Acetic Acid Moiety Research Articles

CYP2C8- and CYP3A-MediatedC-Demethylation of (3-{[(4-tert-Butylbenzyl)-(pyridine-3-sulfonyl)-amino]-methyl}-phenoxy)-acetic Acid (CP-533,536), an EP2 Receptor-Selective Prostaglandin E2 Agonist: Characterization of Metabolites by High-Resolution Liquid Chromatography-Tandem Mass Spectrometry and Liquid Chromatography/Mass Spectrometry-Nuclear Magnetic Resonance

CP-533,536, (3-{[(4-tert-butyl-benzyl)-(pyridine-3-sulfonyl)-amino]-methyl}-phenoxy)-acetic acid (1), an EP2 receptor-selective prostaglandin E2 agonist, is being developed to aid in the healing of bone fractures. To support the development of this program, in vitro metabolism of 1 was investigated in human liver microsomes and major recombinant human cytochrome P450 (P450) isoforms. 1 was metabolized in vitro by at least three recombinant human P450s: CYP3A4, CYP3A5, and CYP2C8. The turnover of 1 was NADPH-dependent and was completely inhibited by ketoconazole and quercetin in the CYP3A4/5 and CYP2C8 incubations, respectively. The major metabolic pathways were caused by oxidation of the tert-butyl moiety to form the omega-hydroxy metabolite (M4), oxidation of the pyridine moiety, and/or N-dealkylation of the methylphenoxy acetic acid moiety. The alcohol metabolite M4 was further oxidized to the corresponding carboxylic acid M3. In addition to these pathways, three unusual metabolites (M22, M23, and M26) resulting from C-demethylation of the tert-butyl group were identified using high-resolution liquid chromatography/tandem mass spectrometry and liquid chromatography/mass spectrometry/NMR. The C-demethylated metabolites were not detected on incubation of carboxylic acid metabolite M3 with either human liver microsomes or CYP3A/2C8 isoforms, suggesting that these metabolites were not derived from decarboxylation of M3. A possible mechanism for C-demethylation may involve the oxidation of M4 to form an aldehyde metabolite (M24), followed by P450-mediated deformylation, to give an unstable carbon-centered radical and formic acid. The carbon-centered radical intermediate then undergoes either oxygen rebound to form an alcohol metabolite M23 or hydrogen abstraction leading to an olefin metabolite M26.

Presynaptic (Type III) cells in mouse taste buds sense sour (acid) taste

Taste buds contain two types of cells that directly participate in taste transduction - receptor (Type II) cells and presynaptic (Type III) cells. Receptor cells respond to sweet, bitter and umami taste stimulation but until recently the identity of cells that respond directly to sour (acid) tastants has only been inferred from recordings in situ, from behavioural studies, and from immunostaining for putative sour transduction molecules. Using calcium imaging on single isolated taste cells and with biosensor cells to identify neurotransmitter release, we show that presynaptic (Type III) cells specifically respond to acid taste stimulation and release serotonin. By recording responses in cells isolated from taste buds and in taste cells in lingual slices to acetic acid titrated to different acid levels (pH), we also show that the active stimulus for acid taste is the membrane-permeant, uncharged acetic acid moiety (CH(3)COOH), not free protons (H(+)). That observation is consistent with the proximate stimulus for acid taste being intracellular acidification, not extracellular protons per se. These findings may also have implications for other sensory receptors that respond to acids, such as nociceptors.

Practical [14C]‐synthesis of molecules containing an acetic acid moiety: application to [14C]‐labeled DP1 antagonists

AbstractEfficient carbon‐14 labeling of four potent and selective DP1 antagonists is reported. The synthetic sequence began with α‐hydroxylation, reduction of an ester, followed by oxidative diol cleavage and aldehyde reduction. The resulting alcohol 4 was converted to a mesylate then nucleophilic substitution with [14C]‐sodium cyanide was performed to yield a nitrile, which upon basic hydrolysis provided the carbon‐14 labeled acid 1. Compound 2 was obtained from the same alcohol intermediate 4 and two diastereomeric compounds 6 and 7 were easily prepared from compound 2. Carbon‐14 synthesis of compounds 1, 2, 6 and 7 were achieved in good yields, high radiochemical purity (>99%) and with high specific activity (45 mCi/mmol). Copyright © 2006 John Wiley & Sons, Ltd.

Adduct formation in electrospray ionization. Part 1: Common acidic pharmaceuticals

This study focuses on pseudo-molecular ion formation in electrospray ionization mass spectrometry (ESI-MS) of six anti-inflammatory pharmaceuticals with similar functionality. The formation of particular pseudo-molecular ions depends on ion affinity and molecular structure of the analyte as well as the solvent/buffer conditions used. Six common anti-inflammatory agents are mixed 1:1 with six different acetonitrile/aqueous buffer solutions at varying concentrations. The analytes are ibuprofen, carprofen, naproxen, ketoprofen, flurbiprofen, and fenoprofen. The pK a and surface activity of the analytes and the pH, concentration, and type of the solvent system strongly affect the ions formed [1,2]. The additives are common liquid chromatography (LC) mobile phase modifiers. The spectral intensities of three major pseudo-molecular ions were measured by flow injection analysis ESI-MS. The ions studied correspond to the deprotonated molecular ion ([M - H] - ), a deprotonated dimer ion ([2M - H] - ), and a deprotonated dimer ion pair with sodium ([2M - 2H+Na] - ). These ions were chosen due to their high relative abundance in a majority of the spectra. The pKa of the analytes studied range from 4.1 to 4.4, due to their aromatic acetic acid moiety. The common carboxylic acid group facilitates ESI of the compounds in the negative ionization mode. The changes in molecular structure of these model compounds allows for a wide variety of solution interactions. Some analytes are effectively declustered under the set conditions creating an intense [M - H] - peak, whereas others prefer to form dimers or complexes with sodium.

1,2,4]Triazino[4,3-a]benzimidazole Acetic Acid Derivatives: A New Class of Selective Aldose Reductase Inhibitors

Acetic acid derivatives of [1,2,4]triazino[4,3-a]benzimidazole (TBI) were synthesized and tested in vitro and in vivo as a novel class of aldose reductase (ALR2) inhibitors. Compound 3, (10-benzyl[1,2,4]triazino[4,3-a]benzimidazol-3,4(10H)-dion-2-yl)acetic acid, displayed the highest inhibitory activity (IC(50) = 0.36 microM) and was found to be effective in preventing cataract development in severely galactosemic rats when administered as an eyedrop solution. All the compounds investigated were selective for ALR2, since none of them inhibited appreciably aldehyde reductase, sorbitol dehydrogenase, or glutathione reductase. The activity of 3 was lowered by inserting various substituents on the pendant phenyl ring, by shifting the acetic acid moiety from the 2 to the 3 position of the TBI nucleus, or by cleaving the TBI system to yield benzimidazolylidenehydrazines as open-chain analogues. A three-dimensional model of human ALR2 was built, taking into account the conformational changes induced by the binding of inhibitors such as zopolrestat, to simulate the docking of 3 into the enzyme active site. The theoretical binding mode of 3 was fully consistent with the structure-activity relationships in the TBI series and will guide the design of novel ALR2 inhibitors.

Benzimidazoles as NMDA glycine-site antagonists: study on the structural requirements in 2-position of the ligand.

A series of different substituted benzimidazole derivatives has been synthesized and evaluated for the ability to displace [3H]MDL-105,519 to rat cortical membranes. Two benzimidazole-2-carboxylic acids 9 b and 9 c, in this substitution pattern not yet described as glycine antagonists, showed IC50 values of 0.89 microM (9 b) and 38.0 microM (9 c). Replacement of the carboxylate function in 2-position by a sulfonic acid moiety appreciably increased solubility, but decreased the affinity giving evidence for the strong need of the carboxylate group within the ligand. Further structure-activity studies using benzimidazole-2-one derivatives with an acetic acid moiety adjacent to a ring nitrogen revealed new insights into the importance of amide functionalities within the heterocycle for the affinity of antagonist glycine-site ligands.

Seeded growth of amyloid-βfibrils is critical for amyloid-βneurotoxicity: Implications for the pathogenesis of Alzheimer's disease

Therapeutic intervention with aldose reductase inhibitors appears to be promising for major pathological conditions (i.e., long-term diabetic complications and inflammatory pathologies). So far, however, clinical candidates have failed due to adverse side-effects (spiroimides) or poor bioavailability (carboxylic acids). In this work, we succeeded in the bioisosteric replacement of an acetic acid moiety with that of 1-hydroxypyrazole. This new scaffold appears to have a superior physicochemical profile, while attaining inhibitory activity in the submicromolar range.

Improving the performance of an acid-labile 4-hydroxymethyl phenoxyacetic acid (HMP) linker on resin and SynPhase? grafted solid-supports

A replacement of the acetic acid moiety by valeric acid within the 4-hydroxymethylphenoxyacetic acid (HMP) linker (Sheppard RC, Williams BJ. Acid-labile resin linkage agents for use in solid phase peptide synthesis. Int. J. Peptide Protein Res. 1982; 20: 451-454) significantly improved its performance in terms of loading capacity, yield and purity of the final products. The results indicated the spacer-linker combination and type of solid supports are important factors for solid-phase synthesis.

Incorporation and characterization of abasic and phenyl residues in peptide nucleic acids

The N-(2-aminoethyl)glycine backbone unit of PNA has been derivatized with phenylacetic acid and acetic acid moieties to produce monomers for incorporation into PNAs. As expected, oligomers containing these residues form PNA·DNA double helices that are destabilized compared to the unsubstituted duplexes. However, unlike the analogous substitutions in DNA, these residues show very little sequence specificity.

Solution phase synthesis of potential DNA-binding molecules based on the PNA backbone

The N-(2-aminoethyl)glycine backbone unit of PNA has been derivatized with pyreneacetic acid and acetic acid moieties to produce monomers for the synthesis of potential polyintercalators. Short oligomers containing these residues have been assembled using solution phase coupling reactions.

Modeling the structure of the combining site of an antisweet taste ligand monoclonal antibody NC10.14.

We report the predicted combining site structure of the monoclonal antibody fragment, NC10.14, which is specific for the superpotent sweetener, N-(p-cyanophenyl-N'-(diphenylmethyl) guanidine acetic acid, using computer-aided molecular modeling and experimental methods, such as fluorescence spectroscopy and circular dichroism. This is the first computer-aided modeling study on a lambda-chain antibody fragment. We have also identified the amino acids that are involved in ligand binding. Aromatic residues, L:91(W), L:96(W), and H:100G(Y) are predicted to make van der Waals contacts with the p-cyanophenyl moiety of the ligand. Residue H:56(K) is predicted to provide a counterion for the acetic acid moiety, and H:50(E) provides the negatively charged potential for interaction with the positive guanidinium group. We also make a comparison of the binding site architecture of NC10.14 with that of a related monoclonal antibody fragment NC6.8.

Modeling the structure of the combining site of an antisweet taste ligand monoclonal antibody NC10.14

We report the predicted combining site structure of the monoclonal antibody fragment. NC10.14, which is specific for the superpotent sweetener, N-(p-cyanophenyl-N′-(diphenylmethyl)guanidine acetic acid, using computer-aided molecular modeling and experimental methods, such as fluorescence spectroscopy and circular dichroism. This is the first computer-aided modeling study on a λ-chain antibody fragment. We have also identified the amino acids that are involved in ligand binding. Aromatic residues. L:91(W), L:96(W), and H:100G(Y) are predicted to make van der Waals contacts with the p-cyanophenyl moiety of the ligand. Residue H:56(K) is predicted to provide a counterion for the acetic acid moiety, and H:50(E) provides the negatively charged potential for interaction with the positive guanidinium group. We also make a comparison of the binding site architecture of NC10.14 with that of a related monoclonal antibody fragment NC6.8. © 1996 John Wiley & Sons, Inc.

Specific bone-protective effects of metabolites/derivatives of tamoxifen and clomiphene in ovariectomized rats

In the ovariectomized (ovx) rat, the nonsteroidal antiestrogens, clomiphene (CLO) and tamoxifen (TAM), at dose levels that prevent development of osteopenia to a degree approaching that of 17β-estradiol are, in contrast to 17β-estradiol, only weakly uterotrophic. Metabolites of CLO and TAM might contribute differentially to these effects. Thus, we have evaluated bone protective and uterine effects in ovx rats of two such metabolites: 4-hydroxy CLO, produced by p-hydroxylation of CLO; and 4HTA, produced from TAM by stepwise replacement of its dimethylaminoethyl side chain with an acetic acid moiety, accompanied by p-hydroxylation. Also reported are effects of D4HTA, the dihydrodesethyl derivative of 4HTA previously characterized as a full estrogen mimetic in vitro. Administration of 4-hydroxy CLO (2.5 mg/kg subcutaneously) 5 days/week for 5 weeks to 3-month-old ovx rats resulted in complete prevention of bone loss and suppression of bone turnover to levels comparable to those of intact controls and to those of ovx animals similarly receiving 17β-estradiol (10 μg/kg). However, uterine weight in animals receiving 4-hydroxy CLO was 64% less than that in 17β-estradiol-treated animals. Although 4HTA (3.7 mg/kg s.c.) had a modest uterotrophic effect, it did not prevent bone loss associated with ovariectomy. In contrast, D4HTA (3.6 mg/kg s.c.) partially reduced bone turnover indicators and cancellous bone loss in a manner similar in many ways to that observed in TAM-treated ovx animals, but it had no uterotrophic effect. These results suggest that, although 4HTA does not contribute to the bone-protective effect of TAM, 4-hydroxy CLO might augment that of CLO.

Potent antiinflammatory 3-thiazole-4(5)-acetic acids of 1,2-benzisothiazole

A number of 1,2-benzisothiazole derivatives, having 2-thiazolyl-4(5)-acetic acid moiety attached to position-3 of 1,2-benzisothiazole nucleus, were prepared and evaluated as antiinflammatory agents. Some of these were found to possess excellent level of antiinflammatory activity in carrageenin-induced rat paw edema assay. A number of 1,2-benzisothiazole derivatives, having 2-thiazolyl-4(5)-acetic acid moiety attached to position-3 of 1,2-benzisothiazole nucleus were prepared and evaluated as potential antiinflammatory agents. Some of these were found to possess significant level of antiinflammatory activity

(−)-(R)-5,5-Dimethylmorpholinyl-2-acetic Acid Ethyl Ester Hydrochloride, C10H20NO3+.Cl−

One of the enantiomers of 5,5-dimethyl­morpholinyl-2-acetic acid is observed to be a GABAB receptor antagonist. The absolute configuration of the inactive enanti­omer is found to be the (R) configuration. The morpholine ring adopts a chair conformation with the acetic acid moiety in an equatorial position. In the crystal packing hydrogen bonds are observed between the ammonium group and the chloride ions.

Solution structures of luminescent chelates of europium (III) with 2,6-bis[ N,N-bis(carboxymethyl) aminomethyl]-4-benzoylphenol

2,6-Bis[ N,N-bis(carboxymethyl)aminomethyl]-4-benzoylphenol forms with europium(III) three structurally different luminescent chelates in aqueous sample solutions. Only the chelate with a dimeric structure, where two Eu(III) cations are encapsulated into the chelating cage consisting of two deprotonated phenolic hydroxyl groups and four 2,2′-(methylenenitrilo)bis(acetic acid) moieties having strong interactions with the deprotonated hydroxyl groups, is capable of initiating the sensitized 5D 0 → 7F j transitions of Eu (III) with an exceptionally long lifetime of 0.97 ms.

3,4-Diphenylpyrrole-2,5-dicarboxylic Acid Acetic Acid Disolvate

3,4-Diphenylpyrrole-2,5-dicarboxylic acid crystallizes as the acetic acid disolvate, C18H13NO4.2CH3CO2H, and exhibits extensive hydrogen bonding involving the carboxylic acid functional groups, the amine group and the acetic acid moieties. The phenyl rings were found to lie at an angle of nearly 50° with respect to the planar pyrrole ring.

Temporary Sulfur Connection in an Intramolecular SN2-Reaction. A Stereocontrolled Synthesis of (±)-Kainic Acid

Homolytic isomerization of isocyanide 7 affords 2β-t-butoxycarbonyl-3β-(t9-butyldimethylsilyloxy)-4α-isopropenyl-5-ethylthio-4H-2,3-dihydropyrrole (8). The conversion of key intermediate 8 into (±)-kainic acid (3) involves, inter alia, temporary sulfur connection of an acetic acid moiety to the chiral isopropylene anchor, followed by its regio- and stereospecific intramolecular bonding to the pyrrolidine backbone. The acetic acid moiety is eventually disconnected from its anchor with concomitant regeneration of the isopropylene group by a new samarium(II) iodide-mediated tandem reductive elimination.

Stereoselective Synthesis of (±)-α-Kainic Acid Using Free Radical Key Reactions

Thiol-mediated free radical isomerization of a deliberately substituted but-3-enyl isocyanide 12a, and n-Bu(3)SnH/AIBN-mediated free radical cyclization of a deliberately substituted but-3-enyl isothiocyanate 22, afforded, respectively, the (ethylthio)pyrroline 13a and the thiopyroglutamates 5 and 23. Reduction, protection, and deprotection of these heterocyclic compounds afforded proline derivatives 6 and 25 which contain all the structural elements of alpha-kainic acid (1) except the C-2 acetic acid moiety. These intermediates were stereospecifically converted into (+/-)-alpha-kainic acid using a new method of temporary sulfur connection. Accordingly, CH(2)CO(2)Me is linked to the chiral isopropenyl anchor and then intramolecularly connected to the pyrrolidine ring and eventually disconnected from its anchor by a sequential reductive double elimination process in which the isopropenyl double bond is restored.

Self-assembled heterodinuclear europium(III)–lanthanide(III) chelates of 2,6-bis[N,N-bis(carboxymethyl)aminomethyl]-4-benzoylphenol and their radiative5D0→7Fjtransitions of EuIII

A photochemical study has been conducted (i) to shed light on the intramolecular T1-relaxation pathways of 2,6-bis[N,N-bis(carboxymethyl)aminomethyl]-4-benzoylphenol (L) to initiate the radiative 5D0→7Fj transitions of EuIII and (ii) to elucidate the effects of different aqua-bridged non-radiative LnIII cations on these EuIII-specific radiative transitions, using the self-assembled heterodinuclear LEuIIILnIIIL chelates where the EuIII and LnIII cations are coordinated to each other by the aqua bridge inside the chelating cage consisting of two deprotonated phenolic hydroxy groups and four partially deprotonated 2,2′-(methylenenitrilo)bis(acetic acid) moieties. Depending on its non-radiative LnIII cation, the encapsulated aqua-bridged EuIIILnIII pair may be (i) as in the case of LnIII= ErIII, HoIII, NdIII or PrIII, a double-nuclear triplet relaxation centre where the T1-relaxation occurs mainly to the excited state of LnIII, (ii) as in the case of LnIII= GdIII or YIII, a single-nuclear triplet relaxation centre where the T1-relaxation is energetically capable of occurring only to the excited state 5Dj of EuIII, so that the resulting radiative 5D0→7Fj transitions of EuIII are to some extent enhanced and, finally, (iii) as in the case of LnIII= YbIII, a single-nuclear triplet relaxation centre where the T1-relaxation occurs only to the excited state of EuIII, so that the resulting excited state 5D0 of EuIII is strongly destabilized by the aqua-bridged YbIII: however, our present experimental results do not exclude the possibility of the aqua-bridged YbIII cation occurring also as the T1-relaxation centre despite the large energy gap ΔE(T1–2F7/2)= 11 560 cm–1.