Nucleophilic displacement reactions in carbohydrates : Part XX. Displacements on alkyl α-l-talopyranoside 4-sulphonate derivatives

The azide displacement reaction on methyl 6-deoxy-4-O-methanesulphonyl-2,3-di-O-methyl-α-l-talopyranoside (6) in N,N-dimethylformamide yielded methyl 4,6-dideoxy-2,3-di-O-methyl-α-l-threo-hex-3-enopyranoside (7, ca. 50%), methyl 4,6-dideoxy-2,3-di-O-methyl-β-d-erythro-hex-4-enopyranoside (8, ca. 10%), and methyl 4-azido-4,6-dideoxy-2,3-di-O-methyl-α-l-mannopyranoside (9, ca. 40%). The corresponding azide 14 (20%) and the unsaturated sugars 12 (68%) and 13 (12%) were obtained from a comparable reaction on benzyl 6-deoxy-4-O-methanesulphonyl-2,3-di-O-methyl-α-l-talopyranoside (11).     

Synthesis, the crystal structure, and high-resolution NMR spectroscopy of methyl 4-O-acetyl-3-azido-2,3,6-trideoxy-6-iodo-alpha-D-arabino-hexopyranoside

Selective tosylation followed by acetylation of methyl 3-azido-2,3-dideoxy-alpha-D-arabino-hexopyranoside (1) in pyridine at room temperature affords a mixture of methyl 4-O-acetyl-3-azido-2,3-dideoxy-6-di-O-p-tolylsulfonyl-alpha-D-arabino-hexopyranoside (4) and methyl 3-azido-2,3-dideoxy-4,6-di-O-p-tolylsulfonyl-alpha-D-arabino-hexopyranoside (3). Compound 4 undergoes nucleophilic displacement with sodium iodide in acetic anhydride to give methyl 4-O-acetyl-3-azido-2,3,6-trideoxy-6-iodo-alpha-D-arabino-hexopyranoside (7), whose crystal structure and (1H) and (13)C NMR data are reported. This compound adopts the 4C(1) conformation.     

Synthesis of sorbistin analogues

D-Galactose was converted into the glycosylating agents 4-azido-2,3-di-O-benzyl-4-deoxy-6-O-propionyl-alpha-D-glucopyranosyl chloride (11) and the methyl beta-D-thiopyranoside 19. Condensation of 11 with 2,5-diazido-1,6-di-O-benzoyl-2,5-di-deoxy-L-iditol in the presence of mercury salts gave 24% of 2,5-diazido-3-O-(4-azido-2,3-di-O-benzyl-4-deoxy-6-O-propionyl-alp ha-D- glucopyranosyl)-1,6-di-O-benzoyl-2,5-dideoxy-L-iditol. Methyl trifluoromethanesulfonate-promoted glycosylation of 1,3-diazido-2-O-benzyl-1,3-dideoxy-5,6-O-isopropylidene-D-gulit ol with 19 in the presence of 2,6-di-tert-butyl-4-methylpyridine gave 1,3-diazido-4-O-(4-azido-2,3-di-O-benzyl-4-deoxy-6-O-propionyl-alp ha-D- glucopyranosyl)-2-O-benzyl-1,3-dideoxy-5,6-O-isopropylidene-D-gulitol (42), whereas, in the absence of base, migration of the O-isopropylidene group occurred, affording 1,3-diazido-6-O-(4-azido-2,3-di-O-benzyl-4-deoxy-6-O-propionyl-alp ha-D- glucopyranosyl)-2-O-benzyl-1,3-dideoxy-4,5-O-isopropylidene-D-gulitol in addition to 42.     

New syntheses of methyl 4,6-O-benzylidene-2-deoxy-3-C-methyl-α-d-arabino-hexopyranoside and its conversion into d-evermicose

Methyl 4,6-O-benzylidene-2-deoxy-3-C-methyl-α-d-arabino-hexopyranoside (4) was prepared from methyl 4,6-O-benzylidene-2,3-dideoxy-3-C-methylene-α-d-erythro-hexopyranoside (1b) and from methyl 4,6-O-benzylidetic-3 C-methyl-α-d-gluco-hexopyranoside (6a) by two different methods. Synthesis of d-evermicose3 (10 (2,6-dideoxy-3-C-methyl-d-arabino-hexose) was then achieved in four steps from 4.     

Synthesis, crystal structure, and high-resolution NMR spectroscopy of methyl 3-azido-2,3-dideoxy-4,6-di-O-p-tolylsulfonyl-alpha-D-xylo-hexopyranoside

Synthesis of methyl 3-azido-2,3-dideoxy-4,6-di-O-p-tolylsulfonyl- and -6-O-p-tolylsulfonyl-alpha-D-xylo-hexopyranosides is presented. High-resolution 1H and 13C NMR spectral data for both compounds and their precursors, and the single-crystal X-ray diffraction analysis for methyl 3-azido-2,3-dideoxy-4,6-di-O-p-tolylsulfonyl-alpha-D-xylo-hexopyranoside are reported. The influence of the O-protective group on the chemical shift of adjacent atoms in the 1H and 13C NMR spectra is discussed.     

Synthesis of a C-linked hyaluronic acid disaccharide mimetic

The synthesis of a C-disaccharide that is designed as a mimetic for the repeating unit disaccharide of hyaluronic acid is described. The target compound was obtained via the SmI2-promoted coupling reaction of the sulfone, 2-acetamido-4,6-O-benzylidene-3-O-tert-butyldimethylsilyl-1,2-dideoxy-1-pyridinylsulfonyl-beta-D-glucopyranose (6), and the aldehyde, p-methoxyphenyl 2,3-di-O-benzyl-4-deoxy-4-C-formyl-6-O-p-methoxybenzyl-beta-D-glucopyranoside (14).     

Synthesis of derivatives of 3-amino-2,3-dideoxy-l-hexoses related to daunosamine (3-amino-2,3,6-trideoxy-l-lyxo-hexose)

The synthesis is described of 3-amino-2,3-dideoxy-l-arabino-hexose (10), methyl 2,3-dideoxy-3-trifluoroacetamido-α-l-lyxo-hexopyranoside (17), methyl 3-amino-2,3-dideoxy-α-l-ribo-hexopyranoside (21), methyl 2,3-dideoxy-3-trifluoroacetamido-α-l-xylo-hexopyranoside (26), and certain derivatives from methyl 4,6-O-benzylidene-2-deoxy-α-l-arabino-hexopyranoside (3). Conversion of 2-deoxy-l-arabino-hexose into 3 by modified, standard procedures, and on a large scale, gave a 75% yield.     

The synthesis of 6-deoxy-6-fluoro-α,α-trehalose and related analogues

Selective acid-catalysed methanolysis of 2,3,2′,3′-tetra-O-benzyl-4,6:4′,6′-di-O-benzylidene-α,α-trehalose yielded the monobenzylidene derivative, which was converted into the 4,6-dimesylate. Selective nucleophilic displacement of the primary sulphonyloxy group then gave 2,3-di-O-benzyl-6-deoxy-6-fluoro-4-O-mesyl-α-d-glucopyranosyl 2,3-di-O-benzyl-4,6-O-benzylidene-α-d-glucopyranoside. Removal of the protecting groups then yielded 6-deoxy-6-fluoro-α,α-trehalose. In addition, 6-deoxy-6-fluoro-4-O-mesyl-α,α-trehalose and a derivative of 4-chloro-4,6-dideoxy-6-fluoro-α-d-galactopyranosyl α-d-glucopyranoside were also prepared from the same substrate. Iodide displacement of 2,3-di-O-benzyl-4,6-di-O-mesyl-α-d-glucopyranosyl 2,3-di-O-benzyl-4,6-di-O-mesyl-α-d-glucopyranoside afforded the 6-iodide and 6,6′-di-iodide in yields of 31 and 36%, respectively. Similarly, the 6-azide and 6,6′-diazide were isolated in yields of 17 and 21%, respectively.     

The synthesis of racemic purpurosamine B

Starting from methyl 4,6-dichloro-4,6-dideoxy-α-D-galactopyranoside (1), D-chalcose (4,6-dideoxy-3-O-methyl-D-xcylo-hexopyranose) (5) was prepared by dechlorination with tributyltin hydride, selective benzoylation with benzoyl cyanide at O-2, methylation at O-3, and acid hydrolysis. D-Chalcose (5) was obtained as well by direct methylation of 1 with diazomethane at O-3, reduction with tin hydride, and hydrolysis. Chalcosyl bromide prepared from 5 was not very suitable for β-glycoside synthesis under Koenigs-Knorr conditions, and better results were obtained with 2- O-acetyl-4,6-dichloro-4,6-dideoxy-3-O-methyl-α-D-galactopyranosyl bromide, which gave β-glycosides with methanol, cyclohexanol, benzyl alcohol, 1,2:3,4-di-O-isopropylidene-α-D-galactopyranose, and methyl 2,3-di-O-benzyl-6-deoxy-α-D-glucopyranoside. After dechlorination with tributyltin hydride, the corresponding β-glycosides of D-chalcose were obtained in good yield.     

Carbohydrates from Cynanchum otophyllum

Four new carbohydrates were isolated from the acidic hydrolysis part of the ethyl acetate extract of Cynanchum otophyllum Schneid (Asclepiadaceae). Their structures were determined as methyl 2,6-dideoxy-3-O-methyl-beta-D-arabino-hexopyranosyl-(1-->4)-6-deoxy-3-O-methyl-beta-D-ribo-hexopyranosyl-(1-->4)-6-deoxy-3-O-methyl-alpha-L-ribo-hexopyranoside (1), methyl 6-deoxy-1,3-di-O-methyl-beta-D-ribo-hexosyl-(1-->4)-2,6-dideoxy-3-O-methyl-alpha-D-arabino-hexopyranoside (2), methyl 2,6-dideoxy-3-O-methyl-beta-D-arabino-hexopyranosyl-(1-->4)-6-deoxy-3-O-methyl-alpha-L-ribo-hexopyranoside (3), and 2,6-dideoxy-3-O-methyl-beta-D-arabino-hexopyranosyl-(1-->4)-2,6-dideoxy-3-O-methyl-alpha-D-arabino-hexopyranosyl-(1-->4)-2,6-dideoxy-3-O-methyl-beta-D-lyxo-hexopyranose (4), respectively, by spectral methods.     

Synthesis of 2-amino-2-deoxy- and 3-amino-3-deoxy-α-d-mannopyranosyl α-d-mannopyranoside by sequential osmylations of a dienic disaccharide

Partial oxyamination of 4,6-di-O-acetyl-2,3-dideoxy-α-d-erythro-hex-2-enopyranosyl 4,6-di-O-acetyl-2,3-dideoxy-α-d-erythro-hex-2-enopyranoside with chloramine-T and osmium tetraoxide gave 4,6-di-O-acetyl-2-deoxy-2-(p-toluene-sulfonamido)-α-d-mannopyranosyl 4,6-di-O-acetyl-2,3-dideoxy-α-d-erythro-hex-2-enopyranoside and its 3-deoxy-3-(p-toluenesulfonamido) regioisomer, each in 18–19% isolated yield. Osmium tetraoxide-catalyzed cis-hydroxylation of the remaining alkenic residue in these products led in high yields to the corresponding triols having the α-d-manno, α-d-manno configuration. These were N-desulfonylated (and simultaneously O-deacetylated) by the action of sodium in liquid ammonia to furnish 2-amino-2-deoxy-α-d-mannopyranosyl α-d-mannopyranoside and 3-amino-3-deoxy-α-d-mannopyranosyl α-d-mannopyranoside as new, trehalose-type amino sugars.     

Synthetic approaches to 6-substituted 9-(3-azido-3,4-dideoxy-β-d,l-erythro-pentopyranosyl)purines

Methyl 3-azido-2-O-benzoyl-3,4-dideoxy-β-dl-erythro-pentopyranoside (6) was synthesized through two routes in five steps from methyl 2,3-anhydro-4-deoxy-β-dl-erythro-pentopyranoside (1). The first route proceeded via selective azide displacement of the 3-tosyloxy group of methyl 4-deoxy-2,3-di-O-tosyl-α-dl-threo-pentopyranoside, followed by detosylation and benzoylation. The second route consisted, with a better overall yield, in the azide displacement of the mesyloxy group of methyl O-benzoyl-4-deoxy-3-O-methylsulfonyl-α-dl-threo-pentopyranoside (10), obtained by benzylate opening of 1, followed by benzoylation, debenzylation, and mesylation. Compound 6 was transformed into its glycosyl chloride, further treated by 6-chloropurine to give the nucleoside 9-(3-azido-2-O-benzoyl-3,4-dideoxy-β-dl-erythro-pentopyranosyl)-6-chloropurine (13). When treated with propanolic ammonia, 13 yielded 9-(3-azido-3,4-dideoxy-β-dl-erythro-pentopyranosyl)adenine.     

Synthesis of (S)-2-fluoro-L-daunosamine and (S)-2-fluoro-D-ristosamine

Derivatives of (S)-2-fluoro-L-daunosamine and (S)-2-fluoro-D-ristosamine were synthesized, starting ultimately from 2-amino-2-deoxy-D-glucose which was converted, according to the literature, into methyl 2-benzamido-4, 6-O-benzylidene-2-deoxy-3-O-(methylsulfonyl)-alpha-D-glucopyranoside (2). Treatment of 2 with tetrabutylammonium fluoride gave a 63% yield of (known) methyl 3-benzamido-4,6-O-benzylidene-2,3-dideoxy-2-fluoro-alpha-D-altropyran oside (4), together with a 6% yield of its 2-benzamido-2,3-dideoxy-3-fluoro-alpha-D-gluco isomer. From 4, the corresponding 6-bromo-2,3,6-trideoxyglycoside 4-benzoate (6) was obtained by Hanessian-Hullar reaction. Dehydrobromination of 6, followed by catalytic hydrogenation of the resulting 5-enoside, and subsequent debenzoylation and N-trifluoroacetylation, afforded the fluorodaunosaminide, methyl 2,3,6-trideoxy-2-fluoro-3-trifluoroacetamido-beta-L-galactopyranos ide. Reductive debromination of 6, followed by debenzoylation and N-trifluoroacetylation, gave the fluororistosaminide, methyl 2,3,6-trideoxy-2-fluoro-3-trifluoroacetamido-alpha-D-altropyran oside. The 1H-n.m.r. spectra of the new aminofluoro sugars are discussed with respect to the effects of neighboring amino and acylamido substituents on geminal and vicinal 1H-19F coupling constants, in comparison with the reported effects of oxygen substituents.     

Synthesis of (S)-2-fluoro- -daunosamine and (S)-2-fluoro- -ristosamine

Derivatives of (S)-2-fluoro- -daunosamine and (S)-2-fluoro- -ristosamine were synthesized, starting ultimately from 2-amino-2-deoxy- -glucose which was converted, according to the literature, into methyl 2-benzamido-4,6-O-benzylidene-2-deoxy-3-O-(methylsulfonyl)-α- -glucopyranoside (2). Treatment of 2 with tetrabutylammonium fluoride gave a 63% yield of (known) methyl 3-benzamido-4,6-O-benzylidene-2,3-dideoxy-2-fluoro-α- -altropyranoside (4), together with a 6% yield of its 2-benzamido-2,3-dideoxy-3-fluoro-α- -gluco isomer. From 4, the corresponding 6-bromo-2,3,6-trideoxyglycoside 4-benzoate (6) was obtained by Hanessian-Hullar reaction. Dehydrobromination of 6, followed by catalytic hydrogenation of the resulting 5-enoside, and subsequent debenzoylation and N-trifluoroacetylation, afforded the fluorodaunosaminide, methyl 2,3,6-trideoxy-2-fluoro-3-trifluoroacetamido-β- -galactopyranoside. Reductive debromination of 6, followed by debenzoylation and N-trifluoroacetylation, gave the fluororistosaminide, methyl 2,3,6-trideoxy-2-fluoro-3-trifluoroacetamido-α- -altropyranoside. The ¹H-n.m.r. spectra of the new aminofluoro sugars are discussed with respect to the effects of neighboring amino and acylamido substituents on geminal and vicinal ¹H–¹⁹F coupling constants, in comparison with the reported effects of oxyge substituents.     

Synthesis of benzyl and methyl 3-benzamido-2,3,6-trideoxy-2-fluoro-β-l-galactopyranoside: Protected C-2 fluoro analogues of daunosamine

The reaction of benzyl 2-benzamido-4,6-O-benzylidene-2-deoxy-3-O-tosyl-α-d-glucopyranoside or benzyl 4,6-O-benzylidene-2,3-benzoylepimino-2,3-dideoxy-α-d-allopyranoside with anhydrous tetrabutylammonium fluoride in hexamethylphosphoric triamide gave ∼40% of benzyl 3-benzamido-4,6-O-benzylidene-2,3-dideoxy-2-fluoro-α-d-altropyranoside (6a). Transformation of 6a into benzyl 3-benzamido-2,3,6-trideoxy-2-fluoro-α-d-arabino-hex-5-enopyranoside (13a) was carried out by well-established methodology. Hydrogenation of the double bond in 13a furnished the title compound in good yield. Methyl 3-benzamido-2,3,6-trideoxy-2-fluoro-β-l-galactopyranoside was also prepared in nine steps from 2-amino-2-deoxy-d-glucose.     

Preparation of Methyl 4,6-O-benzylidene-2-deoxy-2-nitro-β-D-glucopyranoside from the corresponding 3-deoxy-3-nitro derivatives with sodium nitrite

Treatment of methyl 4,6-O-benzylidene-2,3-dideoxy-3-nitro-β-D-erythro-hex-2-enopyranoside (2) with nitrous acid afforded the title 2-nitro sugar (4). The same product was also prepared by heterogeneous reaction of methyl 2-O-acetyl-4,6-O-benzylidene-3-deoxy-3-nitro-β-D-glucopyranoside (1) with sodium nitrite in the presence of a phase-transfer catalyst. Acid hydrolysis of 4 gave methyl 2-deoxy-2-nitro-β-D-glucopyranoside (7). Acetylation of 4, followed by elimination of acetic acid, afforded a 2-nitroalkene (6). 71e 3-acetate 5 reacted with ammonia, dimethylamine, and 2,4-pentanedione to give the products 8, 9, and 10, respectively, having the gluco configuration.     

Fluorinated carbohydrates as potential plasma membrane modifiers. Synthesis of 4- and 6-fluoro derivatives of 2-acetamido-2-deoxy-D-hexopyranoses

2-Amino-2,4-dideoxy-4-fluoro- and 2-amino-2,4,6-trideoxy-4, 6-difluoro-D-galactose, and 2-amino-2,4-dideoxy-4-fluoro- and 2-amino-4-deoxy-4, 4-difluoro-D-xylo-hexose were synthesized, as potential modifiers of tumor cell-surface glyco-conjugate, from benzyl 2-acetamido-3-O-benzyl-2-deoxy-4, 6-di-O-mesyl-alpha-D-glucopyranoside and benzyl 2-acetamido-3, 6-di-O-benzyl-2-deoxy-4-O-mesyl-alpha-D-glucopyranoside, which were converted into the corresponding 4,6-difluoro-2,4, 6-trideoxy and 2,4-dideoxy-4-fluoro derivatives. Benzyl 2-acetamido-2-deoxy-4-O-mesyl-alpha-D-galactopyranoside and benzyl 2-acetamido-3,6-di-O-benzyl-2-deoxy-alpha-D-xylo-hexo-4-ulopyra noside were treated with diethylaminosulfur trifluoride to give 2-amino-2,4-dideoxy-4-fluoro-D-glucose and 2-amino-2,4-dideoxy-4, 4-di-fluoro-D-xylo-hexose derivatives, respectively, to give after deprotection the target compounds. Several of the peracetylated sugar derivatives inhibited L1210 tumor-cell growth in vitro at concentrations of 1-5 10(-5) M. The peracetylated derivative of 2-amino-2,4-dideoxy-4-fluoro-D-galactose inhibited protein and glycoconjugate biosynthesis, and also exhibited antitumor activity in mice with L1210 leukemia.     

Preparation and structure determination of two sugar amino acids via corresponding hydantoin derivatives

(4R)-2,3-O-Isopropylidene-methylspiro[4,6-dideoxy-alpha-L-lyxo+ ++-hexopyranosid-4,5'-imidazolidin]-2',4'-dione and (4R)-2,3-O-isopropylidene-methylspiro[4,6-dideoxy-beta-D-ribo-h exopyranosid-4,5'-imidazolidin]-2',4'-dione were prepared under various reaction conditions starting from methyl 6-deoxy-2,3-O-isopropylidene-alpha-L-lyxo-hexopyranosid-4-++ +ulose. Corresponding alpha-amino acids methyl (4R)-4-amino-4-C-carboxy-4,6-dideoxy-alpha-L-lyxo-hexopyranosid e and methyl (4R)-4-amino-4-C-carboxy-4,6-dideoxy-beta-D-ribo-hexopyranoside were obtained from the above hydantoins by selective acid hydrolysis of the isopropylidene group, followed by basic hydrolysis of the hydantoin ring. The crystal structures of both hydantoin derivatives are also presented.     

Synthesis of a novel N[bond]O-interglycosidic disaccharide

The carbohydrate subunits carrying an N-O-interglycosidic bond play a very important role in the biological activity of the enediyne antibiotics. Condensation of O-(alpha- and beta-D-glucopyranosyl)hydroxylamine (5a and 5b) with the hex-3-ulopyranoside (6) furnished methyl 4,6-O-benzylidene-2,3-dideoxy-3-(2,3,4,6-tetra-O-benzyl-alpha-D-glucopyranosyloxy)imino-alpha- and beta-D-erythro-hexopyranoside (7a and 7b). Stereoselective reduction of the Cz.dbnd6;N bond of 7a and 7b with sodium cyanoborohydride resulted in the formation of the required protected N-O-interglycosidic disaccharides (8a and 8b). Finally, catalytic hydrogenation of 8a afforded methyl 2,3-dideoxy-3-(alpha-D-glucopyranosyloxy)amino-alpha-D-ribo-hexopyranoside (9a). Under similar conditions the beta anomer 8b underwent decomposition.     

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.