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.     

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.     

Total synthesis of 3-O-[2-acetamido-6-O-(N-acetyl-alpha-D-neuraminyl-2-deoxy- alpha-D-galactosyl]-L-serine and a stereoisomer

O-(5-Acetamido-3,5-dideoxy-D-glycero-alpha-D-galacto-2- nonulopyranoxylonic acid)-(2----6)-O-(2-acetamido-2-deoxy-alpha-D-galactopyranosyl)-(1----3) -L-serine, a structural unit occurring in various submaxillary mucins, was synthesized for the first time 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----6)-3,4-di-O-acetyl-2- azido-2-deoxy-D- galactopyranosyl trichloroacetimidate (13) and N-(benzyloxycarbonyl)-L-serine benzyl ester as the key intermediates. The trichloroacetimidate 13 was prepared by starting from two monosaccharide synthons, namely, allyl 2-azido-2-deoxy-beta-D-galactopyranoside and methyl (5-acetamido-4,7,8,9-tetra-O-acetyl-3,5-dideoxy-D-glycero-beta-D- galacto-2-nonulopyranosyl chloride)onate, which were coupled in the presence of silver triflate in tetrahydrofuran to give the desired alpha-(2----6)-linked disaccharide in moderate selectivity.     

Synthesis of a mucin-type O-glycosylated amino acid, beta-Gal-(1----3)-[alpha-Neu5Ac-(2----6)]-alpha-GalNAc-(1----3)- Ser

Total synthesis of O-beta-D-galactopyranosyl-(1----3)-O-[(5-acetamido-3,5-dideoxy- D-glycero-alpha-D-galacto-2-nonulopyranosylonic acid)-(2----6)]-O-(2-acetamido-2-deoxy-alpha-D-galactopyranosyl)-(1----3 )-L- serine was achieved by use of the key glycosyl donor O-(2,3,4,6-tetra-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-D- galactopyranosyl trichloroacetimidate and the key glycosyl acceptor N-(benzyloxycarbonyl)-L- serine benzyl ester in a regiocontrolled way.     

Synthesis of aminoethylglycosides with oligosaccharide GM1 and asialo-GM1 ganglioside chains

4'-O-Glycosylation of 2-azidoethyl 2,3,6-tri-O-benzyl-4-O-(2,3-di-O- benzyl-6-O-benzoyl-beta-D-galactopyranosyl)-beta-D-glucopyranoside with a disaccharide donor, 4-trichloroacetamidophenyl 4,6-di-O-acetyl-2-deoxy-3-O-(2,3,4,6-tetra-O-acetyl-beta-D- galactopyranosyl)-1-thio-2-trichloroacetamido-beta-D-galactopyranoside, in dichloromethane in the presence of N-iodosuccinimide and trifluoromethanesulfonic acid resulted in a tetrasaccharide, 2-azidoethyl (2,3,4,6-tetra-O-acetyl-beta-D-galactopyranosyl)-(1-->3)- (4,6-di-O-acetyl-2-deoxy-2-trichloroacetamido-beta-D-galactopyranosyl)- (1-->4)-(2,3-di-O-benzyl-6-O-benzoyl-beta-D-galactopyranosyl)- (1-->4)-2,3,6-tri-O-benzyl-beta-D-glucopyranoside, in 69% yield. The complete removal of O-protecting groups in the tetrasaccharide, the replacement of N-trichloroacetyl by N-acetyl group, and the reduction of the aglycone azide group to amine led to the target aminoethyl glycoside of beta-D-Gal- (1-->3)-beta-D-GalNAc-(1-->4)-beta-D-Gal-(1-->4)-beta-D-Glc-OCH2CH2NH2 containing the oligosaccharide chain of asialo-GM1 ganglioside in 72% overall yield. Selective 3'-O-glycosylation of 2-azidoethyl 2,3,6-tri-O- benzyl-4-O-(2,6-di-O-benzyl-beta-D-galactopyranosyl)-beta-D-glucopyranoside with thioglycoside methyl (ethyl 5-acetamido-4,7,8,9-tetra-O- acetyl-3,5-dideoxy-2-thio-D-glycero-alpha-D-galacto-2-nonulopyranosyl)oate in acetonitrile in the presence of N-iodosuccinimide and trifluoroacetic acid afforded 2-azidoethyl [methyl (5-acetamido-4,7,8,9-tetra-O-acetyl- 3,5-dideoxy-D-glycero-alpha-D-galacto-2-nonulopyranosyl)oate in acetonitrile in the presence of N-iodosuccinimide and tri-fluoracetic acid afforded 2-azidoethyl[methyl (5-acetamido-4,7,8,9-tetra-O-acetyl- 3,5-dideoxy-D-glycero-alpha-D-galacto-2-nonulopyranosyl) (2,6-di-O-benzyl-beta-D-galactopyranosyl)-(1-->4)-2,3,6-tri-O-benzyl-beta-D- glucopyranoside, the selectively protected derivative of the oligosaccharide chain of GM3 ganglioside, in 79% yield. Its 4'-O-glycosylation with a disaccharide glycosyl donor, (4-trichloroacetophenyl-4,6-di-O-acetyl-2-deoxy-3-O-(2,3,4,6-tetra-O- acetyl-beta-D-galactopyranosyl) 1-thio-2-trichloroacetamido-beta-D-galactopyranoside in dichloromethane in the presence of N-iodosuccinimide and trifluoroacetic acid gave 2-azidoethyl (2,3,4,6-tetra-O-acetyl-beta-D-galactopyranosyl)- (1-->3)-(4,6-di-O-acetyl-2-deoxy-2-trichloroacetamido-beta-D- galactopyranosyl)-(1-->4)-[[methyl (5-acetamido-4,7,8,9-tetra-O-acetyl-3,5-dideoxy-D-glycero-alpha-D- galacto-2-nonulopyranosyl)onate]-(2-->3)]-(2,6-di-O-benzyl-beta-D- galactopyranosyl)-(1-->4)-2,3,6-tri-O-benzyl-beta-D-glucopyranoside in 85% yield. The resulting pentasaccharide was O-deprotected, its N-trichloroacetyl group was replaced by N-acetyl group, and the aglycone azide group was reduced to afford in 85% overall yield aminoethyl glycoside of beta-D-Gal-(1-->3)-beta-D-GalNAc-(1-->4)-[alpha-D-Neu5Ac-(2-->3)]- beta-D-Gal-(1-->4)-beta-D-Glc-OCH2CH2NH2 containing the oligosaccharide chain of GM1 ganglioside. The English version of the paper: Russian Journal of Bioorganic Chemistry, 2004, vol. 30, no. 1; see also http://www.maik.ru.     

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 regio- and stereo-controlled synthesis of beta-D-Glcp NAc6SO3-(1----3)-beta-D-Galp6SO3-(1----4)-beta-D-GlcpNAc 6SO3- (1----3)-D-Galp, a linear acidic glycan fragment of keratan sulfate I

A stereocontrolled synthesis of beta-D-GlcpNAc6SO3-(1----3)-beta-D-Galp6SO3-(1----4)-beta-D- GlcpNAc6SO3- (1----3)-D-Galp, was achieved by use of benzyl O-(2-acetamido-3,4 di-O-benzyl-2-deoxy-6-O-p-methoxyphenyl-beta-D- glucopyranosyl)-(1----3)-O-(2,4-di-O-tert-butyldiphenylsilyl-beta- D- galactopyranosyl-(1----4)-O-(2-acetamido-3-O-benzyl-2-deoxy-6-O-p-methox yphenyl - beta-D-glucopyranosyl)-(1----3)-2,4,6-tri-O-benzyl-beta-D-galactopyranos ide as a key intermediate, which was in turn prepared by employing two glycosyl donors, 3,4-di-O-benzyl-2-deoxy-6-O-p-methoxyphenyl-2-phthalimido-beta-D- glucopyranosyl trichloroacetimidate and O-(3,6-di-O-acetyl-2,4-di-O-benzyl-beta-D-galactopyranosyl)-(1----4)-3-O - benzyl-2-deoxy-6-O-p-methoxyphenyl-2-phthalimido-beta-D-glucopyranosyl trichloroacetimidate, and a glycosyl acceptor, benzyl 2,4,6-tri-O-benzyl-beta-D-galactopyranoside.     

Preparative route to N-glycolylneuraminic acid phenyl 2-thioglycoside donor and synthesis of Neu5Gc-alpha-(2-->3')-lactosamine 3-aminopropyl glycoside

The spacer-armed trisaccharide, Neu5Gc-alpha-(2-->3')-lactosamine 3-aminopropyl glycoside, was synthesized by regio- and stereoselective sialylation of the suitably protected triol acceptor, 3-trifluoroacetamidopropyl 2-acetamido-3,6-di-O-benzyl-2-deoxy-4-O-(6-O-benzyl-beta-D-galactopyranosyl)-beta-D-glucopyranoside, with the donor methyl [phenyl 5-acetoxyacetamido-4,7,8,9-tetra-O-acetyl-3,5-dideoxy-2-thio-D-glycero-alpha,beta-D-galacto-2-nonulopyranosid]onate. The donor was obtained, in turn, from methyl [phenyl 5-acetamido-4,7,8,9-tetra-O-acetyl-3,5-dideoxy-2-thio-D-glycero-alpha,beta-D-galacto-2-nonulopyranosid]onate by N-tert-butoxycarbonylation of the acetamido group followed by total N- and O-deacetylation, per-O-acetylation, subsequent Boc group removal, and N-acetoxyacetylation.     

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 cerebroside, lactosyl ceramide, and ganglioside GM3 analogs containing beta-thioglycosidically linked ceramide

Coupling of the sodium salt of 2,3,4,6-tetra-O-acetyl-1-thio-beta-D-glucopyranose, -beta-D-galactopyranose, O-(2,3,4,6-tetra-O-acetyl-beta-D-galactopyranosyl)-(1----4)-2,3,6-tri-O- acetyl- 1-thio-beta-D-glucopyranose, or O-(methyl 5-acetamido-4,7,8,9-tetra-O-acetyl-3,5-dideoxy-D-glycero-alpha-D-galacto -2- nonulopyranosylonate)-(2----3)-O-(2,3-di-O-acetyl-6-O-bezoyl -beta-D- galactopyranosyl)-(1----4)-3-O-acetyl-2,6-di-O-benzoyl-1-thio-beta-D- glucopyranose, which were prepared from the corresponding 1-S-acetates, 1, 3, 6, and 9, with (2S,3R,4E)-2-azido-3-O-benzoyl-1-O-(p-tolylsulfonyl)-4-oc tadecene-1,3-diol (12) derived by tosylation of 11, gave the corresponding beta-thioglycosides 13, 17, 21, and 25, respectively in good yield. The beta-thioglycosides obtained were converted, via selective reduction of the azide group, condensation with octadecanoic acid, and removal of the protecting groups, into the title compounds.     

Synthesis of novel ganglioside GM4 analogues containing N-deacetylated and lactamized sialic acid: probes for searching new ligand structures for human L-selectin

Novel ganglioside GM4 analogues, which contain N-deacetylated or lactamized sialic acid instead of usual N-acetylneuraminic acid, were synthesized in a highly efficient manner. (Methyl 4,7,8,9-tetra-O-acetyl-3,5-dideoxy-5-trifluoroacetamido-D-glycero-alpha-D-galacto-2-nonulopyranosylonate)-(2-->3)-4,6-di-O-acetyl-2-O-benzoyl-D-galactopyranosyl trichloroacetimidate was coupled with 2-(tetradecyl)hexadecanol to give the desired beta-glycoside in high yield. Successive O- and N-deacylation, and saponification of the methyl ester group afforded the N-deacetylated sialyl derivative that was converted by treatment with 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride in Me2SO into the lactamized sialic acid-containing ganglioside GM4 analogue.     

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.     

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 an appropriately protected core glycotetraoside, a key intermediate for the synthesis of "bisected" complex-type glycans of a glycoprotein

A stereocontrolled synthetic route to a glycotetraoside, allyl O-(3,4,6-tri-O-benzyl-2-deoxy-2-phthalimido-beta-D-glucopyranosyl)-(1--- -4)-O- (3,6-di-O-allyl-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-methoxy-phenyl-2-phthalimido-beta-D-glucopyranoside, an important intermediate for the synthesis of "bisected" complex type glycans of glycoproteins has been established by employing two glycosyl donors, 3,4,6-tri-O-benzyl-2-deoxy-2-phthalimido-beta-D-glucopyranosyl trichloroacetimidate and 4-O-acetyl-3,6-di-O-allyl-2-O-benzyl-alpha-D-mannopyranosyl bromide, and a glycosyl acceptor, allyl 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.     

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.     

An efficient access to protected disialylated glycohexaosyl threonine present on the leukosialin of activated T-lymphocytes

The total synthesis of the threonine-linked core 2 class disialylated hexasaccharide in a completely protected form was accomplished for the first time. The L-threonine conjugate, N-(9-fluorenylmethoxycarbonyl)-O-[(5-acetamido-4,7,8,9-tetra-O-ben zyl-3,5-dideoxy-D-glycero-alpha-D-galacto-2-nonulopyranosylonic acid)-(2-->3)-(2,6-di-O-benzyl-beta-D-galactopyranosyl)-(1-->4)-2-acetam ido-2-deoxy-3,6-di-O-benzyl-beta-D-glucopyranosyl-(1-->6)-[(5-acetamido- 4,7,8,9-tetra-O-benzyl-3,5-dideoxy-D-glycero-alpha-D-galacto-2-nonulo pyranosylonic acid)-(2-->3)-2,6-di-O-benzyl-beta-D-galactopyranosyl-(1-->3)]-2-acetami do-2-deoxy-alpha-D-galactopyranosyl-(1d-->4c:1f-->4e)-dilactone ]-L-threonine allyl ester was synthesized via stereocontrolled glycosylations employing readily accessible monosaccharidic blocks; t-butyl-diphenylsilyl-2-azido-2-deoxy-3,6-di-O-benzyl-beta-D-gluco pyranose, N-(9-fluorenylmethoxycarbonyl)-O-(2-azido-6-O-t-butyldimethylsilyl -2-deoxy-alpha-D-galactopyranosyl)-L-threonine allyl ester, 8, 9 and N-(9-fluorenylmethoxycarbonyl)-O-(2-azido-4,6-O-benzylidene-3-O-ch loroacetyl-2-deoxy-alpha-D-galactopyranosyl)-L-threonine allyl ester. For the introduction of the amino acid, the azide group was used to temporarily mask the amino group of GalNAc so as to obtain an alpha-glycosidic linkage without participation from the C-2 substituent. The threonine was attached to the sugar unit at the monosaccharide stage to avoid loss of oligosaccharide at a later stage. The Fmoc and allyl ester protected amino acid at the reducing end facilitates efficient glycopeptide synthesis on solid-phase support.     

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.     

Syntheses of the methyl glycosides of the repeating units of chondroitin 4- and 6-sulfate

3,4,6-Tri-O-acetyl-D-galactal was transformed into methyl 6-O-acetyl-2-azido-4-O-benzyl-2-deoxy-beta-D-galactopyranoside and its 4-O-acetyl-6-O-benzyl analogue, each of which was glycosylated with activated, O-acetylated derivatives of methyl D-glucopyranosyluronate. The resulting beta-(1----3)-linked disaccharide derivatives were each reductively N-acetylated, hydrogenolysed, O-sulfated, and saponified to afford the disodium salts of methyl 2-acetamido-2-deoxy-3-O-(beta-D-glucopyranosyluronic acid)-4-O-sulfo-beta-D-galactopyranoside and the 6-O-sulfo analogue. D-Galactal was also transformed into activated derivatives of 2-azido-3,6-di-O-benzyl-2-deoxy-D-galactopyranose and their 3,4-di-O-benzyl analogues with various substituents at O-4 and O-6. These glycosyl donors were condensed with 6-O-protected derivatives of methyl 2,3-di-O-benzyl-beta-D-glucopyranoside to give the beta-(1----4)-linked disaccharide derivatives, which were selectively deprotected, then oxidised at C-6 of the gluco unit, reductively N-acetylated, selectively deprotected, O-sulfated at C-4 or C-6 of the galacto unit, and hydrogenolysed to give the disodium salts of methyl 4-O-(2-acetamido-2-deoxy-4-O-sulfo-beta-D-galactopyranosyl)-beta-D- glucopyranosiduronic acid and the 6-O-sulfo analogue.     

Synthesis of an octasaccharide fragment of high-mannose-type glycans of glycoproteins.

O-(alpha-D-Mannopyranosyl)-(1----2)-O-(alpha-D-mannopyranosyl)-(1----3)- O- [(alpha-D-mannopyranosyl)-(1----2)-O-(alpha-D-mannopyranosyl)-(1----6)]- O- (alpha-D-mannopyranosyl)-(1----6)-O-(beta-D-mannopyranosyl)-(1----4)-O-( 2- acetamido-2-deoxy-beta-D-glucopyranosyl)-(1----4)-2-acetamido-2-deoxy- glucopyranose, an octasaccharide fragment of high-mannose type glycan of glycoproteins, was synthesized. Crucial glycosylation of trisaccharide intermediate, benzyl O-(2,4-di-O-benzyl-beta-D-mannopyranosyl)-(1----4)-O-(2-acetamido-3,6-di -O- benzyl-2-deoxy-beta-D-glucopyranosyl)-(1----4)-2-acetamido-3,6-di-O-benz yl-2- deoxy-beta-D-glucopyranoside, was successful only with a di-O-acetyltetradeca-O-benzyl-D-mannopentaosyl chloride. The use of the corresponding hexadeca-O-acetyl-D-mannopentaosyl bromide did not give the desired product.     

Chemical synthesis of the human blood-group P1-antigenic determinant

Condensation of known benzyl 2-acetamido-3,6-di-O-benzyl-2-deoxy-4-O-(2,3,6-tri-O-benzyl-beta-D- galactopyranosyl)-alpha-D-glucopyranoside with 2,3,4,6-tetra-O-benzyl-alpha-D-galactopyranosyl chloride in dichloromethane in the presence of 2,4,6-trimethylpyridine, silver triflate, and molecular sieve 4A gave benzyl O-(2,3,4,6-tetra-O-benzyl-alpha-D-galactopyranosyl)-(1 leads to 4)-O-(2,3,6-tri-O-benzyl-beta-D-galactopyranosyl)-(1 leads to 4)-2-acetamido-3,6-di-O-benzyl-2-deoxy-alpha-D-glucopyranoside. Catalytic hydrogenolysis gave crystalline O-alpha-D-galactopyranosyl-(1 leads to 4)-O-beta-D-galactopyranosyl-(1 leads to 4)-2-acetamido-2-deoxy-alpha -D-glucopyranose, the human blood-group P1-antigenic determinant. A similar sequence of reactions was performed starting from allyl 2-acetamido-3,6-di-O-benzyl-2-deoxy-beta-D-glucopyranoside, in order to prepare a derivative of this determinant suitable for linkage to carrier molecules.