山豆根木葡聚糖的研究

研究了山豆根中一种木葡聚糖的结构．用１ｍｏｌ／ＬＮａＯＨ提取,ＤＥＡＥ－ＳｅｐｈａｄｅｘＡ－２５离子交换柱层析,Ｆｅｈｌｉｎｇ试剂分级得到山豆根木葡聚糖组分ＳＳｂ－１ＦＡ,用完全酸水解,甲基化分析,部分酸水解,三氧化铬氧化和１Ｈ,１３ＣＮＭＲ等方法对其结构进行研究．结果表明：ＳＳｂ－１ＦＡ的分子量为２．６×１０４,比旋光度［α］２０Ｄ＝＋１０．９°（ｃ０．２２,Ｈ２Ｏ）,由Ｌ－Ｆｕｃ,Ｄ－Ｘｙｌ,Ｄ－Ｇａｌ和Ｄ－Ｇｌｃ组成,摩尔比为：２．９２９．９７．５５９．８．ＳＳｂ－１ＦＡ由１→４连接的β－Ｄ－Ｇｌｃ残基构成主链,分枝有α－Ｄ－Ｘｙｌ（１→,β－Ｄ－Ｇａｌ（１→２）α－Ｄ－Ｘｙｌ（１→等类型,部分非还原末端由Ｌ－Ｆｕｃ（１→构成．     

Synthesis of methyl glycoside derivatives of tri- and penta-saccharides related to the antithrombin III-binding sequence of heparin, employing cellobiose as a key starting-material

Two key synthons for the title pentasaccharide derivative, methyl O-(methyl 2-O-benzoyl-3-O-benzyl-alpha-L-idopyranosyluronate)-(1----4)-6-O-acetyl- 2-azido - 3-O- benzyl-2-deoxy-beta-D-glucopyranoside and O-(methyl 2,3-di-O-benzyl-4-O- chloroacetyl-beta-D-glucopyranosyluronate)-(1----4)-3,6-di-O-acetyl-2-az ido-2- deoxy-alpha-D- glucopyranosyl bromide, were prepared from a common starting material, cellobiose. They were coupled to give a tetrasaccharide derivative that underwent O-dechloroacetylation to the corresponding glycosyl acceptor. Its condensation with the known 6-O-acetyl-2-azido-3,4-di-O-benzyl-2-deoxy-alpha-D-glucopyranosyl bromide afforded a 77% yield of suitably protected pentasaccharide, methyl O-(6-O- acetyl-2-azido-3,4-di-O-benzyl-2-deoxy-alpha-D-glucopyranosyl)-(1----4)- O- (methyl 2,3- di-O-benzyl-beta-D-glucopyranosyluronate)-(1----4)-O-(3,6-di-O-acetyl-2- azido-2 - deoxy-alpha-D-glucopyranosyl)-(1----4)-O-(methyl 2-O-benzoyl-3-O-benzyl-alpha-L- idopyranosyluronate)- (1----4)-6-O-acetyl-2-azido-3-O-benzyl-2-deoxy-beta-D-glucopyranoside. Sequential deprotection and sulfation gave the decasodium salt of methyl O-(2- deoxy-2-sulfamido-6-O-sulfo-alpha-D-glucopyranosyl)-(1----4)-O-(be ta-D- glucopyranosyl-uronic acid)-(1----4)-O-(2-deoxy-2-sulfamido-3,6-di-O-sulfo-alpha-D-gluco pyranosyl)- (1----4)-O-(2-O-sulfo-alpha-L-idopyranosyluronic acid)-(1----4)-2-deoxy-2- sulfamido-6-O- sulfo-beta-D-glucopyranoside (3). In a similar way, the trisaccharide derivative, the hexasodium salt of methyl O-(2-deoxy-2-sulfamido-6-O-sulfo-alpha-D- glucopyranosyl)- (1----4)-O-(beta-D-glucopyranosyluronic acid)-(1----4)-2-deoxy-2-sulfamido-3,6- di-O- sulfo-alpha-D-glucopyranoside (4) was synthesized from methyl O-(6-O-acetyl-2- azido- 3,4-di-O-benzyl-2-deoxy-alpha-D-glucopyranosyl)-(1----4)-O-(methyl 2,3-di-O- benzyl-beta- D-glucopyranosyluronate)-3,6-di-O-acetyl-2-azido-2-deoxy-alpha-D- glucopyranoside. The pentasaccharide 3 binds strongly to antithrombin III with an association constant almost equivalent to that of high-affinity heparin, but the trisaccharide 4 appears not to bind.     

A facile synthesis of nitrophenyl oligosaccharides containing the O-alpha-L-fucopyranosyl-(1----3)-2-acetamido-2-deoxy-beta-D-glucopyrano syl unit at their nonreducing end.

A facile approach towards the synthesis of 4-nitrophenyl O-alpha-L-fucopyranosyl-(1----3)-2-acetamido-2-deoxy-beta-D-glucopyra nos ide, 2-nitrophenyl O-alpha-L-fucopyranosyl-(1----3)-O-(2-acetamido-2-deoxy-beta-D-glucop yra nosyl)- (1----6)-2-acetamido-2-deoxy-alpha-D-galactopyranoside, 4-nitrophenyl O-alpha-L-fucopyranosyl-(1----3)-O-(2-acetamido-2-deoxy-beta-D-glucop yra nosyl)- (1----6)-alpha-D-mannopyranoside, and 4-nitrophenyl O-alpha-L-fucopyranosyl-(1----3)-O-(2-acetamido-2-deoxy-beta-D-glucop yra nosyl)-(1----6)-beta-D-galactopyranoside has been accomplished through the development and use of methyl 3,4-O-isopropylidene-2-O-(4-methoxybenzyl)-1-thio-beta-L-fucopyranoside as the glycosyl donor.     

Synthesis of a fully protected derivative of O-(N-acetyl-alpha-D-neuraminyl)-(2----3)-O-beta-D-galactopyranosyl-(1- ---3)-O- [(N-acetyl-alpha-D-neuraminyl)-(2----6)]-O-(2-acetamido-2-deoxy-alpha- D-galactopyranosyl)-(1----3)-L-serine

N-(Benzyloxycarbonyl)-O-[methyl (5-acetamido-4,7,8,9-tetra-O-acetyl-3,5-dideoxy-D-glycero-alpha-D-galact o-2- nonulopyranosyl)onate]-(2----3)-O-(2,4,6-tri-O-acetyl-beta-D - galactopyranosyl)-(1----3)-O-[methyl (5-acetamido-4,7,8,9-tetra-O-acetyl-3,5-dideoxy-D-glycero-alpha-D-galact o-2- nonulopyranosyl)onate-(2----6)]-O-(2-acetamido-4-O-acetyl-2- deoxy-alpha-D- galactopyranosyl)-(1----3)-L-serine benzyl ester was synthesized by using O-[methyl (5-acetamido-4,7,8,9-tetra-O-acetyl-3,5- di-deoxy-D-glycero-alpha-D-galacto-2-nonulopyranosyl)onate]- (2----3)-O-(2,4,6- tri-O-acetyl-beta-D-galactopyranosyl)-(1----3)-O-[methyl (5-acetamido-4,7,8,9-tetra-O-acetyl-3,5-dideoxy-D-glycero-alpha-D-galact o-2- nonulopyranosyl)onate-(2----6)]-4-O-acetyl-2-azido-2-deoxy-a lpha- and -beta-D-galactopyranosyl trichloroacetimidate as a key glycotetraosyl donor which, upon reaction with N-(benzyloxycarbonyl)-L-serine benzyl ester, afforded a 44% yield of a mixture of the alpha- and beta-glycosides in the ratio of 2:5.     

Syntheses of linear tetra-, hexa-, and octa-saccharide fragments of the i-blood group active poly-(N-acetyl-lactosamine) series. Blockwise methods for the synthesis of repetitive oligosaccharide sequences

N-Phthaloylation of lactosamine gave various glycosyl donors (beta-chloride, beta-trichloroacetimidate) and glycosyl acceptors (3',4'-diol). Coupling of the chloride with a methyl beta-D-glycoside led to the tetrasaccharide fragment, beta-D-Galp-(1----4)-beta-D-GlcpNac-(1----3)-beta-D-Galp-(1----4)- beta-D-GlcpNAcOMe. Acetolysis of the protected tetrasaccharide, followed by treatment with hydrogen chloride, gave a tetrasaccharide chloride which was coupled with the methyl beta-glycoside of lactosamine. A hexasaccharide fragment, [beta-D-Galp-(1----4)-beta-D-GlcpNAc-(1----3)]2-beta-D-Galp-(1----4)-bet a- D-GlcpNAcOMe, was thus obtained by this ("n + 1") method. A more efficient ("n + n") method was applied for the synthesis of an octasaccharide fragment, [beta-D-Galp-(1----4)-beta-D-GlcpNAc-(1----3)]3-beta-D-Galp- (1----4)-beta-D-GlcpNAcOMe (38), where di- and tetra-saccharide intermediates having a 3,4-O-isopropylidene-beta-D-galactopyranosyl nonreducing terminal group and a benzyl beta-D-glycoside group were precursors, either as glycosyl donors (beta-trichloroacetimidates) or glycosyl acceptors (3,4-diols as nonreducing terminal groups). Thus, doubling the length of the repetitive oligosaccharide sequence could be efficiently accomplished at each glycosylation step.     

A Study on the Original Plants of the Chinese Drug Guangdougen (Shandougen)

Guangdougen is generally known as Shandougen. It is a traditional Chinese drug. It can be used as antipyretic, antidote, anodyne or antiinflammation agent. In recent years, some compounds (alkaloids, flavones and a new glycoside) such as cytisine, matrine, oxymatrine, pterocarpin and isoprenyl chalcone, have been isolated from roots of Guangdougen for medicinal purposes. They give effects of antiarrhythmia, anticancer or antiulcer. A recent investigation reveals that the Guangdougen comes from Sophora tonkinensis Gagnep. (syn. Sophora subprostrata Chun et T. Chen) and Sophora tonkinensis Gagnep. var. polyphylla S. Z. Huang et Z. C. Zhou, var. nov. Gnangdougen is geographically restricted to SE. and NW. Guangxi and SE. Guizhou and Yunnan (103-109°E, 22-26°N). They have an ecological preference for limestone regions, very commonly growing in mountains of 500-800 m alt.     

Synthesis of some D-mannosyl-oligosaccharides containing the methyl and 4-nitrophenyl beta-D-mannopyranoside units

Methyl 3,4,6-tri-O-benzyl-beta-D-mannopyranoside (2), methyl 2,3-O-isopropylidene-beta-D-mannopyranoside (11), and 4-nitrophenyl 2,3-O-isopropylidene-beta-D-mannopyranoside (12) were each condensed with 2,3,4,6-tetra-O-acetyl-alpha-D-mannopyranosyl bromide (1) in the presence of mercuric cyanide, to give after deprotection, methyl 2-(5) and 6-O-alpha-D-mannopyranosyl-beta-D-mannopyranoside (15), and 4-nitrophenyl 6-O-alpha-D-mannopyranosyl-beta-D-mannopyranoside (20), respectively. A similar condensation of 11 with 3,4,6-tri-O-acetyl-2-O-(2,3,4,6-tetra-O-acetyl-alpha-D-mannopyranosyl)-a lpha-D- mannopyranosyl bromide (21) and 2,3,4-tri-O-acetyl-6-O-(2,3,4,6-tetra-O-acetyl-alpha-D-mannopyranosyl)-a lpha D-mannopyranosyl bromide (25), followed by removal of protecting groups, afforded methyl O-alpha-D-mannopyranosyl-(1----2)-O-alpha-D-mannopyranosyl-(1----6)-beta -D- mannopyranoside (24) and methyl O-alpha-D-mannopyranosyl-(1----6)-O-alpha-D-mannopyranosyl-(1----6)-beta -D- mannopyranoside (28), respectively. Bromide 25 was also condensed with 12 to give a trisaccharide derivative which was deprotected to furnish 4-nitrophenyl O-alpha-D-mannopyranosyl-(1----6)-alpha-D-mannopyranosyl-(1----6)-beta-D - mannopyranoside (31). Phosphorylation of methyl 3,4,6-tri-O-benzyl-2-O-alpha-D-mannopyranosyl-beta-D-mannopyranoside and 15 with diphenyl phosphorochloridate in pyridine gave the 6'-phosphates 6 and 16, respectively. Hydrogenolysis of the benzyl and phenyl groups provided methyl 2-O-(disodium alpha-D-mannopyranosyl 6-phosphate)-beta-D-mannopyranoside (7) and methyl 6-O-(disodium alpha-D-mannopyranosyl 6-phosphate)-beta-D-mannopyranoside (17) after treatment with Amberlite IR-120 (Na+) cation-exchange resin. The structures of compounds 5, 7, 15, 17, 20, 24, 28, and 31 were established by 13C-n.m.r. spectroscopy.     

Synthesis of alpha-D-Manp-(1----3)-[beta-D-GlcpNAc-(1----4)]-[alpha-D-Manp+ ++-(1----6)] - beta-D-Manp-(1----4)-beta-D-GlcpNAc-(1----4)-[alpha-L-Fucp- (1----6)]-D- GlcpNAc, a core glycoheptaose of a "bisected" complex-type glycan of glycoproteins

A synthesis of alpha-D-Manp-(1----3)-[beta-D-GlcpNAc-(1----4)]-[alpha-D-Manp++ +-(1----6)]- beta-D-Manp-(1----4)-beta-D-GlcpNAc-(1----4)-[alpha-L-Fucp-( 1----6)]-D- GlcpNAc was achieved by employing benzyl O-(3,4,6-tri-O-benzyl-2-deoxy-2-phthalimido-beta-D-glucopyranosyl)-(1--- -4)-O- (2-O-benzyl-beta-D-mannopyranosyl)-(1----4)-O-(3,6-di-O-benzyl-2-deoxy-2 - phthalimido-beta-D-glucopyranosyl)-(1----4)-3-O-benzyl-2-deoxy-6-O-p- methoxyphenyl-2-phthalimido-beta-D-glucopyranoside as a key glycosyl acceptor. Highly stereoselective mannosylation was performed by taking advantage of the 2-O-acetyl group in the mannosyl donors. The alpha-L-fucopyranosyl residue was also stereoselectively introduced by copper(II)-mediated activation of methyl 2,3,4-tri-O-benzyl-1-thio-beta-L-fucopyranoside.     

Synthesis of the methyl and 1-octyl glycosides of the P-antigen tetrasaccharide (globotetraose)

The methyl and 1-octyl beta-glycosides of the P-antigen tetrasaccharide [globotetraose, beta-D-GalpNAc-(1----3)-alpha-D-Galp-(1----4)-beta-D-Galp-(1----4) -D-Glc] were synthesised from a tetrasaccharide precursor, prepared using methyl disaccharide 1-thioglycosides as intermediates. In the key glycosidation with silver triflate, HO-2 was used as an alpha-directing group in the glycosyl bromide.     

Determination of 3-deoxy-D-manno-octulosonic acid (KDO), N-acetylneuraminic acid, and their derivatives by ion-exchange liquid chromatography

A liquid chromatography (1.6 MPa) system for the analysis of 3-deoxy-D-manno-2-octulosonic acid (KDO), N-acetylneuraminic acid (Neu5Ac), methyl alpha- and beta-glycosides of Neu5Ac and KDO, alpha-heptosyl-(1----5)-KDO, various sialyllactoses, alpha-KDO-(2----4)-KDO, alpha-KDO-(2----4)-KDO methyl alpha-glycoside, beta-KDO-(2----4)-KDO methyl beta-glycoside, D-glucuronic acid, D-glucurono-3,6-lactone, and D-galacturonic acid has been developed. Separation was achieved within 10 and 30 min by the use of a small column filled with a strongly basic, anion-exchange resin, Aminex A-29, and 0.75 or 10mM sodium sulfate solutions as mobile phases. This method allowed the determination of KDO and sialic acids in amounts of 100 ng (0.5 nmol) and 200 pg (0.6 pmol), respectively.     

Synthesis of trisaccharide methyl glycosides related to fragments of the capsular polysaccharide of Streptococcus pneumoniae type 18C.

The synthesis is reported of methyl 3-O-(4-O-beta-D-galactopyranosyl-alpha-D- glucopyranosyl)-alpha-L-rhamnopyranoside (1), methyl 2-O-alpha-D-glucopyranosyl-4-O-beta-D-glucopyranosyl-beta-D- galactopyranoside (3), methyl 3-O-(4-O-beta-D-galactopyranosyl-alpha-D-glucopyranosyl)-alpha-L- rhamnopyranoside 3"-(sn-glycer-3-yl sodium phosphate) (2), and methyl 2-O-alpha-D-glucopyranosyl-4-O-beta-D- glucopyranosyl-beta-D-galactopyranoside 3-(sn-glycer-3-yl sodium phosphate) (4), which are trisaccharide methyl glycosides related to fragments of the capsular polysaccharide of Streptococcus pneumoniae type 18C ([----4)-beta-D- Glcp-(1----4)-[alpha-D-Glcp-(1----2)]-[Glycerol-(1-P----3)]-beta-D-Galp - (1----4)-alpha-D-Glcp-(1----3)-alpha-L-Rhap-(1----]n). Ethyl 4-O-acetyl-2,3,6-tri-O-benzyl-1-thio-beta-D-glucopyranoside (10) was coupled with benzyl 2,4-di-O-benzyl-alpha-L-rhamnopyranoside (6). Deacetylation of the product, followed by condensation with 2,4,6-tri-O-acetyl-3-O-allyl-alpha-D-galactopyranosyl trichloroacetimidate (18), gave benzyl 2,4-di-O-benzyl-3-O-[2,3,6-tri-O- benzyl-4-O-(2,4,6-tri-O-acetyl-3-O-allyl-beta-D-galactopyranosyl)-alpha- D- glucopyranosyl]-alpha-L-rhamnopyranoside (19). Acetolysis of 19, followed by methylation, deallylation (----22), and further deprotection afforded 1. Condensation of methyl 2,4-di-O-benzyl-3-O-[2,3,6-tri-O-benzyl-4-O-(2,4,6-tri- O-acetyl-beta-D-galactopyranosyl)-alpha-D-glucopyranosyl]-alpha-L- rhamnopyranoside (22) with 1,2-di-O-benzyl-sn-glycerol 3-(triethyl-ammonium phosphonate) (24), followed by oxidation and deprotection, yielded 2. Condensation of ethyl 2,3,4,6-tetra-O-benzyl-1-thio-beta-D-glucopyranoside (27) with methyl 3-O-allyl-4,6-O-benzylidene-beta-D-galactopyranoside (28), selective benzylidene ring-opening of the product, coupling with 2,3,4,6-tetra-O-acetyl-alpha-D-glucopyranosyl trichloroacetimidate (31), and deallylation afforded methyl 6-O-benzyl-4-O-(2,3,4,6-tetra-O-acetyl-beta-D-glucopyranosyl)-2-O- (2,3,4,6-tetra-O-benzyl-alpha-D-glucopyranosyl)-beta-D-galactopyranoside (33). Deprotection of 33 gave 3, and condensation of 33 with 24, followed by oxidation and deprotection, gave 4.     

Total synthesis of sialosylcerebroside, GM4

Described are total syntheses of O-[sodium (5-acetamido-3,5-dideoxy-D -glycero-alpha-D-galacto-2-nonulopyranosyl)onate]-(2----3)-O -beta-D -galactopyranosyl-(1----1)-(2R,3S,4E)-2-N-tetracosanoylsphingen ine,O-[sodium (5-acetamido-3,5-dideoxy-D-glycero-alpha-D-galacto-2-nonulopyranosyl+ ++)onate] -(2----3)-O-alpha-D-galactopyranosyl-(1----1)-(2R,3S,4E)-2-N -tetracosanoylsphingenine, O-[sodium (5-acetamido-3,5-dideoxy-D-glycero-beta -D-galacto-2-nonulopyranosyl)onate]-(2----3)-O-beta-D-gal act opyranosyl -(1----1)-(2R,3S,4E)-2-N-tetracosanoylsphingenine, and O-[sodium (5-acetamido-3,5-dideoxy-D-glycero-beta-D-galacto-2-nonulopyranosyl++ +)onate] -(2----3)-O-alpha-D-galactopyranosyl-(1----1)-(2R,3S,4E)-2-N -tetracosanoylsphingenine by using O-[methyl (5-acetamido-4,7,8,9-tetra-O-acetyl-3,5-dideoxy-D-glycero-alpha-D -galacto-2-nonulopyranosyl)onate]-(2----3)-2,3,4,6-tetra-O-a cetyl-D -galactopyrano-syl trichloroacetimidate and O-[methyl (5-acetamido-4,7,8,9-tetra-O-acetyl-3,5-dideoxy-D-glycero-beta -D-galacto-2-nonulopyranosyl)onate]-(2----3)-2,4,6-tri-O-ace tyl-D-galactopyranosyl trichloroacetimidate as key glycosyl donors, and (2S,3R,4E)-3 -O-benzoyl-2-N-tetracosanoylsphingenine as a key glycosyl acceptor.     

Synthesis of a peripheral trisaccharide sequence of lutropin, a pituitary glycoprotein hormone; use of chitobiose as a key starting material

A chitobiose derivative, methyl O-(3,4,6-tri-O-acetyl-2-deoxy-2-phthalimido-beta-D-glucopyranosyl)-(1--- -4)-3,6 - di-O-acetyl-2-deoxy-2-phthalimido-beta-D-glucopyranoside, was derived from the corresponding N-acetyl derivative and this was converted into the glycosyl bromide (5). Glycosidation reaction between 5 and methyl 3,4,6-tri-O-benzyl-alpha-D-mannopyranoside in the presence of silver trifluoromethanesulfonate gave a beta-D-linked trisaccharide derivative. Replacement of the N,N-phthaloyl group by acetyl groups resulted in a product that was converted into methyl O-(2-acetamido-3,6-di-O-benzyl-2-deoxy-beta-D-glucopyranosyl)-(1----4)-O -(2- acetamido-3,6-di-O-benzyl-2-deoxy-beta-D-glucopyranosyl)-(1----2)-3,4,6- tri-O- benzyl-alpha-D-mannopyranoside (11) by use of a few reaction steps. The 4(3)-hydroxyl group of 11 was methanesulfonylated, and the product subjected to SN2 replacement with acetate anion, to give the D-galactosamine-containing trisaccharide derivative (12). After basic hydrolysis of 12, the 4(3)-hydroxyl group was sulfated, and all benzyl groups were removed by hydrogenolysis, giving methyl O-(2-acetamido-2-deoxy-4-O-sulfo-beta-D-galactopyranosyl)-(1----4)-O-(2- acetamido-2-deoxy-beta-D-glucopyranosyl)-(1----2)-alpha-D-mannopyranosid e monosodium salt, the methyl alpha-glycoside derivative of the peripheral trisaccharide sequence of the pituitary glycoprotein hormone lutropin.     

Differential binding characteristics and applications of DGal beta 1----3DGalNAc specific lectins

The binding properties of Arachis hypogaea (PNA), Bauhinia purpurea alba (BPL), Maclura pomifera ( MPL ) and Sophora japonica (SJL) lectins were studied by quantitative precipitin and precipitin inhibition assays, demonstrating them to be most specific for DGal beta 1---- 3DGalNAc residues. Additionally, each lectin had its own binding characteristic such as different binding activities to DGal beta 1---- 4DGlcNAc or DGal beta 1---- 3DGlcNAc beta 1----linked oligosaccharides, and/or DGalNAc alpha 1----linked to the Ser or Thr of the protein moiety. These differential binding characteristics can be used for investigating fine differences of the carbohydrate structure of the glycoconjugates, especially those having DGal beta 1---- 3DGalNAc residues as terminal non-reducing ends.     

Synthesis of alternate linear and branched repeating units of the Escherichia coli LP 1092 capsular polysaccharide containing 3-deoxy-alpha-D-manno-2-octulosonic acid (KDO) linked to secondary positions of D-ribose

The oligosaccharides, methyl 3-O-(sodium 3-deoxy-alpha-D-manno-2-octulopyranosylonate)-beta-D-ribofuranosid e, methyl 2-O-beta-D-ribofuranosyl-3-O-(sodium 3-deoxy-alpha-D-manno-2-octulopyranosylonate)-beta-D-ribofuranosid e, and methyl O-(sodium 3-deoxy-alpha-D-manno-2-octulopyranosylonate)-(2----2)-O-beta-D- ribofuranosyl-(1----2)-beta-D-ribofuranoside were prepared in high purity and good over-all yields. The constitutions of the trisaccharide derivatives correspond to the repeating units of the proposed linear and branched structures of the capsular polysaccharide(s) from Escherichia coli LP 1092. The alpha-KDO-(2----3)-beta-D-Ribf and alpha-KDO-(2----2)-beta-D-Ribf units were synthesized by a modification of the Helferich procedure using methyl (4,5,7,8-tetra-O-acetyl-3-deoxy-alpha-D-manno-2-octulopyranosyl bromide)-onate and appropriate beta-D-ribofuranosyl derivatives. The constitutional and configurational assignments were based on the 250-MHz 1H-n.m.r.-spectra of protected derivatives of the oligosaccharides.     

Synthesis of a selectively protected trisaccharide building block of the capsular polysaccharide of Streptococcus pneumoniae types 6A and 6B

4-Methoxybenzyl 2,4-di-O-benzyl-3-O-[2,4,6-tri-O-benzyl-3-O-(3,4,6-tri-O-benzyl-alpha-D- galactopyranosyl)-alpha-D-glucopyranosyl]-alpha-L-rhamnopyranoside (22), a building block for the alpha-D-Galp-(1----3)-alpha-D-Glcp-(1----3)-alpha-L-Rhap fragment of the capsular polysaccharides of Streptococcus pneumoniae types 6A and 6B [----2)-alpha-D-Galp-(1----3)-alpha-D-Glcp-(1----3)-alpha-L-Rhap-( 1----X)-D- RibOH-(5-P----]n (6A, X = 3; 6B, X = 4) has been synthesised. Ethyl 3-O-allyl-2,4,6-tri-O-benzyl-1-thio-beta-D-glucopyranoside was coupled with 4-methoxybenzyl 2,4-di-O-benzyl-alpha-L-rhamnopyranoside in ether, using methyl triflate as promoter. The resulting alpha-D-Glcp-(1----3)-alpha-L-Rhap derivative was deallylated with KOBut in N,N-dimethylformamide followed by 0.1M HCl in 9:1 acetone-water. The product was coupled with 3,4,6-tri-O-acetyl-2-O-allyl-alpha,beta-D-galactopyranosyl trichloroacetimidate in ether, using trimethylsilyl triflate, to yield 19. Deacetylation, benzylation, and deallylation then gave 22.     

An efficient synthesis of ganglioside GM3: highly stereocontrolled glycosylations by use of auxiliaries

An efficiently stereocontrolled total synthesis of GM3 alpha-D-Neup5Ac-(2----3)-beta-D-Galp-(1----4)-beta-D-Glcp-(1----1) -Cer was achieved by employing both methyl 5-acetamido-4,7,8,9-tetra-O-benzyl-2-bromo-2,3,5-trideoxy-3- phenylthio-D-erythro-beta-L-gluco-2-nonulopyranosonate for the key sialylation step, and O-[methyl(5-acetamido-4,7,8,9-tetra-O-acetyl-3,5-dideoxy-D-glycero-alpha -D-galacto-2-nonulopyranosyl)onate]-(2----3)-O-(2,4,6-tri-O- acetyl-beta-D-galactopyranosyl-(1----4)-3,6-di-O-acetyl-2-O-pivaloyl- alpha-D-glucopyranosyl trichloroacetimidate and fluoride for the key coupling step with a ceramide derivative. These two steps were significantly altered and improved in comparison with our previous synthesis that had been executed without use of stereocontrolling auxiliaries. GM3 was obtained in 4.5% overall yield in 19 steps starting from allyl O-(2,6-di-O-acetyl-3,4-O-isopropylidene-beta-D-galactopyranosyl)-(1----4 )-2,3,6-tri-O-acetyl-beta-D-glucopyranoside.     

Crystallization of the lectin IV of Griffonia simplicifolia and its complexes with the Lewis b and Y human blood group determinants

Single crystals of the lectin IV from Griffonia simplicifolia have been grown in the tetragonal crystal system. The space group is P4(2)2(1)2 with a = 78.95(5) A and c = 89.01(2) A, and there is one subunit of the dimeric glycoprotein in the crystallographic asymmetric unit. The crystals diffract to at least 2.5 A d spacings and are stable in the x-ray beam for 3 weeks. Crystals of the complex with the Lewis b (Leb) and Y human blood group determinants as the methyl glycosides, alpha-L-Fuc(1----2)beta-D-Gal(1----3)[alpha-L-Fuc(1----4)]beta-D-GlcNAc-OMe (where Fuc is fucose and -OMe is methoxy) and alpha-L-Fuc(1----2)beta-D-Gal(1----4)[alpha-L-Fuc(1----3)]-beta-D-GlcNAc- OMe, respectively, have also been grown and found to be isomorphous with the native lectin. Crystals have also been obtained with several derivatives of the Lewis b-OMe tetrasaccharide including that which has the 6-hydroxyl of the beta-D-GlcNAc unit replaced by iodine. In the latter case, the presence of the iodine atoms was established.     

Biosynthesis of the blood group Pk and P1 antigens by human kidney microsomes.

On human erythrocytes, the membrane components associated with Pk and P1 blood-group specificity are glycosphingolipids that carry a common terminal alpha-D-Galp-(1----4)-beta-D-Gal unit, the biosynthesis of which is poorly understood. Human kidneys typed for P1 and P2 (non-P1) blood-group specificity have been assayed for (1----4)-alpha-D-galactosyltransferase activity by use of lactosylceramide [beta-D-Galp-(1----4)-beta-D-Glcp-ceramide] and paragloboside [beta-D-Galp-(1----4)-beta-D-GlcpNAc-(1----3)-beta-D-Galp- (1----4)-beta-D-Glcp-ceramide] as acceptor substrates. The linkage and anomeric configuration of the galactosyl group transferred into the reaction products were established by methylation analysis before and after alpha- and beta-D-galactosidase treatments, as well as by immunostaining using specific monoclonal antibodies directed against the Pk and P1 antigens. The results demonstrated that the microsomal proteins from P1 kidneys catalyze the synthesis of Pk [alpha-D-Galp-(1----4)-beta-D-Galp-(1----4)-beta-D-Glcp-ceramide] and P1 [alpha-D-Galp-(1----4)-beta-D-Galp-(1----4)-beta-D-GlcpNAc-(1----3)-beta -D-Galp-(1----4)-beta-D-Glcp-ceramide] glycolipids, whereas microsomes from P2 kidney catalyze the synthesis of the Pk glycolipid, but not of the P1 glycolipid. Competition studies using a mixture of two oligosaccharides (methyl beta-lactoside and methyl beta-lacto-N- neotetraoside) or of two glycolipids (lactosylceramide and paragloboside) as acceptors indicated that these substrates do not compete for the same enzyme in the microsomal preparation from P1 kidneys. The results suggested that the Pk and P1 glycolipids are synthesized by two distinct enzymes.     

Total synthesis of the mollu-series glycosyl ceramides alpha-D-Manp-(1----3)-beta-D-Manp-(1----4)-beta-D-Glcp-(1----1)-Cer and alpha-D-Manp-(1----3)-[beta-D-Xylp-(1----2)]-beta-D-Manp-(1----4)-beta- D-Glcp-(1----1)-Cer

The mollu-series glycosphingolipids, O-alpha-D-mannopyranosyl-(1----3)-O-beta-D-mannopyranosyl-(1----4)-O-bet a-D-glucopyranosyl-(1----1)-2-N-tetracosanoyl-(4E)-sphingeni ne and O-alpha-D-mannopyranosyl-(1----3)-O-[beta-D-xylopyranosyl-(1----2])-O- beta-D-mannopyranosyl-(1----4)-O-beta-D-glucopyranosyl-(1----1)-2-N- tetracosanoyl-(4E)-sphingenine, were synthesized for the first time by using 2,3,4-tri-O-acetyl-D-xylopyranosyl trichloroacetimidate, methyl 2,3,4,6-tetra-O-acetyl-1-thio-alpha-D-mannopyranoside, benzyl O-(4,6-di-O-benzyl-beta-D-mannopyranosyl)-(1----4)-2,3,6-tri-O-benzyl-be ta-D- glucopyranoside 9, and (2S,3R,4E)-2-azido-3-O-(tert-butyldiphenylsilyl)-4-octade cene-1,3-diol 6 as the key intermediates. The hexa-O-benzyl disaccharide 9 was prepared by coupling two monosaccharide synthons, namely, 2,3-di-O-allyl-4,6-di-O-benzyl-alpha-D-mannopyranosyl bromide and benzyl 2,3,6-tri-O-benzyl-beta-D-glucopyranoside. It was demonstrated that azide 6 was highly efficient as a synthon for the ceramide part in the coupling with both glycotriaosyl and glycotetraosyl donors, particularly in the presence of trimethylsilyl triflate.