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.     

Preparation of glycosides of 2-deoxy-2-methylamino-D-mannose, 2-deoxy-2-methylamino-D-glucose,and 2-deoxy-2-methylamino-D-galactose: observations on N-methylation of amides

Benzyl 2-[(benzyloxycarbonyl)methylamino]-2-deoxy-α-D-mannopyranoside (10) and its furanose isomer (9), the derived N-methyloxazolidinones 11 and 6, benzyl 2-[(benzyloxycarbonyl)methylamino]-2-deoxy-β-D-glucofuranoside (15) and methyl 2-deoxy-2-methylacetamido-β-D-galactofuranoside (20), were prepared from appropriate diethyl dithioacetals. They were considered the most suitable starting materials for synthesis of O-methyl-2-deoxy-2-methylamino-hexoses because of their ease of preparation and the presence of suitable blocking groups. Oxazolidinones were prepared from N-benzyloxycarbonyl derivatives of 2-amino-2-deoxy-D-mannose by using methanolic sodium methoxide. Their use in preparation of 2-deoxy-2-methyl-amino derivatives is discussed. The Kuhn reagent was used in these syntheses for N-methylating amides. However, certain amides containing comparatively bulky substituents in the vicinity of the NH group are resistant to methylation.     

Nitrous acid deamination of methylated amino-oligosaccharide glycosides

G.l.c.-mass spectrometry has been used to characterize the products of N-deacetylation-nitrous acid deamination of per-O-methylated derivatives (8–11) of methyl 2-acetamido-2-deoxy-3-O-β-D-galactopyranosyl-α-D-glucopyranoside(1), methyl (2) and benzyl (3) 2-acetamido-2-deoxy-4-O-β-D-galactopyranosyl-β-D-glucopyranosides, and methyl 2-acetamido-2-deoxy-6-O-β-D-galactopyranosyl-α-D-glucopyranoside (4). 2,5-Anhydrohexoses have been converted into alditol trideuteriomethyl ethers, alditol acetates, and aldononitriles. The importance of side reactions that lead to the formation of 2-deoxy-2-C-formylpentofuranosides is discussed.     

Preparation of S-(N6,N6-dimethyladenosyl)-L-methionine

4′,5′-Unsaturated nucleosides are obtained by the action of 1,5-diazabicyclo-[5.4.0]undec-5-ene on N¹- and N³-(methyl 2,3,4-tri-O-acetyl-β-d-glucopyranosyluronate)-5-fluorouracil. The ²H₁ conformation of N¹- and N³-(methyl 4-deoxy-α-l-threo-hex-4-enopyranosyluronate)-5-fluorouracil has been established by ¹H-n.m.r. and c.d. methods. Interaction of the heterocyclic base and the double bond of the sugar moiety is demonstrated.     

Hydrophilic ligands derived from glucose: Synthesis, characterization and in vitro cytotoxic activity on cancer cells of Pt(II) complexes

Aiming to contribute to the design of new antitumoral drugs, we synthesized new hydrophilic Pt(II) complexes of general formula [PtCl₂(N,N′)] containing nitrogen bidentate amine-imine and di-imine ligands derived from glucose. Some chemical properties were discussed. The X-ray molecular structure of [PtCl₂(α-d-glucopyranoside-methyl-6-deoxy-6(2-(methylimino)methyl)pyridine) (D) was reported. [PtCl₂(β-d-glucopyranosylimine-N-(2-pyridinylmethyl))] (A), which is well-soluble both in organic solvents and in water, was tested for cytotoxicity.     

Synthesis of alkyl glyco-pyranosides and -furanosides of 2-amino-2-deoxy-d-glucose. Crystal structure of 2-deoxy-2-[(4,4-dimethyl-2,6-dioxocyclohexylidenemethyl)amino]-α-d-glucopyranose

The reaction of 2-amino-2-deoxy-d-glucose hydrochloride with 5,5-dimethyl-2-phenylaminomethylene-1,3-cyclohexanedione in MeOH in the presence of Et₃N afforded 2-deoxy-2-[(4,4-dimethyl-2,6-dioxocyclohexylidenemethyl)amino]-d-glucose (6) in yields > 75%. Glycosidation of 6 with different alcohols (MeOH, CH₂CHCH₂OH, BnOH) under the Fischer conditions afforded mixtures of the corresponding alkyl 2-deoxy-2-[(4,4-dimethyl-2,6-dioxocyclohexylidenemethyl)-amino]-α,β-d-glucopyranoside and -α-d-glucofuranoside. Removal of the N-protecting group gave high yields of the free aminodeoxyglyco-pyranosides and -furanosides. In addition to other known glycosides, allyl and benzyl 2-amino-2-deoxy-α-d-glucopyranoside and ethyl and allyl 2-amino-2-deoxy-α-β-glucofuranoside were obtained. An X-ray crystallographic study of 6 indicated that, in the solid state, it has the α-d configuration and that the pyranoside ring adopts the ⁴C₁ conformation.     

Synthesis of methyl (or propyl) 2-acetamido-2-deoxy-α-D-glucopyranoside 6-(α-D-glucopyranosyl phosphate) and derivatives for the study of the phosphoric ester linkage in the Micrococcus lysodeikticus cell-wall

Methyl 2-acetamido-3-O-allyl-2-deoxy-4-O-methyl-α-D-glucopyranoside, methyl 2-acetamido-2-deoxy-4-O-methyl-α-D-glucopyranoside, and methyl 2-acetamido-3,4-di-O-allyl-2-deoxy-α-D-glucopyranoside, prepared from methyl 2-acetamido-2-deoxy-α-D-glucopyranoside, were coupled with 2,3,4,6-tetra-O-acetyl-α-D-glucopyranosyl phosphate (13), to give the phosphoric esters methyl 2-acetamido-3-O-allyl-2-deoxy-4-O-methyl-α-D-glucopyranoside 6-(2,3,4,6-tetra-O-acetyl-α-D-glucopyranosyl phosphate) (16), methyl 2-acetamido-2-deoxy-4-O-methyl-α-D-glucopyranoside 6-(2,3,4,6-tetra-O-acetyl-α-D-glucopyranosyl phosphate) (23), and methyl 2-acetamido-3,4-di-O-allyl-2-deoxy-α-D-glucopyranoside 6-(2,3,4,6-tetra-O-acetyl-α-D-glucopyranosyl phosphate) (17). Compound 13 was prepared from penta-O-acetyl-β-D-glucopyranose by the phosphoric acid procedure, or by acetylation of α-D-glucopyranosyl phosphate. Removal of the allyl groups from 16 and 17 gave 23 and methyl 2-acetamido-2-deoxy-α-D-glucopyranoside 6-(2,3,4,6-tetra-O-acetyl-α-D-glucopyranosyl phosphate) (19), respectively. O-Deacetylation of 23 gave methyl 2-acetamido-2-deoxy-4-O-methyl-α-D-glucopyranoside 6-(α-D-glucopyranosyl phosphate) (26) and O-deacetylation of 19 gave methyl 2-acetamido-2-deoxy-α-D-glucopyranoside 6-(α-D-glucopyranosyl phosphate) (24). Propyl 2-acetamido-2-deoxy-α-D-glucopyranoside 6-(α-D-glucopyranosyl phosphate) (25) was prepared by coupling 13 with allyl 2-acetamido-3,4-di-O-benzyl-2-deoxy-α-D-glucopyranoside, followed by catalytic hydrogenation of the product to give the propyl glycoside, which was then O-deacetylated. Compounds 24, 25, and 26 are being employed in structural studies of the Micrococcus lysodeikticus cell-wall.     

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.     

Synthesis of D-galactosamine derivatives and binding studies using isolated rat hepatocytes

Derivatives of glycosides of D-galactosamine were prepared in order to study further the binding requirement of the Gal/GalNAc receptor in mammalian hepatocytes. These structures included N-propanoyl, N-benzoyl, and N,N-phthaloyl derivatives of 2-hydroxyethyl-2-amino-2-deoxy-β-D-galactopyranoside, 6-amino-hex-1-yl 2-deoxy-2-(trifluoroacetamido)-β-D-galactopyranoside, the mono- and di-O-methyl derivatives of allyl 2-acetamido-2-deoxy-β-D-galactopyranoside, and allyl 2-acetamido-2,4-dideoxy-4-fluoro-α-D-galactopyranoside. The inhibition results confirmed some of our previous findings on the involvement of the hydroxyl groups, and provided new information on the involvement of the N-substituent, as well as on the requirement of hydrogen bonding of the 4-hydroxyl group in binding.     

Addition of 1-nitroalkanes to methyl 2,3-O-isopropylidene-β-d-ribo-pentodialdo-1,4-furanoside and N6-benzoyl-2′,3′-O-isopropylideneadenosine-5′-aldehyde

Various 1-nitroalkanes reacted with methyl 2,3-O-isopropylidene-β-d-ribo-pentodialdo-1,4-furanoside to yield methyl 6-alkyl-6-deoxy-2,3-O-isopropylidene-6-nitro-β-d-ribofuranosides in 64–79% yield. Similarly, nitromethane and 1-nitropentane reacted with N⁶-benzoyl-2′,3′-O-isopropylideneadenosine-5′-aldehyde, to yield the corresponding 9-[6-alkyl-6-deoxy-2,3-O-isopropylidene-6-nitro-α-l-talo(β-d-allo)furanosyl]-N⁶-benzoyladenines in 74 and 44% yield, respectively. The potential utility of this nitroalkane addition for the synthesis of nucleosides having a C-5′C-6′ bond is discussed.     

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.     

Depolymerization of heparin with diazomethane. Structure of N,O-methylated,even-numbered oligosaccharides produced by β-eliminative cleavage of the 2-amino-2-deoxyglycosylic linkage

The long-period reaction of heparin with excess diazomethane at 20° resulted in cleavage at the β-position of the uronic acid carboxyl group to give a mixture of methyl α- and β-glycosides of N,O-methylated di-, tetra-, and hexa-saccharides having a 4,5-unsaturated uronic acid, nonreducing end-group. The major disaccharides obtained were methyl O-(4-deoxy-3-O-methyl-α-l-threo-hex-4-enopyranosyluronic acid 2-sulfate)-(1→4)-2-deoxy-3-O-methyl-2-(N-methylsulfoamino)-α- and -β-d-glucopyranoside. The reaction of heparin at 4° yielded a mixture of methylated, higher-molecular-weight oligosaccharides, which retained some affinity for antithrombin III-Sepharose.     

Efficient synthesis of a 6-deoxytalose tetrasaccharide related to the antigenic O-polysaccharide produced by Aggregatibacter actinomycetemcomitans serotype c

Concise synthesis of a 6-deoxy-α-l-talose tetrasaccharide, 6-deoxy-α-l-Talp-(1→3)-6-deoxy-α-l-Talp-(1→2)-6-deoxy-α-l-Talp-(1→3)-6-deoxy-α-l-Talp, the dimer of the disaccharide repeating unit of the OPS from Aggregatibacter actinomycetemcomitans serotype c, has been accomplished through suitable protecting group manipulations and stereoselective glycosylation starting from commercially available l-rhamnose. The target oligosaccharide in the form of its p-methoxyphenyl glycoside is suitable for further glycoconjugate formation via selective cleavage of this group.     

Preparation of acetylenic sugar derivatives by way of 2-(N-nitroso)acetamido sugars

N-Nitrosation with dinitrogen tetraoxide was used to convert 2-acetamido-1,3,4,6-tetra-O-acetyl-2-deoxy-α-D-glucopyranose (1) and 2-acetamido-1,3,4,6-tetra-O-acetyl-2-deoxy-β-D-galactopyranose (4) in high yield into the N-nitroso derivatives 2 and 5, respectively. Similarly, 3-acetamido-1,2,4,6-tetra-O-acetyl-3-deoxy-β-D-glucopyranose (12) and methyl 2-acetamido-3,4,5,6-tetra-O-acetyl-2-deoxy-D-gluconate (15) gave their respective, crystalline N-nitroso derivatives 13 and 16. Various other 2-acetamido sugar derivatives were likewise nitrosated. In ethereal solution, compounds 2 and 16 reacted with potassium hydroxide in isopropyl alcohol to give the C₅ acetylene, 1,2-dideoxy-D-erythro-pent-1-ynitol, isolated as the known triacetate 3. By the same procedure, the galacto derivative 5 was converted in high yield into the 3-epimeric C₅ acetylene, 1,2-dideoxy-D-threo-pent-1-ynitol, isolated as its triacetate 6 and characterized by conversion into the known, crystalline 1,2-dideoxy-3-O-(3,5-dinitrobenzoyl)-4,5-O-isopropylidene-D-threo-pent-1-ynitol (7).     

Syntheses of repeating units of Escherichia coli capsular polysaccharides containing d-ribose and 3-deoxy-d-manno-2-octulosonic acid (KDO)

The oligosaccharides, sodium (methyl 3-deoxy-7-O-β-d-ribofuranosyl-β-d-manno-2-octulopyranosid)onate, methyl 2-O-β-d-ribofuranosyl-β-d-ribofuranoside, and the anomeric sodium [methyl 3-deoxy-7-O-(2-O-β-d-ribofuranosyl-β-d-ribofuranosyl)-α- and -β-d-manno-2-octulopyranosid]onate were prepared from 1-O-acetyl-2,3,5-tri-O-benzoyl-β-d-ribofuranose and the anomeric methyl (methyl 8-O-benzyl-4,5-O-carbonyl-3-deoxy-α- and -β-d-manno-2-octulopyranosid)onate in high purity and in acceptable over-all yields. They constitute a first series of model compounds for spectroscopic and immunochemical studies of the capsular polysaccharides from Escherichia coli strains LP 1092 and K 23. The essential, interglycosidic linkages [β-d-Ribf-(1→7)-α- or -β-d-dOclA, and β-d-Ribf-(1→2)-β-d-Ribf] were formed by a modification of the silver triflate procedure using appropriate d-ribofuranosyl bromide derivatives. The constitutional and configurational assignments were based on the 250-MHz ¹H-n.m.r.-spectra of protected derivatives of the oligosaccharides.     

The synthesis and N.M.R. spectroscopy of derivatives of 6-amino-6-deoxy-D-galactose-6-15N

Derivatives of 6-amino-6-deoxy-D-galactose-6-¹⁵N have been synthesized by reaction of the 6-deoxy-6-iodo (1) or 6-O-p-tolylsulfonyl derivative of 1,2:3,4-di-O-isopropylidene-α-D-galactopyranose with potassium phthalimide-¹⁵N. The reaction of 1 also yielded an elimination product, 6-deoxy-1,2:3,4-di-O-isopropylidene-β-L-arabino-hex-5-enopyranose. The structures of the 6-amino-6-deoxy-D-galactose derivatives and their precursors were characterized by proton- and ¹³C-n.m.r. spectroscopy, with confirmation of the ¹³C assignments by selective proton decoupling. Selective broadening of the C-1, C-4, C-5, and C-6 resonances of 6-amino-6-deoxy-1,2:3,4-di-O-isopropylidene-α-D-galactopyranose by low concentrations of cupric ion was observed, and studied by computerized measurements of the ¹³C linewidths. The application of this broadening to ¹³C-spectral assignments of amino sugar derivatives is indicated.     

The behavior of some aldoses with 2,2-dimethoxypropane-N,N-dimethylformamide-p-toluenesulfonic acid. II. At 80 degrees

Four aldohexoses were individually subjected to the reagent mixture and temperature cited in the title; in each case, the 2,2-dimethoxypropane was present in only a small molar excess and the p-toluenesulfonic acid was used in trace amounts. D-Mannose (1) afforded the known 2,3:5,6-di-O-isopropylidene-D-mannofuranose (2) in significantly higher yield than when the reaction was conducted at room temperature. The other three aldoses, however, gave products markedly different from those formed under the milder conditions. 2-Acetamido-2-deoxy-D-mannose (3) gave a mixture of products from which methyl 2-acetamido-2-deoxy-2,3-N,O-isopropylidene-5,6-O-isopropylidene-α-D-mannofuranoside (4), 2-acetamido-2-deoxy-2,3-N,O-isopropylidene-5,6-O-isopropylidene-D-mannofuranose (5a), and methyl 2-acetamido-2-deoxy-5,6-O-isopropylidene-α-D-mannofuranoside (6a) were isolated. 2-Acetamido-2-deoxy-D-galactose (11) gave compounds identified as methyl 2-acetamido-2-deoxy-5,6-O-isopropylidene-β-D-galactofuranoside (12a) and methyl 2-acetamido-2-deoxy-4,6-O-isopropylidene-β-D-galactopyranoside (13a). 2-Acetamido-2-deoxy-D-glucose (16) afforded methyl 2-acetamido-2-deoxy-5,6-O-isopropylidene-β-D-glucofuranoside (17a) and methyl 2-acetamido-2-deoxy-4,6-O-isopropylidene-β-D-glucopyranoside (18a). Evidence in support of the structures assigned to these new derivatives is presented.     

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.     

The synthesis of oligosaccharide-asparagine compounds. V. O- -D-mannopyranosyl-(1 leads to 6)-O-(2-acetamido-2-deoxy- -D-glucopyranosyl)-(1 leads to 4)-2-acetamido-N-(L-aspart-4-oyl)-2-deoxy- -D-glucopyranosylamine

O-α-d-Mannopyranosyl-(1→6)-O-(2-acetamido-2-deoxy-β-d-glucopyranosyl)-(1→4)-2-acetamido-N-(l-aspart-4-oyl)-2-deoxy-β-d-glucopyranosylamine (12), used in the synthesis of glycopeptides and as a reference compound in the structure elucidation of glycoproteins, was synthesized via condensation of 2,3,4,6-tetra-O-acetyl-α-d-mannopyranosyl bromide with 2-acetamido-4-O-(2-acetamido-3-O-acetyl-2-deoxy-β-d-glucopyranosyl)-3,6-di-O-acetyl-2-deoxy-β-d-glucopyranosyl azide (5) to give the intermediate, trisaccharide azide 7. [Compound 5 was obtained from the known 2-acetamido-4-O-(2-acetamido-3,4,6-tri-O-acetyl-2-deoxy-β-d-glucopyranosyl)-3,6-di-O-acetyl-2-deoxy-β-d-glucopyranosyl azide by de-O-acetylation, condensation with benzaldehyde, acetylation, and removal of the benzylidene group.] The trisaccharide azide 6 was then acetylated, and the acetate reduced in the presence of Adams' catalyst. The resulting amine was condensed with 1-benzyl N-(benzyloxycarbonyl)-l-aspartate, and the O-acetyl, N-(benzyloxycarbonyl), and benzyl protective groups were removed, to give the title compound.     

Synthesis and glycosidation of 1-deoxy-1-[(2,2-diacylvinyl)amino]-d-fructoses

The reactions of 1-amino-1-deoxy-d-fructose acetate (1) with methyl 3-methoxy-2-methoxycarbonylacrylate and 5-methoxymethylene-2,2-dimethyl-1,3-dioxane-4,6-dione in the presence of a base afforded 1-deoxy-1-[(2,2-dimethoxycarbonylvinyl)amino]- (2 and 1-deoxy-1-[(2,2-dimethyl-4,6-dioxo-1,3-dioxan-5-ylidenemethyl)amino]-d-fructose (3), respectively, in high yields. 1-Deoxy-1-[(4,4-dimethyl-2,6-dioxocyclohexylidenemethyl)amino]-d-fructose (4) was obtained (85%) by a transamination reaction between 1 and 5,5-dimethyl-2-phenylaminomethylene-1,3-cyclohexanedione in the presence of Et₃N. The isomeric composition of equilibrium solutions of 1–4 was established by ¹³C-n.m.r. spectroscopy. For all the compounds, the β-pyranose form was the main component in D₂O; the α-furanose, the β-furanose, and, for 1, the α-pyranose forms, were also present. The major constituents of 2 in (CD₃)₂SO solution were the β- and the α-furanose forms. Acetylation of 2 afforded the tetra-acetates of the α- and β-furanose forms, the 3,4,6-triacetates of the α- and β-furanose forms, the 3,4,5-triacetate of the β-pyranose form, and 2,3,4,5,6-penta-O-acetyl-1-deoxy-1-[(2,2-dimethoxycarbonylvinyl)amino]-d-arabino-hex-1-enitol. Glycosidation of 2 with MeOHHCl afforded a mixture of methyl 1-deoxy-1-[(2,2-dimethoxycarbonylvinyl)amino]-α- (11α) and -β-d-fructofuranoside (11β), and methyl 1-deoxy-1-[(2,2-dimethoxycarbonylvinyl)-amino]-β-d-fructopyranoside (13). Compounds 11α and 13 were isolated as their tri-acetates (12 and 14, respectively). Deacetylation and removal of the N-protecting group of 12 gave methyl 1-amino-1-deoxy-α-d-fructofuranoside (∼54% from 2).