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.     

Synthesis of 2-acetamido-2-deoxy-4-O-alpha-L-fucopyranosyl-alpha-D-glucopyranose]

Condensation of 2,3,4-tri-O-benzyl-alpha-L-fucopyranosyl bromide with benzyl 2-acetamido-3,6-di-O-benzyl-alpha-D-glucopyranoside in dichloromethane-N,N-dimethylformamide, in the presence of tetraethylammonium bromide, diisopropylethylamine, and molecular sieve (halide ion-catalyzed reaction), gave benzyl 2-acetamido-3,6-di-O-benzyl-2 deoxy-4-O-(2,3,4-tri-O-benzyl-alpha-L-fucopyranosyl)-alpha-D-glucopyranoside in crystalline form in 82% yield. Hydrogenolysis of the benzyl groups gave the title disaccharide, in crystalline form in 90% yield, which was characterized by a crystalline peracetylated alpha-D derivative.     

Synthesis of 1-deoxy-3-C-methyl-d-fructose and 1-deoxy-3-C-methyl-d-sorbose

Hydroxylation of trans-1,3,4-trideoxy-5,6-O-isopropylidene-3-C-methyl-d-glycero-hex-3-enulose with osmium tetraoxide gave a mixture of 1-deoxy-5,6-O-isopropylidene-3-C-methyl-d-arabino- and -d-xylo-hexulose that was partially resolved by acetonation to give 1-deoxy-2,3:4,5-di-O-isopropylidene-3-C-methyl-β-d-fructopyranose (4), 1-deoxy-3,4:5,6-di-O-isopropylidene-3-C-methyl-keto-d-fructose (5), and 1-deoxy-2,3:4,6-di-O-isopropylidene-3-C-methyl-α-d-sorbofuranose (6). Treatment of a mixture of 4 and 5 with sodium borohydride gave, after column chromatography, 4 and 1-deoxy-3,4:5,6-di-O-isopropylidene-3-C-methyl-d-manno- and -d-gluco-hexitol. Deuterated derivatives corresponding to 4–6 were obtained when isopropylidenation was carried out with acetone-d₆. Deacetonation of 4 and 5 yielded 1-deoxy-3-C-methyl-d-fructose, and 6 similarly afforded 1-deoxy-3-C-methyl-d-sorbose.     

Synthesis of 4-deoxy-4-fluoro analogues of 2-acetamido-2-deoxy-D-glucose and 2-acetamido-2-deoxy-D-galactose and their effects on cellular glycosaminoglycan biosynthesis

4-Deoxy-4-fluoro analogues of 2-acetamido-2-deoxy-D-glucose and 2-acetamido-2-deoxy-D-galactose were synthesized and evaluated as inhibitors of hepatic glycosaminoglycan biosynthesis. 2-Acetamido-1,3,6-tri-O-acetyl-2,4-dideoxy-4-fluoro-D-glucopyranose (16) exhibited a reduction of [3H]GlcN and [35S]SO4 incorporation into hepatocyte cellular glycosaminoglycans to 12 and 18%, respectively, of the control cells, at 1.0 mM. Similarly, 2-acetamido-1,3,6-tri-O-acetyl-2,4-dideoxy-4-fluoro-D-galactopyranose (31) exhibited a reduction of [3H]GlcN and [35S]SO4 incorporation to 1 and 9%, respectively, of the control cells, at 1.0 mM. Unlike 16, 31 exhibited a reduction of [14C]Leu incorporation into cellular protein to 57% of control cells, at 1.0 mM.     

Synthesis and biological evaluation of novel 2-deoxy-4-thio-imidazole nucleosides

A study on the use of 3'-directing groups for the synthesis of imidazole 2'-deoxy-4'-thionucleosides led to varying alpha:beta ratios in the glycosylation reaction. The para-nitrobenzoyl group gave the optimum result in the glycosylation step; therefore, this protected thiosugar 10b was used for the synthesis of a series of novel 2'-deoxy-4'-thio-imidazole nucleosides which have been evaluated for antiviral activity in vitro.     

Preparation of 3-deoxy-3-deuteroestrone and 3-deoxy-4-14C-estrone

3-Deoxy-3-deuteroestrone (1,3,5(10)-estratrien-17-one-3-d) and 3-deoxy-4-¹⁴C-estrone (1 ,3 ,5(10)-estratrien-17-one-¹⁴C) have been prepared. The mechanism of reductive dehalogenation of aryl iodides with lithium aluminum deuteride is discussed. The ¹³C-NMR spectrum of 3-deoxy-3-deuteroestrone is discussed.     

Synthesis of 3-methylpseudouridine and 2′-deoxy-3-methyl-pseudouridine

The first chemical synthesis of 3-methyl-ψ-uridine (5) and its 2′-deoxy analogue (9) has been achieved. ψ-Uridine was trimethylsilylated and the crude product was treated with acetyl chloride, to give the 1-acetyl derivative (3). Crude 3 was methylated with dimethoxymethyldimethylamine and then saponified, to give crystalline 5 in 82% overall yield. Treatment of 5 with 1,3-dichloro-1,1,3,3-tetraiso-propyldisiloxane afforded the 3′,5′-protected product, which was converted into the 2′-O-[(imidazol-1-yl)thiocarbonyl] derivative 7. Reduction of 7 with tributyltin hydride followed by deblocking of the product gave crystalline 2′-deoxy-3-methyl-ψ-uridine (9) in 35% yield from 5.     

Base-catalyzed degradation of permethylated 3-O-glycosyl- glycopyranosid-2-uloses

In a modification of the Svensson degradation, otherwise permethylated glycopyranosid-2-uloses bearing 4-O-glycosyl substituents are formed by the Swern oxidation. Base-catalyzed elimination on treatment with triethylamine then gives 4-deoxy-3-O-methylglyc-3-enopyranosid-2-ulose-terminat ed oligosaccharides with liberation of glycosyl substituents as reducing sugars but without further degradation. Mild acid hydrolysis results in removal of the unsaturated sugar residues so that the overall depolymerization occurs with net loss only of the initially oxidized sugar residue.     

Synthesis of 2-deoxy-2-(4-nitroimidazol-1-yl)-D-alditols

Small molecules possessing defined configuration at centres of chirality provide a valuable chiral pool. Among different strategies applied for modification of chiral compounds, the most common is to begin with a single stereoisomer and use a synthesis that does not affect the chiral centres. The ANRORC type reaction has been applied for conversion of unprotected 2-amino-2-deoxy-D-hexopyranoses into 2-deoxy-2-(4-nitroimidazol-1-yl)-D-hexopyranoses in a reaction of some 2-aminosugars with 1,4-dinitroimidazoles. The reaction occurs with retention of configuration at C-2 of sugar ring. The products of the reaction were obtained as anomeric mixtures and separated into anomers after acetylation followed by column chromatography. 2-Deoxy-2-(4-nitroimidazol-1-yl)-D-hexopyranoses treated with sodium borohydride in methanolic solution gave the corresponding 2-deoxy-2-(4-nitroimidazol-1-yl)-D-hexitols, characterised as per-O-acetylated derivatives.     

Synthesis of 3-deoxy-4-O-β-D-galactopyranosyl-D-erythro-hexos-2-ulose and of some of its derivatives from lactose

3-Deoxy-4-O-β-D-galactopyranosyl-D-erythro-hexos-2-ulose (1) was obtained from lactose by reaction with benzoylhydrazine in the presence of a slightly acidic solution of p-toluidine, followed by hydrazinolysis of the product, 3-deoxy-4-O-β-D-galactopyranosyl-D-erythro-hexos-2-ulose bis(benzoylhydrazone) (3), with benzaldehyde. A variety of derivatives of 1 and 3 was prepared. Lactose aroylhydrazones were also prepared. Quantitative determination of the oxidant during the periodate oxidation of 3 was studied. Periodate oxidation of monosaccharide arylhydrazones gave glyoxal mono(arylhydrazones) which afforded the corresponding, mixed bis(hydrazones).     

Metabolism of 3-deoxy-3-fluoro-D-mannose and 4-deoxy-4-fluoro-D-mannose by Saccharomyces cerevisiae S288C.

Incubation of Saccharomyces cerevisiae S288C with 4-deoxy-4-fluoro-D-[1-14C]-mannose resulted in the formation of three metabolites that were characterized as 4-deoxy-4-fluoro-D-[1-14C]mannose 1,6-bisphosphate, 4-deoxy-4-fluoro-D-[1-14C]-mannose 6-phosphate and GDP-4-deoxy-4-fluoro-D-[1-14C]mannose. In addition, radioactive material was incorporated into a particulate fraction composed primarily of cell-wall polysaccharides. Compared with the 4-fluoro sugar, 3-deoxy-3-fluoro-D-[1-14C]mannose was not transported into yeast cells as well, and its conversion into sugar nucleotide was much less efficient. Metabolites that were isolated after incubation with the 3-fluoro analogue were identified as 3-deoxy-3-fluoro-D-[1-14C]mannose 1,6-bisphosphate, 3-deoxy-3-fluoro-D-[1-14C]mannose 6-phosphate and GDP-3-deoxy-3-fluoro-D-[1-14C]mannose. Little radioactivity was transferred into the cell-wall fraction.     

Synthesis of 4-cyanophenyl and 4-nitrophenyl 2-azido-2-deoxy-1,5-dithio-beta-D-arabino- and -beta-D-lyxopyranosides possessing antithrombotic activity

Tri-O-acetyl-5-thio-D-ribopyranosyl bromide was converted into 3,4-di-O-benzoyl-1,5-anhydro-5-thio-D-erythro-pent-1-enitol (3,4-di-O-benzoyl-5-thio-D-ribal), the azidonitration of which afforded an unstable mixture of 2-azido-3,4-di-O-benzoyl-2-deoxy-1-O-nitro-5-thio-D-pentopyranoside++ + isomers. This was converted without separation into the corresponding 1-O-acetyl derivatives from which an alpha,beta anomeric mixture of the 1-O-acetyl-2-azido-3,4-di-O-benzoyl-2-deoxy-5-thio-D-arabinopyranose+ ++ isomers could be isolated in high yield. Glycosidation of this mixture with 4-cyano- or 4-nitrobenzenethiol, using trimethylsilyl triflate or boron trifluoride etherate, respectively, as promoters gave the corresponding D anomers exclusively. Zemplén debenzoylation afforded 4-cyanophenyl as well as 4-nitrophenyl 2-azido-2-deoxy-1,5-dithio-beta-D-arabinopyranoside, respectively. When 1-O-acetyl-2-azido-3,4-di-O-benzoyl-2-deoxy-5-thio-D-lyxopyranose was used as glycosyl donor only the corresponding 1 anomers, i.e., 4-cyanophenyl as well as 4-nitrophenyl 2-azido-2-deoxy-1,5-dithio-beta-D-lyxopyranosides, could be isolated after Zemplén debenzoylation in high yield. All four 1,5-dithioglycosides possess significant oral antithrombotic activity.     

Synthesis of phenyl 2-acetamido-2-deoxy-4-O-α-l-fucopyranosyl-β-d-glucopyranoside and p-nitrophenyl 2-acetamido-2-deoxy-6-O-α-l-fucopyranosyl-β-d-glucopyranoside

Maize and potato amylopectin (57 and 64%, respectively) were recovered as non-cyclic products from 4-h digests of the starches with cyclodextrin glycosyltransferase {(1→4)-α-d-glucan:[(1→4)-α-d-glucopyranosyl]transferase (cyclising), EC 2.4.1.19} from Klebsiella pneumoniae M 5 al. Besides smaller saccharides, highly branched fragments of different sizes (average d.p. 40–140) were obtained by fractionation. The extents of beta-amylolysis varied between 24 and 37%, indicating that the clusters were not equally susceptible to attack by cyclodextrin glycosyltransferase. The fragments of potato amylopectin still contained larger amounts of material of high molecular weight. Accordingly, part of the longer B-chains of the basic structure were protected from the enzymic attack, presumably because of interchain branches. By debranching with pullulanase, it was evident that the beta-limit dextrins of the fragments of potato amylopectin were composed of longer B-chains (average chainlength 17.8) than those of maize amylopectin (average chain-length 14.1). The A/B-chain ratios, which were calculated from h.p.l.c. data for the debranched beta-limit dextrins, were 1.22 (maize) and 1.06 (potato). Some structural differences between potato and maize amylopectin are discussed.