The inhibitory activities of 2-acetamido-2,3-dideoxy-D-hex-2-enonolactones on 2-acetamido-2-deoxy-beta-D-glucosidase.

Treatment of 2-acetamido-2-deoxy-D-mannono-1,4-lactone with dicyclohexylamine in ethanolic solution afforded an unsaturated 1,4-lactone, 2-acetamido-2,3-dideoxy-D-erythro-hex-2-enono-1,4-lactone (1), in good yield. 2-Acetamido-2,3-dideoxy-D-threo-hex-2-enono-1,4-lactone (2) was similarly prepared from 2-acetamido-2-deoxy-D-galactono-1,4-lactone. An unsaturated 1,5-lactone, 2-acetamido-2,3-dideoxy-D-threo-hex-2-enono-1,5-lactone (4), was obtained through the oxidation of 2-acetamido-2-doexy-4,6-0-isopropylidene-D-galactopyranose with silver carbonate on Celite, followed by mild hydrolysis. The inhibitory activity of four isomeric 2-acetamido-2,3-dideoxy-D-hex-2-enonolactones [1, 2, 4, and 2-acetamido-2,3-dideoxy-D-erythro-hex-2-enono-1,5-lactone (3)] was assayed against 2-acetamido-2-deoxy-beta-D-glucosidase from bull epididymis. Only the erythro lactones 1 and 3 are weak competitive inhibitors, whereas the threo lactones 2 and 4 are practically inactive. The 1,4-lactone 1 inhibited 2-acetamido-2-deoxy-beta-D-glucosidase more strongly than the 1,5-lactone 3. The lactones 1-4 were found to be quite stable in aqueous solution or under inhibitory-assay conditions. In addition, two 2-acetamido-2-deoxy-D-glycals, 2-acetamido-1,5-anhydrohex-1-enitol (7) were tested; both are 10 times as active as 1.     

The inhibitory activity of 2-acetamido-2-deoxy-D-gluconolactones and their isopropylidene derivatives on 2-acetamido-2-deoxy-beta-D-glucosidase

2-Acetamido-2-deoxy-D-glucono-1,4-lactone (1) and 2-acetamido-2-deoxy-D-gluconic acid (3) have been examined for inhibitory activity against 2-acetamido-2-deoxy-β-D-glucosidase from bull epididymis. Crystalline 1 and 3 were compared with the known, crystalline 2-acetamido-2-deoxy-D-glucono-1,5-lactone (2), and a correlation of the activities of these compounds with various factors is presented. The inhibition constant of the 1,5-lactone 2 is lower (0.45μM) than that (4.43μM) of the 1,4-lactone 1. The effect of time is the opposite; whereas the activity of solutions of 2 decreases with time, solutions of 1 show an increase in inhibitory power, but both reach an equilibrium after 5 h. The free acid 3 exhibits no inhibitory activity. 2-Acetamido-2-deoxy-5,6-O-isopropylidene-D-glucono- 1,4-lactone (4) and 2-acetamido-2-deoxy-4,6-O-isopropylidene-D-glucono-1,5-lactone (5), which are appropriately protected to prevent conversion into the other lactone isomer, were also tested; 4 has 1/1000th the activity of 5.     

Formation of UDP-2-acetamido-2-deoxy-L-galactose and UDP-2-acetamido-2-deoxy-L-galacturonic acid by Pseudomonas aeruginosa.

The O-specific polysaccharide from the lipopolysaccharide of Pseudomonas aeruginosa NCTC 8505 (IATS serotype O:3) consists of a tetrasaccharide repeating unit comprising L-rhamnose, N-acetyl-D-glucosamine (GlcNAc), bacillosamine, and N-acetyl-L-galactosaminuronic acid (L-GalNAcA) (Y. Tahara and S. G. Wilkinson, Eur. J. Biochem. 134:299-304, 1983). Incubation of GlcN or UDP-GlcNAc with cell extracts or EDTA-treated cells of P. aeruginosa NCTC 8505 yielded a mixture of UDP-ManNAc, UDP-GalNAc, UDP-GlcNAcA, UDP-ManNAcA, UDP-L-GalNAc, and UDP-L-GalNAcA. The last two compounds, here identified for the first time, may be intermediates in the synthesis of the L-GalNAcA moiety of the O-specific portion of the lipopolysaccharide of P. aeruginosa.     

Synthesis of 2-acetamido-2-deoxy-5-thio-d-glucopyranose

2-Acetamido-2-deoxy-5-thio-d-glucopyranose (12) has been synthesized from methyl 2-acetamido-2-deoxy-5,6-O-isopropylidene-β-d-glucofuranoside (1). Benzoylation of 1, followed by O-deisopropylidenation, gave methyl 2-acetamido-3-O-benzoyl-2-deoxy-β-d-glucofuranoside, which was converted, via selective benzoylation and mesylation, into methyl 2-acetamido-3,6-di-O-benzoyl-2-deoxy-5-O-mesyl-β-d-glucofuranoside (5). Treatment of 6, formed by the action of sodium methoxide in chloroform on 5, with thiourea gave methyl 2-acetamido-2,5,6-trideoxy-5,6-epithio-β-d-glucofuranoside (7), which was converted into the 5-thio compound 9 by cleavage of the epithio ring in 7 with potassium acetate. Alkaline treatment of 10, derived from 9 by hydrolysis, afforded the title compound. Evidence in support of the structures assigned to the new derivatives is presented.     

One-pot enzymatic production of 2-acetamido-2-deoxy-D-galactose (GalNAc) from 2-acetamido-2-deoxy-D-glucose (GlcNAc)

2-Acetamido-2-deoxy-D-galactose (GalNAc) is a common monosaccharide found in biologically functional sugar chains, but its availability is often limited due to the lack of abundant natural sources. In order to produce GalNAc from abundantly available sugars, 2-acetamido-2-deoxy-D-glucose (GlcNAc) was converted to GalNAc by a one-pot reaction using three enzymes involved in the galacto-N-biose/lacto-N-biose I pathway of bifidobacteria. Starting the reaction with 600 mM GlcNAc, 170 mM GalNAc was produced at equilibrium in the presence of catalytic amounts of ATP and UDP-Glc under optimized conditions. GalNAc was separated from GlcNAc using water-eluting cation-exchange chromatography with a commonly available cation-exchange resin.     

Synthesis of 4-deoxy analogues of 2-acetamido-2-deoxy-D-glucose and 2-acetamido-2-deoxy-D-xylose and their effects on glycoconjugate biosynthesis

4-Deoxy analogues of 2-acetamido-2-deoxy-D-glucose and 2-acetamido-2-deoxy-D-xylose were synthesized and evaluated as inhibitors of glycoconjugate biosynthesis. Methyl 2-acetamido-2,4-dideoxy-beta-D-xylo-hexopyranoside (11) showed a reduction in [3H]GlcN and [14C]Leu incorporation into hepatocyte cellular glycoconjugates by 89 and 88%, of the control cells, respectively, at 20 mM, whereas the free sugars, 2-acetamido-2,4-dideoxy-alpha,beta-D-xylo-hexopyranoses (15), showed a reduction of [3H]GlcN and [14C]Leu incorporation by 75 and 64%, respectively, at 20 mM. The acetylated analogues of 11 and 15, namely methyl 2-acetamido-3,6-di-O-acetyl-2,4-dideoxy-beta-D-xylo-hexopyranoside and 2-acetamido-1,3,6-tri-O-acetyl-2,4-dideoxy-alpha,beta-D-xylo-hexopyra noses, showed a greater inhibition of [3H]GlcN and [14C]Leu incorporation at 1 mM compared with their non-acetylated counterparts, but were toxic to hepatocytes at concentrations of 10 and 20 mM. Corresponding derivatives of 2-acetamido-2,4-dideoxy-L-threo-pentopyranose showed no biological effect up to 20 mM, suggesting that the C-6 substituent is important for the biological activity.     

Selective pivaloylation of 2-acetamido-2-deoxy sugars

Selective pivaloylation of 2-acetamido-2-deoxy-D-glucose, its methyl alpha- and beta-glycosides, and the methyl alpha-glycoside of N-acetyl-D-muramic acid under various conditions has been studied. The structures of the products were established by 1H-n.m.r. spectroscopy and acetylation. The orders of acylation, HO-6 greater than HO-3 greater than HO-1 greater than HO-4 for 2-acetamido-2-deoxy-D-glucose and HO-6 greater than HO-3 greater than HO-4 for its methyl glycosides, were established. Methyl 2-acetamido-2-deoxy-3,6-di-O-pivaloyl-alpha- and -beta-D-glucopyranosides and 2-acetamido-2-deoxy-1,3,4,6-tetra-O-pivaloyl-D-glucopyranose were hydrolysed by rabbit serum esterases.     

Synthesis of p-nitrophenyl 2-acetamido-2-deoxy-O-beta-D-galactopyranosyl-beta-D-glucopyranosides.

Reaction of p-nitrophenyl 2-acetamido-2-deoxy-4,6-O-(p-methoxybenzylidene)-beta-D-glucopyranoside (2) with 2,3,4,6-tetra-O-acetyl-alpha-D-galactopyranosyl bromide (3) under the usual conditions, followed by removal of the p-methoxybenzylidene group and O-deacylation, produced crystalline p-nitrophenyl 2-acetamido-2-deoxy-3-O-beta-D-galactopyranosyl-beta-D-glucopyranoside (6). Starting from p-nitrophenyl 2-acetamido 3,4-di-O-acetyl-2-deoxy-beta-D-glucopyranoside, the synthesis of p-nitrophenyl 2-acetamido-2-deoxy-6-O-beta-D-galactopyranosyl-beta-D-glucopyranoside was also accomplished.     

The metabolism of acetamidothiazoles in the rat. 2-Acetamido-, 2-acetamido-4-methyl- and 2-acetamido-4-phenyl-thiazole

The metabolism of some anti-inflammatory acetamidothiazoles was studied in the rat. The main metabolites were the corresponding acetylthiohydantoic acids, produced by fission of the thiazole ring. Minor metabolites arising from oxidation of the methyl or phenyl substituents were also identified. The structures of metabolites were established spectroscopically (u.v., i.r., n.m.r. and mass spectroscopy) and by identification with authentic specimens. The excretion of the original compounds and of metabolites, labelled with (14)C is also reported.     

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.