Insight into the medicinal chemistry of the endocannabinoid hydrolase inhibitors.

Endocannabinoid hydrolases are nowadays increasingly considered as potential therapeutic targets for treating several pathological states. So far, numerous classes of endocannabinoid hydrolase inhibitors have been described. We herein review the medicinal chemistry of these inhibitors with a particular emphasis on the basis of their design, chemical structure, structure-activity relationships, and inhibition mechanisms.

DD-ligases as a potential target for antibiotics: past, present and future.

DD-ligases catalyze the synthesis of the D-Ala-D-Ala and D-Ala-D-Ser dipeptides or the D Ala-D-Lac depsipeptide in an early step of peptidoglycan synthesis. Their function is essential for bacterial growth and specific to bacteria, making them attractive targets for the development of novel antibiotics. This review examines the biochemical and structural features of these enzymes and presents the main families of inhibitors described so far. Over the last 20 years, 7 structures of DD-ligases have been solved by X-ray crystallography, giving a detailed view of the general topology of the active site and of the residues in the catalytic pocket that play a central role in substrate recognition. This has paved the way to the rational design of inhibitors, which can be classified as (i) analogues of substrates, (ii) analogues of the product of the reaction, (iii) analogues of the transition state, and (iv) original scaffolds discovered by screening or by rational computer-aided design. The three first strategies have led to molecules that are polar by nature and have therefore poor access to their cytosolic target. The fourth one is potentially most promising as it yields more diverse structures. The most active molecules show affinity constants in the microM range, but microbiological evaluation remains scarce (typical MIC 1-8 mg/L for the tested compounds). These data strongly suggest targeting DD-ligases is a promising approach for discovery of new antibiotics. Future research should, however, aim at finding more potent inhibitors endowed with the appropriate pharmacokinetic properties that ensure access to their intracellular target.

Synthesis and pharmacological evaluation of analgesic 6-substituted 2(3H)-benzothiazolones.

A series of novel 6-substituted-2(3H)-benzothiazolones were synthesized and studied as analgesic agents. Among these compounds, two of them were found to exhibit potent analgesic activity in several in vivo tests (acetic acid writhing, Koster, carrageenan and PGE2 hyperalgesia). In these tests the most active compound of this series, i.e. 6-benzoyl-2(3H)-benzothiazolone (4a) was found to be superior to acetylsalicylic acid and equivalent to glafenine. The present study allows to conclude that 4a represents a new type of antinociceptive agent acting in periphery by inhibiting the cyclo-oxygenase pathway and promoting the release of an opioid peptide.

Synthesis and preliminary pharmacological results on new naphthalene derivatives as 5-HT(4) receptor ligands.

The indole derivative GR 113808 is currently used as the reference ligand for labelling the 5-HT(4) serotoninergic receptors. Previous works in our laboratories established the bioisosteric equivalency of the indole heterocycle and naphthalene in a series of melatonin receptor ligands. Based on this knowledge we designed new analogues of GR 113808 by introducing two bioisosteric modifications: firstly, the indole ring was replaced by a naphthalene one and secondly, the ester linkage was replaced by an amide group. Compound 8 emerged within this novel series as it displayed high and selective affinity at 5-HT(4) receptors (Ki 5-HT(4) = 6 nM, Ki 5-HT(3) = 100 nM, Ki values at other 5-HT receptors were higher than 1000 nM). Compound 8 is currently undergoing further pharmacological evaluation.

3-Alkyl-(5,5'-diphenyl)imidazolidineiones as new cannabinoid receptor ligands.

Twenty-four 3-alkyl-(5,5'-diphenyl)imidazolidinediones were synthesized and evaluated as new cannabinoid receptor ligands. Three compounds exhibited a Ki value around 100 nM against [3H]-SR 141716A binding obtained from human CB1 transfected CHO cells membranes. The lack of change of affinity in the presence of a non hydrolyzable GTP analogue seems to indicate they are cannabinoid antagonists.

Synthesis and antiviral activity of 6-benzoyl-benzoxazolin-2-one and 6-benzoyl-benzothiazolin-2-one derivatives.

The synthesis and antiviral activity of an original series of 6-benzoyl-benzoxazolin-2-one and 6-benzoyl-benzothiazolin-2-one derivatives are described. Several compounds were found to have a selective inhibitory activity against human cytomegalovirus (HCMV) and varicella-zoster virus (VZV) in vitro, being inactive against a variety of other DNA and RNA viruses. 6-(3-fluorobenzoyl)benzoxazolin-2-one, 6-(3-fluorobenzoyl)benzothiazolin-2-one, 6-(3-bromobenzoyl)benzothiazolin-2-one, 6-(3-iodobenzoyl)benzothiazolin-2-one, 3-methyl-6-(3-fluorobenzoyl)benzothiazolin-2-one, 3-benzyl-6-benzoyl-benzothiazolin-2-one, 3-benzyl-6-(3-fluorobenzoyl)benzothiazolin-2-one and 3-benzoyl-6-(3-fluorobenzoyl)benzothiazolin-2-one were the most active of the series against HCMV and VZV with a selectivity index (CC50/IC50) ranging from 10 to 20. They displayed similar activity against thymidine kinase competent (TK+) and deficient (TK-) VZV strains, and also proved to be active against clinical HCMV isolates that were resistant to ganciclovir (GCV). Time-of-addition experiments revealed a site of interaction with the HCMV replicative cycle that may be close or similar to that of GCV and cidofovir (HPMPC). The compounds showed poor, if any, activity against herpes simplex virus type 1 (HSV-1) and HSV-2, and were not inhibitory against human immunodeficiency virus and other DNA and RNA viruses. Therefore, these compounds may represent a novel lead for the development of specific HCMV and VZV drugs.

Design, anticonvulsive and neurotoxic properties of retrobenzamides. N-(Nitrophenyl)benzamides and N-(aminophenyl)benzamides.

Design, anticonvulsant properties in maximal electroshock-induced seizures [MES] and seizures induced by subcutaneous administration of pentetrazole (scPtz), and neurotoxicity of retrobenzamides (N-(nitrophenyl)benzamides and N-(aminophenyl) benzamides are reported. These data are further compared with those on carbamazepine, phenytoin, ameltolide and other reference compounds. Studies on retrobenzamides in mice dosed intraperitoneally point out a good anticonvulsant potential in the MES test for the amino derivatives (N-(aminophenyl)benzamides) and moderate activity for corresponding "nitro" derivatives. In rats dosed orally, aminoretrobenzamides were, however, less active in the MES test than in mice dosed intraperitoneally. Differences between experimental animal species and administration routes lead to hypothesize rapid metabolization of compounds, reduced intestinal resorption and increased removal from body. The presence of a methyl substitution on the N-phenyl moiety of aminoretrobenzamides attenuated these discrepancies between mice and rats. Present results indicate that pharmacological values--including the dose offering anticonvulsant protection in 50% of tested animals (ED50) and protective indices--obtained on some retrobenzamides may compete with phenytoin and carbamazepine values. By contrast with phenytoin, some retrobenzamides further exhibit activity in the scPtz test.

Anticonvulsant phenytoinergic pharmacophores and anti-HIV activity--preliminary evidence for the dual requirement of the 4-aminophthalimide platform and the N-(1-adamantyl) substitution for antiviral properties.

This work is aimed at further exploring the concept that phenytoin-related compounds might present with an anti-HIV potential. We screened for anti-HIV activity, selected compounds whose structural design rests on pharmacophores successfully shown to convey phenytoinergic anticonvulsant activity. We determined the corresponding anticonvulsant protective doses in mice via the i.p. route of administration using the maximal electroshock seizure test (a test in which the anticonvulsant activity of phenytoin is well expressed). Firstly, 4-aminophthalimide pharmacophores were utilized with either N-(2,6-dimethyl)phenyl or N-(1-adamantyl) substitutions. While the former was found to be highly potent, the latter was devoid of significant activity. Secondly, the pharmacophores N-(2,6-dimethylphenyl)phthalimide and N-(1-adamantyl)phthalimide were compared for antiviral (antiHIV-1 and antiHIV-2) properties in CEM (human T-lymphocyte) cells infected with HIV-1 or HIV-2 strains. Various phthalimide C4-substitutions (H, NO2, NH2, Cl, CH3, OCH3, COOH) of these pharmacophores were studied. From this set of experiments, 4-amino-N-(1-adamantyl)phthalimide emerged with EC50 (effective concentration-50) values of 16 and 27 microM against HIV-1 and HIV-2, respectively. The CC50 (cytostatic concentration-50) of this compound was 30 microM. Thirdly, the N-(2,6-dimethylphenyl) and N-(1-adamantyl) substitutions of the 4-aminobenzamide pharmacophore (another known phenytoinergic anticonvulsant platform) were shown to be devoid of anti-HIV activities. A similar negative result was obtained for amantadine. Taken as a whole, the present data indicate that both the 4-aminophthalimide pharmacophore and N-(1-adamantyl) substitutions are required for anti-HIV properties. Molecular modeling studies further provide clues for this dual requirement.

Xenoestrogens, pollution & health: a critical review.

This review article provides basic information concerning the xenoestrogens (i.e. the sexual hormone mimetic or disruptive compounds) in a perspective willingly selective of the recent literature. In the second part, a hypothetical link between xenoestrogens and disturbances of the central nervous system is considered with respect to steroids more directly involved in the CNS, i.e. the neurosteroids. The data accumulated so far on xenoestrogens present in the environment and their possible competition for membrane-bound neurosteroid receptor sites lend support to the working hypothesis that human behaviour could be affected in the daily life by exposure to chemical pollutants.

Anticonvulsant activity and interactions with neuronal voltage-dependent sodium channel of analogues of ameltolide.

Fifteen compounds related to ameltolide (LY 201116) were studied for (i) anticonvulsant potential in the maximal electroshock-induced seizures (MES) and the subcutaneous pentylenetetrazol (sc Ptz) tests in mice and rats and (ii) interactions with neuronal voltage-dependent sodium channels. Compounds were chosen ranging in anticonvulsant activity in mice from very active to inactive. The active compounds were defined as those protecting 50% of the animals at doses between 10 and 50 micromol/kg and inactive compounds as those protecting 50% of the animals at doses greater than 1 mmol/kg. The series studied included three N-(2,6-dimethylphenyl)benzamides (compounds 1, 2 (ameltolide), and 3), three N-(2,2,6, 6-tetramethyl)piperidinyl-4-benzamides (compounds 4, 5, 6), one phenylthiourea (compound 7), five N-(2,6-dimethylphenyl)phthalimides (compounds 8, 9, 10, 13, and 14), two N-phenylphthalimide derivatives (compounds 11 and 12), and one N-(2,2,6, 6-tetramethyl)piperidinyl-4-phthalimide (compound 15). Phenytoin (PHT) was employed as the reference prototype antiepileptic drug. After inital screening in mice, compounds 1, 2, 3, 5, 8, 9, 10, 13, and 14 were selected for further testing in rats. Anticonvulsant ED50s (effective doses in at least 50% of animals tested) of compounds in the MES test were determined in rats dosed orally and amounted to 52 (1), 135 (2), 284 (3), 231 (8), 131 (9), 25 (10), 369 (13), 354 (14), and 121 (PHT) micromol/kg, compound 5 presenting with an ED50 value higher than 650 micromol/kg. In our hands, the apparent IC50s (inhibitory concentrations 50) of compounds toward binding to rat brain synaptosomes of [3H]batrachotoxinin-A-20alpha-benzoate were 0.25 (1), 0.97 (2), 0.35 (3), 25.8 (5), 161.3 (8), 183.5 (9), 0.11 (10), 1.86 (13), 47.8 (14), and 0.86 (PHT) microM. The relationship between the activity in the MES test and the capacity to interact in vitro with neuronal voltage-dependent sodium channels and the fact that the IC50 values obtained in the in vitro test are close to the brain concentrations at which anticonvulsant activities are reported to occur for ameltolide strongly suggest that the anticonvulsant properties of most compounds tested could be a direct result of their interaction with the neuronal voltage-dependent sodium channel.

Novel benzothiazolin-2-one and benzoxazin-3-one arylpiperazine derivatives with mixed 5HT1A/D2 affinity as potential atypical antipsychotics.

Since it was known that 5HT properties (5HT1A agonism or 5HT2A antagonism) combined with D2 antagonism may lead to atypical antipsychotic drugs, a series of 19 benzothiazolin-2-one and benzoxazin-3-one derivatives possessing the arylpiperazine moiety was prepared, and their binding profiles were investigated. All tested compounds displayed very high affinities for the 5HT1A and D2 receptors. Therefore, further pharmacological studies were carried out on selected compounds (24, 27, 30, 46, and 47). This evaluation in rats clearly revealed potent antipsychotic properties along with a decrease of extrapyramidal side effects. These derivatives are currently under preclinical development.

Anticonvulsant profile of 4-amino-(2-methyl-4-aminophenyl)benzamide in mice and rats.

An original ameltolide analogue 4-amino-(2-methyl-4-aminophenyl)benzamide, in which a second amino group has been introduced, was synthesized and evaluated for anticonvulsant activity. After intraperitoneal administration to mice, 4-amino-(2-methyl-4-aminophenyl)benzamide was found active in the maximal electroshock seizure test and against the tonic seizures elicited either by bicuculline or 3-mercaptopropionic acid. 4-amino-(2-methyl-4-aminophenyl)benzamide (4A-2M4A-PB) gave anti maximal electroshock seizures ED50 of 63 micromol/kg (15.4 mg/kg) and a TD50 of 676 micromol/kg (163 mg/kg), yielding a PI of 10.7; the potency is similar to that of the 4-amino-(2-methyl-3-aminophenyl)phthalimide (4A-2M3A-PP), superior to that of 4-amino-(2,6-dimethylphenyl)phthalimide (4A-2,6-DMPP), close to that of phenytoin and carbamazepine and inferior to that of ameltolide. 4A-2M4A-PB with an ED50 of 41[28-60] micromol/kg (9.9 mg/kg) is as active after oral administration to rats as carbamazepine, more active than ameltolide, 4-A-2M3A-PP and phenytoin and slightly less active than the 4A-2,6-DMPP. The introduction of a second amino group on the substituted phenyl ring does not affect drastically the anticonvulsant potency after intraperitoneal administration to mice; moreover, it seems to enhance the activity after oral administration. 4A-2M4A-PB is a good candidate both for further pharmacokinetic studies and for the study of the precise mechanism of action.

Synthesis and anticonvulsant activity of 2(3H)-benzoxazolone and 2(3H)-benzothiazolone derivatives.

A series of 2(3H)-benzoxazolone and 2(3H)-benzothiazolone derivatives were synthesized and evaluated for anticonvulsant activity. The compounds were assayed, intraperitoneally in mice and per os in rats, against seizures induced by maximal electroshock (MES) and pentylenetetrazole (scMet). Neurologic deficit was evaluated by the rotarod test. The compounds were prepared to determine the relationship between the 2(3H)-benzoxazolone and 2(3H)-benzothiazolone derivatives' structures and anticonvulsant activity. Several of these compounds showed significant anticonvulsant activity. Compounds 43 and 45 were the most active of the series against MES-induced seizures with ED50 values of 8.7 and 7.6 mg/kg, respectively. Compound 45 displayed good protection against MES-induced seizures and low toxicity in rats with an oral ED50 of 18.6 mg/kg and a protective index (PI = TD50/ED50) of < 26.9. In vitro receptor binding studies revealed that compounds 43 and 45 bind to sigma 1 receptors with nanomolar affinities.

N-(benzyloxycarbonyl)glycine esters and amides as new anticonvulsants.

Glycine is a small neutral amino acid exhibiting weak anticonvulsant activities in vivo. Recently, studies have demonstrated that N-(benzyloxycarbonyl)glycine (1) antagonized seizures superior to glycine in addition to activity in the maximal electroshock (MES) test, a convulsive model where glycine is inactive. In the present study a series of ester and amide derivatives of 1 as well as esters of N-(3-phenylpropanoyl)glycine (5) have been prepared. The compounds were evaluated in the MES test as well as in several chemically induced seizure models. Among the derivatives investigated, N-(benzyloxycarbonyl)glycine benzylamide (16) was the most potent compound exhibiting an anticonvulsant activity in the MES test comparable to the drug phenytoin. Median effective doses (ED50) of 4.8 and 11.6 mg/kg were determined at 30 min and 3 h after i.p. administration, respectively. Compound 16 also effectively suppressed tonic seizures in different chemically induced models such as the strychnine, 3-mercaptopropionic acid, and pentylenetetrazole tests. Moreover, the compound studied here did not show acute neurotoxicity in the rotorod test up to a dose of 150 mg/kg. It is concluded that N-(benzyloxycarbonyl)glycine amides, especially 16, are potent anticonvulsant agents.

2(3H)-benzoxazolone and 2(3H)-benzothiazolone derivatives: novel, potent and selective sigma1 receptor ligands.

A series of original 2(3H)-benzoxazolone and 2(3H)-benzothiazolone derivatives were evaluated for their affinity at sigma1 and sigma2 receptor subtypes in competition binding experiments, using [3H](+)-pentazocine or [3H]1,3-di-o-tolyl-guanidine (DTG) in the presence of 100 nM (+)-N-allylnormetazocine (NANM) in guinea-pig brain membranes. Several of these derivatives showed preferential selectivity for sigma1 binding sites. Compound 1 [3-(1-piperidinoethyl)-6-propylbenzothiazolin-2-one] emerged as a potent sigma1 receptor ligand (Ki = 0.6 nM) and displayed a moderate selectivity over the sigma2 receptor subtype (Ki for sigma2/Ki for sigma1 = 29). Compounds 2 [3-(1-piperidinopropyl)-6-propanoylbenzothiazolin-2-one] and 3 [3-(1-piperidinopropyl)-6-propanoylbenzoxazolin-2-one] still showed rather high affinities for sigma1 binding sites with Ki values of 2.3 and 8.5 nM, respectively. On the contrary, they had 87- and 58-fold less affinity at sigma2 receptors, respectively. Unlike their potent affinity for sigma binding sites, these compounds had negligible affinity for mu-, delta- and kappa-opioid receptors, 5-HT2, dopamine D2, and muscarinic M2 receptors. Sigma receptor ligands may affect neuronal transmission and display, in animal models, antipsychotic, cognitive, motor, neuroprotective and anticonvulsant activity. Therefore, on the basis of these findings, these novel sigma receptor ligands were assayed, in mice, in three tests: maximal electroshock, subcutaneous pentylenetetrazol and rotarod neurotoxicity. Compound 1, administered intraperitoneally, was the most effective against maximal electroshock-induced seizures and was devoid of significant neurotoxic effects.

Anticonvulsant activity of pyrid-3-yl-sulfonyl ureas and thioureas.

The N-[(4-cycloheptylaminopyrid-3-yl)sulfonyl]-N'-cycloheptyl urea, a neuroprotective agent, and 10 chemically related sulfonyl(thio)ureas were evaluated in the maximal electroshock seizure test in mice. This sulfonylurea, BM 27, and two structurally related sulfonylthioureas, BM 11 and BM 34, emerged with a 50% effective dose (ED50) of 2.87, 1.72, and 1.19 mg/kg, respectively. Their anticonvulsant profiles were found to be similar to that of phenytoin: active in the maximal electroshock seizure (MES) test and inactive in chemically induced seizures (pentetrazole, strychnine, bicuculline, picrotoxine, N-methyl-D,L-aspartic acid). These compounds exhibited a higher protective index and potency than those of phenytoin. Additional work remains necessary, however, to determine whether BM 27 is of clinical interest.

Anticonvulsant and neurotoxicological properties of 4-amino-N-(2-ethylphenyl)benzamide, a potent ameltolide analogue.

A well documented study on the anticonvulsant properties of 4-amino-N-(2-ethylphenyl)benzamide (4-AEPB) is here provided. Initial screening in mice dosed intraperitoneally and rats dosed orally indicated that 4-AEPB is active against maximal electroshock-induced seizures (MES), but does not protect animals against subcutaneous pentylenetetrazole (sc Ptz)-induced seizures. Quantitative evaluation of anti-MES activity and neurotoxicity of 4-AEPB given intraperitoneally to mice provided ED50 and TD50 values amounting to 28.6 and 96.3 mumol/kg respectively, resulting in a protective index (PI = TD50/ED50) equal to 3.36. Further quantitative evaluation in rats dosed orally indicated that the respective ED50 and TD50 values for 4-AEPB were 29.8 and more than 1,530 mumol/kg, resulting in a very high PI value of over 51. Comparison anticonvulsant properties and neurotoxicity of 4-AEPB with those previously reported in the literature for two 4-aminobenzamide derivatives, 4-amino-N-(2,6-dimethylphenyl)benzamide (or ameltolide, an antiepileptic drug prototype developed by Eli Lilly), and phenytoin, underlines the value of 4-AEPB for future pharmacological development. In this perspective, an additional favorable element is represented by the ability of 4-AEPB to increase the seizure threshold in the intravenous Ptz seizure threshold test in mice dosed intraperitoneally. Molecular modeling studies show that the translocation of one carbon unit in the isomerization of the 2,6-dimethylphenyl moiety of ameltolide to the 2-ethylphenyl counterpart succeeds in maintaining the conformational low energy presentation adopted by ameltolide, providing clues as to why the 4-AEPB here described is an anticonvulsant agent derived from the 4-aminobenzamide pharmacophore platform as potent as ameltolide.

Anti-HIV activity of N-1-adamantyl-4-aminophthalimide.

The discovery of new leads acting via novel modes of action in the treatment of the human immunodeficiency virus (HIV), the causative agent of AIDS, remains a challenge. Along this line we synthesized and evaluated a series of N-substituted 4-aminophthalimides which were designed according to the models of thalidomide, phenytoin (PHT) and ameltolide. From a series of 24 compounds only N-1-adamantyl-4-aminophthalimide was endowed with anti-HIV-1 and -HIV-2 activity in CEM cell cultures.

[Rational conception, synthesis and evaluation of phenytoinergic potential anticonvulsants. A series ofretrobenzamides: N-(nitrophenyl) benzamides and N-(aminophenyl) benzamides]. / Conception rationnelle, synthèse et évaluation d'agents anticonvulsivants originaux à potentialité phénytoïnergique. La série des rétrobenzamides: les N-(nitrophényl) benzamides et les N-(aminophényl)benzamides.

Retrobenzamides [N-(nitrophenyl) benzamides and N-(aminophenyl)benzamides] were developed in the perpective of a design for phenytoinergic agents. Anticonvulsant and neurotoxic properties of these compounds were evaluated in mice and rats in two seizure models (maximal electroshock-induced seizures [MES] and seizures induced by subcutaneous administration of pentylenetetrazole [scPtz]) and in the rotorod test. Data obtained were compared with those recorded on carbamazepine and phenytoin (antiepileptic drugs widely utilized in human clinics), ameltolide (anticonvulsant compound recently developed by Eli Lilly in human clinical trials) and other compounds previously reported by our research group. Studies on retrobenzamides in mice administered by intraperitoneal route point out a good anticonvulsant potential in the MES test for the amino derivatives (N-(aminophenyl)benzamides) and moderate activity in the case of the corresponding "nitro" derivatives. In rats dosed orally, aminoretrobenzamides were less active in the MES test than in mice dosed intraperitoneally.