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Carbohydrate-based receptors with multiple thiourea binding sites. Multipoint hydrogen bond recognition of dicarboxylates and monosaccharides.

The binding properties of multitopic sugar thiourea receptors toward dicarboxylate and monosaccharide guests have been examined taking glutarate and octyl beta-D-glucopyranoside as model ligands. For the anionic hydrogen bond acceptor, both the complex stoichiometry and the association constants (K(as)) were found to be strongly dependent on the relative disposition of recognition elements in the host. In contrast, for the glucoside guest a 1:1 stoichiometry was observed in all cases, the K(as) values being largely independent of the unbound state provided that geometrically equivalent supramolecular topologies can be achieved.

Binding Sites↗

Synthesis of mono- and difluoronaphthoic acids.

Aryl carboxamides are useful structural units found in several biologically active compounds. Unlike their benzoic acid counterparts, fluorinated versions of naphthoic acids are relatively unknown. In connection with a recent project, we needed viable syntheses of several mono- and difluorinated naphthoic acids. Herein we describe the synthesis of 5-, 6-, 7-, and 8-fluoro-1-naphthalenecarboxylic acids and 5,7-, 5,8-, 6,7-, and 4,5-difluoro-1-naphthalenecarboxylic acids. The 5-fluoro derivative 1was obtained from the corresponding 5-bromo compound via electrophilic fluorination of the lithio-intermediate. The rest of the monofluoro (2, 3, and 4) and the difluoro acids (5, 6, and 7) were prepared by a new, general route which entailed the elaboration of commercial fluorinated phenylacetic acids to 2-(fluoroaryl)glutaric acids with differential ester groups; selective hydrolysis to a mono acid, intramolecular Friedel-Crafts cyclization, and aromatization furnished the target structures. An alternative process to assemble a naphthalene skeleton is also presented for the difluoro acids 5 and 6. Finally, 4,5-difluoro-1-naphthalenecarboxylic acid (8) was prepared expeditiously from 1,8-diaminonaphthalene by adapting classical reactions.

Journal Article↗

Novel routes to 1,2,3,4-tetrahydropyrrolo[1,2-a]pyrazines and 5,6,9,10,11,11a-hexahydro-8H-pyrido[1,2-a]pyrrolo[2,1-c]pyrazines.

Condensation reactions of benzotriazole and 2-(pyrrol-1-yl)-1-ethylamine (1) with formaldehyde and glutaric dialdehyde, respectively, afforded intermediates 2 and 6. Subsequent nucleophilic substitutions of the benzotriazole group in 2 and 6 with Grignard reagents, sodium cyanide, and sodium borohydride gave 1,2,3,4-tetrahydropyrrolo[1,2-a]pyrazines 3a-e, 4, 5 and 5,6,9,10,11,11a-hexahydro-8H-pyrido[1,2-a]pyrrolo[2,1-c]pyrazines 7a-c, 8, 9, respectively, in good yields.

Molecular Structure↗

Practical asymmetric synthesis of a non-peptidic alphavbeta3 antagonist.

The development of a practical and highly convergent synthesis of an alpha(v)beta3 antagonist is described. The two key fragments present in this compound, a tetrahydropyrido[2,3-b]azepine ring system and a chiral 3-aryl-5-oxopentanoic acid, were constructed independently and then coupled at a late stage using a Wittig reaction. The pyridoazepine moiety was prepared from N-Boc 6-chloro-2-aminopyridine via directed ortho-metalation/alkylation followed by in situ cyclization. A Suzuki reaction was then used to attach the propionaldehyde side-chain required for Wittig coupling. The coupling partner was prepared from asymmetric methanolysis of a 3-substituted glutaric anhydride followed by elaboration of the acid moiety to the requisite beta-keto phosphorane. Using this route, kilogram quantities of the desired drug candidate were prepared.

Azepines↗

Requirement for Hydrogen-Bonding Cooperativity in Small Polyamides: A Combined VT-NMR and VT-IR Investigation.

A study of intramolecular hydrogen bonding in chloroform for a small combinatorial library of nine triamides with varying connecting chain length has been completed. The starting materials for the triamides are three diacids (succinic, glutaric, and adipic acid) and three amino acids (glycine, beta-alanine, and gamma-aminobutyric acid). The preferences for the head-to-tail type of folding pattern are identified for the smaller triamides (1 and 4). The preference for the head-to-tail folding pattern can be explained by the energetic superiority of an optimal hydrogen bond geometry in which the NH---O bond angle is near linearity. The beta-alanine containing triamides 2, 5, and 8 are resistant to intramolecular hydrogen bonding, especially to nearest neighbor hydrogen bonding. At lower temperatures, triamides 2 and 5 exhibit a small population of head-to-tail type of folding, while triamide 8 shows a significant population of bifurcated conformation. Triamide 6, 7, and 9 prefer bicyclic structures involving nearest neighbor hydrogen bonding. A nine-membered ring is large enough to accommodate a near linear N-H--O bond angle. Entropic effects are probably responsible for the preference of the nine-membered ring over a 12- or a 14-membered ring. The enhancement of hydrogen bonding in triamide 9 is enormous, and both NHs have a very large temperature dependence of chemical shifts (-15 ppb/K and -13.3 ppb/K for the terminal and the internal NH protons, respectively). Using appropriate temperature-dependent lower and upper limits of chemical shifts, a van't Hoff analysis gives the hydrogen bond strength for the terminal NH (DeltaH = -3.1 +/- 0.5 kcal/mol) and for the internal NH (DeltaH = -2.8 +/- 0.5 kcal/mol). The increased hydrogen bond strength is taken as evidence for hydrogen-bonding cooperativity from the two mutually enhanced individual hydrogen bonds. A near linear NH--O bond angle is required for this effect.

Journal Article↗

Substituent Effect on Intramolecular Hydrogen Bonding in beta-Amino Acid-Containing Polyamides.

An alkyl substitution in the beta-amino acid-containing polyamides 1, 2, and 3 leads to an increase in the population of intramolecularly hydrogen bonded conformations. However, the most stable conformation is not always the same one when the substituent is changed from a methyl group to an isopropyl group. For the beta-amino acid derivatives of succinic acid, a methyl group enhances the formation of a head-to-tail type of folding pattern through an 11-membered ring (2b), but an isopropyl group appears to decrease the enhancement. For beta-amino acid derivatives of glutaric acid, an isopropyl group promotes the formation of a bifurcated conformation (3c). The thermodynamic parameters for the equilibrium between non-hydrogen-bonded states and the head-to-tail type of folding of 2a and 2b are obtained by a van't Hoff analysis of the variable-temperature NMR data, which gives a DeltaH of -1.0 kcal/mol and a DeltaS of -4.7 eu for triamide 2a and a DeltaH of -1.0 kcal/mol and a DeltaS of -3.7 e.u. for triamide 2b, each with a correlation coefficient of better than 0.99. The increased proportion of the intramolecular amide-amide hydrogen bond observed for triamide 2b is entirely due to entropic effects according to this analysis.

Journal Article↗

Enantioselective Synthesis of Diamino Dicarboxylic Acids.

The preparation of alkyl diamino dicarboxylic acids with high optical purity (100% ee, >98.5% de) and high yields based on asymmetric catalytic hydrogenation is described. The required prochiral precursors are prepared from dialdehydes and Z-, Boc-, and acetyl-protected phosphonoglycines. Aqueous solutions of glyoxal, succinic dialdehyde, and glutaric dialdehyde were used to prepare the diunsaturated precursors for 2,5-diaminoadipic acid (DAA), 2,7-diaminosuberic acid (DAS), and 2,8-diaminoazelaic acid (DAZ). Z-Protected dimethyl esters of DAA, DAS, and DAZ were obtained by hydrogenation of the corresponding prochiral starting materials with [(COD)Rh(S,S)-Et-DuPHOS]OTf.

Journal Article↗

Catalytic oxidation with air of cyclohexanone to dicarboxylic acids on synthetic carbons. Effect of supported metals and solvents.

The oxidation with air of cyclohexanone was conducted in the presence of synthetic carbons catalysts. The effect of carbon activation treatment (CO2 or air burnoff), phosphorus additive, platinum loading, and nature of the solvent (water or water/acetic acid mixture) were studied. Cyclohexanone oxidation at 140 degrees C yielded a mixture of C6, C5, and C4 dicarboxylic acids. Air activated carbons, including those containing phosphorus or those supporting platinum, resulted in a higher yield of adipic acid. The activity and selectivity was associated with the oxygenated functional groups, essentially carbonyl/quinone groups, created during air activation of the carbon. The incorporation of phosphorus into the carbon increased slightly the selectivity to 34.3%, probably because this additive increased the density of oxygenated functional groups. The deposition of platinum by impregnation and liquid-phase reduction with formaldehyde increased the reaction rate and improved the selectivity to adipic acid, where the highest figure was 38.8%. It was suggested that platinum contributed to molecular oxygen activation. In contrast platinum deposition by cationic exchange followed by reduction under H2 resulted often in a detrimental effect probably because the density of the oxygenated groups on carbon is decreased upon H2 reduction in the presence of platinum. When the oxidation of cyclohexanone was carried out in mixtures of water/acetic acid, the selectivity given by the different samples were quite close and generally smaller than those obtained in water which indicates that acetic acid interacts with the oxygenated surface functional groups responsible for the activity and selectivity. Oxidation experiments with methyl-labeled 4-methylcyclohexanone indicated that glutaric acid was produced by oxidative decarbonylation of both the C1 and C2 carbon atoms of the molecule.

Journal Article↗

Electrospray ionization ion mobility spectrometry of carboxylate anions: ion mobilities and a mass-mobility correlation.

A number of carboxylate anions spanning a mass range of 87-253 amu (pyruvate, oxalate, malonate, maleate, succinate, malate, tartarate, glutarate, adipate, phthalate, citrate, gluconate, 1,2,4-benzenetricarboxylate, and 1,2,4,5-benzenetetracarboxylate) were investigated using electrospray ionization ion mobility spectrometry. Measured ion mobilities demonstrated a high correlation between mass and mobility in both N2 and CO2 drift gases. Such a strong mass-mobility correlation among structurally dissimilar ions suggests that the carboxylate functional group that these ions have in common is the source of the correlation. Computational analysis was performed to determine the most stable conformation of the studied carboxylate anions in the gas phase under the current experimental conditions. This analysis indicated that the most stable conformations for multicarboxylate anions included intramolecular hydrogen-bonded ring structures formed between the carboxylate group and the neutral carboxyl group. The carboxylate anions that form ring confirmations generally show higher ion mobility values than those that form extended conformations. This is the first observation of intramolecular hydrogen-bonded ring conformation of carboxylate anions in the gas phase at atmospheric pressure.

Anions↗

Phase changes during hygroscopic cycles of mixed organic/inorganic model systems of tropospheric aerosols.

A correct description of the aerosol's phases is required to determine its gas/particle partitioning, its reactivity and its water uptake and release. In this study, we investigate organic/electrolyte interactions of ammonium sulfate, nitrate and sodium chloride with substances containing carboxylic acids (COOH) and hydroxyl (OH) functional groups. As organic model compounds, we chose polyols with different OH/CHn (n = 0-3) ratios-namely, glycerol, 1,4-butanediol, and 1,2-hexanediol-as well as PEG 400 and a mixture of dicarboxylic acids consisting of malic, malonic, maleic, glutaric, and methylsuccinic acid. Bulk solubility and water activity measurements of these model systems together with a survey of literature data showed that NaCl is a salting-out agent for alcohols and organic acids whereas ammonium nitrate and sulfate exhibited salting-in and salting-out tendencies depending on the nature and number of functional groups as well as on the concentration of the solution. All investigated salts induce a liquid-liquid phase separation in the 1,2-hexanediol/water system. Considering the composition of the tropospheric aerosol, such phase separations might indeed occur frequently when particles in the atmosphere are exposed to varying relative humidity. To complement the bulk experiments, we investigated single particles consisting of ammonium sulfate and dicarboxylic acids as well as of ammonium sulfate and PEG 400 in an electrodynamic balance. Whereas the relative humidities of total deliquescence as well as the water uptake and release of the fully deliquesced particles are in good agreement with the bulk results and represent thermodynamic equilibrium, the water uptake before full deliquescence shows significant deviations. These deviations may be caused by morphological effects.

Journal Article↗

Thermodynamic models of aqueous solutions containing inorganic electrolytes and dicarboxylic acids at 298.15 K. 1. The acids as nondissociating components.

Atmospheric aerosols contain a significant fraction of water-soluble organic compounds, including dicarboxylic acids. Water activities at approximately 298.15 K (including data for highly supersaturated solutions) of oxalic, malonic, succinic, glutaric, maleic, malic, and methyl succinic acids are first correlated as a function of concentration, treating the acids as nondissociating components. Methods proposed by Clegg et al. (J. Aerosol. Sci. 2001, 32, 713-738), and by Clegg and Seinfeld (J. Phys. Chem. A 2004, 108, 1008-1017) for estimating water activities and solute activity coefficients in aqueous mixtures containing both electrolytes and uncharged solutes are then evaluated from comparisons with literature data. These data include water activities, solubilities, and determinations of the eutonic points of solutions containing up to five acids, and solutions containing one or more acids and the salts (NH(4))(2)SO(4), NH(4)NO(3), or NaCl. The extended Zdanovskii-Stokes-Robinson approach of Clegg and Seinfeld yields the more accurate predictions for aqueous mixtures containing dicarboxylic acids only, and for aqueous mixtures of the acids and salts (though by a lesser margin). A number of hybrid modeling approaches, which contain elements of both methods, are outlined.

Ammonium Sulfate↗

Biochemistry of peroxisomes in health and disease.

The ubiquitous distribution of peroxisomes and the identification of a number of inherited diseases associated with peroxisomal dysfunction indicate that peroxisomes play an essential part in cellular metabolism. Some of the most important metabolic functions of peroxisomes include the synthesis of plasmalogens, bile acids, cholesterol and dolichol, and the oxidation of fatty acids (very long chain fatty acids > C22, branched chain fatty acids (e.g. phytanic acid), dicarboxylic acids, unsaturated fatty acids, prostaglandins, pipecolic acid and glutaric acid). Peroxisomes are also responsible for the metabolism of purines, polyamines, amino acids, glyoxylate and reactive oxygen species (e.g. O-2 and H2O2). Peroxisomal diseases result from the dysfunction of one or more peroxisomal metabolic functions, the majority of which manifest as neurological abnormalities. The quantitation of peroxisomal metabolic functions (e.g. levels of specific metabolites and/or enzyme activity) has become the basis of clinical diagnosis of diseases associated with the organelle. The study of peroxisomal diseases has also contributed towards the further elucidation of a number of metabolic functions of peroxisomes.

Animals↗

Inactivation of the reconstituted oxoglutarate carrier from bovine heart mitochondria by pyridoxal 5'-phosphate.

The effect of pyridoxal 5'-phosphate and some other lysine reagents on the purified, reconstituted mitochondrial oxoglutarate transport protein has been investigated. The inhibition of oxoglutarate/oxoglutarate exchange by pyridoxal 5'-phosphate can be reversed by passing the proteoliposomes through a Sephadex column but the reduction of the Schiff's base by sodium borohydride yielded an irreversible inactivation of the oxoglutarate carrier protein. Pyridoxal 5'-phosphate, which caused a time- and concentration-dependent inactivation of oxoglutarate transport with an IC50 of 0.5 mM, competed with the substrate for binding to the oxoglutarate carrier (Ki = 0.4 mM). Kinetic analysis of oxoglutarate transport inhibition by pyridoxal 5'-phosphate indicated that modification of a single amino acid residue/carrier molecule was sufficient for complete inhibition of oxoglutarate transport. After reduction with sodium borohydride [3H]pyridoxal 5'-phosphate bound covalently to the oxoglutarate carrier. Incubation of the proteoliposomes with oxoglutarate or L-malate protected the carrier against inactivation and no radioactivity was found associated with the carrier protein. In contrast, glutarate and substrates of other mitochondrial carrier proteins were unable to protect the carrier. Mersalyl, which is a known sulfhydryl reagent, also failed to protect the oxoglutarate carrier against inhibition by pyridoxal 5'-phosphate. These results indicate that pyridoxal 5'-phosphate interacts with the oxoglutarate carrier at a site(s) (i.e., a lysine residue(s) and/or the amino-terminal glycine residue) which is essential for substrate translocation and may be localized at or near the substrate-binding site.

Animals↗

Reduction of lysine intake while avoiding malnutrition--major goals and major problems in dietary treatment of glutaryl-CoA dehydrogenase deficiency.

Treatment in glutaryl-CoA dehydrogenase deficiency, an inborn error of metabolism of lysine and tryptophan, is mainly based on restriction of lysine intake, supplementation of carnitine, and an intensification of therapy during intercurrent illnesses. The major principle of dietary treatment is to reduce the production of glutaric acid and 3-hydroxyglutaric acid by restriction of natural protein in general and of lysine in particular. In parallel to development, the growing child learns to utilize different protein sources, shifting the primarily milk-based diet to a mixed diet. The changes in nutritional demands and food composition during the first years of life greatly influence nutritional support for affected patients at different ages. This article highlights frequent pitfalls of dietary treatment for this disease and focuses on particular risks of malnutrition in terms of essential amino acids and micronutrients and/or excess intake of lysine between age 3 months and age 6 years. We conclude from the examples given that restriction of natural protein intake plus application of lysine-free amino acid mixtures minimizes the risk of malnutrition and allows a reliable control of protein and lysine intake and, thus, seems particularly recommendable during the vulnerable period for acute encephalopathic crises. The efficacy of these theoretical and experience-based approaches to dietary treatment of glutaryl-CoA dehydrogenase deficiency should be investigated in detail in prospective clinical studies.

Adult↗

Management of movement disorders in glutaryl-CoA dehydrogenase deficiency: anticholinergic drugs and botulinum toxin as additional therapeutic options.

Glutaric aciduria type I is an inborn error of metabolism due to the deficiency of glutaryl-CoA dehydrogenase, an enzyme responsible for the catabolism of lysine, hydroxylysine and tryptophan. The most important neurological symptoms include dyskinesia and dystonia, which can be focal, segmental or generalized. Treatment of the extrapyramidal syndrome is often unsatisfactory. We report our experience in the treatment of generalized and focal dystonia with anticholinergic drugs and botulinum toxin type A, respectively. Both therapies proved beneficial.

Adolescent↗

Synthesis of the Lewis b hexasaccharide and HSA-conjugates thereof.

An efficient and short route has been elaborated for the aminopropyl spacer equipped Leb hexasaccharide. For the preparation of HSA-conjugates of this oligosaccharide, the use of disuccinimidyl suberate (DSS) and disuccinimidyl glutarate (DSG) as cross-linker reagents has been evaluated. This conjugation method emerged as being faster and easier to monitor by standard MALDI-TOF spectrometry than squarate ester based conjugations of similar efficiency if DSS is used as cross-linker.

Cross-Linking Reagents↗

Evidence for a common tumour-associated antigen in extracts of human bronchogenic carcinoma.

Xeno-antiserum specific for antigenic components of bronchogenic carcinoma was raised in rabbits, by passively immunizing them to normal human lung antigens at the same time as immunization with a tumour extract from a squamous-cell carcinoma. Antiserum so raised contained minimal quantities of anti-normal antibody which could be removed by a single absorption with glutaral-dehyde-insolubilized normal lung extract. When tested by quantitative complement fixation with a panel of tumour extracts from surgical specimens, it was found that the antiserum gave positive complement fixation with all squamous-cell carcinoma extracts tested, and with some of the extracts from bronchogenic carcinomas of differing pathological types. The antiserum was essentially negative for pooled extracts from normal lung, liver and spleen but gave a weak positive reaction with an extract of pooled foetal lung tissue.

Antibodies, Neoplasm↗

An integrated relay/nitrate reductase field-effect transistor for the sensing of nitrate (NO3-).

An integrated enzyme-functionalized field-effect transistor (ENFET) device for the sensing of nitrate ions is described. An aminosiloxane-functionalized gate interface is modified with N-methyl-N'-(carboxyalkyl)-4,4'-bipyridinium relay units. The complex formed between nitrate reductase and the bipyridinium units on the gate surface is crosslinked with glutaric dialdehyde to yield a stable relay-enzyme layer on the gate interface. In the presence of sodium dithionite as electron donor, the biocatalyzed reduction of nitrate to nitrite ion is stimulated. The ratio between the oxidized and reduced states of the bipyridinium sites regulates the gate potential, and is controlled by the concentration of NO3- ions in the system. The effect of the chain length tethering the N-methyl-N'-(carboxyalkyl)-4,4'-bipyridinium units to the gate surface on the biocatalyzed reduction of NO3- ions, and on the NO3- FET sensor performance is discussed. The devices that include the bipyridinium units tethered to the gate interface with methylene chain length, -(CH2)n, where n > or = 7, reveal a detection limit of 7 x 10(-5) M for nitrate and a sensitivity of 52 +/- 2 mV dec-1. The response time of the device is as low as 50 s, and the operational time of the system is ca. 85 s. We estimate the surface coverage of nitrate reductase on the gate surface to be ca. 1.2 x 10(-12) mol cm-2.

Journal Article↗