Syntheses of p-aminophenyl 1-thio-α- and -β-d-idopyranosides as analogs of glycosidase substrates

The p-nitrophenyl and p-aminophenyl 1-thio-α- and -β-d-idopyranosides were synthesized for use in structure-activity studies of glycosidases. Zinc chloride-catalyzed fusion of α-d-idopyranose pentaacetate with p-nitrobenzenethiol gave p-nitrophenyl 2,3,4,6-tetra-O-acetyl-1-thio-α-d-idopyranoside as an amorphous glass in 67% yield, and the crystalline β anomer in 13% yield. Deacetylation with catalytic amounts of sodium methoxide in methanol, followed by hydrogenation under pressure over palladium-on-barium sulfate catalyst, afforded p-aminophenyl 1-thio-α- and -β-d-idopyranosides.     

Syntheses of p-aminophenyl α-d-talopyranoside and 1-thio α-d-talopyranoside as analogs of glycosidase substrates

p-Nitrophenyl and p-aminophenyl α-d-talopyranoside and 1-thio-α-d-talopyranosides were prepared for studies on specificity of glycosidases. Reaction of α-d-talopyranose pentaacetate with p-nitrophenol gave exclusively p-nitrophenyl 2,3,4,6-tetra-O-acetyl-α-d-talopyranoside (2) in 63% yield. A similar reaction with p-nitrobenzenethiol afforded the 1-thio analog (3) of 2 in 41.8% yield; the p-nitrophenyl 2,3,4,6-tetra-O-acetyl-1-thio-β-d-talopyranoside (6) was also obtained in low yield (6.7%). The two α-d-talosides 2 and 3 were catalytically deacetylated in near-quantitative yields by methanolic sodium methoxide. The p-nitrophenyl α-d-talopyranoside (4) and 1-thio-α-d-talopyranoside (5) were reduced with palladium on barium sulfate catalyst to the corresponding p-aminophenyl talosides. The acetylated p-nitrophenyl d-talosides 2, 3, and 6 were determined, from their 250-MHz n.m.r. spectra, to exist in the ⁴C₁ (d) conformation in chloroform solution.     

Insulin-like,and insulin-antagonistic,carbohydrate derivatives. The synthesis of aryl and aralkyl d-mannopyranosides and 1-thio-d-mannopyranosides

A number of novel, aryl and aralkyl d-mannopyranosides and 1-thio-d-mannopyranosides were synthesized for evaluation of insulin-like and insulin-antagonistic properties. The substituted-phenyl α-d-mannopyranosides were prepared by the general procedure of Helferich and Schmitz-Hillebrecht, the substituted-phenyl 1-thio-α-d-mannopyranosides by a method corresponding to the Michael synthesis of aromatic glycosides, and the aralkyl 1-thio-α-d-mannopyranosides by aralkylation of 2,3,4,6-tetra-O-acetyl-1-thio-α-d-mannopyranose (15) and subsequent O-deacetylation. Compound 15 was obtained by basic cleavage of the amidino group in 2-S-(tetra-O-acetyl-α-d-mannopyranosyl)-2-thiopseudourea hydrobromide, the product of the reaction of tetra-O-acetyl-α-d-mannosyl bromide with thiourea. Benzyl 1-thio-β-d-mannopyranoside, obtained by reaction of the sodium salt of 1-thio-β-d-mannopyranose with α-bromotoluene, and benzyl 1-thio-α-l-mannopyranoside were also synthesized, in order to assess the stereospecificity of the biological activities measured.     

Syntheses stereoselectives de 1-thioglycosides

2,3,4,6-Tetra-O-acetyl-β-d-mannopyranosyl chloride (2) was obtained in 70% yield by the action of lithium chloride on 2,3,4,6-tetra-O-acetyl-α-d-mannopyranosyl bromide (1) in hexamethylphosphoric triamide. p-Nitrobenzenethiol reacted with 1 and 2 as well as with 2,3,4,6-tetra-O-acetyl-α-d-glucopyranosyl bromide (9) or its β-d-chloro analog (10), giving exclusively and in good yield the corresponding p-nitrophenyl 1-thioglycosides of inverted anomeric configuration. The 1,2-cis-d-manno and -glucop-nitrophenylglycosides were likewise prepared. α-d-Glucopyranosyl 1-thio-α-d-glucopyranoside was similarly obtained by the action of the sodium salt of 1-thio-α-d-glucopyranose on the β-chloride 10 in hexamethylphosphoric triamide, or by treatment of 10 with sodium sulfide, with subsequent deacetylation. Analogous procedures allowed the preparation of β-d-mannopyranosyl 1-thio-β-d-mann opyranoside, the corresponding α,β anomer and α-d-glucopyranosyl 1-thio-α-d-mannopyranoside, starting from bromide 1, 1-thio-α-d-mannopyranose (8),and chloride 10, respectively. When acetone was used as solvent, the reaction between 1 and 8 led instead to the α,α anomer. The thio disaccharides that are interglycosidic 4-thio analogs of methyl 4-O-(β-d-galactopyranosyl)-α-d-galactopyranoside, methyl α-cellobioside, and methyl α-maltoside, respectively, were obtained by way of the peracetates of methyl 4-thio-α-d-galactopyranoside and -glucopyranoside by reaction of the corresponding thiolates with tetra-O-acetyl-α-d-galactopyranosyl bromide, bromide 9, or chloride 10, respectively, in hexamethylphosphoric triamide. These 1-thioglycosides, and (1→1)- and (1→4)-thiodisaccharides, were characterized by ¹H- and ^{1 3}C-n.m.r. spectroscopy. Correlations were established between the polarity of the sulfur atom and certain proton and carbon chemical-shifts in the 1-thioglycosides in comparison with the O-glycosyl analogs; these correlations permitted in particular the unambigous attribution of anomeric configuration.     

Thiodisaccharides with galactofuranose or arabinofuranose as terminal units: Synthesis and inhibitory activity of an exo β-d-galactofuranosidase

Thiodisaccharides having β-d-Galf or α-l-Araf units as non-reducing end have been synthesized by the SnCl₄- or MoO₂Cl₂-promoted thioglycosylation of per-O-benzoyl-d-galactofuranose (1), its 1-O-acetyl analogue 4, or per-O-acetyl-α-l-arabinofuranose (16) with 6-thioglucose or 6-thiogalactose derivatives. After convenient removal of the protecting groups, the free thiodisaccharides having the basic structure β-d-Galf(1→6)-6-thio-α-d-Glcp-OMe (5) or β-d-Galf(1→6)-6-thio-α-d-Galp-OMe (15) were obtained. The respective α-l-Araf analogues 18 and 20 were prepared similarly from 16. Alternatively, β-d-Galf(1→4)-4-thio-3-deoxy-α-l-Xylp-OiPr was synthesized by Michael addition to a sugar enone of 1-thio-β-d-Galf derivative, generated in situ from the glycosyl isothiourea derivative of 1. The free S-linked disaccharides were evaluated as inhibitors of the β-galactofuranosidase from Penicillium fellutanum, being 15 and 20 the more active inhibitors against this enzyme.     

Observations on the possible application of glycosyl disulphides,sulphenic esters,and sulphones in the synthesis of glycosides

Partial desulphuration of tetra-O-acetyl-β-d-glucopyranosyl phenyl disulphide with a phosphine derivative gave 40% of phenyl 2,3,4,6-tetra-O-acetyl-1-thio-α-d- glucopyranoside and a similar proportion of β-d-glucopyranosyl 1-thio-α-d-glucopyranoside octa-acetate, showing that this procedure is of limited value in α-d-thio-glucoside synthesis. Similar treatment of allyl tetra-O-acetyl-,β-d-glucopyranosyl sulphoxide caused abstraction of oxygen, rather than of sulphur, from the derived allyl glucosylsulphenate. The phenylsulphonyl group was not readily displaced from β-d-glucopyranosyl phenyl sulphone, except intramolecularly, nor could it be displaced from the tetrabenzyl ether. Elimination of benzyl alcohol from this compound afforded a new 1-(phenylsulphonyl)glycal derivative.     

An improved method for the syntheses of p-aminophenyl 1-thio-β-d-glycosides

The condensation of the appropriate acetylglycosyl bromides with p-amino-benzenethiol in the presence of sodium methoxide afforded p-aminophenyl 1-thio-β-d-glucopyranoside, 1-thio-β-d-galactopyranoside, 1-thio-β-d-xylopyranoside, and 2-acetamido-2-deoxy-1-thio-β-d-glucopyranoside. p-Aminophenyl 1-thio-β-d-glucopyranosiduronic acid was synthesized by condensation of methyl (2,3,4-tri-o-acetyl-β-d-glucopyranosyl bromide)uronate with p-aminobenzenethiol, followed by saponification with sodium hydroxide.     

Studies of the Pharmacokinetics and Toxicology of 2′,3′-Dideoxy-β-L-5-fluorocytidine (β-L-FddC) and 2′,3′-Dideoxy-β-L-cytidine (β-L-ddC) In Vivo; and Synthesis and Antiviral Evaluations of 2′,3′-Dideoxy-β-L-5-azacytidine

Abstract

The pharmacokinetics and toxicology of 2′,3′-dideoxy-β-L-5-fluorocytidine (β-L-FddC) and 2′,3′-dideoxy-β-L-cytidine (β-L-ddC) in mice was investigated. In addition, 2′,3′-dideoxy-β-L-5-azacytidine (β-L-5-aza-ddC) and its α-L-anomer (α-L-5-aza-ddC) were synthesized by coupling the silylated 5-azacytosine derivative with 1-O-acetyl-5-O-(tert-butyldimethylsilyl)-2,3-dideoxy-L-ribofuranose, followed by separation of the α-and β-anomers and were evaluated in vitro against HBV and HIV. β-L-5-aza-ddC was found to show significant anti-HBV activity at approximately the same level as 2′,3′-dideoxy-β-D-cytidine (ddC), which is a known anti-HBV agent. β-L-5-aza-ddC was not cytotoxic to L1210, P388, S-180, and CCRF-CEM cells up to a concentration of 100 μ. Conversely, the α-L-anomer was not active against HBV at the same concentration.     

Silica gel-catalyzed migration of acetyl groups from a sulfur to an oxygen atom

During the chromatographic separation of 3-S-acetyl-1,2-O-isopropylidene-3-thio-α-d-allofuranose on silica gel, a migration of the acetyl group from S to O was observed to give 6-O-acetyl-1,2-O-isopropylidene-3-thio-α-d-allofuranose, whereas 3-S-acetyl-6-O-benzoyl-1,2-O-isopropylidene-3-thio-α-d-allofuranose gave 5-O-acetyl-6-O-benzoyl-1,2-O-isopropylidene-3-thio-α-d-allofuranose. No acetyl migration was observed, however, in the case of 3-O-acetyl-1,2-O-isopropylidene-α-d-allofuranose.     

Systematic Synthesis of Sulfur-containing p-Nitrophenyl α-Maltopentaoside Derivatives for a Differential Assay of Human α-Amylases

For use in a differential assay of human α-amylases, a variety of 6⁵-S-substituted p-nitrophenyl α-maltopentaoside derivatives (6-54) were systematically synthesized via the key intermediate, p-nitrophenyl O-(2,3-di-O-acetyl-6-S-acetyl-4-O-benzoyl-6-thio-α-D-glucopyranosyl)-(1 →4)-tris[O-(2,3,6-tri-O-acetyl-α-D-glucopyranosyl)-(1→4)]-2,3,6-tri-O-acetyl-α-D-glucopyranoside (4), which was easily prepared from p-nitrophenyl α-maltopentaoside (G5P) in four steps. The sulfoxide and sulfone derivatives were prepared by oxidizing the corresponding sulfides with m-chloroperbenzoic acid.     

A convenient synthesis of 6′-C-substituted β-maltose heptaacetates and of panose

Benzylidenation of β-maltose monohydrate with α,α-dimethoxytoluene in N,N-dimethylformamide in the presence of p-toluenesulfonic acid gave, in 70% yield, 4′,6′-O-benzylidenemaltose, which was acetylated to afford, 1,2,3,6,2′,3′-hexa-O-acetyl-4′,6′-O-benzylidene-β-maltose (4). Removal of the benzylidene group of 4 gave 1,2,3,6,2′,3′-hexa-O-acetyl-β-maltose (5), which was transformed into 1,2,3,6,2′,3′,4′-hepta-O-acetyl-6′-O-p-tolylsulfonyl-β-maltose (8). Several 6′-substituted β-maltose heptaacetates were synthesized by displacement reactions of 8 with various nucleophiles. Condensation of 5 with 2,3,4,6-tetra-O-benzyl-α-d-glucopyranosyl bromide, under catalysis by halide ion, followed by removal of protecting groups, furnished panose in good yield.     

Ring-opening reactions of sucrose epoxides: Synthesis of 4′-derivatives of sucrose

The 2,1′-O-isopropylidene derivative (1) of 3-O-acetyl-4,6-O-isopropylidene-α-d-glucopyranosyl 6-O-acetyl-3,4-anhydro-β-d-lyxo-hexulofuranoside and 2,3,4-tri-O-acetyl-6-O-trityl-α-d-glucopyranosyl 3,4-anhydro-1,6-di-O-trityl-β-d-lyxo-hexulofuranoside have been synthesised and 1 has been converted into 2,3,4,6-tetra-O-acetyl-α-d-glucopyranosyl 1,6-di-O-acetyl-3,4-anhydro-β-d-lyxo-hexulofuranoside (2). The S_N2 reactions of 2 with azide and chloride nucleophiles gave the corresponding 2,3,4,6-tetra-O-acetyl-α-d-glucopyranosyl 1,3,6-tri-O-acetyl-4-azido-4-deoxy-β-d-fructofuranoside (6) and 2,3,4,6-tetra-O-acetyl-α-d-glucopyranosyl 1,3,6-tri-O-acetyl-4-chloro-4-deoxy-β-d-fructofuranoside (8), respectively. The azide 6 was catalytically hydrogenated and the resulting amine was isolated as 2,3,4,6-tetra-O-acetyl-α-d-glucopyranosyl 4-acetamido-1,3,6-tri-O-acetyl-4-deoxy-β-d-fructofuranoside. Treatment of 5 with hydrogen bromide in glacial acetic acid followed by conventional acetylation gave 2,3,4,6-tetra-O-acetyl-α-d-glucopyranosyl 1,3,6-tri-O-acetyl-4-bromo-4-deoxy-β-d-fructofuranoside. Similar S_N2 reactions with 2,3,4,6-tetra-O-acetyl-α-d-glucopyranosyl 1,6-di-O-acetyl-3,4-anhydro-β-d-ribo-hexulofuranoside (12) resulted in a number of 4′-derivatives of α-d-glucopyranosyl β-d-sorbofuranoside. The regiospecific nucleophilic substitution at position 4′ in 2 and 12 has been explained on the basis of steric and polar factors.     

The chemical synthesis of polysaccharides : Part III. Synthesis of 6-O-α-D-mannopyranosyl-D-mannose and 4-O-α-D-mannopyranosyl-D-mannose. Isolation of A (1→6)-linked D-mannan

When 1,2,3,4-tetra-O-acetyl-α-D-mannopyranose was fused with a catalytic amount of toluene-p-sulphonic acid, 6-O-α-D-mannopyranosyl-D-mannose and 4-O-α-D-mannopyranosyl-D-mannose were isolated after deacetylation of the reaction mixture. No β-D-linked disaccharide was detected in the reaction mixture. When the corresponding β-D-tetra-acetate was fused with zinc chloride as catalyst, higher oligomers were formed, and a D-mannan was isolated and shown to be mainly an α-(1→6)-linked polymer having d.p. of 10. With 5% of zinc chloride, the α-D-tetra-acetate showed oligosaccharide formation, and yielded a smaller proportion of a (1→6)-linked D-mannan.     

The chemistry of some 1-mercury(II)thio-d-glucose compounds; a new synthesis of 1-thio sugars

Treatment of tetra-O-acetyl-β-d-glucopyranosyl N,N-dimethyldithiocarbamate (1) with phenylmercury(II) acetate gives tetra-O-acetyl-1-phenylmercury(II)thio-β-d-glucopyranose (3), which can also be made in high yield from other dithiocarbamates, from tetra-O-acetyl-1-thio-β-d-glucopyranose, and from its S-acetyl derivative. The p-diethylamino derivative (7) of compound 3 displays significantly different properties and is readily convertible into bis(tetra-O-acetyl-1-thio-β-d-glucopyranosyl)mercury(II) (8), which is also obtainable by treatment of tetra-O-acetyl-1-thio-β-d-glucopyranose with mercury(II) acetate. Aspects of the chemistry of compounds 3, 7, and 8 are reported; demercuration of 3 affords a convenient synthesis of 2,3,4,6-tetra-O-acetyl-1-thio-β-d-glucose.     

Synthesis of N-[2-O-(2-acetamido-2,3-dideoxy-5-thio-d-glucopyranose-3-yl)-d-lactoyl]-l-alanyl-d-isoglutamine

N-[2-O-(2-Acetamido-2,3-dideoxy-5-thio-d-glucopyranose-3-yl)-d-lactoyl]-l-alanyl-d-isoglutamine, in which the ring-oxygen atom of the sugar moiety in N-acetylmuramoyl-l-alanyl-d-isoglutamine (MDP) has been replaced by sulfur, was synthesized from 2-acetamido-2-deoxy-5-thio-α-d-glucopyranose (1). O-Deacetylation of the acetylated acetal, derived from the methyl α-glycoside of 1 by 4,6-O-isopropylidenation and subsequent acetylation, gave methyl 2-acetamido-2-deoxy-4,6-O-isopropylidene-5-thio-α-d-glucopyranoside (4). Condensation of 4 with l-2-chloropropanoic acid, and subsequent esterification, afforded the corresponding ester, which was converted, viaO-deisopropylidenation, acetylation, and acetolysis, into 2-acetamido-1,4,6-tri-O-acetyl-2-deoxy-3-O-[d-1-(methoxycarbonyl)ethyl]-5-thio-α-d-glucopyranose (12). Coupling of the acid, formed from 12 by hydrolysis, with the methyl ester of l-alanyl-d-isoglutamine, and de-esterification, yielded the title compound.     

Solid-phase synthesis of oligosaccharides. V. Preparation of an inorganic support

D-Glucose side-chains were introduced into amylose and cellulose by condensation of tetra-O-acetyl-α-D-glucopyranosyl bromide with 6-trityl-2,3-dicarbanilate derivatives of the polysaccharides in nitromethane-p-dioxane in the presence of silver perchlorate (reaction A), and with the detritylated derivatives in acetonitrile-p-dioxane in the presence of mercuric cyanide and mercuric bromide (reaction B). The procedures were equally effective. The distance between the branch points in amylose was in the range 2–4 D-glucose residues, and 5–8 D-glucose residues in cellulose. Whereas considerable degradation of the backbone chain was found with reaction A, no degradation occurred in reaction B under suitable conditions. α-(1→6)-Links were preferably formed in reaction B, and β-(1→6)-links in reaction A.     

Synthesis of 5-thio-D-galactose

A synthesis of 5-thio-D-galactose, in the form of its crystalline, anomeric methyl glycopyranosides, is described. Compounds prepared as intermediates included ethyl 2,3-di-O-(tert-butyldimethylsilyl)-5,6-O-carbonyl-β-D-galactofuranoside, the corresponding 5,6-dideoxy-5,6-epithio derivative, and ethyl 2,3,6-tri-O-acetyl-5-S-acetyl-5-thio-β-D-galactofuranoside. On methanolysis, the latter afforded methyl 5-thio-α-D-galactopyranoside which, in turn, was transformed into methyl 5-thio-β-D-galactopyranoside. Acetolysis proved to be less satisfactory for incorporation of the sulfur atom into a pyranose ring-form. Characteristics of the ¹³C-n.m.r. spectra of derivatives of 5-thio-D-galactose are described, including the fact that ¹J_C,H values for the anomeric pyranosides differ by only 1–3 Hz, as compared with ≈ 10 Hz for their oxygen analogs.     

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.     

Equimolar oxymercuration of D-glucal triacetate with mercuric perchlorate and its application to the synthesis of 2′-deoxy disaccharides

A search for appropriate reaction conditions for the equimolar methoxymercuration of D-glucal triacetate was made by using various mercuric salts, bases, and reaction solvents. Under optimum conditions with mercuric perchlorate, sym-collidine, and acetonitrile, D-glucal triacetate underwent methoxymercuration with an equimolar amount of methanol to afford methyl 3,4,6-tri-O-acetyl-2-deoxy-2-perchloratomercuri-β-D-glucopyranoside (1, 26%) and its α-D-manno isomer (2, 49%). Equimolar oxymercuration of D-glucal triacetate with partially protected sugars, followed by subsequent demercuration of the products with sodium borohydride, afforded α- and β-linked 2′-deoxy disaccharide derivatives in moderate yields. The partially protected sugars used were 1,2,3,4-tetra-O-acetyl-β-D-glucopyranose and 1,2:3,4-di-O-isopropylidene-α-D-galactopyranose, and the corresponding products were O-(3,4,6-tri-O-acetyl-2-deoxy-α-D-arabino-hexopyranosyl)-(1→6)-1,2,3,4-tetra-O-acetyl-D-glucopyranose(4, 23%) and its β-linked isomer (5, 11%) from the former, and O-(3,4,6-tri-O-acetyl-2-deoxy-α-D-arabino-hexapyranosyl)-(1→6)-1,2:3,4-di- O-isopropylidene-α-D-galactopyranose (9, 29%) and its β-linked isomer (10, 10%) from the latter. Deacetylation of these 2′-deoxy disaccharides was effected with methanolic sodium methoxide, but deacetonation was unsuccessful owing to simultaneous cleavage of the glycosidic linkage.     

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.