Synthesis and evaluation of pharmacological and pharmacokinetic properties of 11H-[1,2,4]triazolo[4,5-c][2,3]benzodiazepin-3(2H)-ones

LiBF4-Promoted Aromatic Fluorodetriazenation under Mild Conditions

An efficient and mild fluorination method through LiBF4-promoted aromatic fluorodetriazenation of 3,3-dimethyl-1-aryltriazenes is developed. The reaction proceeds smoothly and tends to complete within 2 h in the absence of a protic acid or strong Lewis acid. This method tolerates a wide range of functional groups and affords the aryl fluoride products in moderate to excellent yields.

Recent developments on triazole nucleus in anticonvulsant compounds: a review

Epilepsy is one of the common diseases seriously threatening life and health of human. More than 50 million people are suffering from this condition and anticonvulsant agents are the main treatment. However, side effects and intolerance, and a lack of efficacy limit the application of the current anticonvulsant agents. The search for new anticonvulsant agents with higher efficacy and lower toxicity continues to be the focus and task in medicinal chemistry. Numbers of triazole derivatives as clinical drugs or candidates have been frequently employed for the treatment of various types of diseases, which have proved the importance of this heterocyclic nucleus in drug design and discovery. Recently many endeavours were made to involve the triazole into the anticonvulsants design, which have brought lots of active compounds. This work is an attempt to systematically review the research of triazole derivatives in the design and development of anticonvulsant agents during the past two decades.

Synthesis and preliminary pharmacological evaluation of a new putative radioiodinated AMPA receptor ligand for molecular imaging

A new (radio)iodinated AMPA receptor ligand has been developed and pharmacologically evaluated in vitro and ex vivo using rodents. The new radioligand was directly labeled by electrophilic radioiodo-destannylation with iodine- 131 in high radiochemical yields of 97% within 2 min. The new radioligand showed an excellent initial brain uptake of 2.1%ID/g at 10 min post injection, but a fast wash-out reduced the uptake by about 10-fold at 60 min post injection. Due to high nonspecific binding accompanied with a uniform distribution in brain tissue, however, the new radiotracer appears not suitable for AMPA receptor imaging in vivo.

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.

Determination of a potent non-competitive AMPA receptor antagonist in rat brain

N-acetyl-1-(p-chlorophenyl)-6,7-dimethoxy-1,2,3,4-tetrahydroisoquinoline derivative (PS3Ac) has been determined in brain tissues by high performance liquid chromatography (HPLC) coupled with a diode array detection. In a previous paper we presented a validation method for detecting PS3Ac and its metabolites in plasma samples after intraperitoneal administration to Wistar rats. In the present paper, we report the results of the determination of PS3Ac and its N-deacetyl (PS3) and O-demethyl (PS3OH) metabolites, in the brain after extraction based on a polymeric matrix with a high hydrophilic-lipophilic balance, using Oasis cartridges. The chromatographic separation was performed in an octadecylsilica stationary phase at 25 degrees C using a mixture of 10 mM potassium dihydrogen orthophosphate (pH 2.24) and acetonitrile in ratio of 30:70 (v/v) as mobile phase, with a flow rate of 0.8 ml/min. The method exhibited a large linear range from 0.05 to 2 microg/ml for all studied compounds (n=6). In the within-day assay (n=4), the accuracy ranged from 87.5% determined with 0.05 microg/ml of PS3 to 110.1% determined with 0.2 microg/ml of PS3OH. In the between-day assay the coefficient of variation ranged from 2.4 determined with 0.05 microg/ml of PS3 to 9.7 determined with 0.2 microg/ml of PS3OH. The extraction efficiency ranged from 77.8% for PS3OH at 0.2 microg/ml to 94.3 for PS3Ac at 0.5 microg/ml. The limit of detection for all the tetrahydroisoquinoline derivatives ranged around 50 ng/ml. The method proved to be highly sensitive and specific to determinate PS3Ac and its metabolites and has been successfully applied to value their concentrations in brain matrix over the time.

Synthesis of 8-alkoxy-4,5-dihydro-[1,2,4]triazole[4,3-a]quinoline-1-ones and evaluation of their anticonvulsant properties

A series of 8-alkoxy-4,5-dihydro-[1,2,4]triazole[4,3-a]quinoline-1-one derivatives were synthesized using 7-hydroxy-3,4-dihydro-2(1H)-quinolone as the starting material. Their anticonvulsant activities were evaluated by the maximal electroshock test (MES) and the subcutaneous pentylenetetrazole test (sc-PTZ), and their neurotoxicities were measured by the rotarod neurotoxicity test (Tox). The tests demonstrated that 8-hexyloxy-4,5-dihydro-[1.2.4]triazole[4.3-a]quinoline-1-one (4e) and 8-heptyloxy-4,5-dihydro-[1,2,4] triazole[4,3-a]quinoline-1-one (4f) were the most potent anticonvulsants, with 4e having ED50 values of 17.17 mg/kg and 24.55 mg/kg and protective index (PI = TD50/ED50) values of 41.9 and 29.3 in the MES and sc-PTZ tests, respectively, and 4f having ED50 values of 19.7 mg/kg and 21.2 mg/kg and PI values of 36.5 and 33.9 in the MES and sc-PTZ tests, respectively. The PI values of 4e and 4f were many fold better than that of the marketed drugs phenytoin, carbamazepine, phenobarbital and valproate, which have PI values in the range of 1.6-8.1 in the MES test and < 0.22-5.2 in the sc-PTZ test. Structure-activity relationships were also discussed.

Novel potent anticonvulsant agent containing a tetrahydroisoquinoline skeleton

In our studies on the development of new anticonvulsants, we planned the synthesis of N-substituted 1,2,3,4-tetrahydroisoquinolines to explore the structure-activity relationships. All derivatives were evaluated against audiogenic seizures in DBA/2 mice, and the 1-(4'-bromophenyl)-6,7-dimethoxy-2-(piperidin-1-ylacetyl) derivative (26) showed the highest activity with a potency comparable to that of talampanel, the only noncompetitive alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) antagonist in clinical trials as an anticonvulsant agent. Electrophysiological experiments indicated that 26 acts as noncompetitive AMPA receptor modulator.

Anticonvulsant and toxicity evaluation of some 7-alkoxy-4,5-dihydro-[1,2,4]triazolo[4,3-a]quinoline-1(2H)-ones

To further investigate anticonvulsant activity of quinoline derivatives, a series of 7-alkoxy-4,5-dihydro-[1,2,4]triazolo[4,3-a]quinoline-1(2H)-one derivatives was synthesized starting from 7-hydroxyl-3,4-dihydro-2(1H)-quinoline. In initial (phase I) screening and quantitative (phase II) evaluation, compound 7-benzyloxyl-4,5-dihydro-[1,2,4]thiazolo[4,3-a]quinoline-1(2H)-one (3f) was among the most active but also has the lowest toxicity. In the anti-MES potency test, it showed median effective dose (ED(50)) of 12.3 mg/kg, median toxicity dose (TD(50)) of 547.5 mg/kg, and the protective index (PI) of 44.5, which is much greater than PI of the prototype drugs phenytoin, phenobarbital, carbamazepin, and valproate. Compound 3f was chosen for further evaluation. In phase III pharmacological test, the compound had median hypnotic dose (HD(50)) and median lethal dose (LD(50)) of 1204 mg/kg and >3000 mg/kg, respectively, thus demonstrating much greater margin of safety compared to prototype drugs. The compound 3f also showed significant oral activity against MES-induced seizures and low oral neurotoxicity in mice in phase IV pharmacological test. Possible structure-activity relationship was discussed.

SPE-HPLC determination of new tetrahydroisoquinoline derivatives in rat plasma

Recently a novel class of non-competitive AMPA receptor (AMPAR) antagonists, such as, N-acetyl-1-(p-chlorophenyl)-6,7-dimethoxy-1,2,3,4-tetrahydroisoquinoline (PS3Ac) have been developed using molecular modeling studies. In this study we present a validated method for detecting PS3Ac in biological matrices by high performance liquid chromatography with ultraviolet detection. In this study PS3Ac was administered to Wistar rats. After intraperitoneal administration, the plasma concentrations of PS3Ac and its potential metabolic products, i.e., PS3OH, PS3 and PS3OHAc were determined. Serum samples (0.5 ml) were purified by solid-phase extraction of analytes using Oasis cartridges. The chromatographic separation was performed on a LiChrosorb RP-1 at 30 degrees C. The eluent was made of potassium dihydrogen phosphate/acetonitrile in ratio of 50:50 (v/v); the flow rate was 1 ml/min. The detection was performed at 220 nm. The method exhibited a large linear range from 0.05 to 5 microg/ml for all studied compounds. The intra-assay accuracy ranged from 92% determined at 0.1 microg/ml of PS3OH, to 108% determined at 0.05 microg/ml of PS3OHAc. The average coefficient of variation of inter-assay was 6.27%. The average recovery from plasma was 78.5%. The limits of quantification for all the tetrahydroisoquinoline derivatives was 20 ng. The method proved to be highly sensitive and specific for the determination of the studied compounds in rat plasma and has been successfully applied to the evaluation of the pharmacokinetic profile of the inoculated compound.

Comparative anticonvulsant activity of N-acetyl-1-aryl-6,7-dimethoxy-1,2,3,4-tetrahydroisoquinoline derivatives in rodents

The anticonvulsant activity of competitive 2,3-dihydroxy-6-nitro-7-sulfamoyl-benzo (F)-quinoxaline (NBQX) and noncompetitive 2,3-benzodiazepines and tetrahydroisoquinolines (THIQs) AMPA/kainate receptor antagonists, was tested in different experimental seizure models and compared with diazepam, a conventional antiepileptic drug acting on GABAergic neurotransmission. In particular, the compounds were evaluated against audiogenic and maximal electroshock seizures (MES) test and pentetrazol (PTZ) seizures model, and all of them showed protective action. In addition, NBQX, 2,3-benzodiazepines and THIQs, but not diazepam, were also protective against clonic and tonic seizures and lethality induced by kainate, AMPA and ATPA, but were ineffective against NMDA-induced seizures. Only 2,3-benzodiazepines and some THIQs were able to affect 4-aminopyridine- and mercaptopropionic-acid-induced seizures. The duration of anticonvulsant action of 33 micromol/kg of some 2,3-benzodiazepines and THIQs was also investigated in DBA/2 mice, a strain genetically susceptible to audiogenic seizures, and it was observed that the derivative THIQ-10c, possessing an acetyl group at the N-2 and a chlorine atom on the C-1 phenyl ring, showed higher anticonvulsant activity and longer-lasting protective effects.

Synthesis and anticonvulsant activity of N-3 substituted 2,3-benzodiazepines

A series of new 3-alkylcarbamoyl-1-aryl-3,5-dihydro-7,8-dimethoxy-4H-2,3-benzodiazepin-4-ones was synthesized starting from the corresponding 3-N-unsubstituted derivatives, previously described as noncompetitive AMPA-type glutamate receptor antagonists. The new compounds proved to protect against seizures induced by means of auditory stimulation in DBA/2 mice and some of them showed anticonvulsant properties comparable or better than those of GYKI 52466, the prototype of 2,3-benzodiazepine noncompetitive AMPA receptor antagonists.

Synthesis and anticonvulsant properties of tetrahydroisoquinoline derivatives

As a follow up of our previous structure-activity relationship and molecular modeling studies, we synthesized a novel series of 1-aryl-6,7-dimethoxy-1,2,3,4-tetrahydroisoquinoline derivatives as potential non-competitive AMPA receptor antagonists. When tested for their ability to prevent sound-induced seizures in DBA/2 mice, some of these novel compounds showed high anticonvulsant potency.

Synthesis and evaluation of pharmacological properties of novel annelated 2,3-benzodiazepine derivatives

New cyclofunctionalized 2,3-benzodiazepines characterized by a triazolone or triazindione ring fused on the "c" edge of the heptatomic nucleus have been prepared. These compounds were evaluated as potential anticonvulsant agents, and some of them proved to be more potent noncompetitive 2-amino-3-(3-hydroxy-5-methylisoxazol-4-yl)propionate (AMPA) receptor antagonists. In particular, 8,9-dimethoxy-6-(4-bromophenyl)-11H-[1,2,4]triazolo[4,5-c][2,3]benzodiazepin-3(2H)-one (5b) was almost 10-fold more active than GYKI-52466 and 3.5-fold more active than Talampanel. Furthermore, 5b potently reduced AMPA-evoked currents in electrophysiological experiments.

Pharmacophore modeling as an efficient tool in the discovery of novel noncompetitive AMPA receptor antagonists

A three-dimensional pharmacophore model for the binding of noncompetitive AMPA receptor antagonists was developed in order to map common structural features of highly active compounds. This hypothesis, which consists of two hydrophobic regions, one hydrogen bond acceptor and one aromatic region, was successfully used as framework for the design of a new class of allosteric modulators containing a tetrahydroisoquinoline skeleton and for in silico screening. The promising biological results suggested that the identified molecules might be useful "lead compounds" for future drug development.

Comparative anticonvulsant activity of some 2,3-benzodiazepine derivatives in rodents

The anticonvulsant activities of some 2-amino-3-(3-hydroxy-5-methylisoxazol-4-yl)propionic acid (AMPA)/kainate receptor antagonists, noncompetitive (2,3-benzodiazepines) and a competitive 2,3-dihydroxy-6-nitro-7-sulfamoyl-benzo(F)-quinoxaline (NBQX), were compared in different experimental seizure models. In particular, compounds were evaluated against audiogenic seizure in DBA/2 mice, maximal electroshock seizure (MES) test and various chemoconvulsant models; both groups showed a protective action against audiogenic seizure, MES- and pentylenetetrazole (PTZ)-induced seizures. All 2,3-benzodiazepines were also protective against clonic and tonic seizures and lethality induced by 4-aminopyridine, kainate, AMPA and 3-mercaptopropionic acid but were ineffective against NMDA-induced seizures. NBQX was unable to affect 4-aminopyridine-, mercaptopropionic acid- and NMDA-induced seizures. The duration of anticonvulsant action of 33 micromol/kg of some 2,3-benzodiazepine in DBA/2 mice, genetically susceptible to audiogenic seizures, was also investigated. The derivatives possessing a thiocarbonyl group at the C-4 position of heptatomic ring showed higher anticonvulsant activities and longer lasting protective effects. We conclude that all 2,3-benzodiazepines studied are effective against various models of experimental epilepsy and the presence of thiocarbonyl groups at the C-4 position of heptatomic ring is able to increase the anticonvulsant effect of these compounds.

Discovery of a novel and highly potent noncompetitive AMPA receptor antagonist

N-Acetyl-1-aryl-6,7-dimethoxy-1,2,3,4-tetrahydroisoquinoline derivatives were designed and synthesized as potential noncompetitive AMPA receptor antagonists on the basis of molecular modeling studies. Sound-induced seizure testing showed that this class of compounds possessed anticonvulsant properties. In particular, 10c was more potent than talampanel (2), a noncompetitive AMPA receptor antagonist currently being investigated in phase III trials as an antiepileptic agent. Furthermore, electrophysiological studies indicated that 10c was a highly effective noncompetitive-type modulator of the AMPA receptor.

One-pot synthesis of 2,4-benzodiazepin-1-ones using benzotriazole methodology

2, 4-Benzodiazepin-1-ones were prepared in moderate to good yields by reaction of bis(benzotriazolylmethyl)amines with ortho-metalated N-substituted benzamides.

Synthesis and pharmacological properties of new 3-ethoxycarbonyl-11H-[1,2,4]triazolo[4,5-c][2,3]benzodiazepines

A series of new 3-ethoxycarbonyl-11H-[1,2,4]triazolo[4,5-c][2,3]benzodiazepines was synthesized starting from the corresponding bicyclic 1-aryl-3,5-dihydro-7,8-dimethoxy-4H-2,3-benzodiazepin-4-ones (CFMs), previously described as noncompetitive AMPA-type glutamate receptor antagonists, more potent than GYKI 52466. New synthesized compounds proved to be able to protect against seizures induced by means of auditory stimulation in DBA/2 mice and compound 8f the most active of the series showed anticonvulsant properties comparable to GYKI 52466.

Structural characterization of a cyclic dipeptidomimetic: the effect of ring size on a 1,2,5-trisubstituted-3-oxo-1,4-diazepine system

A series of dipeptidomimetics derived from C(alpha)(i)-to-N(i-1) side chain-to-backbone amide cyclization of adjacent amino acids are structurally characterized. The resulting ring systems are either 1,2,5-trisubstituted-3-oxo-1,4-diazepine (DAP) structurally related to benzodiazepines, commonly used in drug candidates and therapeutic agents, or higher homologs of it. Here, we examine the structural consequences of enlarging the ring size from seven members to eight-, nine-, and ten-membered rings. The structural features determined by high-resolution NMR methods, relying largely on homo- and heteronuclear coupling constants, indicate that variation of the ring leads to alternative conformations and topological orientations of the attached chemical moieties or functional groups. Controlling the topological display of the ring substituents required for biological action, using a molecular scaffold made up entirely of functional groups found in peptides, should facilitate the rational, stepwise transformation of peptide lead candidate into a nonpeptidic drug candidate.

Design and development of 2,3-benzodiazepine (CFM) noncompetitive AMPA receptor antagonists

2,3-Benzodiazepines represent a class of heterocyclic compounds that interact with AMPA-type glutamate receptors in a noncompetitive manner. These compounds have attracted great interest for their pharmacological effects against acute and chronic neurodegenerative diseases, such as ischemia and epilepsy. We synthesized a large number of 2,3-benzodiazepine derivatives, which showed anticonvulsant properties in different seizure models and a noncompetitive blockade of AMPA receptor. This article will briefly mention our work in this field and the main SAR considerations.