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1.
The thermal decomposition of methyl 4,6-O-benzylidene-2,3-di-O-[(methylthio)-thiocarbonyl]-α-d-glucopyranoside afforded methyl 4,6-O-benzylidene-2-thio-α-d-mannopyranoside 3-O,2-S-(S,S-dimethyl trithioorthocarbonate) and methyl 4,6-O-benzylidene-3-thio-α-d-allopyranoside 2-O,3-S-(S,S-dimethyl trithioorthocarbonate) in good yield. This decomposition can be generalized to 1,3-diols derived from sugars. Thus methyl 2,3-di-O-methyl-4,6-di-O-[(methylthio)thiocarbonyl]-α-d-glucopyranoside afforded in the same way the corresponding trithioorthocarbonates, following a regioselective process. The structures of these trithioorthocarbonates are confirmed by spectral and chemical proofs. 相似文献
2.
Fred R. Seymour Morey E. Slodki Ronald D. Plattner Larry W. Tjarks 《Carbohydrate research》1976,46(2):189-193
A new route is described for preparing methyl 4,6-di-O-methyl-α-d-mannopyranoside (5) via methyl 2,3-di-O-p-tolylsulfonyl-α-d-mannopyranoside (3) as an intermediate. The retention of the mannopyranoside configuration and ring form was confirmed by proton n.m.r. spectroscopy and by m.s. of peracetylated aldononitrile derivatives. Mass-spectral fragmentation-pathways previously proposed were confirmed for 5-O-acetyl-2,3,4,6-tetra-O-methyl-, 2,5-di-O-acetyl-3,4,6-tri-O-methyl-, and 3,5-di-O-acetyl-2,4,6-tri-O-methyl-d-mannononitrile. 相似文献
3.
Roger W. Jeanloz 《Carbohydrate research》1982,99(1):51-58
Methanolysis of methylated hyaluronic acid, followed by acetylation, gave, in 70% yield, crystalline methyl 2-acetamido-2-deoxy-4,6-di-O-methyl-3-O-(methyl 4-O-acetyl-2,3-di-O-methyl-β-d-glucopyranosyluronate)-α-d-glucopyranoside. Removal of the O-acetyl and methyl ester groups gave compounds that are useful in the investigation, by 1H-n.m.r. spectroscopy, of interaction within chains of hyaluronic acid in solution. 相似文献
4.
Purified, bael-gum polysaccharide containsd-galactose (71%),l-arabinose (12.5%),l-rhamnose (6.5%), andd-galacturonic acid (7%). Hydrolysis of one mole of the fully methylated polysaccharide gave: (a) from the neutral part, 2,3,4-tri-O-methyl-l-rhamnose (2 moles), 2,3,5-tri-O-methyl-l-arabinose (4 moles), 2,3,4,6-tetra-O-methyl-d-galactose (8 moles), 3,4-di-O-methyl-l-rhamnose (2 moles), 2,5-di-O-methyl-l-arabinose (1 mole), 2,4,6-tri-O-methyl-d-galactose (10 moles), 2,3-di-O-methyl-l-arabinose (1 mole), 2,4-di-O-methyl-d-galactose (14 moles), and 2-O-methyl-d-galactose (2 moles); and (b) from the acidic part, 2,3,4-tri-O-methyl-d-galacturonic acid (1 mole), 2,4,6-tri-O-methyl-3-O-(2,3,4-tri-O-methyl-d-galactopyranosyluronic acid)-d-galactose (2.6 moles), and 2,4,6-tri-O-methyl-3-O-[2,4,6-tri-O-methyl-3-O-(2,3,4-tri-O-methyl-d-galactopyranosyluronic acid)-d-galactopyranosyl]-d-galactose (1 mole). Mild hydrolysis of the whole gum yielded oligosaccharides from which 3-O-β-d-galactopyranosyl-l-arabinose, 5-O-β-d-galactopyranosyl-l-arabinose, 3-O-β-d-galactopyranosyl-d-galactose, and 6-O-β-d-galactopyranosyl-d-galactose could be isolated and characterized. The results of methylation, periodate oxidation, Smith degradation, Barry degradation, and graded hydrolysis studies were employed for the elucidation of the structure of the whole gum. 相似文献
5.
The azide displacement reaction on methyl 6-deoxy-4-O-methanesulphonyl-2,3-di-O-methyl-α-l-talopyranoside (6) in N,N-dimethylformamide yielded methyl 4,6-dideoxy-2,3-di-O-methyl-α-l-threo-hex-3-enopyranoside (7, ca. 50%), methyl 4,6-dideoxy-2,3-di-O-methyl-β-d-erythro-hex-4-enopyranoside (8, ca. 10%), and methyl 4-azido-4,6-dideoxy-2,3-di-O-methyl-α-l-mannopyranoside (9, ca. 40%). The corresponding azide 14 (20%) and the unsaturated sugars 12 (68%) and 13 (12%) were obtained from a comparable reaction on benzyl 6-deoxy-4-O-methanesulphonyl-2,3-di-O-methyl-α-l-talopyranoside (11). 相似文献
6.
The reaction of 1,2:5,6-di-O-isopropylidene-3-C-methylene-α-D-ribo-hexofuranose (4) with mercuric azide in hot 50% aqueous tetrahydrofuran yielded, after reductive demercuration, 3-azido-3-deoxy-1,2:5,6-di-O-isopropylidene-3-C-methyl-α-D-glucofuranose (5). Partial, acid hydrolysis of5 afforded the diol7, which gave 3-azido-3-deoxy-1,2-O-isopropylidene-5,6-di-O-methanesulphonyl-3-C-methyl-α-D-glucofuranose (8) on sulphonylation. On hydrogenation over a platinum catalyst and N-acetylation, the dimethanesulphonate 8 furnished 3,6-acetylepimino-3,6-dideoxy-1,2-O-isopropylidene-5-O-methanesulphonyl-3-C-methyl-α-D-glucofuranose (9), which was also prepared by an analogous sequence of reactions on 3-azido-3-deoxy-1,2-O-isopropylidene-5-O-methanesulphonyl-3-C-methyl-6-O-toluene-p-sulphonyl-α-D-glucofuranose (13). The formation of the N-acetylepimine 9 establishes the D-gluco configuration for 5.1,2-O-Isopropylidene-3-C-methylene-α-D-ribo-hexofuranose (20) reacted with mercuric azide in aqueous tetrahydrofuran at ≈85° to give 3,6-anhydro-1,2-O-isopropylidene-3-C-methyl-α-D-glucofuranose (22) as a result of intramolecular participation by the C-6 hydroxyl group in the initial intermediate. 相似文献
7.
Addition of 2,2′-anhydro-[1-(3-O-acetyl-5-O-trityl-β-D-arabinofuranosyl)uracil] (1) to excess 2-litho-1,3-dithiane (2)in oxolane at ?78° gave 2-(1,3-dithian-2-yl)-1-(5-O-trityl-β-D-arabinofuranosyl)-4(1H)pyrimidinone (3), O2,2′-anhydro-5,6-di-hydro-6-(S)-(1,3-dithian-2-yl)-5′-O-trityluridine (4), and 2-(1,4-dihydroxybutyl)-1,3-dithiane (5) in yields of 15, 30, and 10% respectively. The structure of 3 was proved by its hydrolysis in acid to give 2-(1,3-dithian-2-yl)-4-pyrimidinone (6) and arabinose, and by desulfurization with Raney nickel to yield the known 2-methyl-1-(5-O-trityl-β-D-arabinofuranosyl)-4(1H)-pyrimidinone (7). Detritylation of 3 without glycosidic cleavage could only be effected by prior acetylation to 1-(2,3-di-O-acetyl-5-O-trityl-β-D-arabinofuranosyl)-2-(1,3-dithian-2-yl)-4(1H)-pyrimidinone (8) which, after treatment with acetic acid at room temperature for 65 h followed by the action of sodium methoxide gave 2-(1,3-dithian-2-yl)-1-β-D-arabinofuranosyl-4(1H)-pyrimidinone (10) in 45% yield. Detritylation of 4 in boiling acetic acid gave 5,6-dihydro-6-(S)-(1,3-dithian-2-yl)-1-β-D-arabinofuranosyluracil (12) and 3-[(S)-1-(1,3-dithian-2-yl)]propionamido-(1,2-dideoxy-β-D-arabinofurano)-[1,2-d]-2-oxazolidinone (13) in 10 and 90% yields, respectively. When 12 was kept in water or methanol for 7 days, quantitative conversion into 13 occurred. Acid hydrolysis of 12 afforded arabinose and 5,6-di-hydro-6-(1,3-dithian-2-yl)uracil (14), which was desulfurized with Raney nickel to the known 5,6-dihydro-6-methyluracil (15). Treatment of 13 with trifluoroacetic anhydride-pyridine yielded 77% of the cyano derivative 17. Similar dehydration of 3-(R)-1-methylpropionamido-(1,2-dideoxy-β-D-arabinofurano)-[1,2-d]-2-oxalidinone (18), obtained by desulfurization of 13, gave 60% of the nitrile 19. Hydrogenation of 19 over platinum oxide in acetic anhydride gave the acetamide derivative 20 in 95% yield. Nitrobenzoylation of 13 gave 3-[(S)-1-(1,3-dithian-2-yl)]cyanomethyl-3,5-di-O-p-nitrobenzoyl-(1,2-dideoxy-β-D-arabinofurano)-[1,2-d]-2-oxazolidinone (22), which was converted in 37% yield by treatment with methyl iodide in dimethyl sulfoxide into the aldehyde 24, characterized as the semicarbazone 25. The purification of 5 and its characterization as 2-(1,4-di-O-p-nitrobenzoylbutyl)-1,3-dithiane (27) is described. 相似文献
8.
《Carbohydrate research》1986,148(2):235-247
The photo-oxygenation of ethyl 2-methyl-5-(1,2,3,4-tetra-O-acetyl-d-lyxo-tetritol-1-yl)-3-furoate, ethyl 2-methyl-5-(1,2,3,4-tetra-O-acetyl-d-arabino-tetritol-1-yl)-3-furoate, 3-acetyl-2-methyl-5-(1,2,3,4-tetra-O-acetyl-d-arabino-tetritol-1-yl)furan, and ethyl 5-(1,4-di-O-acetyl-2,3-O-isopropylidene-d-lyxo-tetritol-1-yl)-2-methyl-3-furoate yielded the corresponding 1,4-endo-peroxides (3a–3d as pairs of diastereomers). Each diastereomer of the pairs 3a and 3d was isolated by fractional crystallisation. The rearrangement of the endo-peroxides at room temperature, by dissolution in CDCl3, yielded the corresponding diepoxides and monoepoxides. The reduction of 3a–3d with methyl sulphide yielded the corresponding γ-diketones, ethyl (E)-2-C-acetyl-5,6,7,8-tetra-O-acetyl-2,3-dideoxy-d-lyxo-oct-2-en-4-ulosonate, ethyl (E)-2-C-acetyl-5,6,7,8-tetra-O-acetyl-2,3-dideoxy-d-arabino-oct-2-en-4-ulosonate, 3-C-acetyl-6,7,8,9-tetra-O-acetyl-1,3,4-trideoxy-d-arabino-non-3-eno-2,5-diulose, and ethyl (E)-2-C-acetyl-5,8-di-O-acetyl-2,3-dideoxy-6,7-O-isopropylidene-d-lyxo-oct-2-en-4-ulosonate, which can isomerise into the corresponding Z isomers. 相似文献
9.
Fidel J. Lopez Aparicio Isidoro Izquierdo Cubero Maria D. Portal Olea 《Carbohydrate research》1984,134(1):39-47
Hydroxylation of trans-1,3,4-trideoxy-5,6-O-isopropylidene-3-C-methyl-d-glycero-hex-3-enulose with osmium tetraoxide gave a mixture of 1-deoxy-5,6-O-isopropylidene-3-C-methyl-d-arabino- and -d-xylo-hexulose that was partially resolved by acetonation to give 1-deoxy-2,3:4,5-di-O-isopropylidene-3-C-methyl-β-d-fructopyranose (4), 1-deoxy-3,4:5,6-di-O-isopropylidene-3-C-methyl-keto-d-fructose (5), and 1-deoxy-2,3:4,6-di-O-isopropylidene-3-C-methyl-α-d-sorbofuranose (6). Treatment of a mixture of 4 and 5 with sodium borohydride gave, after column chromatography, 4 and 1-deoxy-3,4:5,6-di-O-isopropylidene-3-C-methyl-d-manno- and -d-gluco-hexitol. Deuterated derivatives corresponding to 4–6 were obtained when isopropylidenation was carried out with acetone-d6. Deacetonation of 4 and 5 yielded 1-deoxy-3-C-methyl-d-fructose, and 6 similarly afforded 1-deoxy-3-C-methyl-d-sorbose. 相似文献
10.
《Carbohydrate research》1986,147(2):237-245
The reaction of diglycol- and thiodiglycol-aldehyde (1a,b) with cyanoacetamide yields cis-3,5-diacetoxy-4-carbamoyl-4-cyano-tetrahydropyran (2a) and -tetrahydrothiopyran (2b). When this reaction is applied to (2S)-2-(3-ethoxycarbonyl-2-methyl-5-furyl)-3,5-dihydroxy-1,4-dioxane (1c), (2S)-3,5-dihydroxy-2-(3-methoxycarbonyl-2-methyl-5-furyl)-1,4-dioxane (1d), and (2S,3R,5S)-2-(3-acetyl-2-methyl-5-furyl)-3,5-dihydroxy-1,4-dioxane (1e), 5-(3-carbamoyl-3-cyano-3-deoxy-β-d-xylo-pentopyranosyl)-3-ethoxycarbonyl-2-methylfuran (2c), 5-(2,4-di-O-acetyl-3-carbamoyl-3-cyano-3-deoxy-β-d-xylo-pentopyranosyl)-3-methoxycarbonyl-2-methylfuran (2e), and 3-acetyl-5-(2,4-di-O-acetyl-3-carbamoyl-3-cyano-3-deoxy-β-d-xylo-pentopyranosyl)-2-methylfuran (2f), respectively, are formed with (4S,5S)-4-carbamoyl-4-cyano-2-(3-ethoxycarbonyl-2-methyl-5-furyl)-5-hydroxy-5,6-dihydropyran (3a) and (4S,5S)-4-carbamoyl-4-cyano-5-hydroxy-2-(3-methoxycarbonyl-2-methyl-5-furyl)-5,6-dihydropyran (3b) as minor products. The dehydration of 2a,b, 5-(2,4-di-O-acetyl-3-carbamoyl-3-cyano-3-deoxy-β-d-xylo-pentopyranosyl)-3-ethoxycarbonyl-2-methylfuran (2d), 2e, and 2f yields cis-3,5-diacetoxy-4,4-dicyano-tetrahydropyran and -tetrahydrothiopyran (2l,m), and the 5-(2,4-di-O-acetyl-3,3-dicyano-3-deoxy-β-d-erythro-pentopyranosyl) derivatives (2n–p) of 3-ethoxycarbonyl-2-methylfuran, 3-methoxycarbonyl-2-methylfuran, and 3-acetyl-2-methylfuran, respectively. 相似文献
11.
Theodorus van Es 《Carbohydrate research》1976,46(2):237-244
Heating of 2,3,5-tri-O-methyl-4-O-p-tolylsulfonyl-D-ribose diethyl dithioacetal and dibenzyl dithioacetal in aqueous pyridine gave 4-S-ethyl-2,3,5-tri-O-methyl-4-thio-l-lyxose and benzyl 2,3,5-tri-O-methyl-α-1,4-dithio-l-lyxofuranoside, respectively. Similar rearrangements to the 4-thiofuranoside were observed with 2,3,5-tri-O-methyl-4-O-p-tolylsulfonyl-D-xylose and -D-lyxose dibenzyl dithioacetals. 2,3,4-Tri-O-methyl- 5-O-p-tolylsulfonyl-D-ribose or -D-xylose dibenzyl dithioacetal, however, gave upon heating with sodium iodide in acetone 2,5-anhydro-3,4-di-O-methyl-D-ribose or -D-xylose dibenzyl dithioacetal, respectively. 相似文献
12.
Chemical studies on the constituents of Eranthis cilicica led to isolation of ten chromone derivatives, two of which were previously known. Comprehensive spectroscopic analysis, including extensive 1D and 2D NMR data, and the results of enzymatic hydrolysis allowed the chemical structures of the compounds to be assigned as 8,11-dihydro-5-hydroxy-2,9-dihydroxymethyl-4H-pyrano[2,3-g][1]benzoxepin-4-one, 5,7-dihydroxy-8-[(2E)-4-hydroxy-3-methylbut-2-enyl]-2-methyl-4H-1-benzopyran-4-one, 5,7-dihydroxy-2-hydroxymethyl-8-[(2E)-4-hydroxy-3-methylbut-2-enyl]-4H-1-benzopyran-4-one, 7-[(β-d-glucopyranosyl)oxy]-5-hydroxy-8-[(2E)-4-hydroxy-3-methylbut-2-enyl]-2-methyl-4H-1-benzopyran-4-one, 7-[(β-d-glucopyranosyl)oxy]-5-hydroxy-2-hydroxymethyl-8-[(2E)-4-hydroxy-3-methylbut-2-enyl]-4H-1-benzopyran-4-one, 9-[(O-β-d-glucopyranosyl-(1→6)-β-d-glucopyranosyl)oxy]methyl-8,11-dihydro-5,9-dihydroxy-2-methyl-4H-pyrano[2,3-g][1]benzoxepin-4-one, 8,11-dihydro-5,9-dihydroxy-9-hydroxymethyl-2-methyl-4H-pyrano[2,3-g][1]benzoxepin-4-one, and 7-[(O-β-d-glucopyranosyl-(1→6)-β-d-glucopyranosyl)oxy]methyl-4-hydroxy-5H-furo[3,2-g][1]benzopyran-5-one, respectively. The isolated compounds were evaluated for their antioxidant activity. 相似文献
13.
Benzylation of methyl 2,3-anhydro-4-O-[2-O-benzyl-3,4-di-O-(β-D-xylop yranosyl]-β-D-xylopyranosyl]-β-D-ribopyranoside (1) afforded the crystalline. fully benzylated tetrasaccharide derivative 2. The octa-O-benzyl derivative 3, having only HO-2 unsubstituted, obtained by treatment of 2 with benzyl alcoholate anion in benzyl alcohol, was allowed to react in dichloromethane with methyl 2,3-di-O-benzyl- 1-chloro-1-deoxy-4-O-methy]-α,β-glucopyranuronate in the presence of silver perchlorate and triethylamine to give the branched, 4-O-methyl-α-D-glucuronic acid-containing pentasaccharide derivative 4a as the major product. Subsequent debenzylation afforded the aldopentaouronic acid derivative 5a, which contains all the basic structural features of branched, hardwood (4-O-methylglucurono)xylans. The structure of 5a was confirmed by analysis of its 13C-n.m.r. spectrum and the mass-spectral fragmentation pattern of the corresponding fully methylated derivative 6a. 相似文献
14.
Christopher D. Warren Mohammed A.E. Shaban Roger W. Jeanloz 《Carbohydrate research》1977,59(2):427-448
2-Methyl-(2-acetamido-3,4,6-tri-O-benzyl-1,2-dideoxy-α-D-glucopyrano)-[2,1-d]-2-oxazoline,2-methyl-(2-acetamido-6-O-acetyl-3,4-di-O-benzyl-1,2-dideoxy-α-D-glucopyrano)-[2,1-d]-2-oxazoline,and 2-methyl-(2-acetamido-4-O-acetyl-3,6-di-O-benzyl-1,2-dideoxy-α-D-glucopyrano)-[2,1-d]-2-oxazoline were synthesized from the allyl 2-acetamido-3,4,6-tri-O-benzyl-2-deoxy-D-glucopyranosides, and from the 3,4-di-O-benzyl or 3,6-di-O-benzyl analogs, respectively, both the α and β anomer being used in each case. The preparation of allyl 2-acetamido-3,4,6-tri-O-benzyl- and 3,6-di-O-benzyl-2-deoxy-β-D-glucopyranoside is also described. Treatment of the tri-O-benzyl oxazoline with dibenzyl phosphate gave a pentabenzylglycosyl phosphate, from which all the benzyl groups were removed by catalytic hydrogenation, giving 2-acetamido-2-deoxy-α-D-glucopyranosyl phosphate. The corresponding β anomer was not detectable. Treatment of the 3,4-, or 3,6-, di-O-benzyl oxazoline with allyl 2-acetamido-3,4-di-O-benzyl-α-D-glucopyranoside readily gave disaccharide products from which the protecting groups were removed, to give the (1→6)-linked isomer of di-N-acetylchitobiose. Under both acidic and basic conditions, this isomer was less stable than the (1→4)-linked compound.Attempts to employ the 3,6-di-O-benzyl oxazoline for the formation of (1→4)-linked disaccharides, by treatment with either anomer of allyl 2-acetamido-3,6-di-O-benzyl-2-deoxy-D-glucopyranoside, were not very successful, presumably owing to hindrance by the bulky benzyl groups. 相似文献
15.
Younosuke Araki Kazunari Nishiyama Kazuo Senna Kazuo Matsuura Yoshiharu Ishido 《Carbohydrate research》1978
Photoirradiation of a solution of 1,2,4,6-tetra-O-acetyl-3-deoxy-β-D-erythro-hex-2-enopyranose (1) in 1:50 acetone-1,3-dioxolane with a high-pressure mercury-lamp, followed by chromatographic separation, gave 1,2,4,6-tetra-O-acetyl-3-deoxy-3-C-(1,3-dioxolan-2-yl)-β-D-glucopyranose (3) (44%) and-mannopyranose (4) (35%). Similar treatment of the α anomer (2) of 1 afforded 1,2,4,6-tetra-O-acetyl-3-deoxy-3-C-(1,3-dioxolan-2-yl)-α-D-glucopyranose (5) (38%), -mannopyranose (6) (31%), and -allopyranose (7) (21%).On the other hand, irradiation of 2 in 1:100 acetone-2-propanol gave 1,2,4,6-tetra-O-acetyl-3-deoxy-3-C-(1-hydroxy-1-methylethyl)-α-D-mannopyranose (8) (76%). Moreover, irradiation of 2 in 1:1 acetone-2-propanol yielded 1,4,6-tri-O-acetyl-3-deoxy-2,3-di-C-(1-hydroxy-1-methylethyl)-α-D-gluco- or -manno-pyranose 2,21,31-orthoacetate (10) (15%), in addition to 8 (44%). 相似文献
16.
2-O-Benzoyl-3,6-di-O-benzyl-4-O-(chloroacetyl)-, 4-O-acetyl-2-O-benzoyl-3,6-di-O-benzyl-, and 2-O-benzoyl-3,4,6-tri-O-benzyl-α-d-galactopyranosyl chloride were converted into the corresponding 2,2,2-trifluoroethanesulfonates, and these were treated with allyl 2-O-benzoyl-3,6-di-O-benzyl-α-d-galactopyranoside, to give allyl 2-O-benzoyl-4-O-[2-O-benzoyl-3,6-di-O-benzyl-4-O-(chloroacetyl)-β-d-galactopyranosyl]-3,6-di-O-benzyl- α-d-galactopyranoside (26; 41% yield), 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 (27; 62% yield), and allyl 2-O-benzoyl-4-O-(2-O-benzoyl-3,4,6-tri-O-benzyl-β-d-galactopyranosyl)-3,6-di-O-benzyl-α-d-galactopyranoside (28; 65% yield). All disaccharides were free from their α anomers. Disaccharides 26 and 27 were found to be base-sensitive, and were de-esterified by KCN in aqueous ethanol, and debenzylated with H2-Pd. Attempts to produce (1→4)-β-d-galactopyranosides from the coupling of a number of fully esterified d-galactopyranosyl sulfonates to allyl 2,3,6-tri-O-benzoyl-α-d-galactopyranoside were unsuccessful. 相似文献
17.
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). 相似文献
18.
Fred R. Seymour 《Carbohydrate research》1974,34(1):65-70
The unambiguous syntheses of methyl 3,4,6-tri-O-methyl-α-d-mannopyranoside (6) and methyl 3,4-di-O-methyl-α-d-mannopyranoside (10) were performed by routes involving methyl 3-O-benzoyl-4,6-O-benzylidene-α-d-mannopyranoside (1) to form methyl 2-O-p-tolylsulfonyl-d-mannopyranoside (4). Compound 4 directly led to 6, and, via a 6-trityl derivative, to 10. 相似文献
19.
Yousif Ali Dolatrai M. Vyas Robert C. Nabinger Walter A. Szarek 《Carbohydrate research》1982,104(2):183-193
Nucleophilic Michael-type additions to aldohexofuranoid 3-C-methylene derivatives, namely, 3-deoxy-1,2:5,6-di-O-isopropylidene-3-C-nitromethylene-α-d-ribo-hexofuranose and 3-C-[cyano(ethoxycarbonyl)methylene]-3-deoxy-1,2:5,6-di-O-isopropylidene-α-d-ribo-hexofuranose employing phase-transfer catalysis, afforded novel gem-di-C-substituted sugars. The conversion of 3-deoxy-1,2:5,6-di-O-isopropylidene-3-C-methyl-3-C-nitromethyl-α-d-allo-hexofuranose into a 3-C-hydroxymethyl-3-C-methyl derivative with titanium trichloride, and that of the nitromethyl groups of 3-deoxy-1,2:5,6-di-O-isopropylidene-3,3-di-C-nitromethyl-α-d-ribo-hexofuranose, and 3-deoxy-1,2:5,6-di-O-isopropylidene-3-C-methyl-3-C-nitromethyl- and -3-C-nitromethyl-α-d-allo-hexofuranose into cyano groups with phosphorus trichloride in pyridine is also described. 相似文献
20.
6-Methylpurine (MeP) is cytotoxic adenine analog that does not exhibit selectivity when administered systemically, and could be very useful in a gene therapy approach to cancer treatment involving Escherichia coli PNP. The prototype MeP releasing prodrug, 9-(β-d-ribofuranosyl)-6-methylpurine, MeP-dR has demonstrated good activity against tumors expressing E. coli PNP, but its antitumor activity is limited due to toxicity resulting from the generation of MeP from gut bacteria. Therefore, we have embarked on a medicinal chemistry program to identify non-toxic MeP prodrugs that could be used in conjunction with E. coli PNP. In this work, we report on the synthesis of 9-(6-deoxy-β-d-allofuranosyl)-6-methylpurine (3) and 9-(6-deoxy-5-C-methyl-β-d-ribo-hexofuranosyl)-6-methylpurine (4), and the evaluation of their substrate activity with several phosphorylases. The glycosyl donors; 1,2-di-O-acetyl-3,5-di-O-benzyl-α-d-allofuranose (10) and 1-O-acetyl-3-O-benzyl-2,5-di-O-benzoyl-6-deoxy-5-C-methyl-β-d-ribohexofuran-ose (15) were prepared from 1,2:5,6-di-O-isopropylidine-α-d-glucofuranose in 9 and 11 steps, respectively. Coupling of 10 and 15 with silylated 6-methylpurine under Vorbrüggen glycosylation conditions followed conventional deprotection of the hydroxyl groups furnished 5′-C-methylated-6-methylpurine nucleosides 3 and 4, respectively. Unlike 9-(6-deoxy-α-l-talo-furanosyl)-6-methylpurine, which showed good substrate activity with E. coli PNP mutant (M64V), the β-d-allo-furanosyl derivative 3 and the 5′-di-C-methyl derivative 4 were poor substrates for all tested glycosidic bond cleavage enzymes. 相似文献