Novel cerebroprotective agents with central nervous system stimulating activity. 1. Synthesis and pharmacology of 1-amino-7-hydroxyindan derivatives.

To develop a novel cerebroprotective agent with central nervous system (CNS) stimulating activity, a series of 1-amino-7-hydroxyindan derivatives was synthesized, and their effects on the survival time of mice under hypoxic conditions were tested. CNS-stimulating activity was also evaluated by examining the promotional effect on the recovery from cerebral concussion induced coma in mice. Several compounds prolonged the survival time of mice in hypoxic conditions at a dose of 30 mg/kg (sc or ip) and 100 mg/kg (po). They also exhibited the promotional effects on recovery from coma at a dose of 100 mg/kg po. The three most potent compounds in both tests, 1-amino-7-hydroxy-6-(1-methylpropyl)indan, 1-amino-7-hydroxy-4, 6-dimethyl-2-phenylindan, and 1-amino-7-hydroxy-2,2,4,6-tetramethylindan were selected for further investigations. Structure-activity relationships were also discussed.     

1-(substituted benzyl)-3,4,5,6-tetrahydro-2(1H)-pyrimidones: a series with stimulant and depressant activities

A series of 1-(substituted benzyl)-3,4,5,6-tetrahydro-2(1H)-pyrimidones was synthesized primarily by catalytic hydrogenation of the corresponding 1-(substituted benzyl)-2(1H)-pyrimidone. The pharmacological evaluation of these compounds in mice revealed a unique profile that included evidence of CNS stimulation and depression within the series and in the same compounds. Some members of this series induced signs of only CNS stimulation, some compounds caused signs of only CNS depression and skeletal muscle relaxation, and some caused signs of both stimulation and depression in the same animal. This apparent dual activity was assessed further in mice with antidepressant tests based on tetrabenazine antagonism and with antianxiety/anticonvulsant tests on the antagonism of a number of convulsants. The 4-chloro-, 4-fluoro-, 4-bromo-, and 3,4-dichlorobenzyl compounds exhibited antidepressant and antianxiety activities in the same dose range. Among these four compounds, the 3,4-dichlorobenzyl compound possessed the lowest antitetrabenazine (17 mg/kg po) and antipentylenetetrazol (23 mg/kg po) ED50 values. The 4-fluoro compound antagonized tetrabenazine-, pentylenetetrazol-, and isoniazid-induced tonic convulsions in the same dose range (congruent to 50 mg/kg po).     

3,4-dihydro-2(1H)-quinolinone as a novel antidepressant drug: synthesis and pharmacology of 1-[3-[4-(3-chlorophenyl)-1-piperazinyl]propyl]-3,4- dihydro-5-methoxy-2(1H)-quinolinone and its derivatives

To develop a novel antidepressant drug with central nervous system-stimulating activity, we prepared a series of 1-[omega-(4-substituted phenyl-1-piperazinyl)alkyl]-3, 4-dihydro-2(1H)-quinolinone derivatives and examined their activities by their effects at 30 and 100 mg/kg po on the sleeping time of mice anesthetized with halothane and on the time required for recovery from coma induced in mice by cerebral concussion. We examined their binding affinities for sigma receptors by evaluating their ability to inhibit [(3)H]-1,3-di(o-tolyl)guanidine ([(3)H]DTG) binding to the rat whole brain membrane in comparison with three putative sigma receptor agonists: 1,3-di(o-tolyl)guanidine (DTG, 66), (+)-1,2,3,4,5,6-hexahydro-6,11-dimethyl-3-(2-propenyl)-2, 6-methano-3-benzazecin-8-ol (SKF10,047, 67), and (+)-1,2,3,4,5, 6-hexahydro-6,11-dimethyl-3-(3-methyl-2-butenyl)-2, 6-methano-3-benzazecin-8-ol (pentazocine, 68). Among the series of derivatives, 1-[3-[4-(3-chlorophenyl)-1-piperazinyl]propyl]-3, 4-dihydro-5-methoxy-2(1H)-quinolinone hydrochloride (34b) and its mesylate (34c), at a dose of 30 mg/kg po, reduced the sleeping time and the time for recovery from coma and they inhibited [(3)H]DTG binding for sigma receptors. The putative sigma receptor agonists reduced the sleeping time and the time for recovery from coma whereas two sigma receptor antagonists, alpha-(4-fluorophenyl)-4-(5-fluoro-2-pyrimidinyl)-1-piperazinebutanol hydrochloride (BMY14802, 69) and cis-9-[3-(3, 5-dimethyl-1-piperazinyl)propyl]carbazole dihydrochloride (rimcazole, 70), were inactive in the two tests. Preadministration of the putative sigma receptor antagonists 69 (3 mg/kg po) and 70 (30 mg/kg po) completely antagonized the actions of 34b and the sigma receptor agonists in the test for recovery from coma. These results suggested that 34b and 34c are sigma receptor agonists. Furthermore, a single administration of 1 and 10 mg/kg po 34b and 34c showed antidepressant-like activity by reducing the immobility time in the forced-swimming test with mice, while a tricyclic antidepressant, 10, 11-dihydro-N,N-dimethyl-5H-dibenz[b,f]azepine-5-propanamine hydrochloride (imipramine, 1) (10 and 30 mg/kg po), did not reduce the time after a single administration. 1 reduced the time after repeated administration of 30 mg/kg po once a day for 4 days. The structure-activity relationship of the series of compounds is also discussed.     

Synthesis and antiallergic activity of 11-(aminoalkylidene)-6,11-dihydrodibenz[b,e]oxepin derivatives.

A new series of 11-substituted 6,11-dihydrodibenz[b,e]oxepin-2-carboxylic acid derivatives was synthesized and demonstrated to be orally active antiallergic agents. These compounds are structurally related to 1 (KW-4994), which we had reported previously to be a new antiallergic agent. Most compounds synthesized exhibited potent inhibitory effects on 48-h homologous passive cutaneous anaphylaxis (PCA) in rats and on IgG1-mediated bronchoconstriction in guinea pigs. Additionally, compounds possessing a terminal carboxyl group at the 2-position of the dibenz[b,e]oxepin ring system exhibited inhibitory effects on specific [3H]pyrilamine binding to guinea pig cerebellum histamine H1 receptors, whereas these demonstrated negligible effects on specific [3H]QNB binding to rat striatum muscarinic acetylcholine M1 receptors. Structure-activity relationship studies revealed that the following key elements were required for enhanced antiallergic activities: (1) a 3-(dimethylamino)propylidene group as the side chain at the 11-position, (2) a terminal carboxyl moiety at the 2-position, and (3) a dibenzoxepin ring system. Among the compounds synthesized, (Z)-11-[3-(dimethylamino)propylidene]-6,11-dihydrodibenz [b,e]oxepin-2-acetic acid hydrochloride (16) was selected for further evaluation. It had an ED50 value of 0.049 mg/kg po in the PCA test in rats and an ID50 value of 0.030 mg/kg po in inhibiting anaphylactic bronchoconstriction in guinea pigs. Furthermore, it had a Ki value of 16 +/- 0.35 nM for the histamine H1 receptor, while it exhibited negligible CNS side effects up to a dose of 600 mg/kg po. Compound 16 is now under clinical evaluation as KW-4679.     

New bronchodilators. 1. 1,5-Substituted 1H-imidazo[4,5-c]quinolin-4(5H)-ones.

A series of novel xanthine-based tricyclic heterocycles in 1H-imidazo[4,5-c]quinolin-4(5H)-ones was designed, synthesized, and tested as potential active bronchodilators. Inhibition of the Schulz-Dale (SD) reaction-induced contraction in trachea and inhibition of antigen inhalation-induced bronchospasm in passively sensitized guinea pigs served as primary in vitro and in vivo assays, respectively. Simultaneous measurement of acute lethal toxicity (minimum lethal dose; MLD, po) in mice allowed determination of a safety margin. The bronchodilatory activity of these heterocycles was considerably varied with the nature of substituents at the 5-position. The most active substituents at the 2- and 5-positions and on the aromatic ring were found to be hydrogen, n-butyl, and hydrogen, respectively. There was a bulk tolerance for lipophilic substituents at the 1-position. 5-Butyl-substituted compounds appeared to be less toxic than theophylline on the basis of MLD data. Thus 5-butyl-1-methyl-1H-imidazo[4,5-c]quinolin-4(5H)-one (10) (IC50 value of the SD assay = 0.25 microM, MLD > 300 mg/kg) was selected for further studies. Compound 10 (KF15570) reduced bronchoconstriction produced by antigen (Konzett-R?ssler preparation in anesthetized guinea pigs, ED50 = 0.42 mg/kg, iv) more effectively than aminophylline (ethylenediamine salt of theophylline, ED50 = 7.8 mg/kg, iv) but had fewer side effects on the heart and CNS than theophylline. Compound 10 and its derivatives showed weak adenosine antagonism and phosphodiesterase (PDE) inhibition which could not account for their potent bronchodilation. Although their precise mechanism of action remains unclear, this series of novel tricyclic heterocycles represents a new class of bronchodilator.     

Acrylamide derivatives as antiallergic agents. 2. Synthesis and structure-activity relationships of N-[4-[4-(diphenylmethyl)-1-piperazinyl]butyl]-3-(3-pyridyl)acryl amides

A new series of 3-(3-pyridyl)acrylamides 16, 17, 19, and 26, and 5-(3-pyridyl)-2,4-pentadienamides 20-25 were prepared and evaluated for their antiallergic activity. Several of these compounds exhibited more potent inhibitory activities than the parent compound 1a [(E)-N-[4-[4-(diphenylmethyl)-1-piperazinyl]butyl]-3- (3-pyridyl)acrylamide] against the rat passive cutaneous anaphylaxis (PCA) reaction and the enzyme 5-lipoxygenase. Particularly, (E)-N-[4-[4-(diphenylmethyl)-1-piperazinyl]butyl]-3- (6-methyl-3-pyridyl)acrylamide (17p) showed an ED50 value of 3.3 mg/kg po in the rat PCA test, which was one-fifth of ketotifen and oxatomide. As compared with ketotifen and oxatomide, compound 17p (AL-3264) possessed a better balance of antiallergic properties due to inhibition of chemical mediator release, inhibition of 5-lipoxygenase, and antagonism of histamine.     

Organic disulfides and related substances. 38. Some disulfide and trisulfide sulfinate salts as antiradiation drugs.

The trisulfide disulfinate [Na32S(CH2)4S]2S (2) is an antiradiation drug which is atypical in having no nitrogen function. At low dose levels of 37.5 and 18.5 mg/kg intraperitoneally (ip), 2 protected respectively about 82 and 35% of lethally irradiated mice. By the oral route (po), 150 mg/kg of 2 protected about 73%, and 75 mg/kg protected about 20%. The LD50 either ip or po exceeded 900 mg/kg. Although a 2,3-diacetoxy analog 3 was inactive, cyclic disulfide and trisulfide sulfinate analogs showed promice. Among these, a sulfinate moiety is related to a di- or trisulfie moiety in the sense of 1,8 in a naphthyl system (4,5), 2,2' in a biphenyl system (6-9), and alpha,alpha' in an o-xylyl system (10,11). The 1,8-naphthyl disulfide sulfinate 4 was not tested biologically because a marked neighboring group effect of -SO2Na on -SS- caused rapid cyclization to the parent disulfide dioxide 14; the corresponding trisulfide 5 was more stable but only slightly protective. Other analogs lacking the coplanarity of 4 also were more stable. The biphenyl compounds 6 and 7 were quite active ip (e.g., 7 led to 90% survival at 4.6 mg/kg, with LD50 EQUALS 130 mg/kg, although protection with 6 and 7 at the doses given po was only fair). Dichloro counterparts 8 and 9 offered no advantages over 6 and 7. The xylylene compounds 10 and 11 were roughly comparable to each other by ip and op routes (e.g., given ip, 10 led to 93-100% survival at 75 mg/kg, with LD50 GREATER THAN 950 mg/kg; given po, 10 gave 100% survival at 60 mg/kg, with LD50 GREATER THAN 900 mg/kg). Compounds 7 and 11 join 2 as promising antiradiation drugs that lack the usual nitrogen function. The fact that sulfinate salts show activity, both ip and po, suggests that the -SO2Na moiety deserves more attention in medicinal chemistry. Hydration of sulfinate salts often made analytical characterization difficult. Confirmatory evidence for typical structures is given.     

Synthesis and antinociceptive activity of 1-[2-(pyridyl)ethyl] and 1-[2-(dihydropyridyl)ethyl] analogues of fentanyl.

The syntheses and antinociceptive activities of all three isomeric 1-[2-(pyridyl)ethyl]-4-(propionanilido)-piperidine isosteres (11a-c) of fentanyl (1) are described. The 2- (11a), 3- (11b) and 4-pyridyl (11c) isomers exhibited 10, 2 and 0.2 times the antinociceptive activity of fentanyl, respectively. The ED50 values for 11a, 11b, 11c and fentanyl in the rat 4% NaCl-induced writhing test were 0.00023, 0.00085, 0.0087 and 0.0021 mg/kg sc, respectively. The 3-pyridyl (11b) and 4-pyridyl (11c) compounds were further elaborated to the 6-phenyl-1,6-dihydropyridine (12), C-2 H, Me, n-Bu and Ph 1,2-dihydropyridine (13a-d) analogues having a phenoxycarbonyl substituent on the dihydropyridine ring nitrogen. The most active compound in this series was 1-(2-[3-(1-phenoxycarbonyl-6-phenyl-1,6-dihydropyridyl)ethyl ])-4- (propionanilido)piperidine (12), which provided a 58% inhibition of writhing at a dose of 0.4 mg/kg sc. 1-(2-[4-(1-phenoxycarbonyl-1,2-dihydropyridyl)ethyl])-4- (propionanilido)piperidine (13a) exhibited an ED50 of 1.3 mg/kg sc, indicating a decrease in antinociceptive activity of about a 100 fold relative to the parent 4-pyridyl compound (11c). The dihydropyridine analogues 12 and 13 exhibit substantial antinociceptive activity relative to meperidine (ED50 = 0.6 mg/kg sc). The muscular rigidity effect induced by the pyridine compounds (11a-c) at a dose of 4 mg/kg sc, was not illicited by the dihydropyridine analogues at the same dose, or at a high dose of 40 mg/kg sc (13a). Compounds 12 and 13 may therefore be useful lead compounds for the development of more useful 4-anilidopiperidines if the antinociceptive activity can be dissociated from the muscular rigidity effect.     

Synthesis of 2-substituted-7-heptyloxy-4,5-dihydro-[1,2,4]-triazolo[4,3-a]quinolin-1(2H)-ones with anticonvulsant activity

A series of 2-substituted-7-heptyloxy-4,5-dihydro-[1,2,4]triazolo[4,3-a]quinolin-1(2H)-ones was synthesized. The anticonvulsant effect and neurotoxicity of the compounds were calculated with maximal electroshock (MES) test, subcutaneous pentylenetetrazole (sc-PTZ), and rotarod tests with intraperitoneally injected mice. Among the synthesized compounds, 2-propionyl-7-heptyloxy-4,5-dihydro-[1,2,4]triazolo[4,3-a]quinoline-1(2H)-one 4b was the most active one and also had the lowest toxicity. In the anti-MES potency test, it showed median effective dose (ED(50)) of 8.2 mg/kg, median toxicity dose (TD(50)) of 318.3 mg/kg, and the protective index (PI) of 39.0 which is much greater than the PI of the reference drugs phenytoin and carbamazepine.     

The usefulness of a model of acute hypoxia for the testing of cerebroprotective drugs

The aim of this study was to find out whether the mouse in acute normobaric hypoxia (3.5% O2) may be appropriate as a screening model for testing cerebroprotective drugs. The survival time of the mice in hypoxia was used to determine drug effects. 39 agents with various pharmacological and toxicological properties were investigated. Cerebroprotective, centrally depressant and stimulating as well as cardiovascular drugs were included. Only 6 out of 16 cerebroprotective drugs used therapeutically prolonged the survival time of mice in acute hypoxia. However, a positive effect was demonstrable especially for those cerebroprotective drugs (extractum Ginkgo bilobae, meclofenoxate, naftidrofuryl, pentoxifylline and pyritinol), which are generally accepted to be active. On the other hand, 12 out of 23 drugs which are therapeutically used as cardiovascular drugs, central stimulants or depressants or have known toxicological effects also prolonged the survival time of mice in hypoxia. Thus, it became clear that the result of this hypoxia test may be influenced by various pharmacological actions. Especially drugs stimulating the cardiovascular system or depressing CNS activity could prolong the survival time of mice in hypoxia, whereas drugs with vasodilating effects could even shorten it. Opposite effects could superpose or neutralize each other. Therefore, the mouse in acute hypoxia seems to be of limited value as a screening model for testing cerebroprotective drugs.     

Synthesis and biological activity of N6-(p-sulfophenyl)alkyl and N6-sulfoalkyl derivatives of adenosine: water-soluble and peripherally selective adenosine agonists.

A series of N6-(p-sulfophenyl)alkyl and N6-sulfoalkyl derivatives of adenosine was synthesized, revealing that N6-(p-sulfophenyl)adenosine (10b) is a moderately potent (Ki vs [3H]PIA in rat cortical membranes was 74nM) and A1-selective (120-fold) adenosine agonist, of exceptional aqueous solubility of > 1.5 g/mL (approximately 3 M). Compound 10b was very potent in inhibiting synaptic potentials in gerbil hippocampal slices with an IC50 of 63 nM. At a dose of 0.1 mg/kg ip in rats, 10b inhibited lipolysis (a peripheral A1 effect) by 85% after 1 h. This in vivo effect was reversed using the peripherally selective A1-antagonist 1,3-dipropyl-8-[p-(carboxyethynyl)phenyl]xanthine (BW1433). The same dose of 10b in NIH Swiss mice (ip) was nearly inactive in locomotor depression, an effect that has been shown to be centrally mediated when elicited by lower doses of other potent adenosine agonists, such as N6-cyclohexyladenosine (CHA) (Nikodijevic et al. FEBS Lett. 1990, 261, 67). HPLC studies of biodistribution of a closely related and less potent homologue, N6-[4-(p-sulfophenyl)butyl]adenosine indicated that a 25 mg/kg ip dose in mice resulted in a plasma concentration after 30 min of 0.46 micrograms/mL and no detectable drug in the brain (detection limit < 0.1% of plasma level). Although 10b at doses > 0.1 mg/kg in mice depressed locomotor activity, this depression was unlike the effects of CHA and was reversible by BW1433. These data suggest that 10b is a potent adenosine agonist in vivo and shows poor CNS penetration.     

Novel antiinflammatory analgesics: 3-(2-/4-pyridylethyl)-benzoxazolinone and oxazolo[4,5-b]pyridin-2-one derivatives

Twenty-two new 3-[2-(2-and/or 4-pyridyl)ethyl]benzoxazolinone and oxazolo[4,5-b]pyridin-2-one derivatives have been synthesized by reacting 2- and/or 4-vinylpyridine and appropriate benzoxazolinones and oxazolo[4,5-b]pyridine-2-one. Their chemical structures have been proven by IR. 1H-NMR, 13C-NMR, mass spectroscopy, and elemental analysis. The analgesic activities of these compounds were investigated by a modified Koster's Test. Test results revealed that, at 100 mg/kg dose level, most of the compounds showed significant analgesic activities when compared to aspirin. Therefore the compounds were screened for their antiinflammatory activities using the carrageenan hind paw edema test. Compounds 1, 7, 10, 11, 12, 13, 15, 18, 20, 21 were found more active than indomethacine. In gastric ulceration studies gastrointestinal bleeding was not observed at 100 mg/kg dose level in compounds 1 and 2.     

6-substituted decahydroisoquinoline-3-carboxylic acids as potent and selective conformationally constrained NMDA receptor antagonists.

We have prepared a series of 6-substituted decahydroisoquinoline-3-carboxylic acids, and structurally similar analogs, as potential N-methyl-D-aspartate receptor antagonists. There is a large body of evidence to support the use of such compounds as cerebroprotective agents in a variety of acute and chronic neurodegenerative disorders, where some component of glutamate-mediated excitotoxicity may exist. The compounds prepared were evaluated in vitro in both receptor binding assays ([3H]CGS19755, [3H]AMPA, and [3H]kainic acid) and in a cortical wedge preparation (versus NMDA, AMPA, and kainic acid) to determine affinity, potency, and selectivity. The new amino acids were also evaluated in vivo for their ability to block NMDA-induced lethality in mice. We synthesized many of the possible diastereomers of the decahydroisoquinoline nucleus in order to examine the spatial and steric requirements for affinity at the NMDA receptor and activity as NMDA antagonists. From our structure-activity relationship we identified two potent and selective NMDA receptor antagonists, the phosphonate- and tetrazole-substituted amino acids 31a and 32a, respectively, that show good activity in animals following systemic administration. For example, 31a and 32a selectively displaced [3H]CGS19755 binding with IC50S of 55 +/- 14 and 856 +/- 136 nM, respectively, and selectively antagonized responses due to NMDA in a cortical wedge preparation with IC50S of 0.15 +/- 0.01 and 1.39 +/- 0.29 microM, respectively. And compounds 31a and 32a blocked NMDA-induced lethality in mice with minimum effective doses of 1.25 and 2.5 mg/kg (intraperitoneal), respectively. These novel amino acids are among some of the most potent NMDA antagonists described thus far, and are excellent candidates for development as neuroprotective agents for a number of CNS disorders.     

Structure-activity relationships of (arylalkyl)imidazole anticonvulsants: comparison of the (fluorenylalkyl)imidazoles with nafimidone and denzimol

A recently discovered and structurally distinct class of antiepileptic drugs is the (arylalkyl)imidazoles. Two independently discovered representatives of this class, denzimol (alpha-[4-(2-phenylethyl)phenyl]-1H-imidazole-1-ethanol) and nafimidone (2-(1H-imidazol-1-yl)-1-(2-naphthalenyl)ethanone), are undergoing clinical evaluation. Our structure-activity relationship (SAR) studies revealed that in addition to the naphthalenyl and phenethylphenyl aryl moieties of nafimidone and denzimol, respectively, fluorenyl, benzo[b]thienyl, and benzofuranyl aryl groups provided several highly active (arylalkyl)imidazole anticonvulsants. These structurally diverse aryl moieties, and comparable anticonvulsant activities, lend credence to the hypothesis that the pharmacophore of this class of anticonvulsants is the alkylimidazole portion of the molecule, with the lipophilic aryl portion enabling penetration of the blood-brain barrier. We focused our SAR studies on the (fluorenylalkyl)imidazole series. A representative compound from this series is 1-(9H-fluoren-2-yl)-2-(1H-imidazol-1-yl)ethanone. This agent was twice as potent as nafimidone in inhibiting maximal electroshock seizures in mice (po ED50's = 25 and 56 mg/kg, respectively) and considerably less toxic in the rat (po LD50's = 4550 and 504 mg/kg, respectively). The tertiary alcohol alpha-(9H-fluoren-2-yl)-alpha-methyl-1H-imidazole-1-ethanol was as potent as denzimol in mice (po ED50's = 10 and 12 mg/kg, respectively). This series of imidazole anticonvulsants was highly selective; while many compounds displayed potent antielectroshock activity, little or not activity was observed against pentylenetetrazole-induced clonic seizures or in the horizontal screen test for ataxia. All active compounds that we tested in this series, as well as denzimol and nafimidone, potentiated hexobarbital-induced sleeping time in mice, probably by imidazole-mediated inhibition of cytochrome P-450. The SAR's for the anticonvulsant activity and the sleeping time potentiation were similar. The propensity of these (arylalkyl)imidazole anticonvulsants to interact strongly with cytochrome P-450 and thereby impair the metabolism of other antiepileptic drugs may severely limit their clinical utility as anticonvulsants.     

Synthesis and pharmacology of a series of 3- and 4-(phosphonoalkyl)pyridine- and -piperidine-2-carboxylic acids. Potent N-methyl-D-aspartate receptor antagonists

We recently prepared a series of 3- and 4-(phosphonoalkyl)pyridine- and -piperidine-2-carboxylic acids as antagonists of neurotransmission at N-methyl-D-aspartate (NMDA) preferring receptors. NMDA antagonists may prove to be useful therapeutic agents, for instance, as anticonvulsants, in the treatment of neurodegenerative disorders such as Alzheimer's disease and in the prevention of neuronal damage that occurs during cerebral ischemia. The compounds prepared were evaluated for their ability to displace [3H]CPP binding (an assay shown to be selective for compounds that bind at the NMDA receptor) and for their ability to block NMDA-induced lethality in mice (an assay that is also specific for competitive and noncompetitive NMDA antagonists). Two of the compounds, cis-4-(phosphonomethyl)piperidine-2-carboxylic acid (11a) and cis-4-(3-phosphonoprop-1-yl)piperidine-2-carboxylic acid (11c) proved to be potent NMDA antagonists. 11a and 11c displaced [3H]CPP binding with IC50's of 95 and 120 nM, respectively, and both protected mice from NMDA-induced lethality, with MEDs (minimum effective dose, the dose at which three of the five animals tested survived) of 10 and 40 mg/kg ip, respectively. The rest of the compounds prepared were weakly active or inactive in these assays. The pattern of activity observed for this series parallels that observed for the acyclic series of omega-phosphono-alpha-amino acids, where AP5 and AP7 possessed NMDA antagonist activity while AP6 and AP8 were inactive. Reduction of conformational mobility by incorporation of the piperidine ring led to enhanced potency relative to the acyclic analogues.     

Synthesis of some thiazolo[3,2-b]-1,2,4-triazole-5(6H)-ones and their novel Michael addition products with anti-inflammatory activities.

In this study, 21 new compounds having 2-methyl-6-benzylidenethiazolo[3,2-b]-1,2,4-triazol-5(6H)-one (2-4) and 2-methyl-6-(alpha-aminobenzyl)thiazolo[3,2-b]-1,2,4-triazole-5-ol (2a-4g) structures were synthesized. The structures of the compounds were proved by spectral and elemental analysis. All of the compounds synthesized were tested for their anti-inflammatory actively and ulcerogenic potential in mice at 10, 20 and 40 mg/kg dose levels. Compound 4b showed higher anti-inflammatory activity than the analogue derivatives and indometacin (CAS 53-86-1), used as a reference drug, at 10 mg/kg dose level. Generally, the compounds were found to be more reliable than indometacin since they did not cause any reaction in the stomach.     

Synthesis of N-substituted 4,6-dioxo-imidazo[3,4-c] thiazoles and their analgesic activity in mice

A new series of N-substituted dioxo-imidazo[3,4-c]thiazoles have been prepared and evaluated for their analgesic activity. The structures of these new derivatives were confirmed by lR, 1H NMR and 13C NMR spectra, and by elemental analysis. When administered intraperitoneally to mice all derivatives were devoid of any toxic effect, even at the high dose of 800 mg kg(-1). In the phenylbenzoquinone-induced abdominal constriction test in mice, eight of the nine synthesized compounds exhibited significant antinociceptive properties with ED50 values (50% effective dose) ranging from 46.7 to 104.7 mg kg(-1) intraperitoneally. Further investigation demonstrated that analgesic activity of the most effective derivatives 5e and 5f partly involved opioidergic and/or noradrenergic pathways.     

Cationic antiprotozoal drugs. Trypanocidal activity of 2-(4'-formylphenyl)imidazo[1,2-a]pyridinium guanylhydrazones and related derivatives of quaternary heteroaromatic compounds

A series of quaternary 2-phenylimidazo[1,2-a]pyridinum salts has been prepared and evaluated for antiparasitic activity. Primary attention was focused on derivatives with amido, substituted hydrazone, and heterocyclic functionality at the para position of the phenyl substituent. Guanylhydrazones and N-substituted guanylhydrazones of the 4'-formyl-substituted compounds are very active against the blood state Trypanosoma rhodesiense in mice by subcutaneous or oral administration. The most potent compounds attain 100% survival for 30 days at doses of less than 1.0 mg/kg (sc) and greater than 5.0 mg/kg (po). Weaker activity is noted for certain other 4'-substituents such as carboxamidines and carboxamide oximes. Considerable variation in structure, including replacing of the imidazo [1,2-a]pyridinium ring by other cationic heterocyclic rings and insertion of linking groups between the heterocyclic ring and phenyl group, can be done, and a high level of activity is maintained. Relationships between these structural changes and biological activity are discussed.     

Design, synthesis and screening of quinoline-incorporated thiadiazole as a potential anticonvulsant

A series of quinoline-incorporated substituted thiadiazole were designed and synthesized using appropriate synthetic route keeping in view the structural requirement of pharmacophore and evaluated for anticonvulsant and CNS activities. After intraperitoneal injection to mice, some synthesized derivatives were examined in the maximal electroshock seizure (MES) and subcutaneous pentylenetetrazol (scPTZ)-induced seizure and neurotoxicity screens. Those found potent were also evaluated for behavioural impairment and depression activity. Among the compounds tested, 6d and 6e showed protection from seizures in both the animal models at dose level of 30 mg/kg while 7f showed protection against both models at 100 mg/kg dose level. These compounds exhibited lesser CNS depression and neurotoxicity compared with clinically effective drug.     

Synthesis, calcium-channel-blocking activity, and antihypertensive activity of 4-(diarylmethyl)-1-[3-(aryloxy)propyl]piperidines and structurally related compounds

A series of 4-(diarylmethyl)-1-[3-(aryloxy)propyl]piperidines and structurally related compounds were synthesized as calcium-channel blockers and antihypertensive agents. Compounds were evaluated for calcium-channel-blocking activity by determining their ability to antagonize calcium-induced contractions of isolated rabbit aortic strips. The most potent compounds were those with fluoro substituents in the 3- and/or 4-positions of both rings of the diphenylmethyl group. Bis(4-fluorophenyl)acetonitrile analogue 79 was similar in potency to bis(4-fluorophenyl)methyl compound 1. The methylene analogue of 1 (78) and derivatives of 1 that contained a hydroxyl (76), carbamoyl (80), amino (81), or acetamido (82) substituent on the methyl group were less potent. In most cases, substituents on the phenoxy ring, changes in the distance between the aryloxy group and the piperidine nitrogen, and the substitution of S, N(CH3), or CH2 for the oxygen atom of the aryloxy group had only a small to moderate effect on the potency. The best compounds in this series were more potent than verapamil, diltiazem, flunarizine, and lidoflazine, but were less potent than nifedipine. Compounds were evaluated for antihypertensive activity in spontaneously hypertensive rats (SHR) at an oral dose of 30 mg/kg. Of the 55 compounds tested, only nine produced a statistically significant (p less than 0.05) reduction in blood pressure greater than 20%; all of these compounds had fluoro substituents in both rings of the diphenylmethyl group. One of the most active compounds in the SHR at 30 mg/kg was 1-[4-[3-[4-[bis(3,4-difluorophenyl)methyl]-1- piperidinyl]propoxy]-3-methoxyphenyl]ethanone (63), which produced a 35% reduction in blood pressure and was similar in activity to nifedipine. At lower doses, however, 4-[bis(4-fluorophenyl)methyl]-1-[3-(4-chlorophenoxy)propyl]piperidine (93) was one of the most effective antihypertensive agents, producing reductions in blood pressure of 17 and 11% at oral doses of 10 and 3 mg/kg, respectively; 63 was inactive at 10 mg/kg.