Showing papers on "Carboxylic acid published in 1998"

Sodium borohydride in carboxylic acid media: a phenomenal reduction system

Abstract: The union of sodium borohydride and carboxylic acids has yielded an amazingly versatile and efficient set of reducing reagents. These acyloxyborohydride species reduce and N-alkylate indoles, quinolines, isoquinolines, related heterocycles, imines, enamines, oximes, enamides, and similar functional groups. They reduce amides and nitriles, aryl alcohols and ketones, aldehydes in the presence of ketones, and β-hydroxyketones to 1,3-diols stereoselectively. This reagent is also extraordinarily useful for the N-alkylation of primary and secondary amines with aldehydes and ketones in a novel reductive amination process.

Isothiazole carboxylic acid amides and the application thereof in order to protect plants

Abstract: The invention relates to novel isothiazole carboxylic acid amides of formula (I) in which R has the meanings given in the description. The invention also relates to additional methods for producing the novel materials and the application thereof in order to protect plants against attack by undesired microorganisms and animal pests.

Photochemically produced carboxylic acids as substrates for freshwater bacterioplankton

Abstract: . High-molecular-weight dissolved organic matter is abundant in humic lakes and is a large potential source of energy for heterotrophic organisms. These substances are hard to degrade enzymatically because of their high aromaticity and complex structure. However, there is increasing evidence that photochemical processes render the material more bioavailable. We demonstrate a substantial photochemical production of four carboxylic acids (oxalic, malonic, formic, and acetic acid) in a humic lake. The combined production rate in the surface water of these four acids was 19 pg C liter-l h-l with natural sunlight. Furthermore, based on radiotracer studies, we found that the amount of carbon assimilated and oxidized to CO, from malonic, formic, and acetic acid exceeded bacterial carbon production, sometimes by more than one order of magnitude. This implies that carboxylic acids were major bacterioplankton substrates. Nevertheless, under natural sunlight at the lake surface, microbial utilization of carboxylic acids was substantially lower than the photochemical production of the acids. Hence, photochemically produced carboxylic acids may accumulate in sunlight exposed environments and may also serve as bacterial substrates after mixing into deeper layers, or during night.

Role of water in formic acid decomposition

Abstract: Formic acid decomposes primarily to CO and H2 0 in the gas phase, but to CO, and H, in the aqueous phase. Ab-initio quantum chemical calculations were performed, using Hartree-Fock and density functional methods, to seek an explanation for this behavior. The effect of water on the two decomposition pathways and on the isomerization of formic acid was determined. The transition state structures were fully optimized and include up to two water molecules. In the absence of water, dehydration is more favorable than decarboxylation. The presence of water reduces the activation barriers for both decomposition pathways, but decarboxylation is consistently more favorable than dehydration. The water molecules actively participate in the bond-breaking and bondforming processes in the transition state. The reduction in the activation barriers with the addition of water indicates that water acts as a homogeneous catalyst for both dehydration and decarboxylation, whereas isomerization of formic acid occurs independently of water. Water has a strong effect on the relative stability of the formic acid isomers, acid - water complexes, and transition states. The relative stability of the transition states plays an important role in determining the faster decomposition pathway.

Hydrolysis of Polylactic Acid (PLA) and Polycaprolactone (PCL) in Aqueous Acetonitrile Solutions: Autocatalysis

Abstract: Polylactic acid (PLA) is a hydrolytically degradable aliphatic polyester The rate of polymer hydrolysis increases with time, and that has been attributed to the high reactivity of the terminal ester and the kinetics of autocatalysis Hydrolysis is carried out in an acetonitrile/water solution to eliminate any solid-state contributions such as diffusion and crystallinity to the degradation process A kinetic equation is derived to describe the autocatalytic effect of the increasing carboxylic acid end-group concentration The results of solution hydrolysis are examined and found to fit the derived equation Hydrolysis was also carried out with polycaprolactone (PCL) in acetonitrile, where reaction kinetics were found to differ from those of PLA The PCL polymer required external acid catalysis by the addition of HCl, whereas hydrolysis of PLA was “selfcatalyzed” by the carboxylic acid end-groups

Stereoselective Synthesis of over Two Million Compounds Having Structural Features Both Reminiscent of Natural Products and Compatible with Miniaturized Cell-Based Assays

Abstract: Understanding the cellular function of a protein usually requires a means to alter the function. This is commonly done by mutating the gene encoding the protein (genetic approach). It can also be done by binding the protein directly with a small molecule ligand (chemical genetic approach). Such ligands, primarily natural products or synthetic variants of them, can either inactivate1 or activate2 protein function. For the chemical genetic approach to have its maximal impact, efficient methods of ligand discovery will be required to provide, in the limit, a small molecule partner for every gene product. Our laboratory has recently described miniaturized cell culture assays for screening large numbers of small molecule ligands, potentially on a genome-wide basis.3 However, despite its success in natural products synthesis, synthetic chemistry has not yet been applied to the synthesis of vast numbers of compounds with structures both reminiscent of natural products and compatible with miniaturized assays. These features of a synthesis will likely be required in order to discover nonnatural compounds having the binding affinities and specificities characteristic of natural products. The synthetic strategy we have undertaken is to develop highly efficient multistep syntheses of natural product-like compounds that include several coupling steps and to use split-pool techniques4 at these steps in order to generate diverse outcomes. This technique requires that one of the coupling substrates be immobilized on a solid support. Our syntheses are further constrained by the water-compatible photolabile supports required when carrying out large numbers (>105) of miniaturized “nanodroplet” cell culture assays aimed at identifying cell permeable ligands.3 This presents a considerable synthetic challenge since the structural elements that provide these properties (e.g., poly(ethylene glycol), nitrobenzyl moieties) are incompatible with numerous reagents used in conventional synthetic chemistry. With these considerations in mind, we first converted shikimic acid, 1, into both enantiomers of epoxycyclohexenol carboxylic acid 2,5 which were then coupled to a photocleavable linker on solid support by standard methods (Figure 1).6 Treatment of the resin-bound epoxycyclohexenol, 3, with various nitrone carboxylic acids,7 7a-f and 9b-d, under esterification conditions yielded tetracyclic compounds 4a-f and 5b-d with complete regioand stereoselectivity, presumably via tandem acylation/1,3-dipolar cycloaddition.8 No intermediate nitrone ester or carboxy isoxazolidine structures were observed. The iodoaryl tetracycles 4b-d and 5b-d were selected for further study since the supportbound aryl iodides could be modified with commercially available reagents, avoiding the need for solution-phase syntheses of numerous nitrone acids. Tetracycles 4b-d and 5b-d are rigid, densely functionalized compounds that can undergo further reactions to introduce a variety of functional groups around the central octahydrobenzisoxazole structure, notably, without the use of protecting groups. The iodoaryl groups can serve as substrates for palladium cross-coupling reactions. The electrophilic lactone and epoxide can react with nucleophiles while simultaneously unmasking alcohols for subsequent reactions. Furthermore, reductive N-O bond cleavage would provide two additional handles for functionalization. We developed several such reactions (Figure 2) with product purity ranging from ∼50 to g98% following photocleavage.9 Since purification is not practical in a large split-pool synthesis, only reactions generating products in g90% purity were acceptable. The most promising reactions were studied in detail to define the scope, limitations, and optimal conditions for each (Figure 3). Iodobenzyl tetracycles 4b-d were selected as scaffolds since (1) See http://www-schreiber.chem.harvard.edu on the Web. (2) Crabtree, G. R.; Schreiber, S. L. Trends in Biochem. Sci. 1996, 21, 418-422. (3) (a) Borchardt, A.; Liberles, S. D.; Biggar, S. R.; Crabtree, G. R.; Schreiber, S. L. Chem. Biol. 1997, 4, 961-968. (b) You, A. J.; Jackman, R. J.; Whitesides, G. M.; Schreiber, S. L. Chem. Biol. 1997, 4, 969-975. (4) (a) Furka, A.; Sebestyen, F.; Asgedom, M.; Dibo, G. Int. J. Pept. Protein Res. 1991, 37, 487-493. (b) Lam, K. S.; Salmon, S. E.; Hersh, E. M.; Hruby, V. J.; Kazmierski, W. M.; Knapp, R. J. Nature 1991, 354, 82-84. (5) (a) Wood, H. B.; Ganem, B. J. Am. Chem. Soc. 1990, 112, 89078909. (b) McGowan, D. A.; Berchtold, G. A. J. Org. Chem. 1981, 46, 23812383. (c) Mitsunobu, O. Synthesis 1981, 1-28. (6) The resin structure shown represents Tentagel S NH2, a poly(ethylene glycol)-polystyrene copolymer, loaded with a photocleavable 3-amino-3-onitrophenylpropionic acid linker. (Brown, B. B.; Wagner, D. S.; Geysen, H. M. Mol. DiV. 1995, 1, 4-12.). (7) Keirs, D.; Overton, K. Heterocycles 1989, 28, 841-848. (8) Tamura, O.; Okabe, T.; Yamaguchi, T.; Gotanda, K.; Noe, K.; Sakamoto, M. Tetrahedron 1995, 51, 107-118. (9) Photocleavage products were analyzed by 1H NMR, FAB-MS, HPLC, and TLC. Figure 1. Synthesis of tetracycles and nitrones. a: X ) H, b: X ) 2-I, c: X ) 3-I, d: X ) 4-I, e: X ) 4-CF3, f: X ) 3,4-(OMe)2.

Biodegradable, anionic polymers derived from the amino acid l-tyrosine

Abstract: A polymer with a hydrolytically labile backbone and having structure (VIII) wherein R9 is an alkyl, aryl or alkylaryl group with up to 18 carbon atoms having a pendent carboxylic acid group or the benzyl ester thereof; R12 is an alkyl, aryl or alkylaryl group with up to 18 carbon atoms having a pendent carboxylic acid ester group selected from straight and branched alkyl and alkylaryl esters containing up to 18 carbon atoms and ester derivatives of biologically and pharmaceutically active compounds covalently bonded thereto, provided that the ester group is not a benzyl group or a group that is removed by hydrogenolysis; each R7 is independently an alkylene group containing up to four carbon atoms; A is selected from: (a) and (b) wherein R8 is selected from saturated and unsaturated, substituted and unsubstituted alkyl, aryl and alkylaryl groups containing up to 18 carbon atoms; k is between about 5 and about 3,000; and x and f independently range from zero to less than one.

Low chlorine content compositions for use in lubricants and fuels

Abstract: Methods are revealed for producing polyolefin substituted carboxylic acylating agents having less than 1000 ppm chlorine, and reaction products formed therefrom such as dispersants. The carboxylic acylating agents are formed by reacting a polyolefin having labile halogen content with an α-β unsaturated carboxylic acid. The products formed in this invention are used in lubricating compositions.

N-(2-Benzoylphenyl)-l-tyrosine PPARγ Agonists. 3. Structure−Activity Relationship and Optimization of the N-Aryl Substituent

Abstract: 3-{4-[2-(Benzoxazol-2-ylmethylamino)ethoxy]phenyl}-(2S)-((2-benzoylphenyl)amino)propionic acid (1) and (2S)-((2-benzoylphenyl)amino)-3-{4-[2-(5-methyl-2-phenyloxazol-4-yl)ethoxy]phenyl}propionic acid (2) are peroxisome proliferator-activated receptor γ (PPARγ) agonists and have antidiabetic activity in rodent models of type 2 diabetes. As part of an effort to develop the SAR of the N-2-benzoylphenyl moiety of 1 and 2, a series of novel carboxylic acid analogues, 23−66, modified only in the N-2-benzoylphenyl moiety were synthesized from l-tyrosine and evaluated as PPARγ agonists. In general, only modest changes in the N-2-benzoylphenyl moiety of 1 and 2 are tolerated. More specifically, the best changes involve bioisosteric replacement of one of the two phenyl rings of this moiety. Addition of substituents to this moiety generally produced compounds that are less active in the cell-based functional assays of PPARγ activity although binding affinity to PPARγ may be maintained. A particularly promising set o...

Molecular imprinting of azobenzene carboxylic acid on a TiO2 ultrathin film by the surface sol-gel process

Abstract: Ultrathin films of titanium oxide gel imprinted with 4-(4-propyloxyphenylazo)benzoic acid (C3AzoCO2H) were prepared by repeated immersion of a gold-coated quartz crystal microbalance (QCM) electrode or a quartz plate in solutions of C3AzoCO2H and titanium butoxide (Ti(O-nBu)4) in toluene/ethanol. Regular film growth was confirmed by frequency decrement in QCM measurements and by the appearance of the azobenzene absorption in UV−vis spectroscopy. The template molecule could be completely removed upon treatment with 1% aqueous ammonia. The resulting films showed saturation binding of the template molecule in acetonitrile in less than 1 min. Binding of the template molecule was greatest among aromatic carboxylic acids that are structurally related to the template. A related ester showed a significant reduction in the binding efficiency. The surface sol-gel process provides a powerful tool for molecular imprinting in ultrathin metal oxide films.

Condensation products of basic amino acids with copolymerizable compounds and a process for their production

Abstract: Condensation products of basic amino acids with copolymerizable compounds which are obtainable by condensing (a) a basic amino acid selected from the group consisting of lysine, arginine, ornithine, tryptophane and mixtures thereof, (b) a copolymerizable compound selected from the group consisting of saturated monobasic carboxylic acids, unsaturated mono-basic carboxylic acids, polybasic carboxylic acids, carboxylic acid anhydrides, diketenes, monohydroxycarboxylic acids, polyhydroxycarboxylic acids and mixtures thereof, and optionally (c) at least one compound selected from the group consisting of amines, lactams, non-proteinogenic acids, alcohols, alkoxylated alcohols, alkoxylated amines, amino sugars, carbohydrates and sugar carboxylic acids in a molar ratio of (a):(b) of from 100:1 to 1:1 at a temperature of at least 120° C., and a process for the production of said condensation products by condensing compounds (a) and (b) and optionally (c) at a temperature of from 120° to 300° C.

Novel thyroid receptor ligands and method

Abstract: Novel thyroid receptor ligands as provided which have general formula (I) in which: R1 is alkyl of 1 to 4 carbons or cycloalkyl of 3 to 7 carbons; R2 and R3 are the same or different and are hydrogen, halogen, alkyl of 1 to 3 carbons or cycloalkyl of 3 to 5 carbons, at least one of R2 and R3 being other than hydrogen; n is an integer from 0 to 4; R4 is an aliphatic hydrocarbon, an aromatic hydrocarbon, carboxylic acid ester thereof, alkenyl carboxylic acid or ester thereof, hydroxy, halogen, cyano, or a phosphonic acid or an ester thereof, or a pharmaceutically acceptable salt thereof A method for treating diseases associated with metabolism dysfunction or which are dependent on the expression of a T3 regulated gene (such as obesity, hypercholesterolemia, osteoporosis, hypothyroidism and goiter) is also provided

Chemical Surface Modification of Poly(ethylene terephthalate)

Abstract: Reactions of semicrystalline poly(ethylene terephthalate) (PET) film with ester-selective reagents at the film−solution interface can be controlled to produce modified film samples containing a thin (less than ∼ 40 A) surface layer of the reagent-induced functionality. Hydrolysis of PET yields a surface mixture of alcohol and carboxylic acid groups. Reduction with lithium aluminum hydride and transesterification with ethylene glycol (glycolysis) both produce surfaces with alcohol functionality (PET−OHR and PET−OHG, respectively). Each of these modification reactions involves chain cleavage and can lead to significant sample degradation (reactive dissolution); for each modification reaction, conditions were optimized to maximize conversion and minimize degradation. The reactivity of surface alcohols (PET−OH) was assessed for samples prepared by both reduction and glycolysis, and a comparative analysis was made: the presence of benzylic alcohols in reduced samples and their absence in glycolyzed samples as...

Use of a hydrophilic agent as dispersing agent for aqueous polyurethane dispersions

Abstract: of EP0916647A hydrophilising agent is obtained by Michael addition of 1-amino-3,3,5-trimethyl-5-aminomethyl-cyclohexane with 1-2 mols of an alpha , beta -unsaturated carboxylic acid. A hydrophilising agent is obtained by Michael addition of 1-amino-3,3,5-trimethyl-5-aminomethyl-cyclohexane with 1-2 mols of an alpha , beta -unsaturated carboxylic acid, optionally followed by neutralization with up to an equivalent amount (based on the COOH groups) of alkali (or alkaline earth) hydroxide and/or amine and/or ammonia. AN Independent claim is also included for the use of the agent.

Handbook of derivatization reactions for HPLC

Abstract: Acyl Halide. Alcohol. Aldehyde. Alkene. Amide. Amine. Amino Acid. Amino Alcohol. Amino Ketone. Anhydride. Azide. Aziridine. Azo Compound. Boric Acid. Carbamate. Carboxylic Acid. Chelating Agent. Chloramine. Cyanate. Cyanide. Cyanohydrin. Diacid. Dialdehyde. Diene. Diketone. Diol. Enal. Epoxide. Ester. Guanidine. Halide. Haloaldehyde. Halogenated Compound. Hydrazine. Hydroxyl Radical. Hydroxylamine. Imine. Isocyanate. Isothiazole. Ketal. Ketoacid. Ketoalchohol. Ketoaldehyde. Ketone. Lactam. Lactone. Metal. Miscellaneous Reactions. Nitrate. Nitrite. Nitro Group. Nitroprusside Nitrosamide. Nitrosamine. Peracid. Peroxide. Phosphate. Phosphatidylcholine. Phosphonic Acid. Phosphoric Acid. Pyridine Ring. Quinone. Selenium. Sulfate. Sulfide. Sulfite. Sulfonate. Sulfonium Compound. Sulfur Dioxide. Tetrahydropyrimidine. Thiocyanate. Thiol. Thiosulfate. Appendices. Indexes.

Attachment of human keratinocytes to plasma co-polymers of acrylic acid/octa-1,7-diene and allyl amine/octa-1,7-diene

Abstract: Plasma co-polymers (PCPs) of acrylic acid/octa-1,7-diene and allyl amine/octa-1,7-diene have been prepared and characterised using X-ray photoelectron spectroscopy (XPS). The use of a hydrocarbon diluent in the monomer feed allowed the deposition of films with controlled concentrations of carboxylic acid and nitrogen-containing functional groups. Human keratinocytes were cultured on these PCP surfaces, tissue culture poly(styrene) (TCPS) and collagen I. The level of keratinocyte attachment over 24 h was measured. PCP surfaces containing low concentrations of carboxylic acid groups (2.3%) were found to promote keratinocyte attachment. The performance of these PCPs was similar to collagen I, a well established substratum for attachment. Nitrogen-containing PCP surfaces were found to promote attachment at higher functional group concentrations, although the attachment did not attain the level achieved on the acid functionalised PCP surfaces.

Antimycobacterial Activity of Substituted Isosteres of Pyridine- and Pyrazinecarboxylic Acids

Abstract: Pyridines and pyrazines substituted with 1,2,4-oxadiazole-5-ones, 1,2,4-oxadiazole-5-thiones, and 1,3,4-oxathiazoline-2-ones were synthesized and tested against Mycobacterium tuberculosis. The two former ring systems were documented in the literature to act as carboxylic acid isosteres. The latter series was synthesized as possible synthetic intermediates to 1,2,4-thiadiazole-3-ones and was included in this study due to their interesting activity. Pivaloyloxymethyl derivatives of the isosteres were also prepared in order to increase their lipophilicity and therefore improve their cellular permeability. The derivatized isosteres were expected to be biotransformed by esterases to the active species after penetration of the mycobacterial cell wall. Biological properties of the compounds were compared with the unmodified polar isosteres of pyrazinoic and nicotinic acids. The majority of the compounds exhibited activities ranging from 0.5 to 16 times the potency of pyrazinamide.

Interfacial interactions of plasma‐polymerized acrylic acid and an oxidized aluminium surface investigated using XPS, FTIR and poly(acrylic acid) as a model compound

Abstract: X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR) are used to characterize the interface between poly(acrylic acid) (PAA) and an aluminium oxyhydroxide (AlOOH) surface. Reaction of the PAA carboxylic acid functionality with hydroxyl groups at the surface of the oxide to form a monodentate carboxylate complex C(O)OAl was identified by FTIR. The degree of conversion of the acid to the salt at the interface was estimated to be 40% from the XPS analysis of PAA overlayers of varying thickness. An equivalent reaction was identified at the interface between AlOOH and a monolayer of strongly bonded plasma-polymerized acrylic acid (ppAAc) that remained after solvent washing. The resistance of the monolayer of ppAAc to solvent washing was attributed to the formation of interfacial carboxylate complexes with the AlOOH surface. © 1998 John Wiley & Sons, Ltd.

Metabolism of rosmarinic acid in rats

Abstract: The urine of rats administered rosmarinic acid (7) orally contained seven metabolites, which were identified as trans-caffeic acid 4-O-sulfate (1), trans-m-coumaric acid 3-O-sulfate (2), trans-ferulic acid 4-O-sulfate (3), trans-caffeic acid (4), m-hydroxyphenylpropionic acid (5), trans-m-coumaric acid (6), and unchanged rosmarinic acid (7) by spectroscopic and chemical data. The total cumulative amount of 1-7 excreted in the urine 48 h after the oral administration of rosmarinic acid was approximately 31.8% of the dose administered. On the other hand, the metabolites attributed to rosmarinic acid could not be found in the bile. Orally administered rosmarinic acid may thus be concluded to be excreted in the urine rather than in the bile, with cleavage of ester bonds, selective para-dehydroxylation, methylation, and sulfate-conjugation. Metabolites 2, 3, 5, and 6 were also detected in the plasma.

Voltammetric measurement of interfacial acid/base reactions

Abstract: The voltammetric response of a Ag(111) electrode coated with a mixed molecular film of 11-mercaptoundecanoic acid and 1-decanethiol is presented. The voltammetric current arises from the reversible, electric field-driven deprotonation of carboxylic acid groups. Voltammetric peak heights for interfacial protonation and deprotonation are a function of solution pH, obtaining maximum values near the pK1/2 (∼8.5) of the molecular film.

Short chain oligogalacturonides induce ethylene production and expression of the gene encoding aminocyclopropane 1-carboxylic acid oxidase in tomato plants.

Abstract: Oligogalacturonic acids (OGAs), derived from plant cell wall pectin, have been implicated in a number of signal transduction pathways involved in growth, development and defense responses of higher plants. This study investigates the size range of OGAs capable of inducing ethylene synthesis in tomato plants, and demonstrates that in contrast with many other effects, only short chain OGAs are active. Oligomers across a range of DP from 2-15 were separated and purified to homogeneity by QAE-Sephadex anion exchange chromatography using a novel elution system. The OGAs were applied to tomato plants and assayed for their ability to induce ethylene gas release and changes in steady state levels of mRNA encoding the ethylene forming enzyme aminocyclopropane-1-carboxylic acid oxidase (ACO). The study demonstrated that only OGAs in the size range of DP4-6 were active both in eliciting ACO expression and in the production of ethylene.

Hydroxamic and carboxylic acid derivatives having mmp and tnf inhibitory activity

Abstract: Compounds of formula (I) are useful as therapeutic agents, by virtue of having MMP and TNF inhibitory activity.