Synthesis of 4-O-glycosylated 1,5-anhydro-d-fructose and of 1,5-anhydro-d-tagatose from a common intermediate 2,3-O-isopropylidene-d-fructose

Four novel disaccharides of glycosylated 1,5-anhydro-d-ketoses have been prepared: 1,5-anhydro-4-O-β-d-glucopyranosyl-d-fructose, 1,5-anhydro-4-O-β-d-galactopyranosyl-d-fructose, 1,5-anhydro-4-O-β-d-glucopyranosyl-d-tagatose, and 1,5-anhydro-4-O-β-d-galactopyranosyl-d-tagatose. The common intermediate, 1,5-anhydro-2,3-O-isopropylidene-β-d-fructopyranose, was prepared from d-fructose and was converted into the d-tagatose derivative by oxidation followed by stereoselective reduction to the 4-epimer. The anhydroketoses thus prepared were glycosylated and deprotected to give the disaccharides.     

Synthesis and antitumor activity of new d-seco and d-homo androstane derivatives

Starting from 3β-hydroxy-17-oxo-16,17-secoandrost-5-ene-16-nitrile (1), the new 16,17-secoandrostane derivatives 4-9 were synthesized. On the other hand, 3β-hydroxy-17-oxa-d-homoandrost-5-ene-16-one (10) yielded the new d-homo derivatives 12, 13 and 15. In vitro antiproliferative activity of selected compounds against three tumor cell lines (human breast adenocarcinoma ER+, MCF-7, human breast adenocarcinoma ER−, MDA-MB-231, prostate cancer AR−, PC-3, and normal fetal lung fibroblasts, MRC-5) was evaluated. Compounds 3 and 12 showed strong antiproliferative activity against PC-3 cells, the IC₅₀ values being 2 μM and 0.55 μM, respectively. Compounds 6 (10 μM) and 14 (9 μM) showed moderate activity against MDA-MB-231 cells. The synthesized compounds 1-3, 5-8, 10 and 12-15 were not toxic to normal fetal lung fibroblasts cells, MRC-5.     

d-Glucose- and d-mannose-based antimetabolites. Part 2. Facile synthesis of 2-deoxy-2-halo-d-glucoses and -d-mannoses

Modified d-glucose and d-mannose analogs are potentially clinically useful metabolic inhibitors. Biological evaluation of 2-deoxy-2-halo analogs has been impaired by limited availability and lack of efficient methods for their preparation. We have developed practical synthetic approaches to 2-deoxy-2-fluoro-, 2-chloro-2-deoxy-, 2-bromo-2-deoxy-, and 2-deoxy-2-iodo derivatives of d-glucose and d-mannose that exploit electrophilic addition reactions to a commercially available 3,4,6-tri-O-acetyl-d-glucal.     

The Hypocrea jecorina (syn. Trichoderma reesei) lxr1 gene encodes a d-mannitol dehydrogenase and is not involved in l-arabinose catabolism

The Hypocrea jecorina LXR1 was described as the first fungal l-xylulose reductase responsible for NADPH dependent reduction of l-xylulose to xylitol in l-arabinose catabolism. Phylogenetic analysis now reveals that LXR1 forms a clade with fungal d-mannitol 2-dehydrogenases. Lxr1 and the orthologous Aspergillus nigermtdA are not induced by l-arabinose but expressed at low levels during growth on different carbon sources. Deletion of lxr1 does not affect growth on l-arabinose and l-xylulose reductase activity remains unaltered whereas d-mannitol 2-dehydrogenase activities are reduced. We conclude that LXR1 is a d-mannitol 2-dehydrogenase and that a true LXR1 is still awaiting discovery.     

Facile synthesis of d-lividosamine

A simple, four-step synthesis of d-lividosamine starting from N-acetyl-d-glucosamine via a furanosyl oxazoline intermediate is described.     

Stereoselective entry into the d-GalNAc series starting from the d-Gal one: a new access to N-acetyl-d-galactosamine and derivatives thereof

A new stereoselective preparation of N-aceyl-d-galactosamine (1b) starting from the known p-methoxyphenyl 3,4-O-isopropylidene-6-O-(1-methoxy-1-methylethyl)-β-d-galactopyranoside (10) is described using a simple strategy based on (a) epimerization at C-2 of 10 via oxidation-reduction to give the talo derivative 11, (b) amination with configurational inversion at C-2 of 11 via a S_N2-type reaction on its 2-imidazylate, (c) anomeric deprotection of the p-methoxyphenyl β-d-galactosamine glycoside 14, (d) complete deprotection. Applying the same protocol to 2,3:5,6:3′,4′-tri-O-isopropylidene-6′-O-(1-methoxy-1-methylethyl)-lactose dimethyl acetal (4), directly obtained through acetonation of lactose, the disaccharide β-d-GalNAcp-(1→4)-d-Glcp (1a) was obtained with complete stereoselectivity in good (40%) overall yield from lactose.     

Synthesis of water-soluble phthalocyanines bearing four or eight d-galactose units

The synthesis and structural characterization of two glycophthalocyanines with four or eight unprotected d-galactose units is reported. The sugar units are linked to the macrocycle via the hydroxyl group located at C-6. The water solubility promoted by the carbohydrate moieties provides a potential application of these phthalocyanine derivatives as photosensitizers in photodynamic therapy.     

Synthesis of new N-substituted 3,4,5-trihydroxypiperidin-2-ones from d-ribono-1,4-lactone

d-Ribono-1,4-lactone was treated with ethylamine in DMF to afford N-ethyl-d-ribonamide 8a in quantitative yield. Using this reaction procedure, N-butyl, N-hexyl, N-dodecyl, N-benzyl, N-(3-methyl-pyridinyl)-, N-(2-hydroxy-ethyl)-, and N-(2-cyano-ethyl)-d-ribonamides 8b-h were obtained in quantitative yield. Bromination of the amides 8a-e with acetyl bromide in dioxane followed by acetylation gave 2,3,4-tri-O-acetyl-5-bromo-5-deoxy-N-ethyl, N-butyl, N-hexyl, N-dodecyl, and N-benzyl-d-ribonamides 9a-e in 40-54% yields. To obtain 2,3,4-tri-O-acetyl-5-bromo-5-deoxy-N-(3-methyl-pyridinyl)-, N-(2-hydroxy-ethyl)-, and N-(2-cyano-ethyl)-9f-h, the bromination is necessary before the amidation reaction. Treatment of the bromoamides 9a-h with NaH in DMF followed by methanolysis affords N-alkyl-d-ribono-1,5-lactams 12a-h in quantitative yield.     

A study of l-leucine, l-phenylalanine and l-alanine transport in the perfused rat mammary gland: possible involvement of LAT1 and LAT2

The transport of l-leucine, l-phenylalanine and l-alanine by the perfused lactating rat mammary gland has been examined using a rapid, paired-tracer dilution technique. The clearances of all three amino acids by the mammary gland consisted of a rising phase followed by a rapid fall-off, respectively, reflecting influx and efflux of the radiotracers. The peak clearance of l-leucine was inhibited by BCH (65%) and d-leucine (58%) but not by l-proline. The inhibition of l-leucine clearance by BCH and d-leucine was not additive. l-leucine inhibited the peak clearance of radiolabelled l-leucine by 78%. BCH also inhibited the peak clearance of l-phenylalanine (66%) and l-alanine (33%) by the perfused mammary gland. Lactating rat mammary tissue was found to express both LAT1 and LAT2 mRNA. The results suggest that system L is situated in the basolateral aspect of the lactating rat mammary epithelium and thus probably plays a central role in neutral amino acid uptake from blood. The finding that l-alanine uptake by the gland was inhibited by BCH suggests that LAT2 may make a significant contribution to neutral amino acid uptake by the mammary epithelium.     

Construction and co-expression of polycistronic plasmid encoding d-hydantoinase and d-carbamoylase for the production of d-amino acids

d-Hydantoinase and d-carbamoylase genes from Agrobacterium radiobacter TH572 were cloned by polymerase chain reaction (PCR). The plasmid pUCCH3 with a polycistronic structure that is controlled by the native hydantoinase promoter was constructed to co-express the two genes and transformed into Escherichia coli strain JM105. To obtain the highest level of expression of the d-carbamoylase and avoid intermediate accumulation, the d-carbamoylase gene was cloned closer to the promoter and the RBS region in the upstream of it was optimized. This resulted in high active expression of soluble d-hydantoinase and d-carbamoylase that is obtained without any inducer. Thus, by the constitutive recombinant JM105/pUCCH3, d-p-hydroxyphenylglycine (d-HPG) was obtained directly with 95.2% production yield and 96.3% conversion yield.     

Ni(II) complexes with Schiff bases derived from amino sugars

It was found by 1H and 13C NMR spectroscopy that the Schiff base, 2-deoxy-2-(2-hydroxybenzaldimino)-D-glucopyranose exhibits enol-imine-keto-amine and anomeric equilibria in methanolic, and in dimethyl sulfoxide solutions. The reaction of the Schiff base with nickel acetate gave the bidentate, mononuclear Ni(II) complex that was characterized by spectroscopic methods and by cyclic voltammetry. The coordination of the Schiff base to the metal is through the enol-imine tautomeric form, and the anomeric equilibrium remains in dimethyl sulfoxide solutions. This complex was also obtained by reaction of D-glucosamine with Ni(II) salicylaldehydate. The same reaction was employed for the synthesis of bis-N-[2-deoxy-D-galactopyranosyl-2-(2-hydroxybenzaldiminate)]Ni(II). The small paramagnetic shifts of the 1H NMR resonances of the complexes suggest that paramagnetic species are present in low proportions.     

Synthesis and structural analysis of a series of d-glucose derivatives as low molecular weight gelators

Low molecular weight gelators are an interesting new type of compounds that are important in supramolecular chemistry and advanced materials. Previously, we had synthesized several acyl derivatives of methyl 4,6-O-benzylidene-α-d-glucopyranoside and found that a number of terminal acetylene-containing esters are good gelators. To understand the structure requirement of the acyl chains, we synthesized a series of analogs containing different functional groups including aryl, alkenyl, and halogen derivatives. X-ray crystal structures of a monoester and a diester derivative were also obtained to help understand the relationship between structure and gelation. For good gelation properties, the carboxyl derivatives should possess alkyl groups containing a terminal acetylene group and aryl derivatives.     

Anomeric selectivity in the synthesis of galloyl esters of d-glucose

The anomeric selectivity of the ester formation between d-glucopyranose and gallic acid was investigated under a variety of conditions. A new protocol was established that allows performing the reaction under conditions where mutarotation is very slow. Highly α- or β-selective transformations are possible when starting with α- or β-d-glucopyranose, respectively. Due to the kinetic anomeric effect, a high α-selectivity is more difficult to achieve than a high β-selectivity. The new methodology presented in this article was compared with established procedures for the synthesis of gallotannins. In addition to the advantages of a high yield and an easy purification protocol, the new procedure uniquely allowed for a highly selective synthesis of α-products.     

Opposite effects of d-fructose on total versus cytosolic ATP/ADP ratio in pancreatic islet cells

d-fructose (10 mM) augments, in rat pancreatic islets, insulin release evoked by 10 mM d-glucose. Even in the absence of d-glucose, d-fructose (100 mM) displays a positive insulinotropic action. It was now examined whether the insulinotropic action of d-fructose could be attributed to an increase in the ATP content of islet cells. After 30-60 min incubation in the presence of d-glucose and/or d-fructose, the ATP and ADP content was measured by bioluminescence in either rat isolated pancreatic islets (total ATP and ADP) or the supernatant of dispersed rat pancreatic islet cells exposed for 30 s to digitonine (cytosolic ATP and ADP). d-fructose (10 and 100 mM) was found to cause a concentration-related decrease in the total ATP and ADP content and ATP/ADP ratio below the basal values found in islets deprived of exogenous nutrient. Moreover, in the presence of 10 mM d-glucose, which augmented both the total ATP content and ATP/ADP ratio above basal value, d-fructose (10 mM) also lowered these two parameters. The cytosolic ATP/ADP ratio, however, was increased in the presence of d-glucose and/or d-fructose. Under the present experimental conditions, a sigmoidal relationship was found between such a cytosolic ATP/ADP ratio and either ⁸⁶Rb net uptake by dispersed islet cells or insulin release from isolated islets. These data provide, to our knowledge, the first example of a dramatic dissociation between changes in total ATP content or ATP/ADP ratio and insulin release in pancreatic islets exposed to a nutrient secretagogue. Nevertheless, the cationic and insulinotropic actions of d-glucose and/or d-fructose were tightly related to the cytosolic ATP/ADP ratio.     

Single-step bioconversion for the preparation of l-gulose and l-galactose

Both carbohydrate monomers l-gulose and l-galactose are rarely found in nature, but are of great importance in pharmacy R&D and manufacturing. A method for the production of l-gulose and l-galactose is described that utilizes recombinant Escherichia coli harboring a unique mannitol dehydrogenase. The recombinant E. coli system was optimized by genetic manipulation and directed evolution of the recombinant protein to improve conversion. The resulting production process requires a single step, represents the first readily scalable system for the production of these sugars, is environmentally friendly, and utilizes inexpensive reagents, while producing l-galactose at 4.6 g L⁻¹ d⁻¹ and l-gulose at 0.90 g L⁻¹ d⁻¹.     

Synthesis of 1,4-dideoxy-1,4-iminoheptitol and 1,5-dideoxy-1,5-iminooctitols from d-xylose

The synthesis of iminosugars from inexpensive d-xylose in high yields has been developed. The key step in this synthesis involves Wittig olefination or chelation-controlled attack of Grignard reagents on lactol and ring-closing metathesis using first or second generation Grubbs’ catalysts.     

Synthesis, physico-chemical properties and complexing abilities of new amphiphilic ligands from d-galacturonic acid

This paper describes a convenient and efficient synthesis of new complexing surfactants from d-galacturonic acid and n-octanol as renewable raw materials in a two-step sequence. In the first step, simultaneous O-glycosidation-esterification under Fischer conditions was achieved. The anomeric ratio of the products was studied based on the main experimental parameters and the activation mode (thermal or microwave). In the second step, aminolysis of the n-octyl ester was achieved with various functionalized primary amines under standard thermal or microwave activation. The physico-chemical properties of these new amphiphilic ligands were measured and these compounds were found to exhibit interesting surface properties. Complexing abilities of one uronamide ligand functionalized with a pyridine moiety toward Cu(II) ions was investigated in solution by EPR titrations. A solid compound was also synthesized and characterized, its relative structure was deduced from spectroscopic data.     

Synthesis and antitumor activity of new d-seco and d-homo androstane derivatives

Starting from 3β-hydroxy-17-oxo-16,17-secoandrost-5-ene-16-nitrile (1), the new 16,17-secoandrostane derivatives 4–9 were synthesized. On the other hand, 3β-hydroxy-17-oxa-d-homoandrost-5-ene-16-one (10) yielded the new d-homo derivatives 12, 13 and 15. In vitro antiproliferative activity of selected compounds against three tumor cell lines (human breast adenocarcinoma ER+, MCF-7, human breast adenocarcinoma ER−, MDA-MB-231, prostate cancer AR−, PC-3, and normal fetal lung fibroblasts, MRC-5) was evaluated. Compounds 3 and 12 showed strong antiproliferative activity against PC-3 cells, the IC₅₀ values being 2 μM and 0.55 μM, respectively. Compounds 6 (10 μM) and 14 (9 μM) showed moderate activity against MDA-MB-231 cells. The synthesized compounds 1–3, 5–8, 10 and 12–15 were not toxic to normal fetal lung fibroblasts cells, MRC-5.     

Phosphorylation of mouse serine racemase regulates d-serine synthesis

Serine racemase (SR) catalyses the synthesis of the transmitter/neuromodulator d-serine, which plays a major role in synaptic plasticity and N-methyl d-aspartate receptor neurotoxicity. We now report that SR is phosphorylated at Thr71 and Thr227 as revealed by mass spectrometric analysis and in vivo phosphorylation assays. Thr71 phosphorylation was observed in the cytosolic and membrane-bound SR while Thr227 phosphorylation was restricted to the membrane fraction. The Thr71 site has a motif for proline-directed kinases and is the main phosphorylation site of SR. Experiments with a phosphorylation-deficient SR mutant indicate that Thr71 phosphorylation increases SR activity, suggesting a novel mechanism for regulating d-serine production.     

Toward the synthesis of fine chemicals from lactose: preparation of d-xylo and l-lyxo-aldohexos-5-ulose derivatives

The transformation of (5R)-2,6-di-O-benzyl-5-C-methoxy-β-d-galactopyranosyl-(1→4)-2,3:5,6-di-O-isopropylidene-aldehydo-d-glucose dimethyl acetal (8) into partially protected derivatives of d-xylo- and l-lyxo-aldohexos-5-ulose has been reported, applying appropriate epimerisation methods to its 3′-O- and 4′-O-protected alcoholic derivatives.