The reaction of 1,2:5,6-di-O-isopropylidene-α-d-ribo-hexofuranos-3-ulose with diazomethane

Dextransucrase was shown to catalyze the hydrolysis of sucrose. The hydrolytic activity was found to be directly correlatable with dextransucrase activity on poly-(acrylamide) disc-gel electrophoresis. In studies on the hydrolysis of sucrose and formation of dextran as a function of time and substrate concentration, the two activities were found to be competitive with each other. Competition was also observed between hydrolysis and the transfer of d-glucosyl groups to added acceptors. The results suggest that the three activities, namely, polymerization, d-glucosyl transfer, and hydrolysis, compete for a form of the enzyme that is common to all three reactions. It is proposed that this form may be a d-glucosylated derivative of the enzyme.     

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.     

Synthesis of p-isothiocyanatophenyl 3-O-(3,5-dideoxy-α-d-ribo-hexopyranosyl)-α-d-mannopyranoside

The synthesis of the title disaccharide derivative (1C), corresponding to the Salmonella O-factor 2¹, is described. Treatment of 2-O-benzyl-4-O-p-nitrobenzoyl-α-paratosyl bromide (5) with p-nitrophenyl 2-O-benzyl-4,6-O-benzylidene-α-d-mannoside in dichloromethane, in the presence of mercuric cyanide, gave the α- and β-linked disaccharide derivatives (6a and 6b) in yields of 34 and 5%, respectively. The disaccharide derivative 10 can react with free amino groups in proteins to produce artificial antigens useful in studies on Salmonella immunology.     

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 of 4-O-α-d-galactopyranosyl-l-rhamnose and 4-O-α-d-galactopyranosyl-2-O-β-glucopyranosyl-l-rhamnose using dioxolane-type benzylidene acetals as temporary protecting-groups

The Halide ion-catalysed reaction of benzyl exo-2,3-O-benzylidene-α-l-rhamnopyranoside with tetra-O-benzyl-α-d-galactopyranosyl bromide and hydrogenolysis of the exo-benzylidene group of the product 2 gave benzyl 3-O-benzyl-4-O-(2,3,4,6-tetra-O-benzyl-α-d-galactopyranosyl)-α-l-rhamnopyranoside (6). Compound 2 was converted into 4-O-α-d-galactopyranosyl-l-rhamnose. The reaction of 6 with tetra-O-acetyl-α-d-glucopyranosyl bromide and removal of the protecting groups from the product gave 4-O-α-d-galactopyranosyl-2-O-β-d-glucopyranosyl-l-rhamnose.     

Synthesis of phenyl O-α-l-fucopyranosyl-(1→2)-O-β-d-galactopyranosyl-(1→3)-2-acetamido-2-deoxy-α-d-galactopyranoside

phenyl 2-acetamido-2-deoxy-4,6-O-(p-methoxybenzylidene)-3-O-[4,6-O-(p-methoxybenzylidene)-β-d-alactopyranosyl]-α-d-galactopyranoside (3) was prepared from phenyl 2-acetamido-2-deoxy-4,6-O-(p-methoxybenzylidene)-3-O-(2,3,4,6-tetra-O-acetyl-β-d-galactopyranosyl)-α-d-galactopyranoside by zemplén deacetylation, followed by reaction with p-methoxybenzaldehyde in the presence of anhydrous zinc chloride. The selective benzoylation of 3 gave the 3′-benzoate which, on condensation with 2,3,4-tri-O-benzyl-α- l-fucopyranosyl bromide under catalysis by halide ion, afforded a crystalline trisaccharide from which the title trisaccharide was obtained by debenzoylation followed by catalytic hydrogenolysis.     

Practical synthesis of O-β-d-mannopyranosyl-, O-α-d-mannopyranosyl-, and O-β-d-glucopyranosyl-(1→4)-O-α-l-rhamnopyranosyl-(1→3)-d-galactoses

The koenigs-Knorr glycosylation of 4,6-O-ethylidene-1,2-O-isopropylidene-3-O-(2,3-O-isopropylidene-α-l-rhamnopyranosyl)-α-d-galactopyranose (3) by 4,6-di-O-acetyl-2,3-O-carbonyl-α-d-mannopyranosyl bromide (10), as well as Helferich glycosylations of 3 by tetra-O-acetyl-α-d-mannopyranosyl and -α-d-glucopyranosyl bromides, proceeded smoothly to give high yields of trisaccharide derivatives (12, 16, and 17). An efficient procedure for the transformation of 12, 16, and 17 into the α-deca-acetates of the respective trisaccharides has been developed. Zemplén de-acetylation then afforded the title trisaccharides in yields of 53, 52, and 62 %, respectively, from 3. A new route to 1,4,6-tri-O-acetyl-2,3-O-carbonyl-α-d-mannopyranose is suggested.     

Syntheses of 3-O-(2-acetamido-2-deoxy-β-d-glucopyranosyl)-α-d-galactopyranose (“lacto-N-biose II”) and 3,4-di-O-(2-acetamido-2-deoxy-β-d-glucopyranosyl)-d-galactopyranose

3- O-(2-Acetamido-2-deoxy-β-d-glucopyranosyl)-α-d-galactopyranose (10, “Lacto-N-biose II”) was synthesized by treatment of benzyl 6-O-allyl-2,4-di-O-benzyl-β-d-galactopyranoside with 2-methyl-(3,4,6-tri-O-acetyl-1,2-dideoxy-α-d-glucopyrano)[2,1-d]-2-oxazoline (5), followed by selective O-deallylation, O-deacetylation, and catalytic hydrogenolysis. Condensation of 5 with benzyl 6-O-allyl-2-O-benzyl-α-d-galactopyranoside, followed by removal of the protecting groups, gave 10 and a new, branched trisaccharide, 3,4-di-O-(2-acetamido-2-deoxy-β-d-glucopyranosyl)-d-galactopyranose (27).     

4-deoxy-4-fluoro-1,2-O-isopropylidene-β-D-xylo-hexulopyranose

A 5-stage synthesis of the title compound (11), the first example of a secondary deoxyfluoroketose, is described. The synthesis comprised the following reaction sequence: D-fructose→1,2:4,5-di-O-isopropylidene-β-D-fructopyranose (4)→1,2:4,5-di-O-isopropylidene-3-O-tosyl-β-D-fructopyranose (3)→ 3,4-anhydro-1,2-O-isopropylidene-β-D-ribo-hexulopyranose (9)→4-deoxy-fluoro-1,2-O-isopropylidene-β-D-xylo-hexulopyranose (11). Fluoride displacement at C-4 in 9 was effected with tetrabutyl-ammonium fluoride in methyl cyanide. Similar treatment of either 3 or 1,2:4,5-di-O-isopropylidene-3-O-tosyl-β-D-ribo-hexulopyranose (5) failed to yield a fluoro derivative. Compound 5 was prepared by the sequence 4→1,2:4,5-di-O-isopropylidene-β-D-erythro-hexo-2,3-diulopyranose (6)→1,2:4,5-di-O-isopropylidene-β-D-ribo-hexulopyranose (7)→5.     

The synthesis of 5-O-(2-acetamido-2-deoxy-α-D-glucopyranosyl)-β-D-glucofuranose

Condensation of dimeric 3,4,6-tri-O-acetyl-2-deoxy-2-nitroso-α-D-glucopyranosyl chloride (1) with 1,2-O-isopropylidene-α-D-glucofuranurono-6,3-lactone (2) gave 1,2-O-isopropylidene-5-O-(3,4,6-tri-O-acetyl-2-deoxy-2-hydroxyimino-α-D-arabino-hexopyranosyl)-α-D-glucofuranurono-6,3-lactone (3). Benzoylation of the hydroxyimino group with benzoyl cyanide in acetonitrile gave 1,2-O-isopropylidene-5-O-(3,4,6-tri-O-acetyl-2-benzoyloxyimino-2-deoxy-α-D-arabino-hexopyranosyl)-α-D-glucofuranurono-6,3-lactone (4). Compound 4 was reduced with borane in tetrahydrofuran, yielding 5-O-(2-amino-2-deoxy-α-D-glucopyranosyl)-1,2-O-isopropylidene-α-D-glucofuranose (5), which was isolated as the crystalline N-acetyl derivative (6). After removal of the isopropylidene acetal, the pure, crystalline title compound (10) was obtained.     

Nucleophilic displacements of methyl 2,3-O-isopropylidene-4-O-toluene-p-sulphonyl-α-d-lyxo- and -β-l-ribo-pyranosides,and deamination of the corresponding 4-amino sugars

Reinvestigation of the reaction of methyl 2,3-O-isopropylidene-4-O-toluene-p-sulphonyl-α-d-lyxopyranoside (4) with azide ion has shown that methyl 4-deoxy-2,3-O-isopropylidene-β-l-erythro-pent-4-enopyranoside (8, ～51.5%) is formed, as well as the azido sugar 7 (～48.5%) of an S_N2 displacement. The unsaturated sugar 8 was more conveniently prepared by heating the sulphonate 4 with 1,5-diazabicyclo-[5.4.0]undec-5-ene. An azide displacement on methyl 2,3-O-isopropylidene-4-O-toluene-p-sulphonyl-β-l-ribopyranoside (12) furnished methyl 4-azido-4-deoxy-2,3-O-isopropylidene-α-d-lyxopyranoside (13, ～66%) and the unsaturated sugar 14 (～28.5%), which was also prepared by heating the sulphonate with 1,5-diazabicyclo[5.4.0]undec-5-ene. Deamination of methyl 4-amino-4-deoxy-2,3-O-isopropylidene-α-d-lyxopyranoside (5), prepared by reduction of 13, with sodium nitrite in 90% acetic acid at ～0°, yielded methyl 2,3-O-isopropylidene-α-d-lyxopyranoside (10a, 26.2%), methyl 2,3-O-isopropylidene-β-l-ribofuranoside (21a, 18.4%), and the corresponding acetates 10b (34.5%) and 21b (21.3%). These products are considered to arise by solvolysis of the bicyclic oxonium ion 29, formed as a consequence of participation by the ring-oxygen atom in the deamination reaction. Similar deamination of methyl 4-amino-4-deoxy-2,3-O-isopropylidene-β-l-ribopyranoside (6) afforded, exclusively, the products 10a (34.4%) and 10b (65.6%) of inverted configuration. Deamination of methyl 5-amino-5-deoxy-2,3-O-isopropylidene-β-d-ribofuranoside (20) gave 22ab, but no other products. An alternative synthesis of the amino sugars 5 and 6 is available by conversion of 10a into methyl 2,3-O-isopropylidene-β-l-erythro-pentopyranosid-4-ulose (11), followed by reduction of the derived oxime 15 with lithium aluminium hydride.     

Synthesis of 2,5-dideoxy-2-C-methyl-d-arabinose derivatives from methyl 2,3-anhydro-5-deoxy-α-d-ribofuranoside

Treatment of methyl 2,3-anhydro-5-deoxy-α-d-ribofuranoside with lithium dimethyl cuprate gave methyl 2,5-dideoxy-2-C-methyl-α-d-arabinofuranoside (54% yield) and methyl 3,5-dideoxy-3-C-methyl-α-d-xylofuranoside (10%). The former was converted into its 3-O-acetyl and 3-O-benzyl derivatives, which, upon acid hydrolysis, afforded 3-O-acetyl- and 3-O-benzyl-2,5-dideoxy-2-C-methyl-d-arabinofuranose in 60–75% overall yield. Treatment of the 3-O-benzyl compound with ethanethiol in the presence of trifluoromethanesulfonic acid afforded 3-O-benzyl-2,5-dideoxy-2-C-methyl-d-arabinose diethyl dithioacetal (20%) and ethyl 3-O-benzyl-2,5-dideoxy-2-C-methyl-1-thio-α-d-arabinoside (73%). The former, which was also available from the latter by equilibration in acidic ethanethiol, was acetylated at O-4 and the product converted into the corresponding dimethyl acetal (85% overall yield). This compound was, after debenzylation, hydrolyzed with acid, to provide 4-O-acetyl-2,5-dideoxy-2-C-methyl-d-arabinose in 70% overall yield.     

Luteolin 3′,4′-di-O-β-d-glucuronide and luteolin 3′-O-β-d-glucuronide from Lunularia cruciata

Luteolin 3′,4′-di-O-β-d-glucuronide is the major flavonoid in the liverwort Lunularia cruciata. It is accompanied by small amounts of luteolin 3′-O-β-d-glucuronide. Both are new natural products and the former appears to be a unique example of a 3′,4′-diglycosylated flavonoid. Luteolin 4′-O-β-d-glucuronide was isolated as a hydrolysis product of the diglucuronide.     

A synthesis of 3-O-(α-d-mannopyranosyl)-d-mannose and its protein conjugate

Methods for the synthesis of 3-O-(α-d-mannopyranosyl)-d-mannose and 2-(4-aminophenyl)ethyl 3-O-(α-d-mannopyranosyl)-α-d-mannopyranoside have been investigated by a number of sequences. Glycosidations with 2,3-di-O-acetyl-4,6-di-O-benzyl-d-mannopyranosyl and 2-O-benzoyl-3,4,6-tri-O-benzyl-d-mannopyranosyl p-toluenesulfonates were found to give better yields than the Helferich modification, the use of a peracylated d-mannopyranosyl halide, or the use of triflyl leaving group. Only the α anomer was obtained. Factors influencing glycosidation reactions are discussed. A mercury(II) complex was used for selective 2-O-acylation of 4,6-di-O-benzyl-α-d-mannopyranosides. A disaccharide—protein conjugate was prepared by the isothiocyanate method.     

Synthesis and 13C-N.M.R. spectroscopy of 2-O- and 6-O-acetyl-3-O-α-l-rhamnopyranosyl-d-galactose,constituents of bacterial cell-wall polysaccharides

Benzyl 2-O-acetyl-4,6-O-benzylidene-3-O-(2,3,4-tri-O-acetyl-α-l-rhamnopyranosyl)-β-d-galactopyranoside (11) has been synthesised by two routes. Partial deacetylation of 11 and then acid hydrolysis yielded benzyl 2-O-acetyl-3-O-α-l-rhamnopyranosyl-β-d-galactopyranoside, catalytic hydrogenolysis of which gave the first title compound in excellent yield. Benzyl 4,6-O-benzylidene-3-O-α-l-rhamnopyranosyl-β-d-galactopyranoside was benzylated, and hydrogenolysis (LiAlH₄-AlCl₃) of the product gave the disaccharide derivative 16 with only HO-6 unsubstituted. Acetylation of 16 followed by catalytic hydrogenolysis gave the crystalline, second title compound. As model compounds for comparative n.m.r. studies, 2-O-, 3-O-, and 6-O-acetyl-d-galactose were also synthesised.     

Branched-chain amino sugars. stereospecific synthesis of 3-C-(2-acetamidoethyl)-3-deoxy-1,2-O-isopropylidene-β-l-lyxofuranose

Condensation of 1,2:5,6-di-O-isopropylidene-α-d-xylo-hexofuranos-3-ulose (1) with diethyl cyanomethylphosphonate afforded a mixture of the cis- and trans-3-cyanomethylene-3-deoxy-1,2:5,6-di-O-isopropylidene-α-d-xylo-hexofuranoses (2) in 80% yield. Catalytic reduction of 2 yielded 3-C-cyanomethyl-3-deoxy-1,2:5,6-di-O-isopropylidene-α-d-gulofuranose (4) exclusively. Palladium and hydrogen was found to rearrange the exocyclic double bond of 2 to give the 3,4-ene (3). Catalytic reduction of 3 also proceeded stereospecifically to yield 4. Selective hydrolysis of 4 yielded the diol 5, which was cleaved with periodate and the product reduced with sodium borohydride to afford crystalline 3-C-cyanomethyl-3-deoxy-1,2-O-isopropylidene-β-l-lyxofuranose (6) in 87% yield. Catalytic reduction of the latter with hydrogen and platinum in the presence of acetic anhydride and ethanol gave the crystalline l-amino sugar, 3-C-(2-acetamidoethyl)-3-deoxy-1,2-O-isopropylidene-β-l-lyxofuranose (7) in 92% yield.     

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%.     

Synthesis of 4-O-β-D-mannopyranosyl-L-rhamnopyranose

The title disaccharide (16) has been synthesized in 50% overall yield by way of condensation of 4,6-di-O-acetyl-2,3-O-carbonyl-α-D-mannopyranosyl bromide 5 with methyl 2,3-O-isopropylidene-α-L-rhamnopyranoside (1) in chloroform solution, in the presence of silver oxide. The disaccharide was characterized as the crystalline isopropyl alcoholate of methyl 4-O-β-D-mannopyranosyl-α-L-rhamnopyranoside (11) and as 1,2,3-tri-O acetyl-4-O- (2,3,4,6-tetra-O-acetyl-β-D-mannopyranosyl)-α-L-rhamnopyranose (15). Methyl β-D-mannopyranoside isopropyl alcoholate 7 was readily obtained in 85% yield via the reaction of bromide 5 with methanol.Reduction of 2,3-di-O-methyl-L-rhamnose with sodium borohydride, followed by acetylation, may result in the formation of an appreciable proportion of a boric ester, namely 1,5-di-O-acetyl-4-deoxy-2,3-di-O-methyl-L-rhamnitol-4-yl dimethyl borate, depending on the procedure used.