|
1. |
Studies on Selectin Binding Inhibitors: Synthesis of Sialyl-Lewis X and Sialyl-Lewis A Epitope Analogs Containing 2-Acetamido Derivative ofN-Methyl-1-Deoxynojirimycin1 |
|
Journal of Carbohydrate Chemistry,
Volume 15,
Issue 1,
1996,
Page 1-14
Makoto Kiso,
Hiroyasu Furui,
Hideharu Ishida,
Akira Hasegawa,
Preview
|
PDF (602KB)
|
|
摘要:
Synthesis of sialyl-Lewis x (15) and sialyl-Lewis a (17) epitope analogs containing the 2-acetamido derivative ofN-methyl-1-deoxynojirimycin has been achieved. A suitably protected 2-acetamido- 1-deoxynojirimycin derivative5, prepared from 1-deoxynojirimycinviathe epoxide intermediate3, was successively coupled with methyl- 1-thioglycosides of L-fucose (6) and β-sialyl-(2→3)-D-galactose (9). The resulting tetrasaccharides (10and13) were each converted, by reductiveN-methylation and deprotection, into the desired epitope analogs.
ISSN:0732-8303
DOI:10.1080/07328309608005420
出版商:Taylor & Francis Group
年代:1996
数据来源: Taylor
|
2. |
New Stereospecific Rearrangements of Pyranosides |
|
Journal of Carbohydrate Chemistry,
Volume 15,
Issue 1,
1996,
Page 15-31
Ralf Miethchen,
Daniel Rentsch,
Michael Frank,
Preview
|
PDF (769KB)
|
|
摘要:
Methyl β-D-arabinopyranoside (1), phenyl 1-thio-β-D-galactopyranoside (3), methyl β-L-fucopyranoside (7), methyl β-L-fucopyranoside (9), 1,6-anhydro-β-D-galactopyranoside (D-galactosan;11), and 1,6-anhydro-β-D-mannopyranoside (D-mannosan;14) were stereospecifically converted in moderate up to good yields into methyl 4-O-cyclohexylcarbamoyl-2,3-O-(2,2,2-trichloroethylidene)-β-D-lyxopyranoside (2), phenyl 4-(9-cyclohexyIcarbamoyl-6-O-formyl-2,3-O-(2,2,2-trichloroethylidene)-1-thio-β-D-gulopyranoside (4) / phenyl 4-O-cyclohexylcarbamoyl-2,3-O-(2,2,2-trichloroethylidene)-1-thio-β-D-gulopyraoside (5), methyl 4-O-cyclohexylcarbamoyl-2,3-O-(2,2,2-trichloroethylidene)-6-deoxy-α-L-gulopyranoside (8), methyl 2,3-O-(2,2,2-trichloroethylidene)-4-O-cyclohexylcarbamoyl-6-deoxy-β-L-gulopyranoside (10), 1,6-anhydro-4-O-cyclohexyl-carbamoyl-2,3-O-(2,2,2-trichloroethylidene)-β-D-gulopyranoside (12), and 1,6-anhydro-2-O-cyclohexylcarbamoyl-3,4-O-(2,2,2-trichloroethylidene)-β-D-altropyranoside (15), respectively, using a nonclassic pathway of chloral acetalisation with dicyclohexylcarbodiimide (DCC) as coagent. In the case of1,3, and9, chloral acetalisations yielded diastereomeric mixtures, e.g., the acetals2,4,5, and10consist ofendo-H/enxo-H dioxolane type acetals with preference of theendo-H form. In contrast to this, the compounds7,11, and14gave exclusively theendo-H diastereomers8,12, and15. Additionally, the structure of the anhydro compound15was confirmed by intramolecular glycosylation of the 2-O-cyclohexylcarbamoyl-3,4-O-(2,2,2-trichloroethylidene)-α-D-altropyranosyl fluoride (17). Finally, the 6-O-formyl-α-D-gulopyranoside4was alternatively deformylated by methanol/triethylamine giving5and methanol/sodium methoxide yielding phenyl 6-O-cyclohexylcarbamoyl-2,3-O-(2,2,2-trichloroethylidene)-1-thio-β-D-gulopyranoside (6). The carbamoyl protecting group of12was cleaved by refluxing with methanolic sodium methoxide solution giving 1,6-anhydro-2,3-O-(2,2,2-trichloroethylidene)-β-D-gulopyranoside (13).
ISSN:0732-8303
DOI:10.1080/07328309608005421
出版商:Taylor & Francis Group
年代:1996
数据来源: Taylor
|
3. |
A Mechanistic Study of the Photochemistry of Carbohydratep-Toluenesulfonates |
|
Journal of Carbohydrate Chemistry,
Volume 15,
Issue 1,
1996,
Page 33-40
R.J. Berki,
E.R. Binkley,
R.W. Binkley,
D.G. Hehemann,
D.J. Koholic,
J. Masnovi,
Preview
|
PDF (331KB)
|
|
摘要:
Photolysis of 1,2:3,4-di-O-isopropylidene-6-O-(p-tolylsulfonyl)-α-D-galactopyranose (5) in methanol under nitrogen in the presence of sodium hydroxide or diazabicyclo[2.2.2]octane (3, DABCO) produces toluene and 1,2:3,4-di-O-isopropylidene-α-D-gatactopyranose (6). Electron transfer from DABCO or hydroxide ion to singlet excited5to generate a radical anion is the first step in this reaction. The radical anion rapidly fragments to give thep-tolylsulfonyl radical (2) and deprotonated6, which accepts a proton from the solvent. Thep-tolylsulfonyl radical (2) then abstracts a hydrogen atom from the solvent to givep-toluenesulfinic acid, a compound that is converted to thep-toluenesulfinate anion (8) under the basic reaction conditions. Photolysis of8completes the reaction sequence by forming toluene.
ISSN:0732-8303
DOI:10.1080/07328309608005422
出版商:Taylor & Francis Group
年代:1996
数据来源: Taylor
|
4. |
Is Sulfate Lost During the Chemical Release of Oligosaccharides from Glycoproteins? |
|
Journal of Carbohydrate Chemistry,
Volume 15,
Issue 1,
1996,
Page 41-49
KevinR. King,
J.Michael Williams,
JohnR. Clamp,
AnthonyP. Corfield,
Preview
|
PDF (462KB)
|
|
摘要:
Model experiments using methyl α-d-galactopyranoside 6-sulfate have implied that the Carlson conditions (1 M sodium borohydride and 0.05 M sodium hydroxide at 45°C) for the release ofO-linked oligosaccharides from glycoproteins do not cause significant loss of sulfate ester groups. However the more vigorous conditions used to releaseN-linked oligosaccharides are more likely to cause considerable sulfate loss from a galactoside 6-sulfate as a result of 3,6-anhydride formation. Experiments with dextran sulfate suggested that sulfate loss due to oxirane formation was also not significant under the Carlson conditions. These results were supported by experiments with [35S]sulfate-labelled human rectal mucus glycoprotein.
ISSN:0732-8303
DOI:10.1080/07328309608005423
出版商:Taylor & Francis Group
年代:1996
数据来源: Taylor
|
5. |
Synthesis ofl-Histidine and (-)-Spinacine Chitooligosyl Amides1 |
|
Journal of Carbohydrate Chemistry,
Volume 15,
Issue 1,
1996,
Page 51-64
JakobP. Ley,
MartinG. Peter,
Preview
|
PDF (757KB)
|
|
摘要:
The synthesis ofN-(2-acetamido-4-O-[2-acetamido-4-O-{2-acetamido-2-deoxy-β-D-glucopyranosyl}-2-deoxy-β-D-glucopyranosyl]-2-deoxy-β-D-glucopyranosyl)-L-histidine amide (3),N-(2-acetamido-2-deoxy-β-D-glucopyranosyl)-(6S)-4,5,6,7-tetrahy-droimidazo[4,5-c]pyridine-6-carboxylic amide (4) andN-(2-acetamido-4-O-[2-acetamido-2-deoxy-β-D-glucopyranosyl]-2-deoxy-β-D-glucopyranosyl)-(6S)-4,5,6,7-tetrahydroimidazo[4,5-c]pyridine-6-carboxamide (5) is achievedviacoupling of the appropiate glycosylamines with Boc-protected L-histidine or with (6S)-4,5,6,7-tetrahydroimidazo[4,5-c]pyridine-6-carboxylic acid ((-)-spinacine), respectively, by means of EEDQ and subsequent deprotection.
ISSN:0732-8303
DOI:10.1080/07328309608005424
出版商:Taylor & Francis Group
年代:1996
数据来源: Taylor
|
6. |
Methods for Debrominating 4,5-Dibromopentanyl Glycosides |
|
Journal of Carbohydrate Chemistry,
Volume 15,
Issue 1,
1996,
Page 65-72
J.Robert Merritt,
JohnS. Debenham,
Bert Fraser-Reid,
Preview
|
PDF (369KB)
|
|
摘要:
Debromination of 4,5-dibromopentanyl glycosides to (re)generaten-pentenyl glycosides has been accomplished using zinc, samarium(II) iodide, and sodium iodide, respectively. The choice of reagent is dependent upon the reactivity of the substrate, as well as the protecting groups thereon.
ISSN:0732-8303
DOI:10.1080/07328309608005425
出版商:Taylor & Francis Group
年代:1996
数据来源: Taylor
|
7. |
Selective Reactions of the Free Hydroxyl Groups of 2,3,4,3′,4′-Penta-O-Benzylsucrose |
|
Journal of Carbohydrate Chemistry,
Volume 15,
Issue 1,
1996,
Page 73-79
Sławomir Jarosz,
Preview
|
PDF (299KB)
|
|
摘要:
Selective transformations of the free hydroxyl groups in 2,3,4,3′,4′-penta-O-benzyl-sucrose (1) were studied. Oxidation of1with the Swern reagent followed by reaction with Ph3P=CH-COOMe gave 2,3,4,3′,4′-penta-O-benzyl-1′,6,6′-tris-(E)(C-carbomethoxy-methylene)sucrose (2) in ca.40% as the single product. Reaction of1withp-nitrobenzoic acid under Mitsunobu conditions gave 6,6′-di-O-p-nitrobenzoyl-2,3,4,3′,4′-penta-O-benzylsucrose (3) which was easily converted into 2,3,4,3′,4′-penta-O-benzyl-1′-methoxy-methylsucrose (5). Reaction of1with one equivalent of pivaloyl chloride gave monoprotected 2,3,4,3′,4′-penta-O-benzyl-6′-O-pivaloylsucrose (6) [30% with triethylamine or 45% yield in the presence of (Bu3Sn)2O] together with a small amount of diprotected 2,3.4,3′,4′-penta-O-benzyl-6,6′-di-O-pivaloylsucrose (7).
ISSN:0732-8303
DOI:10.1080/07328309608005426
出版商:Taylor & Francis Group
年代:1996
数据来源: Taylor
|
8. |
Effects of Salts on the Initial Thermal Degradation of Concentrated Aqueous Solutions of Sucrose1 |
|
Journal of Carbohydrate Chemistry,
Volume 15,
Issue 1,
1996,
Page 81-94
G. Eggleston,
J.R. Vercellotti,
L.A. Edy,
M.A. Clarke,
Preview
|
PDF (644KB)
|
|
摘要:
The effects of salts and other solutes on the degradation of highly pure sucrose in concentrated aqueous solutions (∼65°Brix or % dissolved solids) at 100°C were investigated. Polarimetry and ion chromatography with pulsed amperometric detection (ICIPAD) were used to quantify sucrose degradation. Pseudo-first order kinetic constants of initial degradation rates were calculated. Salt and solute effects were first considered with relation to their effect on water structure around the sucrose molecule. Na+, Mg2+and Ca2+, which act to enhance water structure, slightly increased initial degradation; the latter two ions significantly increased subsequent accelerated degradation. Highly charged, small cations, e.g., Al3+, significantly increased sucrose degradation through polarized hydrated ions/acidic pH effects. Larger cations, e.g., K+, which act to reduce water structure, significantly increased degradation. The Hofmeister (lyotropic) anion order was not followed for sucrose thermal degradation effects, which indicated that anion binding to hydrophobic sites on the sucrose molecule is not critical. Other possible mechanisms of salt-induced sucrose thermal degradation are discussed.
ISSN:0732-8303
DOI:10.1080/07328309608005427
出版商:Taylor & Francis Group
年代:1996
数据来源: Taylor
|
9. |
Improvements in the Regioselectivity of Alkylation Reactions of Stannylene Acetals |
|
Journal of Carbohydrate Chemistry,
Volume 15,
Issue 1,
1996,
Page 95-108
Huiping Qin,
T.Bruce Grindley,
Preview
|
PDF (707KB)
|
|
摘要:
The regioselectivity of benzylation of stannylene acetals oftrans-diols on pyranose rings is improved by performing the reaction in benzyl bromide, for instance, for methyl 4,6-O-benzylidene-2,3-O-dibutylstannylene-α-D-glucopyranoside, the ratio of 2-O-benzyl ether to 3-O-benzyl ether changed from 70:20 in DMF to 74:8 in benzyl bromide, then improved further to 84:2 if the dihexylstannylene acetal was used. Standard conditions for methylation of stannylene acetals are methyl iodide in DMF. Non-polar conditions give much improved regioselectivity, theO-2 toO-3 product ratio for the above dibutylstannylene acetal changed from 57:30 in DMF to 84:13 with methyl iodide in 1,1,2,2-tetrachloroethane or 90:8 with methyl triflate in chloroform. Examples of benzylation and methylation reactions on different dialkylstannylene acetals on three differenttrans-diols are included.
ISSN:0732-8303
DOI:10.1080/07328309608005428
出版商:Taylor & Francis Group
年代:1996
数据来源: Taylor
|
10. |
Practical Synthesis of Sinigrin |
|
Journal of Carbohydrate Chemistry,
Volume 15,
Issue 1,
1996,
Page 109-113
Wojciech Abramski,
Marek Chmielewski,
Preview
|
PDF (236KB)
|
|
摘要:
Sinigrin (1), the most commonly known glucosinolate, is a naturally occurring thiosugar, widely distributed in the botanic family Cruciferae. Sinigrin was first isolated in 1839 from seeds of black mustard in the form of its potassium salt.1Commercially available sinigrin is obtained by extraction from horseradish.2So far a number of natural glucosinolates and their analogs have been synthesized.3-10The only synthesis of compound1, leading to a crystalline product on the miligram scale, has been reported by Benn and Ettlinger3(Scheme 1). Their procedure has been applied by Kjaer and Jensen4for the synthesis of the higher homologue of sinigrin (1), but no information of the overall yield has been provided.
ISSN:0732-8303
DOI:10.1080/07328309608005429
出版商:Taylor & Francis Group
年代:1996
数据来源: Taylor
|
|