Synthèse de trithioorthocarbonates de pyranosides par thermolyse de bis(dithiocarbonates)

The thermal decomposition of methyl 4,6-O-benzylidene-2,3-di-O-[(methylthio)-thiocarbonyl]-α-d-glucopyranoside afforded methyl 4,6-O-benzylidene-2-thio-α-d-mannopyranoside 3-O,2-S-(S,S-dimethyl trithioorthocarbonate) and methyl 4,6-O-benzylidene-3-thio-α-d-allopyranoside 2-O,3-S-(S,S-dimethyl trithioorthocarbonate) in good yield. This decomposition can be generalized to 1,3-diols derived from sugars. Thus methyl 2,3-di-O-methyl-4,6-di-O-[(methylthio)thiocarbonyl]-α-d-glucopyranoside afforded in the same way the corresponding trithioorthocarbonates, following a regioselective process. The structures of these trithioorthocarbonates are confirmed by spectral and chemical proofs.     

Studies on the stereoselective synthesis of a protected α-d-Gal-(1→2)-d-Glc fragment

A novel 1,2-cis stereoselective synthesis of protected α-d-Gal-(1→2)-d-Glc fragments was developed. Methyl 2-O-acetyl-3-O-allyl-4,6-O-benzylidene-α-d-galactopyranosyl-(1→2)-3-O-benzoyl-4,6-O-benzylidene-α-d-glucopyranoside (13), methyl 2-O-acetyl-3-O-allyl-4,6-O-benzylidene-α-d-galactopyranosyl-(1→2)-3,4,6-tri-O-benzoyl-α-d-glucopyranoside (15), methyl 2-O-acetyl-3-O-allyl-4,6-O-benzylidene-α-d-galactopyranosyl-(1→2)-3-O-benzoyl-4,6-O-benzylidene-β-d-glucopyranoside (17), and methyl 2-O-acetyl-3-O-allyl-4,6-O-benzylidene-α-d-galactopyranosyl-(1→2)-3,4,6-tri-O-benzoyl-β-d-glucopyranoside (19) were favorably obtained by coupling a new donor, isopropyl 2-O-acetyl-3-O-allyl-4,6-O-benzylidene-1-thio-β-d-galactopyranoside (2), with acceptors, methyl 3-O-benzoyl-4,6-O-benzylidene-α-d-glucopyranoside (4), methyl 3,4,6-tri-O-benzoyl-α-d-glucopyranoside (5), methyl 3-O-benzoyl-4,6-O-benzylidene-β-d-glucopyranoside (8), and methyl 3,4,6-tri-O-benzoyl-β-d-glucopyranoside (12), respectively. By virtue of the concerted 1,2-cis α-directing action induced by the 3-O-allyl and 4,6-O-benzylidene groups in donor 2 with a C-2 acetyl group capable of neighboring-group participation, the couplings were achieved with a high degree of α selectivity. In particular, higher α/β stereoselective galactosylation (5.0:1.0) was noted in the case of the coupling of donor 2 with acceptor 12 having a β-CH₃ at C-1 and benzoyl groups at C-4 and C-6.     

Novel synthesis of methyl 4,6-O-benzylidenespiro[2-deoxy-α-d-arabino-hexopyranoside-2,2′-imidazolidine] and its homologue and sugar-γ-butyrolactam derivatives from methyl 4,6-O-benzylidene-α-d-arabino-hexopyranosid-2-ulose

Novel methyl 4,6-O-benzylidenespiro[2-deoxy-α-d-arabino-hexopyranoside-2,2′-imidazolidine] and its homologue methyl 4,6-O-benzylidene-3′,4′,5′,6′-tetrahydro-1′H-spiro[2-deoxy-α-d-arabino-hexopyranoside-2,2′-pyrimidine] have been synthesized in good yields by reaction of methyl 4,6-O-benzylidene-α-d-arabino-hexopyranosid-2-ulose with 1,2-diaminoethane and 1,3-diaminopropane. The results are completely different from the reaction with arylamines or alkylamines. One-pot synthesis of novel (E)-methyl 4-[hydroxy (methoxy)methylene]-5-oxo-1-alkyl-(4,6-O-benzylidene-2-deoxy-α-d-glucopyranosido)[3,2-b]pyrrolidines has been achieved by the reaction of alkylamines with the butenolide-containing sugar, derived from the aldol condensation of methyl 4,6-O-benzylidene-α-d-arabino-hexopyranosid-2-ulose with diethyl malonate. These sugar-γ-butyrolactam derivatives are potential GABA receptor ligands.     

O-ethylidene-D-allopyranoses: 1,2-O-,1,2:4,6-, and 2,3:4,6-di-O-ethylidene derivatives

Solutions of 1,2-O-acetoxonium chlorides derived from O-acetylated D-allopyranose derivatives were treated with sodium borohydride to give three pairs of previously unknown 1,2-O-ethylidene-α-D-allopyranose diastereoisomers: 3,4,6-tri-O-acetyl-1,2-O-ethylidene-α-D-allopyranoses; 4,6-di-O-acetyl-3-O-benzyl-1,2-O-ethylidene-α-D-allopyranoses; and 3-O-benzyl-1,2:4,6-di-O-ethylidene-α-D-allopyranoses. Examples of a second class of novel O-ethylidene-D-allopyranoses, the diastereoisomeric methyl 2,3:4,6-di-O-ethylidene-α-D-allopyranosides, were prepared by treating methyl 4,6-O-benzylidene-α-D-alloside with acetaldehyde-sulfuric acid. Assignments of dioxolane ring configurations and pyranose conformations were made by n.m.r. analyses.     

Synthesis of 8-(hydroxyalkyl)adenines

Treatment of methyl 4,6-O-benzylidene-2-O-p-tolylsulfonyl-α-D-ribo-hexopyranosid-3-ulose (1) with triethylamine-methanol at reflux temperature yields methyl 2,3-anhydro-4,6-O-benzylidene-3-methoxy-α-D-allopyranoside (2), a derivative (3) of 3-hydroxy-2-(hydroxymethyl)-4H-pyran-4-one, and methyl 4,6-O-benzylidene-α-D-ribo-hexopyranosid-3-ulose dimethyl acetal (4). The reaction of methyl 4,6-O benzylidene-3-O-p-tolylsulfonyl-α-D-arabino-hexopyranosid-2-ulose (12) with triethylamine-methanol afforded methyl 4,6-O-benzylidene-α-D-ribo-hexopyranosid-2-ulose dimethyl acetal (19) and methyl 2,3-anhydro-4,6-O-benzylidene-2-methoxy-α-D-allopyranoside (20); from the reaction of the β-D anomer (13) of 12, methyl 4,6-O-benzylidene-β-D-ribo-hexopyranosid-2-ulose dimethyl acetal (21) was isolated. Syntheses of the α-keto toluene-p-sulfonates 12 and 13 are described. Mechanisms for the formation of the compounds isolated from the reactions with triethylamine-methanol are proposed.     

Synthèse des l-fucose et l-(3-2H)fucose à partir du d-mannose

Oxidation with the dimethyl sulfoxide-acetic anhydride reagent of methyl 2-O-acetyl-4,6-O-benzylidene-α-d-mannopyranoside, obtained in quantitative yield from the corresponding 4,6-benzylidene acetal by stereoselective opening of a 2,3-orthoester, led in good yield to methyl 2-O-acetyl-4,6-O-benzylidene-α-d-arabino-hexopyranosid-3-ulose, which was reduced with either sodium borohydride or sodium borodeuteride into a methyl 4,6-O-benzylidene-α-d-altropyranoside or its 3-²H derivative. A sequence involving a C-6 halogenation-dehydrohalogenation followed by catalytic hydrogenation of the resulting methyl 6-deoxy-α-d-arabino-hex-5-enopyranoside gave methyl 6-deoxy-β-l-galactopyranoside (methyl β-l-fucopyranoside) and then α-l-fucose, with an overall yield of 24% with respect to the starting methyl α-d-mannopyranoside.     

Synthesis of the allo-analogue of trehalose

Selective benzoylation of HO-2 and HO-2′ of 4,6-O-benzylidene-α-D-glucopyranosyl 4,6-O-benzylidene-α-D-glucopyranoside with N-benzoylimidazole led to the exclusive formation of 2-O-benzoyl-4,6-O-benzylidene-α-D-glucopyranosyl 2-O-benzoyl-4,6-O-benzylidene-α-D-glucopyranoside. Oxidation of either the dibenzoate or the corresponding ditosylate with methyl sulphoxide-phosphorus pentaoxide gave the 3,3′-diulose, and subsequent reduction with borohydride gave the 3,3′diepimers having the allo-allo configuration. De-esterification and hydrolysis of the benzylidene substituents gave α-D-allopyranosyl α-D-allopyranoside.     

Reaktionen von kohlenhydraten mit dichlormethylendimethylammoniumchlorid: ein neuer weg zu 2-chlor-2-desoxy-, und 3-chlor-3-desoxyhexose-, und 3-chlor-3-desoxypentosederivaten

Treatment of methyl 4,6-O-benzylidene-α-D-mannopyranoside with dichloromethylenedimethylammonium chloride gave methyl 4,6-O-benzylidene-3-chloro-3-deoxy-2-(N,N-dimethylcarbamoyl)-α-D-altropyranoside and methyl 4,6-O-benzy]idene-2-chloro-2-deoxy-3-(N,N-dimethylcarbamoyl)-α-D-glucopyranoside. Methyl 4,6-O-benzylidene-α-D-allopyranoside gave under analogous conditions the corresponding 2-chloro-3-(N,N-dimethylcarbamoyl)-α-D-altrose and 3-chloro-2-(N,N-dimethylcarbamoyl)-α-D-glucose derivatives. Methyl 5-O-benzyl-α,β-D-ribofuranoside and methyl 5-O-methyl-β-D-ribofuranoside gave only the corresponding methyl 3-chloro-2-(N,N-dimethylcarbamoyl)-α-D-xylofuranoside derivatives.     

Configurational assignments of C-nitromethyl-C-hydroxy branched-chain carbohydrate derivatives by use of a europium shift-reagent in 1 H-N.M.R. spectroscopy

Configurational assignments for the tertiary alcoholic centers of four branched-chain 3-C-nitromethylglycopyranosides, namely, methyl 2-benzamido-4,6-O-benzylidene-2-deoxy-3-C-nitromethyl-α-D-allopyranoside (1), benzyl 2-acetamido-4,6-O-benzylidene-2-deoxy-3-C-nitromethyl-α-D-glucopyranoside (4), benzyl 2-acetamido-4,6-O-benzylidene-2-deoxy-3-C-nitromethyl-α-D-allopyranoside (5), and methyl 4,6-O-benzylidene-3-C-nitromethyl-2-O-p-tolylsulfonyl-α-D-glucopyranoside (8), were made on the basis of the downfield chemical shifts of their identifiable protons per molar equivalent of added Eu(fod)₃, as compared with those of model compounds, of known configuration, having a close structural relationship. In some cases, the assignments were corroborated by the position of the acetyl resonances in the unshifted 60-MHz p.m.r. spectra of the corresponding O-acetyl derivatives.     

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.     

Studies on the structure of a polysaccharide from Epidermophyton floccosum and approach to a synthesis of the basic trisaccharide repeating units

An alkali-soluble polysaccharide, designated as S-Iawe, has been isolated from the maycelia of Epidermophyton floccosum. Methylation, periodate oxidation, and acetolysis studies suggested that S-lawe is composed of (1→6)-Oα-d-mannopyranosyl-(1→6)-O-[α-d-mannopyranosyl-(1→2)]-O-α-d-mannopyranosyl repeating units. Condensation of 2,3,4,6-tetra-O-acetyl-α-d-mannopyranosyl bromide with methyl 3-O-benzyl-4,6-O-benzylidene-α-d-mannopyranoside in the presence of mercuric cyanide gave in 70% yield methyl 3-O-benzyl-4,6-O-benzylidene-2-O-(2,3,4,6-tetra-O-acetyl-α-d-mannopyranosyl)-α-d-mannopyranoside. Condensation of the debenzylidenated disaccharide with 2,3,4,6-tetra-O-acctyl-α-d-mannopyranosyl bromide afforded the corresponding trisaccharide repeating unit.     

Synthesis of 2-acetamido-2-deoxy-3-O-β-d-mannopyranosyl-d-glucose

Condensation of 4,6-di-O-acetyl-2,3-O-carbonyl-α-d-mannopyranosyl bromide with benzyl 2-acetamido-4,6-O-benzylidene-2-deoxy-α-d-glucopyranoside (2) gave an α-d-linked disaccharide, further transformed by removal of the carbonyl and benzylidene groups and acetylation into the previously reported benzyl 2-acetamido-4,6-O-benzylidene-2-deoxy-3-O-(2,3,4,6-tetra-O-acetyl-α-d-mannopyranosyl)-α-d-glucopyranoside. Condensation of 3,4,6-tri-O-benzyl-1,2-O-(1-ethoxyethylidene)-α-d-glucopyranose or 2-O-acetyl-3,4,6-tri-O-benzyl-α-d-glucopyranosyl bromide with 2 gave benzyl 2-acetamido-3-O-(2-O-acetyl-3,4,6-tri-O-benzyl-β-d-glucopyranosyl)-4,6-O-benzylidene-2-deoxy-α-d-glucopyranoside. Removal of the acetyl group at O-2, followed by oxidation with acetic anhydride-dimethyl sulfoxide, gave the β-d-arabino-hexosid-2-ulose 14. Reduction with sodium borohydride, and removal of the protective groups, gave 2-acetamido-2-deoxy-3-O-β-d-mannopyranosyl-d-glucose, which was characterized as the heptaacetate. The anomeric configuration of the glycosidic linkage was ascertained by comparison with the α-d-linked analog.     

Galactan sulfate from the test of tunicates

Methyl and benzyl 3-O-β-d-xylopyranosyl-α-d-mannopyranoside were prepared by way of d-xylosylation (Koenigs-Knorr) of methyl and benzyl 4,6-O-benzylidene-α-d-mannopyranoside (1 and 17). Analogous 2-O-β-d-xylopyranosyl-α-d-mannopyranosides could not be prepared efficiently by this procedure. However, methyl and benzyl 3-O-acetyl-4,6-O-benzylidene-α-d-mannopyranoside, prepared by limited acetylation of 1 and 17, respectively, could be d-xylosylated by the same method, and afforded, after removal of protective groups, methyl and benzyl 2-O-β-d-xylopyranosyl-α-d-mannopyranoside. Hydrogenolysis of benzyl 2-O- and 3-O-β-d-xylopyranosyl-α-d-mannopyranoside yielded the corresponding, reducing disaccharides. In addition to these disaccharides, disaccharides containing an α-d-xylopyranosyl group, and trisaccharides having d-xylopyranosyl groups at both O-2 and O-3 were obtained as minor products.     

Reactions of carbohydrate α-nitroepoxides with dimethylamine and with methylmagnesium iodide

Methyl 2,3-anhydro-4,6-O-benzylidene-3-C-nitro-β-d-allopyranoside (1), as well as its β-d-manno (2) and α- d-manno (3) isomers, reacted with dimethylamine to give the same, crystalline 3-(dimethylamino) adduct (4) of 1,5-anhydro-4,6-O-benzylidene-2-deoxy-2-(dimethylamino)-d-erythro-hex-1-en-3-ulose (5). The enulose 5 was obtained from 4 by the action of silica gel. Similarly, the β-d-gulo (6) and α-d-talo (7) stereoisomers of 1–3 afforded a 3-(dimethylamino) adduct (8) of the d-threo isomer (9) of 5. Reaction of dimethylamine with 5,6-anhydro-1,2-O-isopropylidene-6-C-nitro-α-d-glucofuranose (10) yielded a mixture of two diastereoisomeric (possibly anometic at C-6) 5-deoxy-5-(dimethylamino)-1,2-O-isopropylideric-α-d-hexodialdo-1,4:6,3-difuranoses (11). The β-glycoside 1 and the α-glycoside 3 reacted with methylmagnesium iodide to produce methyl 4,6-O-benzylidene-3-deoxy-3-C-methyl-3-(N-hydroxy-N-methylamino)-β- and -α-d-hexopyranosides (12) and (13), respectively; both products had the 1,2-trans configuration, but their configurations at the quaternary center C-3 have not been determined.     

Multi-nuclear (119Sn, 13C, 1H), fourier-transform,N.M.R. studies of di- and tri-butylstannyl ethers of carbohydrates

¹¹⁹Sn-N.m.r. spectra are reported for toluene solutions of the tributylstannyl ethers of 2,3,4,6-tetra-O-methyl-d)-glucose, 1,2:3,4-di-O-isopropylidene-α-d-galactopyranose, methyl 2,3-di-O-methyl-α-d-glucopyranoside, and methyl 4,6-O-benzylidene-α-d-glucopyranoside, and the dibutylstannyl ether of the last sugar. In the reaction of bis(tributyltin) oxide with methyl 4,6-O-benzylidene-α-d-glucopyranoside in toluene, HO-3 is much more reactive than HO-2. The presence of the various tin-containing species is readily apparent from the ¹¹⁹Sn-spectra. The importance of suppressing the nuclear Overhauser effect is demonstrated. The appearance of ¹¹⁹Sn satellites in the ¹³C-n.m.r. spectra demonstrates couplings of the types, ²J(¹¹⁹Sn-O-¹³C) and ³J(¹¹⁹Sn-O-C-¹³C), forthe first time, and, together with the ¹³C-chemical shifts, facilitates the determination of the site of substitution. The ¹¹⁹Sn-chemical shifts show that different states of coordination may be recognised. However, although different sites of substitution produce separate resonances, no simple relationship between shift and position is found. ¹³C-Chemical shifts are reported for methyl 4,6-O-benzylidene-α-d-glucopyranoside and its tributylstannyl ethers, and substituent effects are discussed.     

The synthesis of 3-amino-3-deoxy-α-d-glucopyranosyl α-d-glucopyranoside (3-amino-3-deoxy-α,α-trehalose

The preparation of 2,3-di-O-benzoyl-4,6-O-benzylidene-α-d-glucopyranosyl-2-O-benzoyl-4,6-O-benzylidene-α-d-ribo-hexopyranosid-3-ulose (3) from 4,6:4′,6′-di-O-benzylidene-α,α-trehalose (1) via the 2,3,2′-tribenzoate 2 has been improved. Reduction of 3 with sodium borohydride gave 2-O-benzoyl-4,6-O-benzylidene-α-d-allopyranosyl 2,3-di-O-benzoyl-4,6-O-benzylidene-α-d-glucopyranoside (4), which was converted into the methanesulfonate 5 and trifluoromethanesulfonate 6. Displacement of the sulfonic ester group in 6 with lithium azide was very facile and afforded a high yield of 3-azido-2-O-benzoyl-4,6-O-benzylidene-3-deoxy-α-d-glucopyranosyl 2,3-di-O-benzoyl-4,6-O-benzylidene-α-d-glycopyranoside (7), whereas similar displacement in 5 proceeded sluggishly, giving a lower yield of 7 together with an unsaturated disaccharide (8). The azido sugar 7 was converted by conventional reactions into the analogous 2,3,2′-triacetate 9, the corresponding 2,3,2′-triol 10, and deprotected 3-azido-3-deoxy-α-d-glucopyranosyl α-d-glucopyranoside (11). Hydrogenation of 11 over Adams' catalyst furnished crystalline 3-amino-3-deoxy-α,α-trehalose hydrochloride (12), the overall yield from 3 being 35%.     

An approach to branched-chain amino sugars,particularly derivatives of l-vancosamine (3-amino-2,3,6-trideoxy-3-C-methyl-l-lyxo-hexose) and its d enantiomer,via the cyanohydrin route

Methyl 4,6-O-benzylidene-2-deoxy-α-d-erythro-hexopyranosid-3-ulose reacted with potassium cyanide under equilibrating conditions to give, initially, methyl 4,6-O-benzylidene-3-C-cyano-2-deoxy-α-d-ribo-hexopyranoside (7), which, because it reverted slowly to the thermodynamically stable d-arabino isomer, could be crystallised directly from the reaction mixture. The mesylate derived from the kinetic product 7 could be converted by published procedures into methyl 3-acetamido-2,3,6-trideoxy-3-C-methyl-α-d-arabino-hexopyranoside, which was transformed into methyl N-acetyl-α-d-vancosaminide on inversion of the configuration at C-4. A related approach employing methyl 2,6-dideoxy-4-O-methoxymethyl-α-l-erythro-hexopyranosid-3-ulose gave the kinetic cyanohydrin and thence, via the spiro-aziridine 27, methyl 3-acetamido-2,3,6-trideoxy-3-C-methyl-α-l-arabino-hexopyranoside, a known precursor of methyl N-acetyl-α-l-vancosaminide.     

Studies on the reaction with N-bromosuccinimide of fixed 2-phenyl-1,3-dioxolane systems in methyl di-O-benzylidene-α-D-hexopyranosides

The reaction of methyl 2,3:4,6-di-O-benzylidene-α-D-mannopyranoside (5) with N-bromosuccinimide gave mainly three, isomeric dibromo dibenzoates, identified as the 3,6-dibromo-altro (1), 3,6-dibromo-manno (2), and 4,6-dibromo-ido (3) derivatives by subsequent chemical transformation and by extended n.m.r.-spectral studies. The reaction of methyl 2,3:4,6-O-benzylidene-α-D-allopyranoside (22) with N-bromosuccinimide gave two isomeric dibromo dibenzoates, the 2,6-dibromo-altro (23) and 3,6-dibromo-gluco (24) products, and their structures were similarly assigned. A similar reaction-sequence with methyl 2,3:4,6-di-O-benzylidene-α-D-glucopyranoside (32), however, yielded two isomeric monobenzoates 33 and 34, which could be identified straightforwardly. The results are consistent with the intermediate formation of benzoxonium ions that undergo favored axial attack. Thus the observed products and their ratios in reactions of 5 and of 22 with N-bromo-succinimide are explicable. Compound 32, however, does not appear to react by way of an intermediate, five-membered 2,3-trans benzoxonium ion.     

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.     

Synthesis of benzyl 2-acetamido-2-deoxy-3-O-β-d-fucopyranosyl-α-d-galactopyranoside and benzyl 2-acetamido-6-O-(2-acetamido-2-deoxy-β-d-glucopyranosyl)-2-deoxy-3-O-β-d-fucopyranosyl-α-d-galactopyranoside

Condensation of benzyl 2-acetamido-4,6-O-benzylidene-2-deoxy-α-d-galactopyranoside with 2,3,4-tri-O-acetyl-α-d-fucopyranosyl bromide in 1:1 nitromethane-benzene, in the presence of powdered mercuric cyanide, afforded benzyl 2-acetamido-4,6-O-benzylidene-2-deoxy-3-O-(2,3,4-tri-O-acetyl-β-d-fucopyranosyl)-α-d-galactopyranoside (3). Cleavage of the benzylidene group of 3 with hot, 60% aqueous acetic acid afforded diol 4, which, on deacetylation, furnished the disaccharide 5. Condensation of diol 4 with 2-methyl-(3,4,6-tri-O-acetyl-1,2-di-deoxy-α-d-glucopyrano)-[2,1-d]-2-oxazoline in 1,2-dichloroethane afforded the trisaccharide derivative (7). Deacetylation of 7 with Amberlyst A-26 (OH^?) anion-exchange resin in methanol gave the title trisaccharide (8). The structures of 5 and 8 were confirmed by ¹³C-n.m.r. spectroscopy.