摘要:

Methyl 3,6-di-O-benzyl-4-O-benzoyl-2-deoxy-2-methoxycarbonylamino-α-D-glucopyranoside (8) was prepared form D-glucosamine via its 4,6-O-benzylidene derivative. The methyl glycoside moiety of8was hydrolyzed in the presence ofd-camphorsulfonic acid in acetic acid to give hemiacetal12. The oxime14derived from the latter was subjected to the radical cyclization mediated by tributyltin hydride, providing three types of cyclopentane derivatives. One isomer,15, having an allosamizoline (2)-like configuration was converted into theN,N′-isopropylidene derivative3, which is a potential intermediate for the syntheses of analogs of chitinase inhibitor allosamidin (1).

ISSN:0732-8303    

DOI:10.1080/07328309508002071

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The reduction of 3,4-di-O-acetyl-6-azido-6-deoxy-D-glucal (3a) with nickel boride gives the aminoglycal1; whereas reduction with thiolacetic acid leads directly to the amidoglycal2. The aminoglycal1is sensitive to aqueous acid and rearranges to (1R)-(2-furyl)-2-acetamidoethanol (4). This furan gives a Diels-Alder adduct5withN-phenylmaleimide in which the nitrogen and oxygen on the side chain have interchanged positions. In contrast, the amidoglycal2reacts with ammonium nitrate in trifluoroacetic anhydride and with acidic mercuric sulfate to give (E)-5-acetamido-(3S)-acetoxy-(4R)-formoxy-1-nitro-1-pentene (6) and 6-acetamido-4-O-acetyl-2,3,6-trideoxy-aldehydo-D-erythro-trans-hex-2-enose (7) respectively. The amidoglycal2also undergoes an intramolecular palladium (II) catalyzed cyclization reaction leading to a pair of diastereomeric (4R)-acetoxy-7-acetyl-7-aza-2-oxabicyclo[3.2.1]oct-5-enes (8).

ISSN:0732-8303    

DOI:10.1080/07328309508002072

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Syntheses are described of the three disaccharides: methyl 3-O-L-glycero-α-D-manno-heptopyranosyl-L-glycero-α-D-manno-heptopyranoside 4-phosphate, methyl 3-O-(L-glycero-α-D-manno-heptopyranosyl 4-phosphate)-L-glycero-α-D-manno-heptopyranoside, and methyl 3-O-(L-glycero-α-D-manno-heptopyranosyl 4-phosphate)-L-glycero-α-D-manno-heptopyranoside 4-phosphate together with their 2-(4-trifluoroacetamidophenyl)ethyl glycoside analogues. These correspond to phosphorylated structures found in the inner core region of lipopolysaccharides fromSalmonella. The known derivative methyl 6,7-di-O-acetyl-2,3,4-tri-O-benzyl-L-glycero-α-D-manno-heptopyranoside was used as a common heptose precursor. Phosphorylation on suitably protected disaccharide derivatives was performed by treatment with phosphorus triimidazolate in dichloromethane followed by the addition of benzyl alcohol andin situoxidation withm-chloroperbenzoic acid to give the dibenzyltriester phosphate derivatives, which after deprotection gave the target compounds.

ISSN:0732-8303    

DOI:10.1080/07328309508002073

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Treatment of methyl 4,6-O-benzylidene-2-(dicyanomethylene)-2,3-dideoxy-α-D-erythro-hexopyranoside (2) with 3-benzyl-2-methylthio-2-thiazolinium iodide (3), 4,5-dihydro-3-methyl-2-methylthio-1,3-thiazinium iodide (5) and 3-benzyl-4,5-dihydro-2-methylthio-1,3-thiazinium iodide (6), respectively, gave methyl 4,6-O-benzylidene-3-[(2Z)-3-benzyl-2-thiazolidinylidene, 3-methyl-1,3-thiazinan-2-ylidene and 3-benzyl-1,3-thiazinan-2-ylidene]-2-(dicyanomethylene)-2,3-dideoxy-α-D-erythro-hexopyranoside (4), (7), (8), respectively.

ISSN:0732-8303    

DOI:10.1080/07328309508002074

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The method of electrochemically induced formation of ether and ester derivatives of saturated mono- and disaccharides was applied to 1, 2-unsaturated monosaccharides (D-glycals). The influence of the supporting electrolyte on the product distribution was investigated by variation of the cation. To provide data for comparison, alkylation was also carried out chemically in the presence of different bases, e.g. LiH and NaH.

ISSN:0732-8303    

DOI:10.1080/07328309508002075

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The glycosidic coupling reaction of 1,2-anhydro-3,4,6-tri-O-benzyl-β-d-mannopyranose (7), 1,2-anhydro-3,4,6-tri-O-benzyl-α-d-galactopyranose (21), and 1,2-anhydro-3,4-di-O-benzyl-α-d-xylopyranose (18) withN-tosyl- (10) orN-benzyloxycarbonyl- (11) L-serine methyl ester provides a new stereocontrolled synthesis of 1,2-trans linked glycopeptides. The 1,2-anhydro sugars are shown to react smoothyl with10or11in the presence of Lewis acid (ZnCl2or AgOTf) as well as powdered 4A molecular sieves in CH2Cl2at room temperature to afford glycosyl serine derivatives with high stereoselectivity and high yield in less than 30 min. An improved method using 2-O-acetyl-3,4,6-tri-O-benzyl-α-d-mannopyranosyl chloride (6) as the key intermediate for ring closure was applied for the synthesis of 1,2-anhydro-3,4,6-tri-O-benzyl-β-d-mannopyranose.

ISSN:0732-8303    

DOI:10.1080/07328309508002076

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Four sialyl and sulfo Lexanalogs containing glucose in place ofN-acetylglucosamine, and a ceramide or 2-(tetradecyl)hexadecyl residue, have been synthesized. Condensation ofO-(methyl 5-acetamido-4,7,8,9-tetra-O-acetyl-3,5-dideoxy-d-glycero-α-d-galacto-2-nonulopyranosylonate)-(2→3)-O-(4-O-acetyl-2,6-diO-benzoyl-β-d-galactopyranosyl)-(1→4)-O-[(2,3,4-tri-O-acetyl-α-L-fucopyranosyl)-(1→3)]-2,4-di-O-benzoyl-α-d-glucopyranosyl trichloroacetimidate (1) with (2S,3R,4E)-2-azido-3-O-benzoyl-4-octadecene-1,3, diol (2) or 2-(tetradecyl)-hexadecyl-1-ol (3) gave the corresponding β-glycosides4and7. Compound4was converted into the ganglioside6viaselective reduction of the azido group, coupling with octadecanoic acid,O-deacylation, and saponification of the methyl ester group. Hydrolysis of theO-acyl groups in7followed by saponification of the methyl ester, gave sialyl Lexganglioside analog8containing a branched fatty alkyl residue. On the other hand, glycosylation ofO-(4-O-acetyl-2,6-di-O-benzoyl-3-O-levulinyl-β-d-galactopyranosyl)-(1→4)-[O-(2,3,4-tri-O-acetyl-α-L-fucopyranosyl)-(1→3)]-2,6-di-O-benzoyl-α-d-glucopyranosyl trichloroacetimidate (13), prepared from 2-(trimethylsilyl)ethylO-(2,6-di-O-benzoyl-β-d-galactopyranosyl)-(1→4)-O-[(2,3,4-tri-O-benzyl-α-L-fucopyranosyl)-(1→3)]-2,6-di-O-benzoyl-β-d-glucopyranoside (9)viaselective 3-O-levulinylation, acetylation, removal of the 2-(trimethylsilyl)ethyl group, with2or3, gave the desired β-glycosides14and19. Selective reduction of the axido group in14followed by coupling with octadecanoic acid gave the ceramide derivative16. Removal of the levulinyl group in16and19, treatment with sulfur trioxide pyridine complex and subsequent hydrolysis of the protecting groups yielded the corresponding sulfo Lexanalogs18and21.

ISSN:0732-8303    

DOI:10.1080/07328309508002077

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Sulfo and sialy Lexepitope analogs containing the 1-deoxy-N-acetylglucosamine in place of GlcNAc residue have been synthesized. Glycosylation of 2-acetamido-1,5-anhydro-3,6-di-O-benzyl-2-deoxy-D-glucitol (10) with 2,4,6-tri-O-benzoyl-3-O-levulinyl-α-D-galactopyranosyl trichloroacetimidate (6) prepared from 2-(trimethylsilyl)ethyl β-D-galactopyranoside (1) in five steps, or with the α-sialyl-(2→3)-galactose donor, afforded the dessired β-glycosides12and15, respectively. Glycosylation of the acceptor14derived from12in two steps, or16derived from15by reductive removal of the benzyl group followed by selectiveO-benzoylation, with methyl 2,3,4-tri-O-benzyl-1-thio-β-fucopyranoside (17), using dimethyl(methylthio)sulfonium triflate, gave the trisaccharide18and tetrasaccharide23. Compound18was convertedviareductive removel of the benzyl groups,O-acetylation, selective removel of the levulinyl group, treatment with sulfur trioxidepyridine complex, andO-deacylation, into the title sulfo Lexanalog22. Compound23was transformed by reductive removal of the benzyl groups,O-acetylation,O-deacylation and subsequent hydrolysis of the methyl ester, into the sLexepitope analog25.

ISSN:0732-8303    

DOI:10.1080/07328309508002078

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Sialyl-, sulfo- and phosphono-Lexanalogs containing 1-deoxy and 1,2-dideoxy-D-glucose in place ofN-acetylglucosamine have been synthesized. Glycosylation ofO-(2,6-di-O-benzoyl-3,4-O-isopropylidene-β-D-galactopyranosyl)-(1→4)-1,5-anhydro-2,6-di-O-benzoyl-D-glucitol (5), prepared from per-O-lactose in five steps, orO-(2,6-di-O-benzoyl-3,4-O-isopropylidene-β-D-galactopyranosyl)-(1→4)-1,5-anhydro-6-O-benzoyl-2-deoxy-D-arabino-hexitol(9), prepared from per-O-acetyllactal (2) in four steps, with the methyl 1-thioglycoside derivative of L-fucose, gave the corresponding trisacchrides11and18. These are transformed into the glycosyl acceptors12and19for the sialyl Lexanalogs, and15and22for the sulfo- and phosphono Lexanalogs. Selective hydrolysis of the isopropylidene group of11and18yielded12and19, respectively. The latter compounds were then converted to15and22, respectively, by selective levulinylation, reductive removal of the benzyl groups followed by acetylation and removal of the levulinyl group.15and22were then converted in good yields, by sulfonation followed byO-deacylation, into the target compounds17and24. Treatment of22with diphenyl chlorophosphate, and subsequent hydrogenolysis of the phenyl groups with Adams Platinum followed byO-deacylation afforded the phosphono-Lexanalog. Glycosylation of12or19with methyl (phenyl 5-acetamido4,7,8,9-tetra-O-acetyl-3,5-dideoxy-2-thio-D-glycero-D-galacto-2-nonulopyranosid)onate (27), usingN-iodosuccinimide (NIS)-trifluoromethanesulfonic acid (TfOH), afforded the desired tetrasaccharides, which were converted in good yields,viahydrogenolysis of the benzyl groups,O-acetylation,O-deacylation and deesterification into the sialyl Lexanalogs.

ISSN:0732-8303    

DOI:10.1080/07328309508002079

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Reaction of 5-azido-3,5-dideoxy-3-fluoro-1,2-O-isopropylidene-α-D-glucofuranose (1) with trifluoromethanesulfonic anhydride followed by tris(dimethylamino)sulfonium difluorosilicate gave a 1:2 mixture of 5-azido-3,5,6-trideoxy-3-fluoro-1,2-O-isopropylidene-α-D-xylohex-5-enofuranose (2) and 5-azido-3,5,6-trideoxy-3,6-difluoro-α-D-glucofuranose (3) in 74% yield. When 5-azido-5-deoxy-1,2-O-isopropylidene-α-D-allofuranose (7) was similarly treated, it yielded instead, 5-azido-5-azido-3-O-trifluoromethanesulfonyl-1,2-O-isopropylidene-α-D-ribo-hex-5-enofuranose (8). Further treatment of8with TASF gave2. The 3-O-benzoate4also did not yield the expected product, but instead, gave 5-azido-6-O-benzoyl-3,5-dideoxy-3-fluoro-1,2-O-isopropylidene-α-D-glucofuranose (5). Deacetalation and hydrogenation of3gave 1,3,6-trideoxy-3,6-difluornojirimycin [(2S,3R,5S)-4-fluoro-3,5-dihydroxy-2-fluoromethylpiperidine] (10).

ISSN:0732-8303    

DOI:10.1080/07328309508002080

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor