N-substituted Analogues Research Articles

Redox-active chalcogen-containing glutathione peroxidase mimetics and antioxidants inhibit tumour promoter-induced downregulation of gap junctional intercellular communication between WB-F344 liver epithelial cells.

Evidence is mounting supporting a role for oxidative stress in the mechanism of tumour promotion in response to agents such as 12-O-tetradecanoylphorbol-13-acetate (TPA). In this paper we demonstrate that glutathione peroxidase-mimetic xenobiotics, ebselen, ebselen-glutathione, alpha-(phenylselenenyl) acetophenone and bis-(4-aminophenyl) telluride (at concentrations between 10 microM and 50 microM) all demonstrate protective effects on TPA-induced downregulation of gap-junctional intercellular communication (GJIC) between WB-F344 rat liver epithelial cells. These effects were, in each case, diminished if the cells were depleted of their intracellular glutathione, and potentiated if glutathione was supplemented into the incubations. Additionally, bis-(4-aminophenyl) selenide and several N-substituted analogues, possessing potent antioxidant activity but being devoid of GSH peroxidase-mimetic activity, demonstrated remedial activity against TPA-induced downregulation of GJIC. Structure-activity relationships between these molecules showed a strong correlation to the oxidation potential of the selenium atom in the compound as the bis-(4-nitrophenyl)- and bis-(4-cyanophenyl)- derivatives, which possess poor antioxidant capacity and a half-wave redox potential well above +1.0 V, did not affect TPA-induced effects on GJIC. Examination of the mechanism of action of these redox-active compounds demonstrated correlations between their abilities to (i) prevent TPA-induced downregulation of GJIC, (ii) abolish the accumulation of intracellular oxidants and (iii) prevent the hyper-phosphorylation and internalization of connexin 43 in the cells. The active compounds were also able to prevent the rapid, TPA-induced translocation of protein kinase C to the particulate fraction of the cells, without affecting phorbol ester binding. These data support a synergistic role for oxidants and other TPA-dependent responses within the cell in mediating the downregulation of GJIC. Such oxidative metabolism may play a role in the control of translocation of protein kinase C from the cytosol to membranes in response to TPA within these cells. Despite the nature of the in vitro test system studied, the data also clarify the molecular basis for a potential anti-tumour promotive effect of antioxidants, based on established redox chemistries of several series of structurally-related molecules.

Diastereofacial selectivity in reduction of chiral tetramic acids

The reduction of (5S)-5-alkyl-2,4-dioxopyrrolidines, so-called tetramic acids, by NaBH 4 gives only partial diastereofacial selectivity in the case of the N-substituted analogues 9f-i, unlike the carbamate derivatives 9a-e which give the reduced cis-pyrrolidinones 10βa-e. Increasing the steric hindrance of either the N- or C-5-substituents enhances the re-face selectivity. On the other hand, reduction of the heterobicyclic compound 9n leads to a dramatic reversal of the stereoselectivity. Preliminary calculations show that the N-atom of the ring is slightly pyramidalized; the direction of hydride addition could be a consequence of this finding

Polypyrrole-based anion-exchange polymers

Two new 3-substituted cationic polymers and a precursor alkyl bromide substituted polymer are studied and compared in this paper to a previously reported N-substitued analogue. Compared to the N-substituted analogue, the new 3-substituted cationic polymers have simliar electrochemical and ion-exchange properties, lower redox potentials, enhanced conductivity at low potentials, and lower maximum conductivity. This may be due to polymer swelling in electrolyte solution and associated morphological changes. 33 refs., 8 figs., 4 tabs.

Effect of N-alkylation on the affinities of analogues of spiperone for dopamine D2 and serotonin 5-HT2 receptors.

Two series of N-substituted spiperone analogues were prepared and evaluated in vitro to measure their affinities for dopamine D2 and serotonin 5-HT2 receptors. Substitution of the amide nitrogen with an alkyl group of five carbon units or less resulted in analogues displaying a low selectivity for D2 compared to 5-HT2 receptors. However, a moderate improvement in selectivity for D2 receptors was observed with N-benzylspiperone. Substitution at either the ortho or para position of the benzyl group resulted in a further reduction in affinity for 5-HT2 receptors and improvement in the selectivity ratio. Examination of N-substituted analogues of spiperone may provide insights into the topography of the antagonist binding region of the 5-HT2 receptor. The results also suggest that an 18F-labeled analogue of N-(4-nitrobenzyl)spiperone (4p) may be a suitable tracer for studying D2 receptors with positron emission tomography since this compound displays a high selectivity for D2 receptors relative to that of spiperone and N-methylspiperone.

Contraluminal transport of organic cations in the proximal tubule of the rat kidney. II. Specificity: anilines, phenylalkylamines (catecholamines), heterocyclic compounds (pyridines, quinolines, acridines).

In order to study the quantitative structure/activity relationship of organic cation transport across the contraluminal side of the proximal renal tubule cell, the stopped-flow capillary microperfusion method was applied and the inhibitory potency (apparent Ki values) of different homologous series of substrates against N1-[3H]methylnicotinamide (NMeN+) transport was evaluated. Aniline and its ring- or N-substituted analogues as well as the aminonaphthalines do not interact with the contraluminal NMeN+ transporter except for the quaternary trimethylphenylammonium and pararosaniline, which bear a permanent positive charge, and for 1,8-bis-(dimethylamino)naphthaline, which forms an intramolecular hydrogen bond. If, however, one or more than one methylene group is interposed between the benzene ring and the amino group, the compounds interact with the contraluminal NMeN+ transporter in proportion to their hydrophobicity parameter, i.e. the octanol/water partition coefficient (log octanol). The catecholamines and other hydroxyl-substituted phenylethyl analogues also follow this rule. In addition, the N-heterocyclic pyridine, quinoline, isoquinoline and acridine analogues also interact with the contraluminal NMeN+ transporter, when their pKa values are higher than 5.0, and, an inverse correlation between pKa and log Ki,NMeN was observed. An exception to this rule are those hydroxy compounds of pyridine, quinoline and isoquinoline that show tautomerism. These compounds slightly inhibit NMeN+ transport despite low pKa values. The quaternary nitrogen compounds of aniline and the N-heterocyclic analogues, as far as tested, all interact with the contraluminal NMeN+ transporter in relation to their hydrophobicity. The data indicate that the contraluminal NMeN+ transporter interacts with N-compounds according to their hydrophobicity and/or according to their basicity (affinity to protons). The reason for deviation of the aniline analogues and the OH-tautomeric heterocyclic N-compounds from this behaviour is discussed.

N-Aralkylated derivatives of 1-aminobenzotriazole as isozyme-selective, mechanism-based inhibitors of guinea pig hepatic cytochrome P-450 dependent monooxygenase activity

The mechanism-based inactivation of hepatic cytochrome P-450 by the suicide inhibitor 1-aminobenzotriazole and two of its derivatives, N-benzyl-1-aminobenzotriazole and N-alpha-methylbenzyl-1-aminobenzotriazole, was investigated in microsomes from untreated, phenobarbital-induced, and beta-naphthoflavone-induced guinea pigs. Microsomal 7-ethoxyresorufin O-deethylase, 7-pentoxyresorufin O-dealkylase, and benzphetamine N-demethylase activities, and cytochrome P-450 content were determined following incubation with 1-aminobenzotriazole and its analogues. The loss of hepatic cytochrome P-450 content and monooxygenase activity was dependent on inhibitor concentration and required NADPH. N-Benzyl-1-aminobenzotriazole and N-alpha-methylbenzyl-1-aminobenzotriazole were more potent inhibitors of monooxygenase activity than the parent compound in microsomes from untreated and phenobarbital-induced guinea pigs. In microsomes from phenobarbital-induced guinea pigs, N-alpha-methylbenzyl-1-aminobenzotriazole (10 microM) was highly selective for the inactivation of the major cytochrome P-450 isozyme catalyzing 7-pentoxyresorufin O-dealkylation (the guinea pig ortholog of P-450IIB1) compared with those isozymes catalyzing 7-ethoxyresorufin O-deethylation or benzphetamine N-demethylation (88 +/- 3% loss of activity vs. 35 +/- 11 and 13 +/- 7%, respectively). N-Benzyl-1-aminobenzotriazole was also selective for the inactivation of 7-pentoxyresorufin O-dealkylase activity, but to a lesser degree (56 +/- 6 vs. 31 +/- 8 and 21 +/- 8%, respectively). In hepatic microsomes from untreated guinea pigs, the two N-substituted analogues were selective for the inhibition of 7-pentoxyresorufin O-dealkylation compared with benzphetamine N-demethylation, but not 7-ethoxyresorufin O-deethylation.(ABSTRACT TRUNCATED AT 250 WORDS)

REACTION OF (2-BENZOTHIAZOLYL)-SULFENAMIDES WITH P-CONTAINING REAGENTS

Abstract The title reaction was investigated to find that only substitution reaction on amino group occurred when (2-benzothiazolyl)sulfenamides 1 reacted with P(NR2,)3, whereas the treatment of 1 with (RO)P(NR2,)2, gave derivatives of phosphorodiarnidothioic acid together with 2-alkylthiobenzothiazole and its isomer in addition to substitution products, and no substitution products obtained when N-substituted analogues of 1 were treated similarly.

Synthesis and structural requirements of N-substituted norapomorphines for affinity and activity at dopamine D-1, D-2, and agonist receptor sites in rat brain

A series of N-substituted analogues of (R)-(-)-norapomorphine were synthesized to study the optimal structural requirements of the N-alkyl side chain to interact with D-1 and D-2 dopaminergic receptors as well as dopamine (DA) agonist binding sites. Evaluations included testing the affinity of these compounds for DA receptor sites in rat striatal tissue and assessing stereotypy as a behavioral index of dopaminergic activity. The electronic, steric, and lipophilic properties of the N-alkyl side chain were found to be related to affinity, D-2 selectivity, and dopaminergic activity. All 11 compounds evaluated had relatively low affinity at D-1 sites. Optimum D-2 and agonist-site affinity as well as agonist activity were exhibited by N-cyclopropylmethyl (7) greater than or equal to N-allyl (8) greater than or equal to N-propyl (4) or N-ethyl (3) substituted compounds. Branching of the N-alkyl side chain as in N-isopropyl (5) and N-isobutyl (6) markedly reduced the D-2 affinity and activity, presumably due to steric effects. The N-trifluoroethyl (10) and N-pentafluoropropyl (11) derivatives had low affinity for all their dopamine receptor sites and no agonistic activity; evidently, the highly electronegative F atoms decrease basicity of the N atom and therefore decrease the ability of the N atom to be cationic at physiological pH, a proposed requirement for high-affinity binding to DA receptors.

Synthesis of 1,2-benzisothiazoles by the oxidative ring contraction of 2-aryl- and 4-aryl-3,4-dihydro-2H-1,3-benzothiazines

Sodium periodate oxidation of 6,7-dimethoxy-2-aryl-3,4-dihydro-2H-1,3-benzothiazines (1a-e) gave 5,6-dimethoxy-1,2-benzisothiazole (4). The N-substituted analogues (6a-c) and the 4-aryl isomers of the latter (11a, b) furnished 2-substituted 1,2-benzisothiazolidine 1-oxides (7a-c) and their 3-aryl analogues (12a, b), respectively. The observed conversions of the 1,3-benzothiazines to 1,2-benzisothiazole and to 1,2-benzisothiazolidines are new ring transformation reactions of 3,4-dihydro-1,3-benzothiazines, representing a new route for the synthesis of 1,2-benzisothiazoles and their hydrogenated derivatives.

Liquid chromatographic and mass spectral analysis of N-substituted analogues of 3,4-methylenedioxyamphetamine.

The C1 to C3 N-alkyl, N,N-dimethyl, and N-hydroxy analogues of 3,4-methylenedioxyamphetamine (MDA) are identified by high performance liquid chromatographic (HPLC) and spectrometric techniques. The compounds are separated using reversed-phase procedures on C18 stationary phase with an acidic (pH 3) aqueous methanol mobile phase. The mass spectra of the compounds are distinctive and reference spectra are provided. The N-hydroxy derivative is unstable at high temperatures and decomposes to MDA and the oxime of 3,4-methylenedioxyphenyl-2-propanone.

Synthesis and nuclear magnetic resonance spectroscopic, mass spectroscopic, and plasma amine oxidase inhibitory properties of analogues of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine.

Seventeen analogues of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine were synthesized using three reaction pathways: condensation of phenols with 1-methyl-4-piperidone, reaction of Grignard reagents with 1-methyl-4-piperidone followed by dehydration of the product, and aminomethylation of olefins. The identity of the products of synthesis was established by nuclear magnetic resonance spectroscopy, mass spectroscopy, and elemental analysis. Thirteen analogues were shown to inhibit the oxidation of benzylamine by bovine plasma amine oxidase. Increasing the length of the aliphatic chain of N-substituted analogues resulted in increased inhibition. In 4-phenyl-substituted analogues, both the position and electronic character of the substituent group affected the degree of inhibition.

N-substituted 1,2,3,4,4a,5,6,10b-octahydrobenzo[f]quinolines and 3-phenylpiperidines: effects on central dopamine and sigma receptors.

N-Substituted analogues of trans-7- and trans-9-hydroxy-1,2,3,4,4a,5,6,10b-octahydrobenzo[f]quinoline (trans-7- and trans-9-OH-OHBQ) were tested for dopamine (DA) D2 receptor affinity by using in vitro [3H]spiperone and in vivo 5,6-di-n-Pr-ADTN binding assays. Potencies at central pre- (auto-) and postsynaptic DA receptors were determined by a biochemical and a behavioral method, respectively. Corresponding data were included for analogous, resolved 3-(3-hydroxyphenyl)piperidines and a few other substituted, racemic 3-phenylpiperidines. Beside the central dopaminergic effects of these compounds, previously reported sigma receptor affinity data [[3H]-(+)-3-(3-hydroxyphenyl)-N-n-propylpiperidine; [3H]-(+)-3-PPP] were also taken into account for a comparison of the structure-activity/affinity relationships of these compounds at these two receptor types. Larger N-substituents in both phenylpiperidines and OHBQs increase both pre- and postsynaptic dopaminergic activity. An n-propyl group gives high dopaminergic efficacy at both receptor sites (pre- and postsynaptic) in all series. However, even higher dopaminergic potency is observed for trans-7-OH-OHBQs and (S)-3-(3-hydroxyphenyl)piperidines with N-substituents larger than n-propyl. In contrast, trans-4-n-Bu-9-OH-OHBQ is inactive, and (R)-3-(3-hydroxyphenyl)-N-n-butylpiperidine is less active at central DA receptors than its corresponding n-propyl analogue. This implies interesting differences in N-substituent sensitivity for the different classes of compounds with respect to the direction of their respective N-substituents at the drug-receptor interaction. The stereochemical and steric demands for sigma receptor affinity are much less stringent. The general trend is that, up to a certain size, the more lipophilic the N-substituent, the higher the affinity for sigma receptor sites.

Pharmacological evaluation of the β-adrenoceptor agonist and thromboxane antagonist properties of N-substituted trimetoquinol analogues

The β 1− and β 2-adrenoceptor agonist and U46619 (a thromboxane A 2 agonist) antagonist properties of trimetoquinol (TMQ, I) and its optical isomers, and N-substituted TMQ analogues (methyl, II; 2-hydroxyethyl, III; cyclic sulfite N-2-chloroethyl, IV; 2-chloroethyl, V; benzyl, VI) were studied in guinea pig atria and trachea and rat aorta respectively. All compounds gave concentration-dependent responses inatria and trachea, and the rank order of β-adrenoceptor agonist potency was I>II>III>IV>V>VI. Whereas N-substitution reduced potency for β-agonism, the β 2/β 1-selectivity ratio was enhanced by increasing the size of the N-substituent. All analogues possessed equal or greater (up to 41-fold more) β 2-selectivity than I. Propanolol was a competitive antagonist of selected TMQ analogues in guinea pig trachea and atria, thus confirming the β-adrenoceptor actions of these drugs. The optical isomers of TMQ gave a rank order of agonist potency of S(−)-TMQ>R(+)-TMQ, and a β 2/β 1-selectivity equal to or greater than racemic-TMQ. Each TMQ analogue also blocked the contractile responses of U46619 in rat aorta in a competitive manner, and the rank order of inhibition of U46619-induced contraction in rat aorta was I>VI>II=III>IV>V. N-Benzyl TMQ (VI) possessed the greatest potency for U46619 blockade and β 2/β 1-selectivity ratio of the N-substituted analogues. The results show that varying the N-substituents on TMQ produces compounds which retain β 2-selectivity and give a different activity profile for β-adrenoceptor activation vs. endoperoxide/thromboxane A 2 antagonism.

Pyrimidinones. 3. N-substituted 6-phenylpyrimidinones and pyrimidinediones with diuretic/hypotensive and antiinflammatory activity.

In an extensive analysis of the antiviral and interferon-induction structure-activity relationship of 6-arylpyrimidinones we found that modifications at positions 1-4 of the pyrimidine ring resulted in a loss of activity. However, we uncovered interesting hypotensive and antiinflammatory activity with a series of N-substituted analogues, the results of which we report herein.

ChemInform Abstract: NOVEL ORALLY ACTIVE INHIBITORS OF PASSIVE CUTANEOUS ANAPHYLAXIS IN RATS: N‐(2‐(4‐PYRIDINYL)‐4‐PYRIMIDINYL) UREAS AND DIALKYL (((2‐(4‐PYRIDINYL)‐4‐PYRIMIDINYL)AMINO)METHYLENE)MALONATES

4-Chloro-2-(4-pyridinyl)pyrimidines were treated with alkylamines to afford the corresponding N-substituted amino derivatives. 4-Amino-2-(4-pyridinyl)pyrimidines and their N-substituted analogues were converted to amides, carbamates, aminomethylenemalonates, and ureas. Many of these compounds were found to have potential antiallergic activity as indicated by the rat passive cutaneous anaphylaxis screen. The most compounds were found in the last two series.

Discriminative stimulus effects of N-substituted analogs of phencyclidine in rhesus monkeys

In daily sessions of a two-lever, discrete-trial, food-reinforced procedure, rhesus monkeys were trained to discriminate between subcutaneous injections of ketamine (1.0 or 1.8 mg/kg) and control injections. In tests of stimulus generalization, cumulative doses of drugs were administered in single sessions and either control- or ketamine-appropriate responding produced food. Ketamine (1.8 and 3.2 mg/kg) and phencyclidine (0.32 mg/kg) produced an average of more than 90% ketamine-appropriate responding. In contrast, d-amphetamine, atropine, chlorpromazine, codeine, diazepam and quipazine, tested at doses up to and including those that markedly reduced response rates, produced exclusively control-appropriate responding. Dose-related ketamine-appropriate responding was produced by each of ten 1-phenylcyclohexylamines, the potencies of which varied with the length, electronegativity, and number of N-alkyl chains present. The most potent analog of phencyclidine, N-ethyl-1-phenylcyclohexylamine, was approximately equipotent with phencyclidine. These data are consistent with previous reports that the discriminative stimulus effects produced by phencyclidine are representative of a unique class of drugs, and that alkyl substitutions in the region of the piperidine ring alter the potency, but not the characteristic pharmacological activity, of the resulting analogs. The potencies of some of these analogs compared to phencyclidine in rhesus monkeys, however, differed from their relative potencies in rodents. Thus, there appear to be species differences in the role of the nitrogen pharmacophore of these compounds in producing phencyclidine-like behavioral effects.

Novel orally active inhibitors of passive cutaneous anaphylaxis in rats: N-[2-(4-pyridinyl)-4-pyrimidinyl]ureas and dialkyl [[[2-(4-pyridinyl)-4-pyrimidinyl]amino]methylene]malonates.

4-Chloro-2-(4-pyridinyl)pyrimidines were treated with alkylamines to afford the corresponding N-substituted amino derivatives. 4-Amino-2-(4-pyridinyl)pyrimidines and their N-substituted analogues were converted to amides, carbamates, aminomethylenemalonates, and ureas. Many of these compounds were found to have potential antiallergic activity as indicated by the rat passive cutaneous anaphylaxis screen. The most compounds were found in the last two series.

ChemInform Abstract: STUDIES ON ANTICOCCIDIAL AGENTS. 13. SYNTHESIS AND ANTICOCCIDIAL ACTIVITY OF NITROPYRIDINE‐2‐ AND ‐3‐SULFONAMIDES AND DERIVATIVES

AbstractVerschiedene Nitropyridinsulfonamide werden auf den im Formelschema angegebenen Wegen dargestellt, von denen drei N‐Oxidvertreter hergestellt werden.

Studies on anticoccidial agents. 13. Synthesis and anticoccidial activity of nitropyridine-2- and -3-sulfonamides and derivatives.

Eight nitropyridinesulfonamides and pyridinesulfonamide N-oxides as their bioisosteres were prepared and evaluated for anticoccidial activity. Of these compounds, 2-, 4- and 5-nitropyridine-3-sulfonamides and pyridine-2- and -3-sulfonamide N-oxides were found to be active against Eimeria tenella. Thus, the relative positions, ortho or meta, of the substituents in nitropyridine-3-sulfonamides and pyridinesulfonamide N-oxides are important for anticoccidial activity. N-Substituted analogues of 5-nitropyridine-3-sulfonamide were also prepared and optimal anticoccidial activity was attained with the sulfonamide and its lower N-alkyl derivatives. The mode of action of 5-nitropyridine-3-sulfonamide was examined and found to be active in the sporozoite and the first schizogony stages.

Reactions of asparaginase II of Saccharomyces cerevisiae. A mechanistic analysis of hydrolysis and hydroxylaminolysis.

Detailed kinetic analysis was performed on asparaginase II, a cell wall glycoprotein from Saccharomyces cerevisiae. The enzyme was highly active in the hydrolysis and hydroxylaminolysis reactions with D- and L-asparagine and with a variety of N-substituted analogues. The data from studies involving pH dependencey, substrate saturation, and product inhibition support the hypotheses that (a) the yeast asparaginase mechanism proceeds via an acyl enzyme intermediate; (b) an ionizable group on the enzyme, pK approximately 6.0, is involved in the acylation and deacylation reactions; and (c) yeast asparaginase II is a peptidoasparaginase.