摘要:

Ten sulfated and three phosphorylated β-D-galactopyranoside dimers and one sulfated β-D-galactopyranoside trimer containing fatty alkyl residues in place of ceramide have been synthesized. The coupling of 2,3,4,6-tetra-O-acetyl-α-D-galactopyranosyl bromide (2) with branched fatty alkyl diols and a triol (1a-1j) using mercury bromide as an activating agent gave the corresponding parent glycolipids (4a-4j) in good yields. Regioselective sulfation of these parent glycolipids through the dibutylstannylene acetals produced the target sulfated glycolipids, 3-sulfate (5a-5j) while stepwise phosphorylation with dibenzyloxy(diisopropylamino) phosphine gave the phosphorylated glycolipids, 3,4-bisphosphate (9e, g, i). The synthetic glycolipids were assayed for their ability to block the adhesion of HL-60 cells to immobilized P-, L- and E-selectin.

ISSN:0732-8303    

DOI:10.1080/07328309808002333

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

KDN-Lexganglioside analogs (10, 13, 16and19) containing the modified reducing terminal and L-rhamnose in place of L-fucose have been synthesized. Glycosidation of methyl 2,3,4-tri-O-benzyl-1-thio-α-L-rhamnopyranoside (1) with 2-(trimethylsilyl)ethylO-(2-acetamido-4,6-O-benzylidene-2-deoxy-β-D-glucopyranosyl)-(1→3)-O-(2,4,6-tri-O-benzyl-α-D-galacopyranoside (2), followed by reductive ring opening of the benzylidene acetal, gave 2-(trimethylsilyl)ethylO-(2,3,4-tri-O-benzyl-α-L-rhamnopyranosyl)-(1→3)-O-(2-acet-amido-6-O-benzyl-2-deoxy-β-D-glucopyranosyl)-(1→3)-O-(2,4,6-tri-O-benzyl-β-D-galactopyranosyl)-(1→4)-2,3,6-tri-O-benzyl-β-D-glucopyranoside (4). The tetrasaccharide4was coupled with methylO-(methyl 4,5,7,8,9-penta-O-acetyl-3-deoxy-D-glycero-α-D-galacto-2-nonulopyranosylonate)-(2→3)-2,4,6-tri-O-benzoyl-1-thio-β-D-galactopyranoside(5), using dimethyl(methylthio)sulfonium triflate (DMTST), to give the hexasaccharide6, which was converted into compound11in the usual manner. Compounds8and11were transformed,viabromination of the reducing terminal, radical reduction,O-deacylation and saponification of the methyl ester, into the desired KDN-Lexhexasaccharides (10, 13). On the other hand, glycosylation of 2-(tetradecyl)hexadecanol with α-trichloroacetimidates14and17, afforded the target ganglioside analogs16and19.

ISSN:0732-8303    

DOI:10.1080/07328309808002334

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The mouse monoclonal anti-human HNK-1 antibody (also variously known as L2, Leu-7, CD57, VC1.1), monoclonal anti-sulfoglucuronosyl glycosphingolipids (SGGLs) antibody (mAb NGR50), and human sera from patients with demyelinating neuropathy and IgM paraproteinemia, are known to react with not only SGGLs, including sulfoglucuronosyl paragloboside (SGPG) and sulfoglucuronosyl lactosaminyl paragloboside (SGLPG), but also glycoproteins, such as myelin-associated glycoprotein (MAG), PO, PMP22, and certain adhesion molecules. These antigens are known to possess the so-called HNK-1 epitope (3-sulfoglucuronic acid, SGA) moiety. To further define the precise structural requirement of this carbohydrate epitope, we chemically synthesized 14 SGGLs, and their nonsulfated derivatives with defined carbohydrate chain lengths and aglycone structures. The various aglycones include ceramide, 2-(tetradecyl)hexadecyl (B30), and 2-(trimethylsilyl)ethyl (SE). These synthetic SGGLs were tested for their immunoreactivity with the above antibodies by high-performance thin-layer chromatography (HPTLC)-immunoblotting and ELISA. The anti-HNK-1 antibody (VC1.1) reacted with SGGL analogues containing a minimum of two sugars (SGA-Gal-Cer), but not with non-sulfated derivatives of SGGLs nor with SGGLs having a modified ceramide structure. mAb NGR50, on the other hand, reacted with only SGPG and SGLPG. A human patient serum (LT) reacted with all synthetic SGGLs except those with an SE aglycone structure. On the other hand, another human patient serum (YT). like the anti-HNK-1 antibody, VC1.1, reacted with SGPG, SGLPG, and SGGL analogues containing a minimum of two sugars (SGA-Gal-Cer). All antibodies reacted more strongly with synthetic SGGLs with longer carbohydrate chains. These results indicate that anti-SGGL antibodies recognize a minimum of two sugars bearing the following structure (3-sulfoglucuronosyl β 1-3 galactosyl, SGA-Gal-) and that the aglycone (“ceramide”) structure appears to play an important role for antibody-antigen interaction.

ISSN:0732-8303    

DOI:10.1080/07328309808002335

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Benzyl- and acetyl-protected glycosyl dimethylthiophosphates were readily prepared from corresponding 1-hydroxyl sugars in good yield, and acted as very stable and efficient glycosyl donors in the construction of glycosidic bonds in the presence of various promoters.

ISSN:0732-8303    

DOI:10.1080/07328309808002336

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

When treated with Bu2SnO in a suitable solvent, reducing sugars preferentially form 1,2-O-stannylene acetals and, on prolonged treatment with a slight excess of the reagent at reflux temperature, they undergo epimerization. This allows simple preparation of rare monosaccharides from readily available, unprotected starting materials. The process is equilibrium driven, and the equilibrium is shifted largely in favor of structures having an axial hydroxyl group at position 2.

ISSN:0732-8303    

DOI:10.1080/07328309808002337

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Two derivatives of β-maltosyl-(1→4)-trehalose monodeoxygenated at C-2 or C-2′ have been synthesized in [2+2] block syntheses.N-Iodosuccinimide-mediated coupling of tetra-O-benzyl-glucose to tri-O-acetyl-D-glucal followed byO-acetylation furnished 3,4,6-tri-O-acetyl-2-deoxy-2-iodo-α-D-mannopyranosyl 2,3,4,6-tetra-O-benzyl-α-D-glucopyranoside (7), which was used as a starting material for both tetrasaccharides. For the preparation of the 2′-monodeoxygenated saccharide the deoxyiodo pyranose moiety of7was further elaborated by de-O-acetylation,O-benzylidenation,O-benzylation, and selective reductive opening of the benzylidene acetal to give glycosyl acceptor10. Glycosylation with hepta-O-acetylmaltosyl bromide and deprotection including removal of the iodo substituent afforded the 2′-deoxymaltosyl-(1→4)-trehalose14. On the other hand, the non-iodinated pyranose moiety of7was transformed to a glycosyl acceptor. The removal of the benzyl groups of7necessitated also the reduction of the iodo group at this early stage. The resulting 3,4,6-tri-O-acetyl-2-deoxy-α-D-arabino-hexopyranosyl α-D-glucopyranoside was subjected to a similar reaction sequence as above to finally result in the 2-deoxymaltosyl-(1→4)-trehalose22.

ISSN:0732-8303    

DOI:10.1080/07328309808002338

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The synthesis of a cellobiouronic thioglycoside donor12, protected with a selectively removable 3′-O-benzyl group is described. The donor12is suitable as a monomer building block in the construction of oligomer structures corresponding to the capsular polysaccharide ofStreptococcus pneumoniaetype 3. The carboxyl function was introduced through regioselective TEMPO-oxidation of a 4′,6′-diol cellobiose derivative. If the oxidation was performed on a 2,3,2′,3′,4′,6′-hexaol derivative, oxidation also of the secondary 2- and 3-hydroxyl groups was observed to give a tricarboxyl derivative as one of the major products. The thioglycoside was formed by acidic mercaptolysis of a 1,6-anhydro bridge. The donor12was transformed into a suitable starting monomer acceptor through glycosylation with a spacer alcohol and subsequent debenzylation.

ISSN:0732-8303    

DOI:10.1080/07328309808002339

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Five sialyl Lew is X ganglioside analogs containing 4-(2-tetradecylhexadecanoylamino)benzyl group in place of ceramide and a variety of lengths of ethylene glycol chains as the spacer, have been synthesized. Glycosidation ofO-(methyl 5-acetamido-4,7,8,9-tetra-O-acetyl-3,5-dideoxy-D-glycero-α-D-glacto-2-nonulopyranosylonate)-(2→3)-O-(4-O-acetyl-2,6-di-O-benzoyl-β-D-galactopyranosyl)-(1→4)-O-[(2,3,4-tri-O-acetylα-L-fucopyranosyl)-(1→3)]-2,4-di-O-benzoyl-α-D-glucopyranosyl trichloroacetimidate (13) with oligo ethyleneglycol monobenzyl ether derivatives9, 10, 11and12, prepared from the corresponding oligo ethyleneglycols by 4-nitrobenzylation, reduction andN-acylation with 2-tetradecylhexadecanoic acid, using boron trifluoride etherate gave the corresponding glycolipid derivatives14, 15, 16and17. A similar glycosidation of13with 4-nitrobenzyl alcohol gave the 4-nitrobenzyl glycoside18, which was convertedviareduction of nitro group andN-acylation into the corresponding glycolipid derivative19. Compounds14-17and19were transformed into the title compounds byO-deacylation and hydrolysis of methyl ester group in good yields.

ISSN:0732-8303    

DOI:10.1080/07328309808002340

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The relative reactivity of various thioglycosyl donors having ethyl, phenyl, orpara-substituted phenyl groups with electron donating (N-Ac) or electron withdrawing (NO2) substituents were compared using 1,2:3,4-di-O-isopropylidene-α-D-galactopyranose (3) as standard glycosyl acceptor. The reactivity order was found to decrease from ethyl > phenyl >p-acetamidophenyl >p-nitrophenyl. In the latter situation, when the thioglycosyl donor was also equipped with “disarming” ester protecting groups, they were found to be inert or inactive toward common thiophilic promotors. Alternatively, it was possible to selectively activate the “armed” perbenzylatedp-nitrophenyl 1-thio-β-D-galactopyranoside (21) in the presence of the corresponding “disarmed” perbenzoylatedp-nitrophenyl 2,3,4-tri-O-benzoyl-1-thio-β-D-galactopyranoside (15) which served as the glycosyl acceptor. When both “armed” perbenzylated thioglycosides7and25were used as thioglycosyl donor and thioglycosyl acceptor, respectively, the milder thiophilic promotor methyl triflate was required for chemoselective activation. These results further demonstrate the potential of “armed and disarmed” “active and latent” thioglycosides in blockwise oligosaccharide syntheses.

ISSN:0732-8303    

DOI:10.1080/07328309808002341

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

A new class of glycopeptides8and10, were synthesized from 3-carboxypropyl lactoside4and tricosapeptide6on a solid support. Their amino acid sequences include a dimerization motif of glycophorin A transmembrane domain. The dimerizable properties of the synthesized glycopeptides and non-glycosylated peptides were investigated by Tris-Tricine-SDS-PAGE.

ISSN:0732-8303    

DOI:10.1080/07328309808002342

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor