Methylation Of Group Research Articles

Quantum chemical studies of pyrimidin-4-ones Part 6. On peculiarities of the reactions with nitrating agents of some carboxylic acids of the thieno[2,3-d]pyrimidin-4-one series and their esters

Quantum chemical calculations of the energies, electronic structures, and molecular geometries of 5-methyl-, 2,5-dimethyl-, 3,5-dimethyl-, and 2,3,5-trimethyl-4-oxothieno[2,3-d]pyrimidine-6-carboxylic acids; 5-methyland 3,5-dimethyl-2,4-dioxothieno[2,3-d]pyrimidine6-carboxylic acids; 5-methyland 3,5-dimethyl-4-oxo-2-thiothieno[2,3-d]pyrimidine-6-carboxylic acids; and their ethyl esters were performed in terms of the HF and DFT (B3LYP) approximations in the 3-21G basis set. The reactions routes with nitrating agents were examined, and the factors governing the direction of the reactions, the probability of their occurrence were determined. Selective ipso-substitution of the 5-methyl group by the nitro group at the C(5) atom of the thiophene fragment is hindered for all compounds studied. The reasons for the unfavorable ipso-substitution were discussed taking into account effects of solvents and substituents in positions 2, 3, and 6 of 6-carboxyand 6-ethoxycarbonyl-substituted thieno[2,3-d]pyrimidin-4-ones.

Synthesis and biological evaluation of novel orally available 1-phenyl-6-aminouracils containing dimethyldihydrobenzofuranol structure for the treatment of allergic skin diseases.

We have designed and efficiently synthesized novel 1-phenyl-6-aminouracils by replacing the chroman moiety in CX-659S, a nonsteroidal dermatologic candidate, with dimethyldihydrobenzofuranol to cancel CX-659S asymmetric center. Medicinal chemistry effort culminated in the discovery of 13d bearing a 3-methyl group at the 1-phenyl group as a promising compound. Compound 13d, having good in vitro ADME profile and moderate oral bioavailability in mice, showed potent anti-inflammatory activity against hapten-induced contact hypersensitivity reaction in mice following topical and oral administration. The effects of 13d were equipotent to that of tacrolimus or prednisolone. In addition, compound 13d, having potent hydroxyl radical-scavenging activity, showed more potent suppressive effect on substance P-induced pruritus in mice than oxatomide.

Rubipodanin A, the First Natural N-Desmonomethyl Rubiaceae-Type Cyclopeptide from Rubia podantha, Indicating an Important Role of the N9-Methyl Group in the Conformation and Bioactivity.

One new cyclic hexapeptide named rubipodanin A (1), which is the first identified natural N-desmonomethyl Rubiaceae-type cyclopeptide, together with six known Rubiaceae-type cyclopeptides (2–7) were obtained using the TLC cyclopeptide protosite detection method with ninhydrin from the roots and rhizomes of Rubia podantha. The cyclopeptide structures were elucidated by extensive spectroscopic analysis, including 1D-NMR, 2D-NMR, IR, UV and MS. The solution conformation and biological activities of 1 and RA-V (4) were evaluated, and the results demonstrated that the N 9-methyl group plays a vital role in the maintenance of the conformation and bioactivity.

Metabolic profile of mephedrone: Identification of nor-mephedrone conjugates with dicarboxylic acids as a new type of xenobiotic phase II metabolites.

Metabolic profile of mephedrone (4-methylmethcathinone, 4-MMC), a frequently abused recreational drug, was determined in rats in vivo. The urine of rats dosed with a subcutaneous bolus dose of 20mg 4-MMC/kg was analysed by LC/MS. Ten phase I and five phase II metabolites were identified by comparison of their retention times and MS(2) spectra with those of authentic reference standards and/or with the MS(2) spectra of previously identified metabolites. The main metabolic pathway was N-demethylation leading to normephedrone (4-methylcathinone, 4-MC) which was further conjugated with succinic, glutaric and adipic acid. Other phase I metabolic pathways included oxidation of the 4-methyl group, carbonyl reduction leading to dihydro-metabolites and ω-oxidation at the position 3'. Five of the metabolites detected, namely, 4-carboxynormephedrone (4-carboxycathinone, 4-CC), 4-carboxydihydronormephedrone (4-carboxynorephedrine, 4-CNE), hydroxytolyldihydro-normephedrone (4-hydroxymethylnorephedrine, 4-OH-MNE) and conjugates of 4-MC with glutaric and adipic acid, have not been reported as yet. The last two conjugates represent a novel, hitherto unexploited, type of phase II metabolites in mammals together with an analogous succinic acid conjugate of 4-MC identified by Pozo et al. (2015). These conjugates might be potentially of great importance in the metabolism of other psychoactive amines.

Design, synthesis, and pharmacological evaluation of JDTic analogs to examine the significance of the 3- and 4-methyl substituents

The design and discovery of JDTic as a potent and selective kappa opioid receptor antagonist used the N-substituted trans-3,4-dimethyl-4-(3-hydroxyphenyl)piperidine pharmacophore as the lead structure. In order to determine if the 3-methyl or 4-methyl groups were necessary in JDTic and JDTic analogs for antagonistic activity, compounds 4a–c, and 4d–f which have either the 3-methyl or both the 3- and 4-methyl groups removed, respectively, from JDTic and analogs were synthesized and evaluated for their in vitro opioid receptor antagonist activities using a [35S]GTPγS binding assay. Other ADME properties were also assessed for selected compounds. These studies demonstrated that neither the 3-methyl or 3,4-dimethyl groups present in JDTic and analogs are required to produce potent and selective κ opioid receptor antagonists.

Guanine nucleobase adducts formed by a monofunctional complex: [Pt(N-(6-methyl-2-picolyl)-N-(2-picolyl)amine)Cl]Cl

Monofunctional Pt(II) complexes bind to G residues in DNA and, if the carrier ligands are bulky, cause DNA structural distortions that lead to anticancer activity. We assessed the steric effects of the tridentate carrier ligand, N(H)6-Medpa (N-(6-methyl-2-picolyl)-N-(2-picolyl)amine), bearing a 6-methyl group and a 6′-proton projecting toward the nucleobase in Pt(N(H)6-Medpa)G adducts (G=9-ethylguanine, 3′-GMP, 5′-GMP, 5′-GTP). Pt(N(H)6-Medpa)G adducts form syn and anti rotamers with the guanine O6 and the central N–H of N(H)6-Medpa on the same or opposite side of the coordination plane, respectively. Pt(N(H)6-Medpa)G adducts have some properties (ease of rotamer interchange and extent of conversion to bis adducts, Pt(N(H)6-Medpa)G2) intermediate to properties reported for analogs having a tridentate ligand with zero or two methyl groups. However, in comparison, the syn rotamer of Pt(N(H)6-Medpa)G adducts has an unexpectedly high abundance. This result is attributable to guanine base canting, such that the 6-membered guanine ring is positioned away from the bulky 6-Me group. This canting both relieves electrostatic repulsion between the partially positive H6′ and the guanine H8 protons and creates a favorable electrostatic attraction between the H6′ proton and the partially negative guanine O6. This combined information provides insight useful for designing monofunctional anticancer agents.

Structure-activity correlations for three pyrido[2,3-d]pyrimidine antifolates binding to human and Pneumocystis carinii dihydrofolate reductase.

To further define the interactions that enhance the selectivity of binding and to directly compare the binding of the most potent analogue {N(6)-methyl-N(6)-(3,4,5-trifluorophenyl)pyrido[2,3-d]pyrimidine-2,4,6-triamine; compound 26} in the series of bicyclic pyrido[2,3-d]pyrimidine analogues of piritrexim (PTX) with native human (h), Pneumocystis carinii (pc) and Pneumocystis jirovecii (pj) dihydrofolate reductase (DHFR) enzymes, the crystal structures of hDHFR complexed with N(6)-methyl-N(6)-(4-isopropylphenyl)pyrido[2,3-d]pyrimidine-2,4,6-triamine (compound 22), of hDHFR complexed with compound 26 and of pcDHFR complexed with N(6)-methyl-N(6)-1-naphthylpyrido[2,3-d]pyrimidine-2,4,6-triamine (compound 24) are reported as ternary complexes with NADPH. This series of bicyclic pyrido[2,3-d]pyrimidines were designed in which there was a transposition of the 5-methyl group of PTX to the N9 position of the pyrido[2,3-d]pyrimidine. It was hypothesized that the N9-methyl group would preferentially interact with Ile123 of pcDHFR (and Ile123 of pjDHFR), but not with the shorter Val115 in hDHFR. Structure-activity data for this series of antifolates revealed that a trifluoro derivative (26) was the most selective against pjDHFR compared with mammalian DHFR (h/pj = 35.7). Structural data for the hDHFR-26 complex revealed that 26 binds in a different conformation from that observed in the pcDHFR-26 complex. In the hDHFR-26 complex the trifluorophenyl ring of 26 occupies a position near the cofactor-binding site, with close intermolecular contacts with Asp21, Ser59 and Ile60, whereas this ring in the pcDHFR-26 complex is positioned away from the cofactor site and near Ile65, with weaker contacts with Ile65, Phe69 and Ile123. Comparison of the intermolecular contacts between the N9-methyl group with Val115/Ile123 validates the hypothesis that the N9-methyl substituent preferentially interacts with Ile123 compared with Val115 of hDHFR, as the weaker contact with Val115 in the hDHFR structure is consistent with its weaker binding affinity compared with pcDHFR. The results for the structures of hDHFR-22 and pcDHFR-24 show that their inhibitor-binding orientation is similar to that observed in pcDHFR-26 and the pcDHFR variant (F69N) reported previously. The naphthyl moiety of 24 makes several intermolecular contacts with the active-site residues in pcDHFR that help to stabilize the binding, resulting in a more potent inhibitor.

On the stereoselectivities of some hindered Diels–Alder reactions

The cis-fused lactones were the major products isolated from Diels–Alder reactions of (2E,4E)-2,4-dimethylhexa-2,4-dienyl methyl fumarate and maleate and from the cyclisation of the all (E)-2,4,6,8-tetramethyldeca-2,4,6,8-tetraenyl methyl fumarate in contrast to the Diels–Alder reactions of analogous substrates that lack the dienyl 2-methyl group. All of these Diels–Alder reactions led to the introduction of a methyl bearing quaternary centre. An intramolecular Diels–Alder reaction of a 3-(5,7-dimethylnona-5,7-dienoyl)pyrrolinone also gave mainly the endo-product, in this case with two adjacent quaternary centres.

Intermolecular 'cross-torque': the N4-cytosine propargyl residue is rotated to the 'CH'-edge as a result of Watson-Crick interaction

Propargyl groups are attractive functional groups for labeling purposes, as they allow CuAAC-mediated bioconjugation. Their size minimally exceeds that of a methyl group, the latter being frequent in natural nucleotide modifications. To understand under which circumstances propargyl-containing oligodeoxynucleotides preserve base pairing, we focused on the exocyclic amine of cytidine. Residues attached to the exocyclic N4 may orient away from or toward the Watson–Crick face, ensuing dramatic alteration of base pairing properties. ROESY-NMR experiments suggest a uniform orientation toward the Watson–Crick face of N4-propargyl residues in derivatives of both deoxycytidine and 5-methyl-deoxycytidine. In oligodeoxynucleotides, however, UV-melting indicated that N4-propargyl-deoxycytidine undergoes standard base pairing. This implies a rotation of the propargyl moiety toward the ‘CH’-edge as a result of base pairing on the Watson–Crick face. In oligonucleotides containing the corresponding 5-methyl-deoxycytidine derivative, dramatically reduced melting temperatures indicate impaired Watson–Crick base pairing. This was attributed to a steric clash of the propargyl moiety with the 5-methyl group, which prevents back rotation to the ‘CH’-edge, consequently preventing Watson–Crick geometry. Our results emphasize the tendency of an opposing nucleic acid strand to mechanically rotate single N4-substituents to make way for Watson–Crick base pairing, providing no steric hindrance is present on the ‘CH’-edge.

Synthesis of 3,8-dichloro-6-ethyl-1,2,5,7-tetramethyl-BODIPY from an asymmetric dipyrroketone and reactivity studies at the 3,5,8-positions.

The asymmetric BODIPY 1 a (BODIPY=4,4-difluoro-4-bora-3a,4a-diaza-s-indacene), containing two chloro substituents at the 3,8-positions and a reactive 5-methyl group, was synthesized from the asymmetric dipyrroketone 3, which was readily obtained from available pyrrole 2 a. The reactivity of 3,8-dichloro-6-ethyl-1,2,5,7-tetramethyl-BODIPY 1 a was investigated by using four types of reactions. This versatile BODIPY undergoes regioselective Pd(0) -catalyzed Stille coupling reactions and/or regioselective nucleophilic addition/elimination reactions, first at the 8-chloro and then at the 3-chloro group, using a variety of organostannanes and N-, O-, and S-centered nucleophiles. On the other hand, the more reactive 5-methyl group undergoes regioselective Knoevenagel condensation with an aryl aldehyde to produce a monostyryl-BODIPY, and oxidation with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) gives the corresponding 5-formyl-BODIPY. Investigation of the reactivity of asymmetric BODIPY 1 a led to the preparation of a variety of functionalized BODIPYs with λmax of absorption and emission in the ranges 487-587 and 521-617 nm, respectively. The longest absorbing/emitting compound was the monostyryl-BODIPY 16, and the largest Stokes shift (49 nm) and fluorescence quantum yield (0.94) were measured for 5-thienyl-8-phenoxy-BODIPY 15. The structural properties (including 16 X-ray structures) of the new series of BODIPYs were investigated.

Amino equatorial effect of a six-membered ring amino acid on its peptide 310- and α-helices

Two diastereomeric six-membered ring α,α-disubstituted α-amino acids (1R,3R)- and (1S,3R)-1-amino-3-methylcyclohexanecarboxylic acids (Ac6c3M); side-chain restricted leucine analogs, were stereoselectively synthesized from (3R)-3-methylcyclohexanone by a Bucherer–Bergs or Strecker reaction. Two series of homo-chiral homopeptides Cbz-[(1R,3R)- and (1S,3R)-Ac6c3M]n-OMe, up to hexapeptides (n=6), were prepared, respectively, and the preferred conformations of cyclohexane rings of amino acid residues and the peptide-backbones were studied. In solution, these peptides formed helical structures, but the helical-screw control to one-handedness was not possible for the hexapeptide length. In the crystal state, all (1R,3R)-Ac6c3M residues formed cyclohexane chair form conformations with a 3-methyl substituent at equatorial orientation and an amino group at the axial position, whereas all (1S,3R)-Ac6c3M residues assumed cyclohexane chair forms with the 3-methyl and amino groups at equatorial orientations. The preferred peptide-backbone structure of (1R,3R)-Ac6c3M hexapeptide had (P) and (M) 310-helices, and that of (1S,3R)-Ac6c3M hexapeptide had (P) and (M) α-helices in the crystal state.

Antioxidant effects of coumarins include direct radical scavenging, metal chelation and inhibition of ROS-producing enzymes.

Coumarins represent a large group of 1,2-benzopyrone derivatives which have been identified in many natural sources and synthetized as well. Several studies have shown that their antioxidant capacity is not based only on direct scavenging of reactive oxygen and nitrogen species (RONS) but other mechanisms are also involved. These include: a) the chelation of transient metals iron and copper, which are known to catalyse the Fenton reaction; and b) the inhibition of RONS-producing enzymes (e.g. xanthine oxidase, myeloperoxidase and lipoxygenase), suggesting that mechanism(s) involved on cellular level are complex and synergistic. Moreover, many factors must be taken into account when analysing structure-antioxidant capacity relationships of coumarins due to different in vitro/in vivo methodological approaches. The structural features necessary for the direct RONS scavenging and metal chelation are apparently similar and the ideal structures are 6,7-dihydroxy- or 7,8-dihydroxycoumarins. However, the clinical outcome is unknown, because these coumarins are able to reduce copper and iron, and may thus paradoxically potentiate the Fenton chemistry. The similar structural features appear to be associated with inhibition of lipoxygenase, probably due to interference with iron in its active site. Contrarily, 6,7-dihydroxycoumarin seems to be the most active coumarin in the inhibition of xanthine oxidase while its derivative bearing the 4-methyl group or 7,8-dihydroxycoumarin are less active or inactive. In addition, coumarins may hinder the induction of inducible NO-synthase and cyclooxygenase- 2. Sparse data on inhibition of myeloperoxidase do not enable any clear conclusion, but some coumarins may block it.

De Novo Design of Potent and Selective Neuronal Nitric Oxide Synthase (nNOS) Inhibitors by a Fragment-Based Approach

Nitric oxide, a gaseous free radical molecule (NO) behaves, as a secondary messenger in various tissues. It is responsible for different physiological functions and pathological symptoms. Mammals contain three different nitric oxide synthase (NOS) isoforms: neuronal NOS (nNOS: in the brain, in peripheral nervous system and muscle tissues), inducible NOS (iNOS: in macrophage cells), endothelial NOS (eNOS: in endothelial cells). Under certain pathological conditions and/or after certain ages excessive NO produced in brain causes tissue damage and oxidative stress. It also reacts with other free radicals to create specific molecular modifications. The excessive production of NO, especially by nNOS (in brain) is implicated in various disease states such as neurodegeneration, stroke, migraine and Parkinsons, Alzheimers, and Huntingtons diseases. The active sites of three NOS isoforms show great similarity; therefore, designing of selective nNOS inhibitors is not an easy task. The computational results carried out with all of the docking tools clearly demonstrate that the selected scaffold is a potential candidate for further modifications and optimization for designing selective and potent nNOS inhibitors. Subtle differences in the conformations of amino acid sequences (e.g. ASP597 in nNOS) of the three isoforms in the active site region were the determining factors for the selectivity and the potency of the compounds. In this study several hundred compounds were screened in silico using the ZINCv12 lead library for prioritization of lead candidates. De novo design method was used rationally for the modifications of selected scaffold within a target-binding site in order to enhance its binding affinity and selectivity to nNOS enzyme. The potency and the selectivity of nNOS isoform were achieved by introducing 1-methyl amino group at the forth position of the imidazole moiety of the best inhibitor. The positively charged 1-methyl amino group makes three hydrogen bonds with the two-propionate groups of the heme cofactor, which does not occur in eNOS and iNOS. Removing of 1-methyl amino group from scaffold totally abolished both potency and selectivity for nNOS. Newly designed inhibitor 7 shows nNOS inhibition 23 and 17 fold better than both eNOS and iNOS, respectively.

Monoamine transporter and receptor interaction profiles of novel psychoactive substances: Para-halogenated amphetamines and pyrovalerone cathinones

The pharmacology of novel psychoactive substances is mostly unknown. We evaluated the transporter and receptor interaction profiles of a series of para-(4)-substituted amphetamines and pyrovalerone cathinones. We tested the potency of these compounds to inhibit the norepinephrine (NE), dopamine (DA), and serotonin (5-HT) transporters (NET, DAT, and SERT, respectively) using human embryonic kidney 293 cells that express the respective human transporters. We also tested the substance-induced efflux of NE, DA, and 5-HT from monoamine-loaded cells, binding affinities to monoamine receptors, and 5-HT2B receptor activation. Para-(4)-substituted amphetamines, including 4-methylmethcathinone (mephedrone), 4-ethylmethcathinone, 4-fluoroamphetamine, 4-fluoromethamphetamine, 4-fluoromethcatinone (flephedrone), and 4-bromomethcathinone, were relatively more serotonergic (lower DAT:SERT ratio) compared with their analogs amphetamine, methamphetamine, and methcathinone. The 4-methyl, 4-ethyl, and 4-bromo groups resulted in enhanced serotonergic properties compared with the 4-fluoro group. The para-substituted amphetamines released NE and DA. 4-Fluoramphetamine, 4-flouromethamphetamine, 4-methylmethcathinone, and 4-ethylmethcathinone also released 5-HT similarly to 3,4-methylenedioxymethamphetamine. The pyrovalerone cathinones 3,4-methylenedioxypyrovalerone, pyrovalerone, α-pyrrolidinovalerophenone, 3,4-methylenedioxy-α-pyrrolidinopropiophenone, and 3,4-methylenedioxy-α-pyrrolidinobutiophenone potently inhibited the NET and DAT but not the SERT. Naphyrone was the only pyrovalerone that also inhibited the SERT. The pyrovalerone cathinones did not release monoamines. Most of the para-substituted amphetamines exhibited affinity for the 5-HT2A receptor but no relevant activation of the 5-HT2B receptor. All the cathinones exhibited reduced trace amine-associated receptor 1 binding compared with the non-β-keto-amphetamines. In conclusion, para-substituted amphetamines exhibited enhanced direct and indirect serotonergic agonist properties and are likely associated with more MDMA-like effects. The pharmacological profile of the pyrovalerone cathinones predicts pronounced stimulant effects and high abuse liability.

Stacking interactions in RNA and DNA: Roll-slide energy hyperspace for ten unique dinucleotide steps.

Understanding dinucleotide sequence directed structures of nuleic acids and their variability from experimental observation remained ineffective due to unavailability of statistically meaningful data. We have attempted to understand this from energy scan along twist, roll, and slide degrees of freedom which are mostly dependent on dinucleotide sequence using ab initio density functional theory. We have carried out stacking energy analysis in these dinucleotide parameter phase space for all ten unique dinucleotide steps in DNA and RNA using DFT-D by ωB97X-D/6-31G(2d,2p), which appears to satisfactorily explain conformational preferences for AU/AU step in our recent study. We show that values of roll, slide, and twist of most of the dinucleotide sequences in crystal structures fall in the low energy region. The minimum energy regions with large twist values are associated with the roll and slide values of B-DNA, whereas, smaller twist values correspond to higher stability to RNA and A-DNA like conformations. Incorporation of solvent effect by CPCM method could explain the preference shown by some sequences to occur in B-DNA or A-DNA conformations. Conformational preference of BII sub-state in B-DNA is preferentially displayed mainly by pyrimidine-purine steps and partly by purine-purine steps. The purine-pyrimidine steps show largest effect of 5-methyl group of thymine in stacking energy and the introduction of solvent reduces this effect significantly. These predicted structures and variabilities can explain the effect of sequence on DNA and RNA functionality.

Benzimidazole-containing HCV NS5A inhibitors: Effect of 4-substituted pyrrolidines in balancing genotype 1a and 1b potency

The treatment of HCV with highly efficacious, well-tolerated, interferon-free regimens is a compelling clinical goal. Trials employing combinations of direct-acting antivirals that include NS5A inhibitors have shown significant promise in meeting this challenge. Herein, we describe our efforts to identify inhibitors of NS5A and report on the discovery of benzimidazole-containing analogs with subnanomolar potency against genotype 1a and 1b replicons. Our SAR exploration of 4-substituted pyrrolidines revealed that the subtle inclusion of a 4-methyl group could profoundly increase genotype 1a potency in multiple scaffold classes.

Mechanisms of the hydroxyl and superoxide anion radical scavenging activity and protective effect on lipid peroxidation of thymoquinone: a DFT study

The mechanism of thymoquinone (2-isopropyl-5-methyl-1,4-benzoquinone) for scavenging peroxide radicals was explicated in gas phase and in liquid phase (benzene, water) using density functional theory approach. The calculated bond dissociation enthalpy, ionization potential, and proton dissociation enthalpy revealed that the H-atoms at positions 2-isopropyl and 5-methyl groups can be readily abstracted. In fact, the 2-isopropyl C–H bond dissociation enthalpy is lower than the 5-methyl C–H dissociation enthalpy. Analysis of spin density distribution indicates that H-atom abstraction in 2-isopropyl site generates more stable radical. The plots of highest occupied molecular orbital of thymoquinone demonstrate that the whole molecule can be easily attacked by electrophilic agents like radicals. In this paper, we studied the interaction of thymoquinone with hydroxyl, hydroperoxyl, and superoxide anion radicals, using potential energy surface scans and natural bond orbital analysis. Calculated potential energy barriers for hydroxyl radical attack (~2.5 kJ/mol) revealed an instant scavenging by thymoquinone. Modeling of the reaction between thymoquinone and lipid peroxyl radical shows a barrier energy around 26.23 kJ/mol. .

5-Hydroxymethyl-2'-deoxyuridine residues in the thrombin binding aptamer: investigating anticoagulant activity by making a tiny chemical modification.

We report an investigation into analogues of the thrombin binding aptamer (TBA). Individual thymidines were replaced by the unusual residue 5-hydroxymethyl-2'-deoxyuridine (hmU). This differs from the canonical thymidine by a hydroxyl group on the 5-methyl group. NMR and CD data clearly indicate that all TBA derivatives retain the ability to fold into the "chair-like" quadruplex structure. The presence of the hmU residue does not significantly affect the thermal stability of the modified aptamers compared to the parent, except for analogue H9, which showed a marked increase in melting temperature. Although all TBA analogues showed decreased affinities to thrombin, H3, H7, and H9 proved to have improved anticoagulant activities. Our data open up the possibility to enhance TBA biological properties, simply by introducing small chemical modifications.

Discovery of 6-[5-(4-fluorophenyl)-3-methyl-pyrazol-4-yl]-benzoxazin-3-one derivatives as novel selective nonsteroidal mineralocorticoid receptor antagonists

In the course of our study on selective nonsteroidal mineralocorticoid receptor (MR) antagonists, a series of novel benzoxazine derivatives possessing an azole ring as the core scaffold was designed for the purpose of attenuating the partial agonistic activity of the previously reported dihydropyrrol-2-one derivatives. Screening of alternative azole rings identified 1,3-dimethyl pyrazole 6a as a lead compound with reduced partial agonistic activity. Subsequent replacement of the 1-methyl group of the pyrazole ring with larger lipophilic side chains or polar side chains targeting Arg817 and Gln776 increased MR binding activity while maintaining the agonistic response at the lower level. Among these compounds, 6-[1-(2,2-difluoro-3-hydroxypropyl)-5-(4-fluorophenyl)-3-methyl-1H-pyrazol-4-yl]-2H-1,4-benzoxazin-3(4H)-one (37a) showed highly potent in vitro activity, high selectivity versus other steroid hormone receptors, and good pharmacokinetic profiles. Oral administration of 37a in deoxycorticosterone acetate-salt hypertensive rats showed a significant blood pressure-lowering effect with no signs of antiandrogenic effects.

Alkaline Durable 2-Methyl-1-Vinylimidazolium-Based Anion Exchange Membranes Prepared by Radiation-Induced Grafting for Hydrazine Hydrate Fuel Cells

Introduction An anion exchange membrane (AEM) is one of the key materials for alkaline-type fuel cells (AEMFC), which have potential advantages against proton exchange membrane fuel cells (PEMFC). In the AEMFC, electrochemical reactions are more facile than in acidic medium, and non-precious metals such as nickel, cobalt and iron can replace platinum as the catalyst.1,2 Because of high temperature and highly basic fuel cell operating condition, it is desirable to develop alkaline durable AEMs. In recent years, we have developed imidazolium-type AEMs by radiation-induced grafting for AEMFCs, especially in direct hydrazine fuel cells and found that poly(1-vinylimidazolium (VIm))-grafted and copoly(VIm/styrene)-grafted AEMs (AEM1 and AEM2) shows moderate alkaline stability; the AEMs degraded via the initial β-elimination and following ring opening reactions of the imidazolium unit.3,4 Therefore, we synthesized the AEM based on a poly(2-methyl-1-vinylimidazolium (MVIm)) grafts by radiation-induced grafting to improve long-term stability by suppressing β-elimination and ring opening reactions. Experimental The ETFE films were irradiated with a 60Co γ-ray source (JAEA Takasaki, Gunma, Japan) at room temperature in argon atmosphere with an absorption dose of 50 kGy. The pre-irradiated ETFE films were immediately immersed into the argon-purged monomer solution consisting of 50 wt% MVIm or a mixture of MVIm/stylene (8 : 2 weight ratio) in 1,4-dioxane. The imidazole groups in the grafted-ETFE were N-alkylated using methyl iodide. The resultant AEMs (an iodide form) were immersed in 1 M NaHCO3 solution at 60°C for 24 h to convert into a HCO3 - form, followed by the ion-exchange reaction with OH- in 1 M KOH solution at room temperature for 16 h to givethe anion forms of the AEMs (AEM3 and AEM4), as shown in Scheme 1. The ionic conductivity was measured by two-point probe AC impedance spectroscopy at 100% relative humidity in N2-purged deionized water. The ion exchange capacity (IEC) was measured using standard back titration methods. Results and discussion The poly(MVIm)- and copoly(MVIm/styrene)-grafted ETFE films (precursors of AEM3 and AEM4) were prepared with grafting degrees of 36 and 55%, respectively. The copolymer-type AEM4 was synthesized for reduction of steric and electrostatic repulsions between adjacent imidazolium cations. The N-alkylation for AEM3 proceeds quantitatively. Thus, molar ratio of MVIm and stylene in AEM4 determined from the weight gain after N-alkylation given that the N-alkylation of the imidazole groups proceeded in a quantitative maner was estimated as 1.0 : 1.4. AEM3 and AEM4 with IECs of 0.99 and 0.93 mmol g-1 showed ionic conductivities of 55 and 53 mS cm-1 at 60°C, respectively.The alkaline stability of AEMs was evaluated by monitoring the change in conductivity of AEMs in 1 M KOH at 80°C. Figure 1 shows the normalized conductivities of the AEMs on the basis of the initial conductance as a function of immersion time. The homopolymer-type AEM1 and AEM3 showed similar profiles for conductivity decreases, indicating the donimant β-elimination at an initial stage for homopolymer-type imidazolium grafts in the AEMs due to the steric and electrostatic repulsions. Copolymer-type AEM3, which had no 2-methyl group on the imidazolium group, showed a slower degradation rate after the fast decrease at the initial stage. Furthermore, copolymer-type AEM4, which had 2-methyl group on the imidazolium group, showed slower decreases at the initial stage and kept excellent long-term stability with keeping maintenance factor of 22% (12 mS cm-1) after 600 h immersion. The above results strongly indicate that the introducition of methyl group at 2-position of imidazolium unit drastically enhances the long-term durability in alkaline solutions at elevated temperatures due to the resistance of nucleophilic ring opening reactions of the imidazolium cations. Accordingly, the 2-methylimidazolium units in copolymer grafts in AEMs are promising an anion exchange group for highly alkaline durable direct hydrazine fuel cells. Acknowledgement This work was supported by the Advanced Low Carbon Technology Research and Development Program (ALCA) from the Japan Science and Technology Agency (JST).