Modulation of native GABA(A) receptor activity by triazolo 1,5-benzodiazepines.

In previous work our group described the synthesis and the activity on rat cerebellum granule cell GABAA receptors of new 1,5-benzodiazepine compounds. Here we are describing the synthesis of new triazolobenzodiazepines (mainly 1,5-benzodiazepine derivatives) and the evaluation of their biological activity in terms of effects on those GABAA receptors. Their effects were compared to those of 1,4-benzodiazepine agonists and some known 1,5-benzodiazepines. The activities were evaluated for the two GABAA receptor populations present in cerebellar granule cells, one mediating phasic inhibition and the other one mediating tonic inhibition. Some of the compounds displayed a profile of agonist at the component mediating phasic inhibition. This agonistic activity was prevented by the benzodiazepine site antagonist flumazenil. Interestingly, the active compounds displayed an agonistic activity at these receptors significantly greater than that of "classical" 1,4-benzodiazepine agonists, such as diazepam, flunitrazepam and alprazolam.

New 1,5-benzodiazepine compounds: activity at native GABA(A) receptors.

Various new 1,5-benzodiazepine compounds were synthesized and tested for their biological activity in terms of effects on GABA(A) receptors of rat cerebellar granules in culture. Their effects were compared to those of a 1,4-benzodiazepine agonist, flunitrazepam and the already known 1,5-benzodiazepine antiepileptic clobazam. The effects were evaluated for the two different GABA(A) receptor populations present in these neurons, one mediating phasic inhibition and the other one mediating tonic inhibition. Many such compounds display a profile of inverse agonist to both GABA(A) receptor populations. One of them presents a profile of full agonist at the component mediating phasic inhibition. Interestingly, substitution of just one oxygen atom in that compound with sulphur in a specific position of a morpholine ring resulted in a remarkable change of activity from full agonist to a probable inverse agonist. This indicates such a position as a proton accepting one for the ligand within the benzodiazepine binding pocket of the relevant GABA(A) receptors. In addition, that position appears to be critical for the pharmacological activity.

1,5-Benzodiazepine tricyclic derivatives exerting anti-inflammatory effects in mice by inhibiting interleukin-6 and prostaglandinE(2)production.

The 1,4- and the 1,5-benzodiazepines (BDZ) are commonly used as anxiolytic and anticonvulsive drugs. It has been suggested that they influence, particularly through stimulation of peripheral BDZ receptors, some immune cell properties such as pro-inflammatory cytokine production. The availability of a new class of [1,2,4]triazolo[4,3-a][1,5]benzodiazepine derivatives (compounds IV), endowed with anti-inflammatory and/or analgesic properties but no anti-pentylenetetrazole activity, prompted us to investigate in more detail the anti-inflammatory properties of three selected compounds IV (N,N-dimethyl-1-phenyl-4H-[1,2,4]triazolo[4,3-a][1,5]benz- odiazepin-5-amine; N,N-dibutyl-4H-[1,2,4]triazolo[4,3-a][1,5]benzodiazepin-5-amine; 1-methyl-N,N-dimethyl-4H-[1,2,4]triazolo[4,3-a][1,5]benzodiazepin-5-amine) and one structurally related compound (1-phenyl-4H-[1,2,4]triazolo[4,3-a][1,5]benzodiazepin-5(6H)-one). These BDZ derivatives have lost their affinity for the central and peripheral BDZ receptors. The in vivo effect on leukocyte migration of these compounds was investigated by using the mouse air-pouch model of local inflammation. Compounds A and B, significantly inhibited the carrageenan-induced leukocyte recruitment in a dose-dependent manner starting from the dose of 50 mgkg(-1), whereas compound C was effective only at the higher dose of 100 mgkg(-1). Compound D did not exert such effects at any of the doses considered. The effect of compounds A, B and C on leukocyte recruitment was paralleled by a significant inhibition of interleukin-6 and prostaglandin E(2)production in the exudate, similarly to indomethacin, and by a partial reduction of vascular permeability. These features may be relevant for the design and development of innovative anti-inflammatory molecules among the 4H-[1,2,4]triazolo[4,3-a][1,5]benzodiazepin-5-amine derivatives.

1,5-Benzodiazepines. Part XII. Synthesis and biological evaluation of tricyclic and tetracyclic 1,5-benzodiazepine derivatives as nevirapine analogues.

A number of properly substituted 5H-pyrimido[4,5-b][1,5]benzodiazepines (2) and pyrazolo[3,4-b][1,5]benzodiazepines (3 and 4), as well as compounds 5-7, which are derivatives of new tetracyclic systems, were prepared as nevirapine analogues through multistep synthetic routes. The cytotoxic and anti-HIV-1 properties of compounds 2-7 were evaluated in cell-based assays, together with their inhibitory activity against the HIV-1 recombinant reverse transcriptase (rRT) in enzyme assays. The modifications introduced into nevirapine heterocyclic skeleton proved to have a negative effect for the anti-HIV-1 activity. It is worth noting that some of the new derivatives proved to be cytotoxic in the low micromolar range.

Synthesis, antiplatelet activity and comparative molecular field analysis of substituted 2-amino-4H-pyrido[1,2-a]pyrimidin-4-ones, their congeners and isosteric analogues.

2-(1-Piperazinyl)-4H-pyrido[1,2-a]pyrimidin-4-one (5a) is a recently described in vitro inhibitor of human platelet aggregation which specifically inhibits the activity of high affinity cAMP phosphodiesterase. A number of substitution derivatives, isosteres, and analogues of 5a were now synthesized and tested in vitro for their inhibitory activity on human platelet aggregation induced in platelet-rich plasma by ADP, collagen, or the Ca2+ ionophore A23187. Among the most effective compounds, the 6-methyl, 8-methyl and 6,8-dimethyl derivatives of 5a resulted nearly as active as the lead when platelet aggregation was induced by ADP or A23187, but less active when collagen was the inducer. On the basis of present results and those previously obtained by us in this and 2-aminochromone structural fields, we have developed a statistically significant 3-D QSAR model, using comparative molecular field analysis (CoMFA), describing the variation of the antiplatelet activity in terms of molecular steric and electrostatic potential changes.

1,8-Naphthyridines IV. 9-substituted N,N-dialkyl-5-(alkylamino or cycloalkylamino) [1,2,4]triazolo[4,3-a][1, 8]naphthyridine-6-carboxamides, new compounds with anti-aggressive and potent anti-inflammatory activities.

The title compounds (8) were synthesized through the cyclocondensation of the corresponding N-substituted 4-amino-2-chloro-1,8-naphthyridine-3-carboxamides (4) with the proper hydrazides, in order to evaluate their anti-inflammatory and anti-aggressive properties. Several compounds 8 exhibited high anti-inflammatory activity (carrageenin-induced paw edema assay in the rat) along with appreciable anti-aggressive properties (isolation-induced aggressiveness test in mice). With respect to anti-inflammatory activity, the most active compounds (8n and 8c) produced a 61% edema inhibition at the 25 mg/kg dose, and 50 or 35% inhibition, respectively, at the 12.5 mg/kg dose. The structure-activity relationships are discussed.

Pyran derivatives. XX. 2-Aminochromone benzo-fused derivatives with antiproliferative properties.

The N-substituted 2-aminochromones 1 and their benzo-fused derivatives 2-4 described herein were mostly prepared by treating the corresponding (methylthio) derivatives 10-13 with an excess of the proper amines. Only the morpholino derivatives 3d and 4c were obtained from the reaction of the ethyl 3-morpholino-3-oxopropanoate/POCl3 reagent with 1-naphthol or 1-methyl-2-naphthol, respectively. The amino derivatives 1-4, as well as their methylthio analogues 10-13, were tested in vitro for their inhibitory activity on the infectivity of T2 bacteriophage, on the macromolecular synthesis in Ehrlich cells and on the clonal growth capacity of HeLa cells. Several of the angular or linear aminonaphthopyranones 2 and 3 or 4, respectively, and the (methylthio) derivatives 10, 11 and 13 induced a significant inhibition of DNA synthesis, but usually a clearly lower inhibition of clonal growth. Only the linear 2-amino-10-methyl-4H-naphtho[2,3-b]pyran-4-ones 4a and 4b significantly inhibited the clonal growth in HeLa cells and T2 bacteriophage infectivity, respectively.

Mechanism of action of two new pyrimidoquinoline and isoquinoline derivatives in human platelets.

In the present study the "in vitro" influence of 3-(1-piperazinyl)-1H-pyrimido[1,2-a]quinolin-1-one (AQ11) and 2-(piperazinyl)-4H-pyrimido[2,1-a]isoquinolin-4-one (IQ3b) on human platelet aggregation, cAMP elevation, cytosolic calcium and fibrinogen binding has been investigated. Both drugs inhibited platelet aggregation in a concentration-dependent manner. In PRP AQ11 was slightly more active than IQ3b when aggregation was induced by ADP, collagen, A23187 or PMA, whereas in washed platelets challenged by thrombin, IQ3b was more effective than AQ11. Both compounds produced increase in cAMP intracellular level being the effect potentiated by the adenylate cyclase activator iloprost and IQ3b was more powerful than AQ11. Moreover IQ3b was more effective in inhibiting cAMP in high affinity phosphodiesterase (IC50 values: IQ3b 11 +/- 5 microM; AQ11 43 +/- 8 microM) and calcium elevation (IC50 values: IQ3b 9 +/- 4 microM; AQ11 32 +/- 6 microM). These compounds also inhibited fibrinogen binding in platelets challenged by ADP or thrombin. The results suggest that these new potent agents inhibit platelet phosphodiesterase activity causing an elevation in cAMP levels sufficient to inhibit calcium rise and fibrinogen binding. This mechanism can be responsible for the ability of the compounds to prevent platelet aggregation.

Effect of 2-(1-piperazinyl)-4H-pyrido[1,2-a]pyrimidin-4-one (AP155) on human platelets in vitro.

The effect on human platelets of 2-(1-piperazinyl)-4H-pyrido[1,2-a]pyrimi din-4-one (AP155) was tested in vitro by measuring cyclic adenosine monophosphate (cAMP) level, cytosolic Ca++, [(125I)]fibrinogen binding as well as aggregation induced by several agonists. AP155 dose-dependently inhibited aggregation both in platelet rich plasma (PRP) and in washed platelets (WP), exerting its maximal power in the presence of collagen, ADP and platelet activating factor (PAF). It specifically inhibited the activity of cAMP high affinity phosphodiesterase (PDE), resulting in a sufficient increase in cAMP levels to activate cAMP-dependent protein kinase. AP155 was able to inhibit aggregation, the increase in cytosolic Ca++ induced by thrombin, and fibrinogen binding to ADP or thrombin-stimulated platelets. Thus, this new pyridopyrimidine derivative exerts its antiplatelet activity by increasing cAMP intracellular concentration.

1,8-Naphthyridines. III. N,N-dialkyl-5-chloro[1,2,4]-triazolo[4,3-a][1,8]naphthyridine-6-carboxa mides with anti-inflammatory activity.

Fifteen N,N-dialkyl-5-chloro[1,2,4]triazolo[4,3-a][1,8]naphthyridine-6-carboxami des (7a-o) were synthesized through the cyclocondensation of the corresponding N,N-dialkyl-2,4-dichloro-1,8-naphthyridine-3-carboxamides with proper hydrazides, in order to evaluate their anti-inflammatory, antiaggressive, and analgesic properties. Four of the compounds tested showed a statistically significant and dose-dependent anti-inflammatory activity.

Pyran derivatives XIX. (Dialkylamino) substituted 1-benzopyranones and naphthopyranones with platelet antiaggregating activity.

2-(Dialkylamino)chromones 4 and 4-(1-piperazinyl)coumarins 11, as well as their angular benzo-fused derivatives 1, 2 and 12, 13, respectively, were synthesized and tested in vitro for their inhibitory activity on human platelet aggregation induced in platelet-rich plasma by ADP (5.0 microM), collagen (10.0 micrograms/ml), and A 23187 (calcimycin) (20.0 microM). Among the dialkylamino substituents used, and the ring systems examined, 1-piperazinyl and 1-benzopyran or naphtho[2,1-b]pyran, respectively, resulted the most effective ones for antiplatelet activity, both in the chromone and coumarin fields. 7-Ethoxy-4-(1-piperazinyl)coumarin 11b showed the highest activity, and higher than those of all reference compounds (ASA, trifluoperazine, propranolol, and dipyridamole) towards all platelet aggregation inducers.

1,8-naphthyridines II. 2,4-disubstituted N,N-dialkyl-1,8-naphthyridine-3-carboxamides with anti-inflammatory and/or antiaggressive activities.

The preparation of the novel N,N-dialkyl-2,4-dichloro-1,8-naphthyridine-3-carboxamides 1c, e and N,N-dialkyl-2-(alkylamino or cycloalkylamino)-4-chloro-1,8-naphthyridine-3- carboxamides 2b, d-g, j-p is described. These compounds and the previously obtained analogs 1a, b, d, f and 2a, c, h, i have been tested for their anti-inflammatory and antiaggressive activities, as well as for their gross behavioral effects and acute toxicity. Nine of the twenty-two tested compounds exhibited a statistically significant anti-inflammatory activity in the carrageenin-induced edema assay in the rat (1e, f and 2h, o were the most active compounds). On the other hand, an interesting antiaggressive activity was displayed by ten compounds in the isolation-induced aggressiveness test in mice (compounds 2d, i, k showed the highest activity). Structure-activity relationships are briefly discussed.

1,2-fused pyrimidines. VI. Substituted 2-amino-4H-pyrido[1,2-a]pyrimidin-4-ones with antiplatelet activity.

The N-substituted 2-amino-4H-pyrido[1,2-a]pyrimidin-4-ones 2 d,g-i,l-p,r,s and derivatives 4,5 b,6 a,b, 7 a,b were prepared. Both these novel compounds (except the insoluble 7a) and compounds 2 a-c,e,f,j,k,q, 5a, previously prepared by us, were tested in vitro for their inhibitory activity on human platelet aggregation induced by ADP, collagen, or A23187. On the whole, the compounds tested proved to be more active towards collagen than towards ADP and A23187. The 2-(4-methyl-1-piperazinyl)derivative 2 g was the most active compound both towards ADP and collagen, whereas the 2-(diethylamino)derivative 2 b proved to be the most active one towards A23187.

1,5-Benzodiazepines. X. Dialkylamino substituted 1,5-benzodiazepine and [1,2,4]triazolo [4,3-a][1,5] benzodiazepine derivatives with inhibitory activity on PAF-induced platelet aggregation.

Novel 4-(dialkylamino) substituted (4, 5 c, 8) and 2,4-bis(dialkylamino) substituted (6) 1,5-benzodiazepine derivatives were synthesized. Both these new compounds and the substituted 4H-[1,2,4]triazolo[4,3-a][1,5]benzodiazepine-5-amines 2 a-h, recently described by us, were tested in vitro for their inhibitory activity on the PAF-induced aggregation of human platelets. Actually, bicyclic compounds 4 d, 5 c and tricyclic compounds 2 g, h showed a significant activity: in all them the dialkylamino substituent was the 4-(ethoxycarbonyl)-1-piperazinyl group. On the contrary, compounds 4 d, 5 c, 2 g,h showed practically no inhibitory activity when platelet aggregation was induced by ADP, A23187, or collagen.

[Synthesis and preliminary pharmacological screening of 2,4-disubstituted N,N-dialkyl-1,8-naphthyridine-3-carboxamides]. / Sintesi ed esame farmacologico preliminare di N,N-dialchil-1,8-naftiridin-3-carbossammidi 2,4-disostituite.

By treating at 100 degrees C 2-aminonicotinic acid with ethyl N,N-dialkylmalonamate (I) and phosphorus oxychloride N,N-dialkyl-4-chloro-1,2-dihydro-2-oxo-1,8-naphthyridine- 3-carboxamides (II) were obtained. The reaction of compounds (II) with an excess of refluxing phosphorus oxychloride afforded N,N-dialkyl-2,4-dichloro-1,8-naphthyridine-3-carboxamides (III), which in turn were treated at room temperature with excess primary amines to give a mixture of isomeric N,N-dialkyl-2-(alkylamino or cycloalkylamino)-4-chloro-1,8-naphthyridine-3-carboxamides (IV) and N,N-dialkyl-4-(alkylamino or cycloalkylamino)-2-chloro-1,8-naphthyridine-3-carboxamides (V). When this last reaction was performed at 160 degrees C, only N,N-dialkyl-2,4-bis(alkylamino or cycloalkylamino)-1,8-naphthyridine-3-carboxamides (VI) were obtained; under the same conditions (IV c) or (V c) reacted with methylamine to give isomeric 2,4-bis(alkylamino)derivatives (VII) or (VIII), respectively. Compounds (II b), (III b), (IV a,c,d), (V a,c,d) were submitted to a wide preliminary pharmacological screening. Some of them, depending on the structure, showed antihypertensive [(IV c)], anti-inflammatory [(IV c) greater than (III b)], or, in the behavioral test, anti-aggressive [(IV d) greater than (III b)] activity. Furthermore compound (III b) caused moderate inhibition of the 5-HT induced contraction of the guinea-pig ileum.

HPLC analysis of the nitrosation products of chlordiazepoxide.

Products originated from Chlordiazepoxide (I) hydrochloride/sodium nitrite interaction were analyzed by HPLC. The studied reactions were carried out in diluted hydrochloric acid solutions at pH values ranging between 0.5-5.0. Depending on the reaction pH values and molar ratios it was possible to find and assess variable amounts of the N-nitrosochlordiazepoxide (II), the dihydroquinazoline (III) and the lactam (IV). The highest degree of N-nitrosation was found at pH 3.5. At this pH value the yields of (II) were respectively 54.8% and 18.3% when the drug (I)/nitrite molar ratios were correspondingly 0.41 and 0.25. When the reaction was performed in concentrations which is possible to find in the gastric juice of patients taking (I) together with nitrite-rich foods the yield of (II) at pH 3.5 was 2.5%. Since in the meantime the genotoxicity of (II) was proved, "in vivo" formation of N-nitrosochlordiazepoxide (II) represents a potential risk not to be underestimated.

[Derivatives of pyrimidine 1,2-condensate. IV. Synthesis and pharmacological properties of the N,N-disubstituted 4-amino-2H-pyrido(1,2-a)pyrimidin- 2-ones and 2-amino-4H-pyrido(1,2-a)pyrmidin-4-ones]. / Derivati di pirimidine 1,2-condensate. Nota IV--Sintesi e proprietà farmacologiche di 4-ammino-2H-pirido[1,2-a]pirimidin-2-oni e 2-ammino-4H-pirido[1,2-a]pirimidin-4-oni N,N-disostituiti.

The N,N-disubstituted 4-amino-2H-pyrido[1,2-a]pyrimidin-2-ones (III) and isomer 2-amino-4H-pyrido[1,2-a]pyrimidin-4-ones (IV) were obtained from the reaction of 2-aminopyridine with the N,N-disubstituted ethyl malonamate/phosphorus oxychloride reagent (II), in refluxing 1,2-dichloroethane. 2-[(N-Benzyl, N-ethyl)amino]derivative (IV b) was also prepared in excellent yield by treating 2-chloro-4H-pyrido[1,2-a]pyrimidin-4-one (V) with N-ethylbenzylamine. Finally, hydrogenation (Raney Nickel) of 4-[(N-ethyl,N-phenyl)amino]-2H-pyrido[1,2-a]pyrimidin-2-one (III e) afforded 6,7,8,9-tetrahydroderivative (VI) which in turn was treated with potassium borohydride to give 1,6,7,8,9,9a-hexahydroderivative (VII). Several compounds described in the present paper, along with some other compounds (III) and (IV) previously synthesized by us (1,2), were tested for various pharmacological activities. The antiallergic activity (PCA in the rat), even though found in several compounds examined, turned out to be submaximal in any case, in spite of the high dose administered (500 mg/kg p.o. as a rule). The most active compound (the activity being estimated at 0.42 times that of thiaramide hydrochloride) was the 4-aminoderivative (III e). The 2-aminoderivatives (IV) series, was found to have marked antiinflammatory properties (carrageenin oedema in the rat); nevertheless, this activity was related to toxic symptoms with the exception of compound (IV b), almost asymptomatic at the administered dose (200 mg/kg p.o.). Moreover the 2-aminoderivatives (IV) generally showed weak adrenolitic activity in vitro (rat seminal vesicles), which was estimated to be from 100 to 1000 times less than that of phenoxybenzamine.

[Chemistry and pharmacology of pyran derivatives. XVII. Synthesis of 2-(dialkylamino)-5-hydroxychromones and their transformation to derivatives of 2H-pyran[4,3,2-de]-1-benzopyran]. / Ricerche chimiche e farmacologiche su derivati piranici. Nota XVII. Sintesi dei 2-(dialchilammino)-5-idrossicromoni e loro trasformazione in derivati del 2H-pirano [4,3,2-de]-1-benzopirano.

Through the reaction of resorcin with N,N-dialkylethoxy-carbonylacetamides in suitable conditions 2-(dialkylamino)-5-hydroxychromones (II) were available. Transformation of these compounds into [5-acetoxy-2-(dialkylamino)-4H-chromen-4-ylidene] malononitriles (VII) by reaction with malononitrile in acetic anhydride and treatment of (VII) with hydrochloric acid gave rise to the formation of 5-(dialkylamino)-2-imino-2H-pyrano [4,3,2-de]-1-benzo-pyrans (VIII). Furthermore 5-hydroxychromones (II) when treated with methyl iodide gave the corresponding 5-methoxychromones (III) which in turn yielded 4H-chromen-4-ylidene derivatives (X) by reaction with malononitrile in acetic anhydride. The hydrolysis of the latter compounds with hydrochloric acid resulted in the formation of 2-(dialkylamino)-4-methyl-5-methoxychromenilium salts (XI). Among the compounds which were submitted to pharmacological screening for their antiallergic properties 5-methoxychromone (III a) and 2H-pyrano [4,3,2-de]-1-benzopyran (VIII b) showed a notable activity but also high toxicity.

[Derivatives of 1,2-condensed pyrimidines. II. Synthesis and pharmacological study of N,N-disubstituted 5-amino-7H-thiazol [3,2-a]pyrimdine-7-ones]. / Derivati di pirimidine 1,2-condensate. Nota II. Sintesi e studio farmacologico di 5-ammino-7H-tiazolo[3,2-a]-pirimidin-7-oni N,N-disostituiti.

Reaction of 2-aminothiazole with the N,N-dialkyl or (N-alkyl, N-phenyl) ethoxycarbonylacetamide/POCl3 reactant (I), in refluxing 1,2-dichloroethane, yielded the corresponding N,N-disubstituted 5-amino-7H-thiazolo[3,2-a]pyrimidin-7-ones (VII) along with lower quantities of isomeric N,N-disubstituted 7-amino-5H-thiazolo[3,2-a]pyrimidin-5-ones (VIII). Structures attributed to isomeric compounds (VII) and (VIII) were supported both by spectroscopic and chemical evidences. Some compounds (VII) were submitted to pharmacological investigation and results are described: only (N-alkyl, N-phenyl)derivatives (VII f,g) showed a significant, even if mild, activity as peripheral analgesics.

[Chemical and pharmacological research on pyran derivatives. XIV. 3-alkylaminoaphtho/2,1-b/pyran-1-ones and derivatives]. / Richerche chimiche e farmacologiche su derivati piranici. Nota XIV - 3-alchilamminonafto[2,1-b]piran-1-oni e derivati.

3-Alkyl(phenyl)aminoaphtho[2,1-b]pyran-1-ones (III) were prepared from N-alkyl or N-phenylethoxycarbonylacetamides and 2-naphthol in the presence of phosphorus oxychloride, in order to evaluate their pharmacological activity on the CNS in comparison with previously described 3-dialkylaminoaphtho[2,1-b]pyran-1-ones. Compounds (III) gave 2-morpholinomethyl derivatives as well as N-acetyl and N-ethtoxycarbonyl derivatives. The reaction of (III) in which R = alkyl and N,N-dimethylformamide-POCl3 afforded 2-formyl derivatives and in some cases also 8-alkyl-9,10-bisdimethylaminoaphtho[1',2':5,6]pyrano[2,3-b]pyrrol-11(8H)-ones; when R = phenyl, only naphtho[1',2':5,6]pyrano[2,3-b]quinolin-14-one was obtained from the same reaction. Pharmacological evaluation showed that compounds (III) had a weak CNS depressant activity. Some of them also exhibited antagonist effect on reserpine-induced blepharospasm and hypothermia and on metrazole-induced seizures in the mouse. Within the limits of these activities a special behavior was found for the compound 3-ethylaminoaphtho[2,1-b]pyran-1-one [(III b) - K 12479].