak interactions allow the incorporation of the ring-oxygen atoms into an interconnected network.     

Synthesis and anticytokinin activity of 4-substituted-7-(β-d-ribofuranosyl)-pyrrolo[2,3-d]pyrimidines

A series of 4-substituted-7-(β-d-ribofuranosyl)-pyrrolo[2,3-d]pyrimidines in which the 4-substituents were systematically varied has been syn     

Identification of neoschaftoside as 6-C-β-d-glucopyranosyl-8-C-β-l-arabinopyranosylapigenin

The structure of neoschaftoside is shown for the first time to be 6-C-β-d-glucopyranosyl-8-C-β-l-arabinopyranosylapigenin. A variety of chemical and spectroscopic techniques are involved.     

The synthesis of 3-amino-3-deoxy-α-d-glucopyranosyl α-d-glucopyranoside (3-amino-3-deoxy-α,α-trehalose

The preparation of 2,3-di-O-benzoyl-4,6-O-benzylidene-α-d-glucopyranosyl-2-O-benzoyl-4,6-O-benzylidene-α-d-ribo-hexopyranosid-3-ulose (3) from 4,6:4′,6′-di-O-benzylidene-α,α-trehalose (1) via the 2,3,2′-tribenzoate 2 has been improved. Reduction of 3 with sodium borohydride gave 2-O-benzoyl-4,6-O-benzylidene-α-d-allopyranosyl 2,3-di-O-benzoyl-4,6-O-benzylidene-α-d-glucopyranoside (4), which was converted into the methanesulfonate 5 and trifluoromethanesulfonate 6. Displacement of the sulfonic ester group in 6 with lithium azide was very facile and afforded a high yield of 3-azido-2-O-benzoyl-4,6-O-benzylidene-3-deoxy-α-d-glucopyranosyl 2,3-di-O-benzoyl-4,6-O-benzylidene-α-d-glycopyranoside (7), whereas similar displacement in 5 proceeded sluggishly, giving a lower yield of 7 together with an unsaturated disaccharide (8). The azido sugar 7 was converted by conventional reactions into the analogous 2,3,2′-triacetate 9, the corresponding 2,3,2′-triol 10, and deprotected 3-azido-3-deoxy-α-d-glucopyranosyl α-d-glucopyranoside (11). Hydrogenation of 11 over Adams' catalyst furnished crystalline 3-amino-3-deoxy-α,α-trehalose hydrochloride (12), the overall yield from 3 being 35%.     

X-ray crystal structure of maltitol (4-O-α-d-glucopyranosyl-d-glucitol

Maltitol, crystallised from aqueous solution, has m.p. 146.5–147°, [α]_d + 106.5° (water), and is orthorhombic with the space group P2₁2₁2₁ and Z = 4, and with cell dimensions a = 8.166(5), b = 12.721(9), and c = 13.629(6) Å. The molecule shows a fully extended conformation with no intramolecular hydrogen-bonds. All nine hydroxyl groups are involved in intermolecular hydrogen-bond networks and in bifurcated, finite chains. The d-glucopyranosyl moiety has the ⁴C₁ conformation, and the conformation about the C-5–C-6 bond is gauche-gauche. The d-glucitol residue has the bent [ap, Psc, Psc (APP)] conformation. The empirical formula for the solubility in water is C = 119.1 + 1.204 T + 4.137 × 10^?2 T² ? 7.137 × 10^?4 T³ + 7.978 × 10^?6 T⁴. The thermal properties are as follows: ΔH_f = 13.5 kcal.mol^?1, and Q = ?5.57 kcal.mol^?1.     

Synthesis of 5-O-α-and-β-d-glucopyranosyl-d-glucofuranose and 5-O-α-d-glucopyranosyl-d-fructopyranose (leucrose)

Reaction of 1,2-O-cyclopentylidene-α-d-glucofuranurono-6,3-lactone (2) with 2,3,4,6-tetra-O-acetyl-α-d-glucopyranosyl bromide (1) gave 1,2-O-cyclopentylidene- 5-O-(2,3,4,6-tetra-O-acetyl-α-d-glucopyranosyl)-α-d-glucofuranurono-6,3-lactone (3, 45%) and 1,2-O-cyclopentylidene-5-O-(2,3,4,6-tetra-O-acetyl-β-d-glucopyranosyl)-α-d-glucofuranurono-6,3-lactone (4, 38%). Reduction of 3 and 4 with lithium aluminium hydride, followed by removal of the cyclopentylidene group, afforded 5-O-α-(9) and -β-d-glucopyranosyl-d-glucofuranose (12), respectively. Base-catalysed isomerization of 9 yielded crystalline 5-O-α-d-glucopyranosyl-d-fructopyranose (leucrose, 53%).     

Synthesis and crystal structure of 7-acetamido-6,7,8-trideoxy-1,2:3,4-Di-O-isopropylidene-α-d-glycero-d-galacto-octo-pyranose

7-Acetamido-6,7,8-trideoxy-1,2:3,4-di-O-isopropylidene-α-d- and -β-l-glycero-d-galacto-octopyranoses (8) and (9), intermediates for the synthesis of analogs of the antibiotic lincomycin, have been synthesized from cis-6,7,8-trideoxy-1,2:3,4-di-O-isopropylidine-7-C-nitro-α-d-galacto-oct-6-enose (4). The configuration of C-7 in compound 8 was determined by X-ray crystallagraphy. The crystals are orthorhombic, space group P2₁,2₁2₁ with Z4, in a unit cell of dimensions a2.457(1) nm, b1.380(1) nm, and c526(1) pm. The conformation of compound 8 in the solid state is °S₂, slightly distorted towards °H₅.     

Synthesis of 2-(6-aminohexanamido)ethyl 1-thio-β-d-galactopyranoside and 1-thio-β-d-glucopyranoside,and related compounds

2-(6-Aminohexanamido)ethyl 1-thio-β-d-galactopyranoside (5) and 1-thio-β-d-glucopyranoside (9) were prepared by the following scheme: 2,3,4,6-tetra-O-acetyl-1-thio-β-d-aldopyranoses, generated from 2-S-(2,3,4,6-tetra-O-acetyl-β-d-aldopyranosyl)-2-thiopseudourea hydrobromides, were aminoethylated with ethylenimine, followed by N-acylation of the products with 6-(trifluoroacetamido)hexanoic acid (1), and O-deacylation. These reactions could be carried out consecutively without isolation of intermediates, and the products obtained after gel chromatography were de(trifluoroacetyl)ated to obtain the final products. The chain lengths of the aglycons were further extended by repeating the acylation and the de(trifluoroacetyl)ation. An analog containing glycerol in lieu of a sugar was prepared by a similar reaction-scheme.     

The crystal structure of methyl 3,4-O-isopropylidene-2,6-di-O-(2,3,4,6-tetra-O-acetyl-β-d-galactopyranosyl)-α-d-galactopyranoside at 97 K

The crystal structure of methyl 3,4-O-isopropylidene-2,6-di-O-(2,3,4,6-tetra-O-acetyl-β-d-galactopyranosyl)-α-d-galactopyranoside (1), C₃₈H₅₄O₂₄ · (C₄H₈O₂)_0.32 was determined by X-ray diffraction;1 crystallises in space group P2₁ with a = 12.480(3), b = 8.821(3), c = 21.182(4)Å, β = 98.46(3)°, and Z = 2. The structure was solved by Patterson-search and Fourier-recycling procedures and refined to R_w(R) = 0.048(0.063), using 4348 [3112 with I> 2σ(I)] independent reflections. The β-d-galactosyl rings are slightly distorted and, due to the isopropylidene group, the α-d-galactoside ring is severely distorted. The conformation near the β-(1→6) and β-(1→2) linkages between the pyranoid rings is not significantly affected by the acetyl groups, but the anomeric C-O-C bridge angles have unusual values. The C-6O-6 bond in the β-d-galactosyl group (1→2)-linked to the α-d-galactoside residue has an unusual gauche—trans conformation with respect to C-4 and O-5. The CH₃-(C = O)-O-C moieties are planar within 0.01Å, and 32.6% of all unit cells contain a molecule of ethyl acetate.     

The synthesis of methyl 4-O-(4-O-α-d-galactopyranosyl-β-d-galactopyranosyl)-β-d-glucopyranoside: The methyl β-glycoside of the trisaccharide related to Fabry's disease

As part of a program to synthesize the ceramide trisaccharide (1) related to Fabry's disease, methyl 4-O-(4-O-α-$\text{d}$-galactopyranosyl-β-$\text{d}$-galactopyranosyl)-β-$\text{d}$-glucopyranoside (12) was prepared. Methyl β-lactoside (2) was converted into methyl 4-O-(4,6-O-benzylidene-β-$\text{d}$-galactopyranosyl)-β-$\text{d}$-glucopyranoside (4). Methyl 2,3,6-tri-O-benzoyl-4-O-(2,3,6-tri-O-benzoyl-β-$\text{d}$-galactopyranosyl)-β-$\text{d}$-glucopyranoside (7) was synthesized from 4 through the intermediates methyl 2,3,6-tri-O-benzoyl-4-O-(4,6-O-benzylidene-2,3-di-O-benzoyl-β-$\text{d}$-galactopyranosyl)-β-$\text{d}$-glucopyranoside (5) and methyl 2,3,6-tri-O-benzoyl-4-O-(2,3-di-O-benzoyl-β-$\text{d}$-galactopyranosyl)-β-$\text{d}$-glucopyranoside (6). The halide-catalyzed condensation of 7 with 2,3,4,6-tetra-O-benzyl-$\text{d}$-galactopyranosyl bromide (8) gave methyl 2,3,6-tri-O-benzoyl-4-O-[2,3,6-tri-O-benzoyl-4-O-(2,3,4,6-tetra-O-benzyl-α-$\text{d}$-galactopyranosyl)- β-$\text{d}$-galactopyranosyl]-β-$\text{d}$-glucopyranoside (10). Stepwise deprotection of 10 led to 12, the methyl β-glycoside of the trisaccharide related to Fabry's disease.     

2′-Azido-2′-deoxy- and 2′-amino-2′-deoxy-β-d-arabino-furanosyl purine nucleosides

A general method for the preparation of 2′-azido-2′-deoxy- and 2′-amino-2′-deoxyarabinofuranosyl-adenine and -guanine nucleosides is described. Selective benzoylation of 3-azido-3-deoxy-1,2-O-isopropylidene-α-d-glucofuranose afforded 3-azido-6-O-benzoyl-3-deoxy-1,2-O-isopropylidene-α-d-glucofuranose (1). Acid hydrolysis of 1, followed by oxidation with sodium metaperiodate and hydrolysis by sodium hydrogencarbonate gave 2-azido-2-deoxy-5-O-benzoyl-d-arabinofuranose (3), which was acetylated to give 1,3-di-O-acetyl-2-azido-5-O-benzoyl-2-deoxy-d-arabinofuranose (4). Compound 4 was converted into the 1-chlorides 5 and 6, which were condensed with silylated derivatives of 6-chloropurine and 2-acetamido-hypoxanthine. The condensation reaction gave α and β anomers of both 7- and 9-substituted purine nucleosides. The structures of the nucleosides were determined by n.m.r. and u.v. spectroscopy, and by correlation of the c.d. spectra of the newly prepared nucleosides with those published for known purine nucleosides.     

Vacuum ultraviolet circular dichroism of (1 → 6)-β-d-glucan

V.u.c.d. spectra recorded for freshly prepared aqueous solutions of (1 → 6)-β)-D-glucan(pustulan) contained a single positive band near 177 nm. This band was similar in position and magnitude to the single positive band observed in the spectrum of (1 → 6)-α-D-glucan (dextran). Pustulan solutions (20 mg/ml) were observed to gel with time at 10 C. Concurrently, a negative band at 190 nm developed in the pustulan v.u.c.d. spectrum followed by a blue shift of both bands with continued aging. Crystalline films of pustulan yield spectra which resembled the blue shifted spectra of aged gels. The time dependent development of the negative band was attributed to pustulan attaining a helical conformation in solution, and the blue shift to aggregation of helices, Na⁺ and Ca²⁺ were found to accelerate gelation presumably by decreasing the activity of the aqueous solvent.     

Synthesis of O-β-d-mannopyranosyl-(1→4)-O-α-l-rhamnopyranosyl-(1→3)-d-galactopyranose,the trisaccharide repeating-unit of the O-specific polysaccharide from Salmonella anatum

Glycosylation of 1,2:5,6-di-O-isopropylidene-α-d-galactofuranose with 2,3-di-O-acetyl-4-O-(2,3,4,6-tetra-O-acetyl-β-d-mannopyranosyl)-α-l-rhamnopyranosyl bromide, followed by removal of the protecting groups, gave O-β-d-mannopyranosyl-(1→4)-O-α-l-rhamnopyranosyl-(1→3)-d-galactose, which is the trisaccharide repeating-unit of the O-specific polysaccharide chain of the lipopolysaccharide from Salmonella anatum. The formation of the β-d-mannopyranosyl linkage was achieved by a glucose-mannose conversion via stereoselective reduction of the corresponding oxo-disaccharide.     

β-Elimination of 2-O-(4-O-methyl-α-d-glucopyranosyluronic acid)-d-xylose with methylsulphinyl carbanion and hydrolysis of the hex-4-enopyranosiduronic linkage

On treatment with m sodium methylsulphinylmethanide at 25°, 2-O-(4-O-methyl-α-d-glucopyranosyluronic acid)-d-xylose (1) was rapidly degraded by β-elimination, to form 2-O-(4-deoxy-β-l-threo-hex-4-enopyranosyluronic acid)-d-xylose (2). The kinetics of hydrolysis of 1 and 2 in 0.5m sulphuric acid have been studied. Compound 2 was hydrolysed 70 times faster than 1. Compared with the rate coefficients of other related compounds, 2 was hydrolysed at approximately the same rate as 2-O-(4-O-methyl-α-d-glucopyranosyl)-d-xylose, 3.5 times more slowly than xylobiose, and twice as fast as the xylosidic bond in O-(4-O-methyl-α-d-glucopyranosyluronic acid)-(1→2)-O-β-d-xylopyranosyl-(1→4)-d-xylose.     

Synthesis and Biological Activity of 4-Amino-1-(β-D-ribofuranosyl)imidazo[4,5-d]pyridazin-7-one

Abstract

The Lewis acid catalyzed ribosylation of 5(4)-cyano-4(5)-(5-methyl-1,2,4-oxadiazol-3-yl)-1H-imidazole (2) with 1-O-acetyl-2,3,5-tri-O-benzoyl-B-D-ribose gave only 4-(5-methyl-1,2,4-oxadiazol-3-yl)-1-(2,3,5-tri-O-benzoy 1-B-D-ribofuranosyl)imidazole-5-carbonitrile (3). Treatment of 3 with methanolic ammonia gave 4-(5-methyl-1,2,4-oxadiazol-3-yl)-1-(6-D-ribofuranosyl)imidazole-5-carbonitrile (4). Treatment of 4 with hydrogen peroxide in ammonia gave -(5-methyl-1,2,4-oxadiazol-3-yl)-1-(B-D-ribofuranosyl)imidazole-5-carboxamide (5). When 5 was treated with sodium hydride in dimthyl-sulfoxide a rearrangement (mononuclear heterocyclic rearrangement, m.h.r.) occurred to give a modest 17% yield of 4-acetamido-1-(B-D ribofuranosyl)imidazo[4,5-d]pyridazin-7-one (6). Treatment of 6 with aqueous ammonia gave4-amino-l-(B-D-ribofuranosyl)imidazo[4,5-d]pyridazin-7-one (1). The synthesis of compound 1 using the m.h.r. for the preparation of a single regioisomer of the imidazo[4,5-d]pyridazin-7-one ring system, has demonstrated the potential of this methodology. Neither compound 5 nor 6 affected the growth or replication of human foreskin fibroblasts (HFF cells) or human cytomegalovirus (HCMV). In contrast, compound 1 inhibited the replication of HCMV (IC₅₀=29 μM) but produced visual cytotoxicity in uninfected HFF cells (IC₅₀=70μM). Compound 1 also inhibited the proliferation of L1210 murine leukemic cells (IC₅₀=25μM), whereas the precursors 4 and 6 did not.     

Synthesis of two purple-membrane glycolipids and the glycolipid sulfate O-(β-d-glucopyranosyl 3-sulfate)-(1→6)-O-α-d-mannopyranosyl-(1→2)-O-α-d-glucopyranosyl-(1→1)-2, 3-di-O-phytanyl-sn-glycerol

The two purple-membrane glycolipids O-β-d-glucopyranosyl- and O-β-d-galactopyranosyl-(1→6)-O-α-d-mannopyranosyl-(1→2)-O-α-d-glucopyranosyl-(1→1)-2, 3-di-O-phytanyl-sn-glycerol were prepared by coupling O-(2,3,4-tri-O-acetyl-α-d-mannopyranosyl)-(1→2)-O-(3,4,6-tri-O-acetyl-α-d-glucopyranosyl)-(1→1)-2, 3-di-O-phytanyl-sn-glycerol (9) with 2,3,4,6-tetra-O-acetyl-α-d-glucopyranosyl bromide or 2,3,4,6-tetra-O-acetyl-α-d-mannopyranosyl bromide, respectively, followed by deacetylation. The glycolipid sulfate O-(β-d-glucopyranosyl 3-sulfate)-(1→6)-O-α-d-mannopyranosyl-(1→2)-O-α-d-glucopyranosyl-(1→1)-2,3-di-O-phytanyl-sn-glycerol was prepared by coupling of 9 with 2,4,6-tri-O-acetyl-3-O-trichloroethyloxycarbonyl-α-d-glucopyranosyl bromide in the presence of Hg(CN)₂/HgBr₂ followed by selective removal of the 3?-trichloroethyloxycarbonyl group, sulfation of HO-3?, and deacetylation. The suitably protected key-intermediate 9 could be prepared by two distinct approaches.     

Synthesis,crystal structure,and conformation of 3-O-(6-O-acetyl-2,3-anhydro-4-deoxy-α-l-ribo-hexopyranosyl)-1,2:5,6-di-O-isopropylidene-α-d-glucofuranose

3-O-(6-O-Acetyl-2,3-anhydro-4-deoxy-α-l-ribo-hexopyranosyl)-1,2:5,6-di-O-isopropylidene-α-d-glucofuranose has been synthesised and its monocrystal investigated by X-ray diffraction methods. The compound crystallises in the orthorhombic system, space group P2₁2₁2₁, with cell constants a = 8.790(7), b = 11.678(4), and c = 21.457(10) Å. The intensity data were collected with a four-circle CAD-4 diffractometer. From a total of 1684 intensities, 1275 were of I > 2σ_I. The structure was solved by direct methods and refined by the full-matrix, least-squares procedure, resulting in R 0.057. The 4-deoxy-2,3-anhydropyranose ring is characterised by a sofa conformation (₅E), the 1,2-O-isopropylidene ring has a hybrid conformation (E + T), and the 5,6-O-isopropylidene and the α-d-glucofuranose rings have twist (T) conformations. The φ and ψ torsion angles for the glycosidic linkage are 54(4)° and 29(4)°, respectively.     

Identification of 3-O-[2-O-(β-D-xylopyranosyl)-β-D-galactopyranosyl] flavonoids in horseradish leaves acting as feeding stimulants for a flea beetle

The concentration of flavonol glycosides in leaves of Armoracia rusticana harvested at various times during the growing season has been determined. Quantitatively dominating were 3 - O - [2 - O - (β - D - xylopyranosyl) - β - D - galactopyranosyl] - quercetin and 3 - O - [2 - O - (β - D - xylopyranosyl) - β - D -galactopyranosyl] - kaempferol. The latter was present in highest concentration in leaves throughout the growing season, the highest concentration being found in spring. This compound had the highest feeding stimulatory effect towards the flea beetle Phyllotreta armoraciae. The glycosides are new natural products which have been identified by use of enzymatic and spectroscopic methods, including ¹³C NMR.     

Influence of the solvent in low temperature glycosylations with O-(2,3,5,6-tetra-O-benzyl-β-d-galactofuranosyl) trichloroacetimidate for 1,2-cis α-d-galactofuranosylation

Glycosylation studies for the construction of 1,2-cis α-linkages with O-(2,3,5,6-tetra-O-benzyl-β-d-galactofuranosyl) trichloroacetimidate (1) and several acceptors, including d-mannosyl and l-rhamnosyl derivatives were performed. The reactions were conducted at low temperatures using CH₂Cl₂, Et₂O, and acetonitrile as solvents. A non-participating solvent such as CH₂Cl₂ at −78 °C, favored the α-d-configuration. In contrast, acetonitrile strongly favored the β-d-configuration, whereas no selectivities were observed with Et₂O. The use of thiophene as an additive did not enhance the α-d-selectivity as in the pyranose counterpart. Although selectivities strongly depended on the acceptor, trichloroacetimidate 1 constitutes a valuable donor for the synthesis of α-d-Galf-(1→2)-l-Rha and α-d-Galf-(1→6)-d-Man. As these motifs are present in pathogenic microorganisms, these procedures described here are useful for the straightforward synthesis of natural oligosaccharides.     

The crystal and molecular structure of O-α-D-mannopyranosyl-(1→3)-O-β-D-mannopyranosyl-(1→4)-2-acetamido-2-deoxy-α-D-glucopyranose

The crystal structure of α-D-Manp-(1→3)-β-D-Manp-(1→4)-α-D-GlcNAcp has been determined by the direct method using the multi-solution, tangent formula, and “magic integer” procedures. The space group is P2₂, and 2 molecules are in the unit cell with a  9.894 (5), b  10.372 (6), c  11.816 (6) Å, and β  95.03° (6). The structure was refined to R 0.059 for 2099 reflections measured with Mo Kα radiation. Difference synthesis showed all the hydrogen atoms, and indicated a partial (～30%) substitution of the α-anomer molecules by the β-anomer molecules. The D-mannopyranose and the D-glucopyranose have the normal ⁴C₁ conformation; an intramolecular hydrogen-bond O-3″-H.....O-5′ (2.703 Å) stabilises the GlcNAc in relation to β-D-mannopyranose.