Synthesis of methyl O-(3-deoxy-3-fluoro-β- -galactopyranosyl)-(1→6)-β- -galactopyranoside and methyl O-(3-deoxy-3-fluoro-β- -galactopyranosyl)-(1→6)-O-β- -galactopyranosyl-(1→6)-β- -galactopyranoside

Condensation of 2,4,6-tri-O-acetyl-3-deoxy-3-fluoro-α- -galactopyranosyl bromide (3) with methyl 2,3,4-tri-O-acetyl-β- -galactopyranoside (4) gave a fully acetylated (1→6)-β- -galactobiose fluorinated at the 3′-position which was deacetylated to give the title disaccharide. The corresponding trisaccharide was obtained by reaction of 4 with 2,3,4-tri-O-acetyl-6-O-chloroacetyl-α- -galactopyranosyl bromide (5), dechloroacetylation of the formed methyl O-(2,3,4-tri-O-acetyl-6-O-chloroacetyl-β- -galactopyranosyl)-(1→6)- 2,3,4-tri-O-acetyl-β- -galactopyranoside to give methyl O-(2,3,4-tri-O-acetyl-β- -galactopyranosyl)-(1→6)-2,3,4-tri-O-acetyl-β- -galactopyranoside (14), condensation with 3, and deacetylation. Dechloroacetylation of methyl O-(2,3,4-tri-O-acetyl-6-O-chloroacetyl-β- -galactopyranosyl)-(1→6)-O-(2,3,4-tri-O-acetyl- β- -galactopyranosyl)-(1→6)-2,3,4-tri-O-acetyl-β- -galactopyranoside, obtained by condensation of disaccharide 14 with bromide 5, was accompanied by extensive acetyl migration giving a mixture of products. These were deacetylated to give, crystalline for the first time, the methyl β-glycoside of (1→6)-β- -galactotriose in high yield. The structures of the target compounds were confirmed by 500-MHz, 2D, ¹H- and conventional ¹³C- and ¹⁹F-n.m.r. spectroscopy.     

Synthesis of methyl glycosides of β-(1→6)-linked -galactobiose, galactotriose, and galactotetraose having a 3-deoxy-3-fluoro-β- -galactopyranoside end-residue

Methyl 2,4-di-O-acetyl-3-deoxy-3-fluoro-β- -galactopyranoside was synthesized by sequential tritylation, acetylation, and detritylation of methyl 3-deoxy-3-fluoro-β- -galactopyranoside, and used as the initial nucleophile in the synthesis of methyl β-glycosides of (1→6)-β- -galacto-biose, -triose (20), and -tetraose (22) having a 3-deoxy-3-fluoro-β- -galactopyranoside end-residue. The extension of the oligosaccharide chais, to form the internal units in 20 and 22, was achieved by use of 2,3,4-tri-O-acetyl-6-O-bromoacetyl-α- -galactopyranosyl bromide as a glycosyl donor, and mercuric cyanide or silver triflate as the promotor. While fewer by-products were formed in the reactions involving mercuric cyanide, the reactions catalyzed by silver triflate were stereospecific and yielded only the desired β (trans) products.     

Synthesis, and carbon-13 n.m.r. study, of O-α- -rhamnopyranosyl-(1→3)-O-α- -rhamnopyranosyl-(1→2)- -rhamnopyranose and O-α- -rhamnopyranosyl-(1→3)-O-α- -rhamnopyranosyl (1→3)- -rhamnopyranose, constituents of bacterial, cell-wall polysaccharides

O-α- -Rhamnopyranosyl-(1→3)- -rhamnopyranose (19) and O-α- -rhamnopyranosyl-(1→2)- -rhamnopyranose were obtained by reaction of benzyl 2,4- (7) and 3,4-di-O-benzyl-α- -rhamnopyranoside (8) with 2,3,4-tri-O-acetyl-α- -rhamnopyranosyl bromide, followed by deprotection. The per-O-acetyl α-bromide (18) of 19 yielded, by reaction with 8 and 7, the protected derivatives of the title trisaccharides (25 and 23, respectively), from which 25 and 23 were obtained by Zemplén deacetylation and catalytic hydrogenolysis, With benzyl 2,3,4-tri-O-benzyl-β- -galactopyranoside, compound 18 gave an ≈3:2 mixture of benzyl 2,3,4-tri-O-benzyl-6-O-[2,4-di-O-acetyl-3-O-(2,3,4-tri-O-acetyl-α- -rhamnopyranosyl)-α- -rhamnopyranosyl]-β- -galactopyranoside and 4-O-acetyl-3-O-(2,3,4-tri-O-acetyl-α- -rhamnopyranosyl)-β- -rhamnopyranose 1,2-(1,2,3,4-tetra-O-benzyl-β- -galactopyranose-6-yl (orthoacetate). The downfield shift at the α-carbon atom induced by α- -rhamnopyranosylation at HO-2 or -3 of a free α- -rhamnopyranose is 7.4-8.2 p.p.m., ≈1 p.p.m. higher than when the (reducing-end) rhamnose residue is benzyl-protected (6.6-6.9 p.p.m.). α- -Rhamnopyranosylation of HO-6 of gb- -galactopyranose deshields the C-6 atom by 5.7 p.p.m. The 1 2-orthoester ring structure [O₂,C(me)OR] gives characteristic resonances at 24.5 ±0.2 p.p.m. for the methyl, and at 124.0 ±0.5 p.p.m. for the quaternary, carbon atom.     

Synthesis and biological activity of O-(N-acetyl-β-muramoyl-l-alanyl-d-isoglutamine)-(1→6)-2-acylamino-2-deoxy-d-glucoses

Benzoylation of benzyl 2-acetamido-2-deoxy-4,6-O-isopropylidene-α-d-glucopyranoside, benzyl 2-deoxy-2-(dl-3-hydroxytetradecanoylamino)-4,6-O-isopropylidene-α-d-glucopyranoside, and benzyl 2-deoxy-4,6-O-isopropylidene-2-octadecanoylamino-β-d-glucopyranoside, with subsequent hydrolysis of the 4,6-O-isopropylidene group, gave the corresponding 3-O-benzoyl derivatives (4, 5, and 7). Hydrogenation of benzyl 2-acetamido-4,6-di-O-acetyl-2-deoxy-3-O-[d-1-(methoxycarbonyl)ethyl]-α-d-glucopyranoside, followed by chlorination, gave a product that was treated with mercuric actate to yield 2-acetamido-1,4,6-tri-O-acetyl-2-deoxy-3-O-[d-1-(methoxycarbonyl)ethyl]-β-d-glucopyranose (11). Treatment of 11 with ferric chloride afforded the oxazoline derivative, which was condensed with 4, 5, and 7 to give the (1→6)-β-linked disaccharide derivatives 13, 15, and 17. Hydrolysis of the methyl ester group in the compounds derived from 13, 15, and 17 by 4-O-acetylation gave the corresponding free acids, which were coupled with l-alanyl-d-isoglutamine benzyl ester, to yield the dipeptide derivatives 19–21 in excellent yields. Hydrolysis of 19–21, followed by hydrogenation, gave the respective O-(N-acetyl-β-muramoyl-l-alanyl-d-isoglutamine)-(1→6)-2-acylamino-2-deoxy-d-glucoses in good yields. The immunoadjuvant activity of these compounds was examined in guinea-pigs.     

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.     

2′-Azido-2′-deoxy- and 2′-amino-2′-deoxy-β-d-arabino-furanosyl purine nucleosides

A general method for the preparation of 2′-azido-2′-deoxy- and 2′-amino-2′-deoxyarabinofuranosyl-adenine and -guanine nucleosides is described. Selective benzoylation of 3-azido-3-deoxy-1,2-O-isopropylidene-α-d-glucofuranose afforded 3-azido-6-O-benzoyl-3-deoxy-1,2-O-isopropylidene-α-d-glucofuranose (1). Acid hydrolysis of 1, followed by oxidation with sodium metaperiodate and hydrolysis by sodium hydrogencarbonate gave 2-azido-2-deoxy-5-O-benzoyl-d-arabinofuranose (3), which was acetylated to give 1,3-di-O-acetyl-2-azido-5-O-benzoyl-2-deoxy-d-arabinofuranose (4). Compound 4 was converted into the 1-chlorides 5 and 6, which were condensed with silylated derivatives of 6-chloropurine and 2-acetamido-hypoxanthine. The condensation reaction gave α and β anomers of both 7- and 9-substituted purine nucleosides. The structures of the nucleosides were determined by n.m.r. and u.v. spectroscopy, and by correlation of the c.d. spectra of the newly prepared nucleosides with those published for known purine nucleosides.     

Synthesis of 2,3-di-O-glycosyl derivatives of methyl α- and β- -glucopyranoside

The syntheses are described of 2,3-di-O-glycosyl derivatives of methyl α- and β- -glucopyranoside having α- -manno-, β- -galacto-, α- -rhamno-, α- -fuco-, and β- -fuco-pyranosyl substitutents at O-2 and O-3. The syntheses involved glycoslation of methyl 4,6-O-(benzylidene-α- (24) and β- -glucopyranoside (21), and substituted derivatives of 21 bearing 2-O-(2,3,4,6-tetra-O-benzyl-α- -mannopyranosyl)-, -(2,3,4,6-tetra-O-acetyl-β- -galactopyranosyl)-, -(2,3,4-tri-O-benzyol-α- -rhamnopyranosyl)-, and-(2,3,4-tri-O-benzoyl-β- -fucopyranosyl) groups.     

Synthesis of 4-O-α- -galactopyranosyl- -rhamnose and 4-O-α- -galactopyranosyl-2-O-β-glucopyranosyl- -rhamnose using dioxolane-type benzylidene acetals as temporary protecting-groups

The Halide ion-catalysed reaction of benzyl exo-2,3-O-benzylidene-α- -rhamnopyranoside with tetra-O-benzyl-α- -galactopyranosyl bromide and hydrogenolysis of the exo-benzylidene group of the product 2 gave benzyl 3-O-benzyl-4-O-(2,3,4,6-tetra-O-benzyl-α- -galactopyranosyl)-α- -rhamnopyranoside (6). Compound 2 was converted into 4-O-α- -galactopyranosyl- -rhamnose. The reaction of 6 with tetra-O-acetyl-α- -glucopyranosyl bromide and removal of the protecting groups from the product gave 4-O-α- -galactopyranosyl-2-O-β- -glucopyranosyl- -rhamnose.     

Synthesis of monodeoxy and mono-O-methyl congeners of methyl β-d-mannopyranosyl-(1→2)-β-d-mannopyranoside for epitope mapping of anti-Candida albicans antibodies

A panel of six complementary monodeoxy and mono-O-methyl congeners of methyl β-d-mannopyranosyl-(1→2)-β-d-mannopyranoside (1) were synthesized by stereoselective glycosylation of monodeoxy and mono-O-methyl monosaccharide acceptors with a 2-O-acetyl-glucosyl trichloroacetimidate donor, followed by a two-step oxidation–reduction sequence at C-2′. The β-manno configurations of the final deprotected congeners 2–7 were confirmed by measurement of ¹J_C1,H1 heteronuclear and ³J_1′,2′ homonuclear coupling constants. These disaccharide derivatives will be used to map the protective epitope recognized by a protective anti-Candida albicans monoclonal antibody C3.1 (IgG3) and to determine its key polar contacts with the binding site.     

Sequential synthesis and C-N.m.r. spectra of methyl β-glycosides of (1→4)-β-d-xylo-oligosaccharides

The reaction of 2,3-di-O-acetyl-4-O-benzyl-α,β-d-xylopyranosyl bromide (2) with methyl 2,3-di-O-acetyl-β-d-xylopyranoside gave methyl O-(2,3-di-O-acetyl-4-O-benzyl-β-d-xylopyranosyl)-(1→4)-2,3-di-O-acetyl-β-d-xylopyranoside (22). Catalytic hydrogenolysis of 22 exposed HO-4′ which was then condensed with 2. This sequence of reactions was repeated three more times to afford, after complete removal of protecting groups, a homologous series of methyl β-glycosides of (1→4)-β-d-xylo-oligosaccharides. ¹³C-N.m.r. spectra of the synthetic methyl β-glycosides (di- to hexa-saccharide) are presented together with data for six other, variously substituted, homologous series of (1→4)-d-xylo-oligosaccharides.     

Derivatives of β- -fructofuranosyl α- -galactopyranoside

De-etherification of 6,6′-di-O-tritylsucrose hexa-acetate (2) with boiling, aqueous acetic acid caused 4→6 acetyl migration and gave a syrupy hexa-acetate 14, characterised as the 4,6′-dimethanesulphonate 15. Reaction of 2,3,3′4′,6-penta-O-acetylsucrose (5) with trityl chloride in pyridine gave a mixture containing the 1′,6′-diether 6 the 6′-ether 9, confirming the lower reactivity of HO-1′ to tritylation. Subsequent mesylation, detritylation, acetylation afforded the corresponding 4-methanesulphonate 8 1′,4-dimethanesulphonate 11. Reaction of these sulphonates with benzoate, azide, bromide, and chloride anions afforded derivatives of β- -fructofuranosyl α- -galactopyranoside (29) by inversion of configuration at C-4. Treatment of the 4,6′-diol 14 the 1,′4,6′-triol 5, the 4-hydroxy 1′,6′-diether 6 with sulphuryl chloride effected replacement of the free hydroxyl groups and gave the corresponding, crystalline chlorodeoxy derivatives. The same 4-chloro-4-deoxy derivative was isolated when the 4-hydroxy-1′,6′-diether 6 was treated with mesyl chloride in N,N-dimethylformamide.     

Synthesis of p-nitrophenyl 6-O-(2-acetamido-2-deoxy-β-d-glucopyranosyl)-α-d-mannopyranoside

The reaction of p-nitrophenyl 2,3-O-isopropylidene-α-d-mannopyranoside and 2-methyl-(3,4,6-tri-O-acetyl-1,2-dideoxy-α-d-glucopyrano)-[2,1-d]-2-oxazoline gave a crystalline, 6-O-substituted disaccharide derivative which, on de-isopropylidenation followed by saponification, produced the disaccharide p-nitrophenyl 6-O-(2-acetamido-2-deoxy-β-d-glucopyranosyl)-α-d-mannopyranoside. Synthesis of methyl 6-O-(2-acetamido-2-deoxy-β-d-glucopyranosyl)-α-d-mannopyranoside was also accomplished by a similar reaction-sequence. The structures of these disaccharides have been established by ¹³C-n.m.r. spectroscopy.     

Conversion of amylose into a (1→4)-2-amino-2-deoxy-α-D-glucopyranuronan and its 2-N-sulfo derivative, a heparin analog

By a modification of a previously established reaction-sequence involving successive oxidation with methyl sulfoxide-acetic anhydride, oximation, and reduction with lithium aluminum hydride, 6-O-tritylamylose (1) was converted into a 6-O-tritylated (1→4)-α-D-linked glucan (3) containing 2-amino-2-deoxy-D-glucose residues and some O-(methylthio)methyl groups. Removal of the ether groups from this product gave a 2-aminated amylose (4) of degree of substitution (d.s.) by amine of 0.54 that underwent cleavage by fungal alpha-amylase to give oligosaccharides containing amino sugar residues. N-Trifluoroacetylation of 3 followed by removal of the ether groups, oxidation at C-6 with oxygen-platinum, and removal of the N-substituent, gave a (1 →4)-2-amino-2-deoxy-α-D-glucopyranuronan 7 having d.s. by amine of up to 0.65, and by carboxyl, of 0.46. Sulfation of this product with sulfur trioxide-pyridine and then with chlorosulfonic acid-pyridine gave a (1→4)-2-deoxy-2-sulfoamino-α-D-glucopyranuronan, isolated as its sodium salt 8, which showed appreciable blood-anticoagulant activity.     

Improved synthesis and the crystal structure of methyl 4,6-dideoxy-4-(3-deoxy- -glycero-tetronamido)-α- -mannopyranoside, the methyl α-glycoside of the intracatenary repeating unit of the O-polysaccharide of Vibrio cholerae O:1

The crude product of deamination of the commercially available -homoserine was acetylated and the 2-O-acetyl-3-deoxy- -glycero-tetronolactone (18) formed was used to N-acylate methyl perosaminide (methyl 4-amino-4,6-dideoxy-α- -mannopyranoside, 12) and its 2,3-O-isopropylidene derivative. The major product isolated from the reaction was the crystalline methyl 4-(4-O-acetyl-3-deoxy- -glycero-tetronamido)-4,6-dideoxy-α- -mannopyranoside (1, 70–75%) resulting from acetyl group migration in the initially formed 2'-O-acetyl derivative. O-Deacetylation of 1 gave the title amide 2. Compound 2, obtained crystalline for the first time, was fully characterized, and its crystal structure was determined. Deoxytetronamido derivatives diastereomeric with 1 and 2, respectively, were obtained by the acylation of 12 with 2-O-acetyl-3-deoxy- -glycero-tetronolactone (prepared from -homoserine), and subsequent deacetylation. Structures of several byproducts of the reaction of 12 with 18 have been deduced from their spectral characteristics. Since these byproducts were various O-acetyl derivatives of 2, the title compound could be obtained in ≈ 90% yield by deacetylating (Zemplén) the crude mixture of N-acylation products, followed by chromatography.     

The stepwise synthesis of methyl α-isomaltooligoside derivatives and methyl α-isomaltopentaoside

Methyl 2,3,4-tri-O-benzyl-α-D-glucopyranoside was treated with 2,3,4-tri-O-benzyl-6-O-(N-phenylcarbamoyl)-1-O-tosyl-D-glucopyranose in diethyl ether to give methyl 2,3,4,2',3',4'-hexa-O-benzyl-6'-O-(N-phenylcarbamoyl)-α-isomaltoside. The disaccharide was decarbanilated in ethanol with sodium ethoxide to give methyl 2,3,4,2',3',4'-hexa-O-benzyl-α-isomaltoside. The sequence of coupling with the same 1-O-tosyl-D-glucose derivative followed by removal of the N-phenylcarbamate group was repeated until the hexasaccharide derivative, methyl octadeca-O-benzyl-α-isomaltohexaoside, was formed. Methyl α-isomaltopentaoside was prepared by debenzylation of the corresponding benzylated oligosaccharide. The structures of the oligosaccharides were determined with the aid of both ¹H- and ¹³C-n.m.r. spectroscopy. From spectral data, we estimate the coupling reaction to be 95% stereoselective.     

Deoxyfluoroketohexoses: 4-deoxy-4-fluoro- -sorbose and -tagatose and 5-deoxy-5-fluoro- -sorbose

4-Deoxy-4-fluoro-α- -sorbose (6) was prepared in crystalline form by the action of potassium hydrogen fluoride on 3,4-anhydro-1,2-O-isopropylidene-β- -psicopyranose (3) followed by deacetonation. Under identical conditions 3,4-anhydro-1,2-O-isopropylidene-β- -tagatopyranose (7) underwent epoxide migration to give 4,5-anhydro- 1,2-O-isopropylidene-β- -fructopyranose (12), which after deacetonation yielded 4-deoxy-4-fluoro- -tagatose (15) 5-deoxy-5-fluoro-α- -sorbopyranose (16) the latter as the crystalline free sugar. The action of glycol-cleavage reagents on the isopropylidene acetals of the deoxyfluoro sugars was consistent with the assigned structures. The structures were established by ¹³C n.m.r. studies of the free deoxyfluoro sugars 6 and 16 of the isopropylidene acetal 13, and by ¹H n.m.r. studies on the acetylated isopropylidene acetals 5 diacetate, 13 diacetate, and 14 diacetate. 5-Deoxy-5-fluoro- -sorbose (16) was biologically active producing in mice effects characteristic of deoxyfluorotrioses and of fluoroacetate. 4-Deoxy-4-fluoro- -tagatose (15) and 4-deoxy-4-fluoro- -sorbose (6) produced no apparent effects in mice up to a dose of 500 mg/kg. The implications of these findings with respect to transport phosphorylation, and the action of aldolase on ketohexoses are discussed.     

Synthesis of Neu5Ac- and Neu5Gc-α-(2→6′)-lactosamine 3-aminopropyl glycosides

In order to prepare 3-aminopropyl glycosides of Neu5Ac-α-(2→6′)-lactosamine trisaccharide 1, and its N-glycolyl containing analogue Neu5Gc-α-(2→6′)-lactosamine 2, a series of lactosamine acceptors with two, three, and four free OH groups in the galactose residue was studied in glycosylations with a conventional sialyl donor phenyl [methyl 5-acetamido-4,7,8,9-tetra-O-acetyl-3,5-dideoxy-2-thio- -glycero-α- and β- -galacto-2-nonulopyranosid]onates (3) and a new donor phenyl [methyl 4,7,8,9-tetra-O-acetyl-5-(N-tert-butoxycarbonylacetamido)-3,5-dideoxy-2-thio- -glycero-α- and β- -galacto-2-nonulopyranosid]onates (4), respectively. The lactosamine 4′,6′-diol acceptor was found to be the most efficient in glycosylation with both 3 and 4, while imide-type donor 4 gave slightly higher yields with all acceptors, and isolation of the reaction products was more convenient. In the trisaccharides, obtained by glycosylation with donor 4, the 5-(N-tert-butoxycarbonylacetamido) moiety in the neuraminic acid could be efficiently transformed into the desired N-glycolyl fragment, indicating that such protected oligosaccharide derivatives are valuable precursors of sialo-oligosaccharides containing N-modified analogues of Neu5Ac.     

Studies on the koenigs-knorr reaction : Part V. Synthesis of 2-acetamido-2-deoxy-3-O-α-L-fucopyranosyl-α-D-glucose

Optically pure 2-acetamido-2-deoxy-3-O-α-L-fucopyranosyl-α-D-glucose was synthesized by the Koenigs-Knorr reaction of 2-O-benzyl-3,4-di-O-p-nitrobenzoyl-α-L-fucopyranosyl bromide with benzyl 2-acetamido-4,6-O-benzylidene-2-deoxy-α-D-glucopyrainoside. Reaction of 2,3,4-tri-O-acetyl-α-L-fucopyranosyl bromide gave the β-L-fucopyranosyl anomer. In contrast to the stereospecificity shown in this reaction by these two bromides, 2,3,4-tri-O-benzyl-α-L-fucopyranosyl bromide afforded a mixture of α-L and β-L anomers in almost equimolar proportions. The disaccharides synthesized were crystallized and characterized, and their optical purity demonstrated by g.l.c. of the per(trimethylsilyl) ethers of the corresponding alditols.     

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.     

The synthesis ofP1-[2-acetamido-2-deoxy-3-O-(β-D-glucopyranosyluronic acid)-α-D-glucopyranosyl] P2-dolichyl diphosphate (N-acetylhyalobiosyluronic dolichyl diphosphate)

Starting from 2-acetamido-4,6-di-O-acetyl-2-deoxy-3-O-(methyl 2,3,4-tri-O-acetyl-β-D-glucopyranosyluronate)-α-D-glucopyranose (20), a crystalline intermediate prepared by a conventional sequence of reactions, the total synthesis of N-acetyl-hyalobiosyluronic dolichyl diphosphate was achieved. One of the key steps involved the transformation of the disaccharide 20 into the methyloxazoline 26, which was then converted into the stable, crystalline disaccharide phosphate derivative in ～30% yield. The methyloxazoline 26 was directly prepared from the corresponding methyl α-glycoside by acetolysis. Similarly, the allyl α-glycoside was transformed into 26.