Rhamnazin- und rhamnetin-3-O-trioside aus Rhamnus petiolaris

From the fruits of Rhamnus petiolaris two new flavonol-3-O-triosides were isolated and identified as rhamnazin-3-O-[α-l-rhamnopyranosyl (1 → 4)-α-l-rhamnopyranosyl (1 → 6)]-β-d-galactopyranoside and rhamnetin-3-O-α-l-rhamnopyranosyl (1 → 2)-α-l-rhamnopyranosyl (1 → 6)]-β-d-galactopyranoside, respectively.     

7-O-methyl-(2R:3R)-dihydroquercetin 5-O-β-D-glucoside and other flavonoids from Podocarpus nivalis

In the course of a chemotaxonomic survey of New Zealand Podocarpus species, a number of new flavonoid glycosides have been isolated from P. nivalis. These are: luteolin 3′-O-β-D-xyloside, luteolin 7-O-β-D-glucoside-3′-O-β-D-xyloside, dihydroquercetin 7-O-β-D-glucoside, 7-O-methyl-(2R:3R)-dihydrokaempferol 5-O-β-D-glucopyranoside, 7-O-methyl-(2R:3R)-dihydroquercetin 5-O-β-D-glucopyranoside, 7-O-methylkaempferol 5-O-β-D-glucopyranoside and 7-O-methylquercetin 5-O-β-D-glucopyranoside. Diagnostically useful physical techniques for distinguishing substitution patterns in dihydroflavonols are discussed and summarized. Glucosylation of the 5-hydroxyl group in (+)-dihydroflavonols is shown to reverse the sign of rotation at 589 nm.     

Enzyme kinetics of ginsenosidase type IV hydrolyzing 6-O-multi-glycosides of protopanaxatriol type ginsenosides

In this work, the kinetics of ginsenosidase type IV hydrolyzing the 6-O-multi-glycosides of protopanaxatriol type ginsenosides (PPT) from Aspergillus sp.39g strain were investigated. The enzyme molecular weight was about 56 kDa. The enzyme hydrolyzes the 6-O-α-l-(1 → 2)-rhamnoside of ginsenoside Re and 6-O-β-d-(1 → 2)-xyloside of R1 into Rg1, and subsequently hydrolyzes 6-O-β-d-glucoside of Rg1 into F1. The enzyme hydrolyzes 6-O-α-l-(1 → 2)-rhamnoside of Rg2 and 6-O-β-d-(1 → 2)-glucoside of Rf into Rh1, and subsequently hydrolyzes 6-O-β-d-glucoside of Rh1 into its aglycone. The enzyme K_m and V_max for Re were 22.2 mM, and 7.94 mM/h; the K_m and V_max for R1 were 7.06 mM and 1.61 mM/h; the enzyme transformation velocity (V₀) at 5 mM substrate was 1.46 mM/h for Re, and 0.67 mM/h for R1. Therefore, the enzyme hydrolysis on the Re rhamnoside was faster than that on R1 xyloside. The enzyme V₀ on Rg1 was 0.05 mM/h that indicated the enzyme hardly hydrolyzed the 6-O-β-d-glucoside of Rg1. The enzyme kinetic parameters of Rg2 and Rf were 5.74 and 9.43 mM for K_m; 2.70 and 2.84 mM/h for V_max; 1.26 and 0.98 mM/h for V₀ at 5 mM substrate, respectively. Thus the enzyme hydrolysis on Rg2 rhamnoside was faster than that on the glucoside of Rf.     

Structures of 3,28-O-bisglycosidic triterpenoid saponins of Fatsia japonica

Four novel 3,28-O-bisglycosidic triterpenoid saponins were isolated from the mature fruits of F. japonica. They were characterized as the 28-O-α-l-rhamnopyranosyl-(1 → 4)-β-d-glucopyranosyl-(1 → 4)-β- d-glucopyranosides of 3-O-α-l-arabinopyranosyl echinocystic acid, 3-O-α-l-arabinopyranosyl hederagenin, 3-O-β-d-glucopyranosyl-(1 → 2)-α-l-arabinopyranosyl oleanolic acid and 3-O-β- d-glucopyranosyl-(1 → 2)-α-l-arabinopyranosyl hederagenin respectively.     

The preparation of 6-deoxy-3-O-methyl-6-nitro-D-altrose

The title compound(9) a new nitro sugar and potential starting-point for the synthesis of hitherto unknown stereoisomers in the deoxynitroinositol series, was prepared by a sequence of high-yielding reactions. Methyl 2.3-anhydro-4.6-O- benzylidene-α-D-mannopyranoside was converted into methyl 3-O-methyl-α-D-altropyranoside(3) by the action of sodium methoxide followed by debenzylidenation esssentially according to established procedures. Acetolysis of3 and subsequent Zemple´n transesterification gave syrupy 3-O-methyl-D-altrose, from which the furanoid 1,2:5.6-di-O-isopropylidene and 1,2-O-isopropylidene(7) derivatives were prepared by standard acetonation and partial Hydrolysis Periodate oxidation of 7, and addition of nitromethane to the product. furnished crystalline 6-deoxy-1.2-O-isopropylidene-3-O-methyl-6-nitro-β-D-altrofuranose(8) as the chief epimer. Deacetonation of8 by trifluoroacetic acid9 in crystalline form.     

Synthesis of 4-O-glycosylated 1,5-anhydro-d-fructose and of 1,5-anhydro-d-tagatose from a common intermediate 2,3-O-isopropylidene-d-fructose

Four novel disaccharides of glycosylated 1,5-anhydro-d-ketoses have been prepared: 1,5-anhydro-4-O-β-d-glucopyranosyl-d-fructose, 1,5-anhydro-4-O-β-d-galactopyranosyl-d-fructose, 1,5-anhydro-4-O-β-d-glucopyranosyl-d-tagatose, and 1,5-anhydro-4-O-β-d-galactopyranosyl-d-tagatose. The common intermediate, 1,5-anhydro-2,3-O-isopropylidene-β-d-fructopyranose, was prepared from d-fructose and was converted into the d-tagatose derivative by oxidation followed by stereoselective reduction to the 4-epimer. The anhydroketoses thus prepared were glycosylated and deprotected to give the disaccharides.     

Preparation and structure of 1,2,6,2,′3′,4′,6′-hepta-O-benzoyl-β-cellobiose and 6-O-benzoylcellobiose

1,2,6,2′,3′,4′,6′-hepta-O-benzoyl-β-cellobiose (1) was prepared and its structure ascertained. Ammonolysis of 1 gave 6-O-benzoylcellobiose and cellobiose.     

Differential turnover of isoflavone 7-O-glucoside-6″-O-malonates in Cicer arietinum roots

Pulse labelling experiments and studies with a molecular inhibitor of phenylalanine ammonia lyase showed that in roots of Cicer arietinum formononetin 7-O-glucoside-6″-O-malonate is rapidly metabolized whereas biochanin A 7-O-glucoside-6″-O-malonate appears to be metabolically rather inert.     

13C-N.M.R. characterizations of the sarsasapogenin disaccharides,the filiferins a and b: 2-O-(β-d-xylopyranosyl)- and 2-O(β-d-glucopyranosyl)-β-d-galactopyranosides

Filiferin B is identical to timosaponin A-III, which had previously been shown to be 3-O-[2-O-(β-d-glucopyranosyl)-β-d-galactopyranosyl]sarsasapogenin. A larger-scale isolation of filiferin B from the seeds of Yucca filifera led to the isolation of filiferin A, now shown to be 3-O-[2-O-β-d-xylopyranosyl)-β-d-galactopyranosyl]-sarsasapogenin. The presence of the xylose residue was established by way of hydrolysis. 8-Methoxycarbonyloctyl 2-O-(β-d-glucopyranosyl)-β-d-galactopyranoside was synthesized to serve as a model for interpretation of the ¹³C-n.m.r. spectrum of filiferin B. The information thus gained, together with the ¹³C-n.m.r. spectra of other, simple model-compounds, permitted assignment of the structure for filiferin A. 8-Methoxycarbonyloctyl 2-O-(α-d-glucopyranosyl)-β-d-galactopyranoside was also synthesized.     

Apigenin 4′-O-β-d-glucoside 7-O-β-d)- glucuronide: The copigment in the blue pigment of Centaurea cyanus

The copigment present in the crystalline blue pigment isolated from Blue Boy cornflowers (Centaurea cyanus L.) was identified as apigenin 4′-O-β-glucoside 7-O-β-d-glucuronide. The NMR spectra of aryl glucuronides are discussed.     

Syntheses of 2-acetamido-2-deoxy-4-O-α-D-glucopyranosyl-α-d-glucopyranose (n-acetylmaltosamine) and 2-acetamido-2-deoxy-4-O-β-d-glucopyranosyl-α-d-glucopyranose

Condensation of benzyl 2-acetamido-3,6-di-O-benzyl-2-deoxy-α-D-glucopyranoside with 2,3,4,6-tetra-O-benzyl-1-O-(N-methyl)acetimidoyl-β-D-glucopyranose gave benzyl 2-acetamido-3,6-di-O-benzyl-2-deoxy-4-O-(2,3,4,6-tetra-O-benzyl-α-D-glucopyranosyl)-α-D-glucopyranoside which was catalytically hydrogenolysed to crystalline 2-acetamido-2-deoxy-4-O-α-D-glucopyranosyl-α-D-glucopyranose (N-acetylmaltosamine). In an alternative route, the aforementioned imidate was condensed with 2-acetamido-3-O-acetyl-1,6-anhydro-2-deoxy-β-D-glucopyranose, and the resulting disaccharide was catalytically hydrogenolysed, acetylated, and acetolysed to give 2-acetamido-1,3,6-tri-O-acetyl-2-deoxy-4-O-(2,3,4,6-tetra-O-acetyl-α-D-glucopyranosyl)-α-D-glucopyranose Deacetylation gave N-acetylmaltosamine. The synthesis of 2-acetamido-2-deoxy-4-O-β-D-glucopyranosyl-α-D-glucopyranose involved condensation of benzyl 2-acetamido-3,6-di-O-benzyl-2-deoxy-α-D-glucopyranoside with 2,3,4,6-tetra-O-acetyl-α-D-glucopyranosyl bromide in the presence of mercuric bromide, followed by deacetylation and catalytic hydrogenolysis of the condensation product.     

Synthesis of 3-O Substituted D-Mannoses

1,2,4,6-Tetra-O-acetyl-3-O-benzyl-α-D-mannopyranose (7) was obtained in good yield from 3,4,6-tri-O-benzyl-1,2-O-(1-methoxyethylidene)-β-D-mannopyranose (1) by acetolysis. Hydrogenolysis of 7 afforded 1,2,4,6-tetra-O-acetyl-α-D-mannopyranose which is a versatile intermediate for the preparation of other 3-O-substituted D-mannoses, such as 3-O-methyl-D-mannose and 3-O-α-D-mannopyranosyl-D-mannose. 3,4-Di-O-methyl-D-mannose was readily prepared from 1,2,6-tri-O-acetyl-3,4-di-O-benzyl-α-D-mannopyranose, which was also obtained from 1 by controlled acetolysis.     

Cycloartane-type glycosides from Astragalus amblolepis

Five cycloartane-type triterpene glycosides were isolated from the methanol extract of the roots of Astragalus amblolepis Fischer along with one known saponin, 3-O-β-D-xylopyranosyl-16-O-β-D-glucopyranosyl-3β,6α,16β,24(S),25-pentahydroxy-cycloartane. Structures of the compounds were established as 3-O-β-D-xylopyranosyl-25-O-β-D-glucopyranosyl-3β,6α,16β,24(S),25-pentahydroxy-cycloartane, 3-O-[β-D-glucuronopyranosyl-(1 → 2)-β-D-xylopyranosyl]-25-O-β-D-glucopyranosyl-3β,6α,16β,24(S),25-pentahydroxy-cycloartane, 3-O-β-D-xylopyranosyl-24,25-di-O-β-D-glucopyranosyl-3β,6α,16β,24(S),25-pentahydroxy-cycloartane, 6-O-α-L-rhamnopyranosyl-16,24-di-O-β-D-glucopyranosyl-3β,6α,16β,24(S),25-pentahydroxy-cycloartane, 6-O-α-L-rhamnopyranosyl-16,25-di-O-β-D-glucopyranosyl-3β,6α,16β,24(S),25-pentahydroxy-cycloartane by using 1D and 2D-NMR techniques and mass spectrometry. To the best of our knowledge, the glucuronic acid moiety in cycloartanes is reported for the first time.     

Synthesis and characterization of propyl O-β-d-galactopyranosyl-(1→4)-O-β-d-galactopyranosyl-(1→4)-α-d-galactopyranoside

Allyl 4-O-(4-O-acetyl-2-O-benzoyl-3,6-di-O-benzyl-β-d-galactopyranosyl)-2-O-benzoyl-3,6-di-O-benzyl-α-d- galactopyranoside was O-deallylated to give the 1-hydroxy derivative, and this was converted into the corresponding 1-O-(N-phenylcarbamoyl) derivative, treatment of which with dry HCl produced the α-d-galactopyranosyl chloride. This was converted into the corresponding 2,2,2-trifluoroethanesulfonate, which was coupled to allyl 2-O-benzoyl-3,6-di-O-benzyl-α-d-galactopyranoside, to give crystalline allyl 4-O-[4-O-(4-O-acetyl-2-O-benzoyl-3,6-di-O-benzyl-β-d-galactopyranosyl)-2-O-benzoyl-3,6-di- O-benzyl-β-d-galactopyranosyl]-2-O-benzoyl-3,6-di-O-benzyl-α-d-galactopyranoside (15) in 85% yield, no trace of the α anomer being found. The trisaccharide derivative 15 was de-esterified with 2% KCN in 95% ethanol, and the product O-debenzylated with H₂-Pd, to give the unprotected trisaccharide. Alternative sequences are discussed.     

Synthesis,crystal structure,and conformation of 1(S)-acetoxy-3-[6(R)-O-benzyl-1,2:3,4-di-O-isopropylidene-α-d-galactopyranos-6-yl]-1-(methyl 2,3,4-tri-O-benzyl-6-deoxy-β-d-galactopyranosid-6-yl)propyne

Condensation of 6-O-benzyl-7,8-dideoxy-1,2:3,4-di-O-isopropylidene-d-glycero-α-d-galacto-oct-7-ynopyranose with methyl 2,3,4-tri-O-benzyl-6-deoxy-β-d-galacto-heptodialdo-1,5-pyranoside afforded a 2:1 mixture of the 1S and 1R isomers (1a and 1b) of 3-[6(R)-O-benzyl-1,2:3,4-di-O-isopropylidene-α-d-galactopyranos-6-yl]-1-hydroxy-1-(methyl 2,3,4-tri-O-benzyl-6-deoxy-β-d-galactopyranosid-6-yl)propyne. A single crystal of the 1-O-acetyl derivative (1c) of 1a was investigated by X-ray diffraction methods in a four-circle diffractometer. Compound 1c crystallises in the monoclinic system, space group P2₁ (Z = 2) with cell dimensions a = 14.896(2), b = 8.295(1), c = 20.547(3) Å, and β = 102.66(1)°. The structure was solved by direct methods and refined by a full-matrix, least-squares procedure against 3839 unique reflections (F > 2σ_F), resulting in a final R = 0.045 (unit weights). The configuration at the new chiral center (C-1) was established as S(d). The galactopyranose rings have conformations ⁴C₁ (tri-O-benzylated moiety) and °S₅ + °T₂ (di-O-isopropylidenated moiety). The 1,2- and 3,4-O-isopropylidene rings have ³T₂ and ²E conformations, respectively.     

Oligofuro- and spiro-stanosides of Asparagus adscendens

Two oligofurostanosides and two spirostanosides, isolated from a methanol extract of Asparagus adscendens (leaves), were characterized as 3-O-[{α-l-rhamnopyranosyl (1 → 4)} {α-l-rhamnopyranosyl (1 → 6)}-β-d-glucopyranosyl]-26-O-[β-d-glucopyranosyl]-22α-methoxy-(25S)-furost-5-en-3β,26-diol (Adscendoside A), 3-O-[{α-l-rhamnopyranosyl (1 → 4)} {α-l-rhamnopyranosyl (1 → 6)}-β-d-glucopyranosyl]-26-O-[β-d-glucopyranosyl]-(25S)-furost-5-en-3β,22α,26-triol-(Adscendoside B), 3-O-[{α-l-rhamnopyranosyl (1 → 6)}-β-d-glucopyranosyl]-(25S)-spirostan-5-en-3β-ol (Adscendin A) and 3-O-[{α-l-rhamnopyranosyl (1 → 4)} {α-l-rhamnopyranosyl (1 → 6)}-β-d-glucopyr anosyl]-(25S)-spirostan-5-en-3β-ol (Adscendin B), respectively. Adscendin B and Adscendoside A are the artefacts of Adscendoside B formed through hydrolysis and methanol extraction respectively.bl]     

Stereoselective Synthesis of 2,3-O-Isopropylidene-DL-Ribofuranose and Methyl β-DI-Ribopyranoside from furfuryl alcohol

Methyl 2,3-dideoxy-DL-pent-2-enopyranosid-4-ulose (2) and 1-O-benzoyl-2,3- dideoxy-DL-pent-2-enopyranos-4-ulose (3), obtained from furfuryl alcohol, gave methyl β-DL-erythro-pentopyranosid-4-ulose (6) and 1-O-benzoyl-β-DL-erythro-pentopyranos-4-ulose (7), respectively, on cis-hydroxylation with silver chlorate- osmium tetroxide. Reduction of the isopropylidene derivatives (8 and 9) of 6 and 7 with lithium aluminium hydride and sodium borohydride, respectively, afforded DL-ribose derivatives.     

Chemical synthesis of 1-O-alkyl and 1-O-acyl dihydroxyacetone-3-phosphate

A method for the chemical synthesis of 1-O-hexadecyl dihydroxyacetone-3-phosphate is described. The synthesis was started with the preparation of O-hexadecyl glycolic acid by condensing 1-iodohexadecane with ethyl glycolate in the presence of silver oxide, followed by saponification and free acid liberation with HC1. O-Hexadecyl glycolic acid was converted to the acid chloride (with oxalyl chloride) which was condensed with diazomethane in diethyl ether to form hexadecyloxy diazoacetone. The diazoketone was decomposed by H₃PO₄ in dioxane to give the desired product, 1-O-hexadecyl dihydroxyacetone-3-phosphate. The product was purified by chromatography on silicic acid column followed by an acid wash. The final yield was 50% starting from O-hexadecyl glycolic acid. Analytical, spectral (IR, NMR) and chromatographic properties of 1-O-hexadecyl dihydroxyacetone-3-phosphate are described. The method described here may be used to prepare different acyl and alkyl derivatives of dihydroxyacetone phosphate in good yield as illustrated by describing the procedure for the synthesis of 1-O-palmitoyl dihydroxyacetone-3-phosphate, 1-O-hexadecyl dihydroxyacetone-3-[³²P] phosphate and the dimethyl ketal of 1-O-palmitoyl [2-¹⁴C]dihydroxyacetone phosphate.     

Synthèse de nucléosides pyrimidiquesàpartir de 1,2-anhydro-4-désoxy-3-O-méthyl-pentopyranoses

Monotosylation of 4-deoxy-3-O-methyl-dl-threo- and -erythro-pentopyranose led, in 62–68% yield, to the 2-O-tosyl derivatives which, on treatment at room temperature with sodium hydride in anhydrous ether, gave quantitatively 1,2-anhydro-4-deoxy-3-O-methyl-dl-threo- and -erythro-pentopyranose, respectively. These epoxides reacted with 2,4-dimethoxypyrimidine in the presence of pyridinium hydrochloride to give, in 68–78% yield, 1-(4-deoxy-3-O-methyl-β-dl-erythro- and -α,β-dl-threo-pentopyranosyl)-4-methoxy-2-pyrimidinone, respectively. Isomers having a trans-1′,2′ configuration were preponderantly formed by an Sn2 reaction.     

Synthesis of the tetrasaccharide repeating-unit of the O-specific polysaccharide from Salmonella senftenberg

The oligosaccharide β-d-Man-(1 → 4)-α-l-Rha (1 → 3)-d-Gal-(6 ← 1)-α-d-Glc, which is the repeating unit of the O-specific polysaccharide chain of the lipopolysaccharide from Salmonella senftenberg, was obtained by glycosylation of benzyl 2,4-di-O-benzyl-6-O-(2,3,4-tri-O-benzyl-6-O-p-nitrobenzoyl-α-d-glucopyranosyl)-β-d-galactopyranoside or benzyl 2-O-acetyl-6-O-(2,3,4-tri-O-benzyl-6-O-p-nitrobenzoyl-α-d-glucopyranosyl)-β-d-galactopyranoside with 3-O-acetyl-4-O-(2,3,4,6-tetra-O-acetyl-β-d-mannopyranosyl)-β-l-rhamnopyranose 1,2-(methyl orthoacetate) followed by removal of protecting groups.