Discovery of novel antitubercular 3a,4-dihydro-3H-indeno[1,2-c]pyrazole-2-carboxamide/carbothioamide analogues

In the present investigation, a series of 3a,4-dihydro-3H-indeno[1,2-c]pyrazole-2-carboxamide/carbothioamide analogues were synthesized and were evaluated for antitubercular activity by two fold serial dilution technique. All the newly synthesized compounds showed low to high inhibitory activities against Mycobacterium tuberculosis H(37)Rv and INH resistant M. tuberculosis. The compound 3-(4-fluorophenyl)-6,7-dimethoxy-3a,4-dihydro-3H-indeno[1,2-c]pyrazole-2-carbothioamide (4o) was found to be the most promising compound active against M. tuberculosis H(37)Rv and isoniazid resistant M. tuberculosis with minimum inhibitory concentration 3.12 μM and 6.25 μM, respectively.     

Chemopreventive potential of 3-[2,6-bis(4-fluorophenyl)-3-methylpiperidin-4-ylideneamino]-2-thioxoimidazolidin-4-one on 7,12-dimethylbenz[a]anthracene (DMBA) induced hamster buccal pouch carcinogenesis

In the present work, a new bis heterocyclic compound comprising both the piperidone and thiohydantoin nuclei namely 3-[2,6-bis(4-fluorophenyl)-3-methylpiperidin-4-ylideneamino]-2-thioxoimidazolidin-4-one was synthesised and characterised with the help of mp, elemental analysis, FT-IR, MS and one-dimensional NMR (¹H and ¹³C) spectra. The inhibitory effect of 3-[2,6-bis(4-fluorophenyl)-3-methylpiperidin-4-ylideneamino]-2-thioxoimidazolidin-4-one on 7,12-dimethylbenz[a]anthracene (DMBA) induced buccal pouch carcinogenesis was investigated in Syrian male hamsters. All the hamsters that were painted with DMBA on their buccal pouches for 14 weeks developed squamous cell carcinoma. Administration of 3-[2,6-bis(4-fluorophenyl)-3-methylpiperidin-4-ylideneamino]-2-thioxoimidazolidin-4-one effectively suppressed the oral carcinogenesis initiated with the DMBA as revealed by a reduced incidence of neoplasms. Lipid peroxidation, glutathione (GSH) content and the activities of glutathione peroxidase (GPx), glutathione S-transferase (GST) were used to biomonitor the chemopreventive potential of 3-[2,6-bis(4-fluorophenyl)-3-methylpiperidin-4-ylideneamino]-2-thioxoimidazolidin-4-one. Lipid peroxidation was found to be significantly decreased, whereas GSH, GPx, GST and GGT were elevated in the oral mucosa of tumour bearing animals. Our data suggest that 3-[2,6-bis(4-fluorophenyl)-3-methylpiperidin-4-ylideneamino]-2-thioxoimidazolidin-4-one may exert its chemopreventive effects in the oral mucosa by modulation of lipid peroxidation, antioxidants and detoxification systems.     

Synthetic studies towards a new scaffold, spirobicycloimidazoline

A new scaffold consisting of a carbocycle and a substituted imidazoline in an orthogonal arrangement was synthesized as a potential specific inhibitor of glycosidases. The spirobicycloimidazoline, (5R,6R,7R,8R)-8-(hydroxymethyl)-2-phenyl-1,3-diazaspiro[4.4]non-1-ene-6,7-diol, was synthesized from methyl 2-O-p-methoxybenzyl-3,4-di-O-benzyl-alpha/beta-D-gluco-6-enopyranoside via (1R,2S,3S,4R,5S)-3,4-bis(benzyloxy)-2-(4-methoxybenzyloxy)-5-vinyl-cyclopentanol. The ring contraction of the 6-enopyranoside in the presence of zirconocene equivalent ('Cp(2)Zr') reagent gave exclusively the corresponding cyclopentanol without cleavage of the PMB protecting group. In the course of the study, a new alpha-mannosidase inhibitor, (1R,2R,3R,5R)-5-amino-3-hydroxymethyl-cyclopentane-1,2-diol, was also discovered.     

Synthesis and biological evaluation of novel carbon-11-labelled analogues of citalopram as potential radioligands for the serotonin transporter

Three serotonin reuptake inhibitors where the 5-cyano group in citalopram [1-(3-dimethylamino-propyl)-1-(4-fluorophenyl)-1,3-dihydroisobenzofuran-5-carbonitrile (1)] was replaced with a methyl, acetyl and piperidinyl carbonyl group, respectively, were synthesized. In a Stille reaction applying [(11)C]methyl iodide the labelled compound [5-methyl-(11)C][3-[1-(4-fluorophenyl)-5-methyl-1,3-dihydroisobenzofuran-1-yl]-propyl]-dimethylamine ([(11)C]-2) was synthesized in 60-90% radiochemical yield. [5-carbonyl-(11)C][1-[1-(3-dimethylaminopropyl)-1-(4-fluorophenyl)-1,3-dihydroisobenzofuran-5-yl]-1-piperidin-1-yl-methanone] ([(11)C]-3) was synthesized in 62% radiochemical yield in a palladium mediated cross-coupling reaction utilizing [(11)C]carbon monoxide. The specific activity of [(11)C]-2 was highly dependent on whether the corresponding trimethyltin or tributyltin precursor was applied. In ex vivo rodent studies compound [(11)C]-2 exhibited a good blood-brain barrier (BBB) penetration whereas [(11)C]-3 did not. The brain distribution of [(11)C]-2 was investigated in a non-human primate using PET. There was a rapid uptake of radioactivity into the brain. Accumulation of the radiotracer was in agreement with the known distribution of serotonin transporters. The maximal thalamus to cerebellum ratio of 1.3 was reached after 85 min and the specific binding was partly blocked after pre-treatment with citalopram. Thus, [(11)C]-2 does not exhibit appropriate properties as radioligand for visualization of the serotonin transporter in vivo.     

1,2,3,4-Tetrahydroisoquinoline Derivatives as a Novel Deoxyribonuclease I Inhibitors

Herein we report an assessment of 24 1,2,3,4-tetrahydroisoquinoline derivatives for potential DNase I (deoxyribonuclease I) inhibitory properties in vitro. Four of them inhibited DNase I with IC₅₀ values below 200 μM. The most potent was 1-(6,7-dimethoxy-1,2,3,4-tetrahydroisoquinolin-1-yl)propan-2-one ( 2 ) (IC₅₀=134.35±11.38 μM) exhibiting slightly better IC₅₀ value compared to three other active compounds, 2-[2-(4-fluorophenyl)-1,2,3,4-tetrahydroisoquinolin-1-yl]-1-phenylethan-1-one ( 15 ) (IC₅₀=147.51±14.87 μM), 2-[2-(4-fluorophenyl)-1,2,3,4-tetrahydroisoquinolin-1-yl]cyclohexan-1-one ( 18 ) (IC₅₀=149.07±2.98 μM) and 2-[6,7-dimethoxy-2-(p-tolyl)-1,2,3,4-tetrahydroisoquinolin-1-yl]cyclohexan-1-one ( 22 ) (IC₅₀=148.31±2.96 μM). Cytotoxicity assessment of the active DNase I inhibitors revealed a lack of toxic effects on the healthy cell lines MRC-5. Molecular docking and molecular dynamics simulations suggest that interactions with Glu 39, His 134, Asn 170, Tyr 211, Asp 251 and His 252 are an important factor for inhibitors affinity toward the DNase I. Observed interactions would be beneficial for the discovery of new active 1,2,3,4-tetrahydroisoquinoline-based inhibitors of DNase I, but might also encourage researchers to further explore and utilize potential therapeutic application of DNase I inhibitors, based on a versatile role of DNase I during apoptotic cell death.     

Further exploration of 1-[2-[Bis-(4-fluorophenyl)methoxy]ethyl]piperazine (GBR 12909): role of N-aromatic,N-heteroaromatic,and 3-oxygenated N-phenylpropyl substituents on affinity for the dopamine and serotonin transporter

A series of N-aromatic, N-heteroaromatic, and oxygenated N-phenylpropyl derivatives of 1-(2-benzhydryloxyethyl)-piperazine and 1-[2-[bis-(4-fluorophenyl)methoxy]ethyl]piperazine, analogues of GBR 12909 (1a) and 12935 (1b), was synthesized and examined for their dopamine (DAT) and serotonin (SERT) transporter binding properties. One of these compounds, racemic 3-[4-(2-benzhydryloxyethyl)piperazin-1-yl]-1-(3-fluorophenyl)-propan-1-ol (33), had DAT affinity as good as, or better than, GBR 12909 and 12935, and was more selective for DAT over SERT than the GBR compounds. Both trans- (43) and cis- (47) (+/-)-2-(4-[2-[bis-(4-fluorophenyl)-methoxy]ethyl]piperazin-1-ylmethyl)-6-methoxy-1,2,3,4-tetrahydronaphthalen-1-ol had relatively good SERT selectivity and, as well, showed high affinity for SERT.     

Diastereoselective reduction of 1-(4-fluorophenyl)-3(R)-[3-oxo-3-(4-fluorophenyl)-propyl]-4(S)-(4-hydroxyphenyl)azetidin-2-one to Ezetimibe by the whole cell catalyst Rhodococcus fascians MO22

The asymmetric microbial reduction of 1-(4-fluorophenyl)-3(R)-[3-oxo-3-(4-fluorophenyl)-propyl]-4(S)-(4-hydroxyphenyl)azetidin-2-one to 1-(4-fluorophenyl)-3(R)-[3(S)-hydroxy-3-(4-fluorophenyl)-propyl]-4(S)-(4-hydroxyphenyl)azetidin-2-one (Ezetimibe) by Rhodococcus fascians MO22 is described. The catalytic capability of the microorganism for reduction has been examined also with protected ketone, an intermediate from chemical synthesis of Ezetimibe. Various parameters of the bioreduction have been optimized: the strain converted 94.8% of ketone and 63% of protected ketone into Ezetimibe with the same de of 99.9%. In the later case, two chemical steps are replaced with a single biotransformation.     

Novel diphenylalkyl piperazine derivatives with high affinities for the dopamine transporter

The novel diphenyl piperazine derivatives containing the phenyl substituted aminopropanol moiety, including 1-[4,4-bis(4-fluorophenyl)butyl]-4-[2-hydroxy-3-(phenylamino)propyl]piperazine 1, which were modified at the connective between the diphenyl and piperazine moieties, have been found to be potent dopamine uptake inhibitors. To study the further structure-activity relationship (SAR) of these compounds, a new series was synthesized, with modifications at the 2-hydroxy-3-phenylaminopropyl moiety of 1. The series was evaluated for dopamine transporter (DAT) binding affinity with [3H]GBR12935 in rat striatal membranes. Most of the compounds showed moderate to high DAT binding affinities and some were approximately equivalent in activity to compound 1 or GBR12909 as a dopamine uptake inhibitor, with IC(50) values of nanomolar range. The SAR suggested that on exhibiting a potent interaction with the DAT, there is probably a steric limitation around the benzene ring of the phenylamino moiety of 1, allowing only small-sized substituents with the exception of basic moieties at the 4-position. In addition, the SAR at the 3-amino-2-propanol moiety of 1 suggested that either the nitrogen atom with an electron donating substituent or the unsubstituted nitrogen atom and also the hydroxy group are desirable for elicitation of a potent DAT binding affinity.     

Antioxidative activities of novel diphenylalkyl piperazine derivatives with high affinities for the dopamine transporter

A new series of diphenylalkyl piperazine derivatives with high affinities for the dopamine transporter (DAT), which were modified at both the diphenylalkyl moiety and the phenyl ring in the phenylamino moiety of 1-[4,4-bis(4-fluorophenyl)butyl]-4-[2-hydroxy-3-(phenylamino)propyl]piperazine 1, was evaluated for their inhibitory activities against auto-oxidative lipid peroxidation in canine brain homogenates. Some of these were approximately equivalent in activity to alpha-tocopherol as a potent antioxidant with IC(50) values of low micromolar order, and the 4-hydroxyphenyl derivative 11 showed the most potent antioxidative activity with an IC(50) value of 0.32 microM, exhibiting approximately 5-fold more potent activity than alpha-tocopherol. The structure-activity relationship (SAR) studies of the antioxidative activity of these derivatives are presented.     

3-{2-[Bis-(4-fluorophenyl)methoxy]ethyl}-6-substituted-3,6-diazabicyclo[3.1.1]heptanes as novel potent dopamine uptake inhibitors

A series of analogues 2a-i related to 3-{2-[bis-(4-fluorophenyl)methoxy]ethyl}-8-(1H-indol-2-ylmethyl)-3,8-diazabicyclo[3.2.1]octane (1) in which the 3,8-diazabicyclo[3.2.1]octane core was replaced by 3,6-diazabicyclo[3.1.1]heptane ring system has been synthesized and evaluated for their ability to inhibit DA reuptake into striatal nerve endings (synaptosomes). Biological data showed that compound 2a, the closest analogue of lead 1, possessed an increased reuptake inhibition activity over 1 (2a, K(i)=5.5 nM). Replacement of the indole ring with bioisosteric aromatic rings--benzothiophene (2b), benzofurane (2c), or indene (2d)--resulted, with the exception of 2d, in a double digit nanomolar activity. Changing the indenyl moiety of 2d with simplified aryl groups led to compounds 2e-h which displayed a similar or slightly decreased activity with respect to the ground term. Naphthalene derivative (2i) demonstrated a weaker activity than aromatic analogues.     

Antipsychotic action of selective group II metabotropic glutamate receptor agonist MGS0008 and MGS0028 on conditioned avoidance responses in the rat

The present study was designed to investigate the antipsychotic-like effects of selective group II metabotropic glutamate receptor (mGluR) agonists, 5-[2-[4-(6-fluoro-1H-indole-3-yl) piperidin-1-yl]ethyl]-4-(4-fluorophenyl)thiazole-2-carboxylic acid amide (MGS0008) and (1R, 2S, 5S, 6S)-2-amino-6-fluoro-4-oxobicyclo[3.1.0]hexane-2,6-dicarboxylic acid monohydrate (MGS0028) on conditioned avoidance responses in rats. MGS0008 (1, 3 and 10 mg/kg, p.o.) and MGS0028 (0.3, 1 and 3 mg/kg, p.o.) significantly and reduced conditioned avoidance responses in a dose-dependent fashion. Similar effects were seen with LY418426 (0.3, 1 and 3 mg/kg, p.o.), but not with LY354740 (3, 10 and 30 mg/kg, p.o.), both of which are selective agonists for group II mGluR. Since this effect is seen with a wide range of antipsychotics, such as haloperidol and clozapine [Life Sciences 71 (2002) 947], group II mGluR agonists deserve further attention for possible antipsychotic activity.     

Indole alkoloids from Nauclea officinalis with weak antimalarial activity

Five indole alkaloids (naucleofficines A-E) were isolated from the stems (with bark) of Nauclea officinalis: (E)-2-(1-beta-d-glucopyranosyloxybut-2-en-2-yl)-3-(hydroxymethyl)-6,7-dihydro-indolo[2,3-a]quinolizin-4(12H)-one (1), (E)-1-propenyl-12-beta-d-glucopyranosyloxy-2,7,8-trihydro-indolo[2,3-a]pyran[3,4-g]quinolizin-4,5(13H)-dione (2), (E)-2-(1-hydroxybut-2-en-2-yl)-11-beta-d-glucopyranosyloxy-6,7-dihydro-indolo[2,3-a]quinolizin-4(12H)-one (3), (E)-1-propenyl-4-hydroxy-2,4a,7,8,13b,14,14a-hepthydro-(4alpha,4abeta,13balpha,14abeta)indolo[2,3-a]pyran[3,4-g]quinolizin-5(13H)-one (4) and 1-(1-hydroxyethyl)-10-hydroxy-7,8-dihydro-indolo[2,3-a]pirydine[3,4-g]quinolizin-5(13H)-one (10-hydroxyangustoline) (5), together with two known compounds, naucleidinal (6) and angustoline (7). All of the structures of the seven compounds above were elucidated by spectroscopic methods including use of 1D- and 2D-NMR spectroscopic analyses. Compounds 2 and 3 are rare examples of monoterpene indole alkaloids with a glucopyranosyloxy group attached to position C-12. In vitro activity screening of the above seven compounds showed weak to moderate inhibitory activity against Plasmodium falciparum.     

Biosynthesis of riboflavin. Enzymatic formation of 6,7-dimethyl-8-ribityllumazine from pentose phosphates

The xylene ring of riboflavin originates by dismutation of the precursor, 6,7-dimethyl-8-ribityllumazine. The formation of the latter compound requires a 4-carbon unit as the precursor of carbon atoms 6 alpha, 6, 7, and 7 alpha of the pyrazine ring. The formation of riboflavin from GTP and ribose phosphate by cell extract from Candida guilliermondii has been observed by Logvinenko et al. (Logvinenko, E. M., Shavlovsky, G. M., Zakal'sky, A. E., and Zakhodylo, I. V. (1982) Biokhimiya 47, 931-936). We have studied this enzyme reaction in closer detail using carbohydrate phosphates as substrates and synthetic 5-amino-6-ribitylamino-2,4-(1H,3H)-pyrimidinedione or its 5'-phosphate as cosubstrates. Several pentose phosphates and pentulose phosphates can serve as substrate for the formation of riboflavin with similar efficiency. The reaction requires Mg2+. Various samples of ribulose phosphate labeled with 14C or 13C have been prepared and used as enzyme substrates. Radioactivity was efficiently incorporated into riboflavin from [1-14C]ribulose phosphate, [3,5-14C]ribulose phosphate, and [5-14C]ribulose phosphate, but not from [4-14C]ribulose phosphate. Label from [1-13C]ribose 5-phosphate was incorporated into C6 and C8 alpha of riboflavin. [2,3,5-13C]Ribose 5-phosphate yielded riboflavin containing two contiguously labeled segments of three carbon atoms, namely 5a, 9a, 9 and 8, 7, 7 alpha. 5-Amino-6-[1'-14C] ribitylamino-2,4 (1H,3H)-pyrimidinedione transferred radioactivity exclusively to the ribityl side chain of riboflavin in the enzymatic reaction. It follows that the 4-carbon unit used for the biosynthesis of 6,7-dimethyl-8-ribityllumazine consists of the pentose carbon atoms 1, 2, 3, and 5 in agreement with earlier in vivo studies.     

4-Amino-2-alkyl-butyramides as small molecule CCR2 antagonists with favorable pharmacokinetic properties

A systematic examination of the central aromatic portion of the lead (2S)-N-[3,5-bis(trifluoromethyl)benzyl]-2-(4-fluorophenyl)-4-(1'H-spiro[indene-1,4'-piperidin]-1'-yl)butanamide (9) led to the discovery of a novel class of CCR2 receptor antagonists, which carry small alicyclic groups such as cyclopropyl, cylobutyl, or cyclopropylmethyl attached at C2 of the carbon backbone. The most potent compound discovered, namely (2S)-N-[3,5-bis(trifluoromethyl)benzyl]-2-cyclopropyl-4-[(1R,3'R)-3'-methyl-1'H-spiro[indene-1,4'-piperidin]-1'-yl]butanamide (29), showed very high binding affinity (IC50 = 4 nM, human monocyte) and excellent selectivity toward other related chemokine receptors. The excellent pharmacokinetic profile of this new lead compound allows for extensive in vivo evaluation.     

Design, synthesis, computational and biological evaluation of new anxiolytics

New anxiolytics have been discovered by prediction of biological activity with computer programs pass and derek for a heterogeneous set of 5494 highly chemically diverse heterocyclic compounds (thiazoles, pyrazoles, isatins, a-fused imidazoles and others). The majority of tested compounds exhibit the predicted anxiolytic effect. The most potent activity was found in 2-(4-nitrophenyl)-3-(4-phenylpiperazinomethyl)imidazo[1,2-a]pyridine 8, 1-[(4-bromophenyl)-2-oxoethyl]-3-(1,3-dioxolano)-2-indolinone 3, 5-hydroxy-3-methoxycarbonyl-1-phenylpyrazole 5 and 2-(4-fluorophenyl)-3-(4-methylpiperazinomethyl)imidazo[1,2-a]pyridine 7. The application of the computer-assisted approach significantly reduced the number of synthesized and tested compounds and increased the chance of finding new chemical entities (NCEs).     

A multigram chemical synthesis of the gamma-secretase inhibitor LY411575 and its diastereoisomers

An improved chemical synthesis of N-2((2S)-2-(3,5-difluorophenyl)-2-hydroxyethanoyl)-N1-((7S)-5-methyl-6-oxo-6,7-dihydro-5H-dibenzo[b,d]azepin-7-yl)-l-alaninamide (LY411,575, 9a), a known gamma-secretase inhibitor, is described. The key synthetic steps, which used no chiral chromatography in the entire sequence, involved (1) improved microwave-assisted synthesis of a seven-membered lactam (+/-)-(5,7-dihydro-6H-dibenz-[b,d]azepin-6-one 2, and (2) convenient isolation of pure LY411575 from a mixture of four diastereomers by simple flash silica gel chromatography. Starting from the resolved aminolactams 5a and 5b, all four diastereomers were produced in enantiomerically pure form.     

Novel lipase-catalysed enantioselective deacetylation of (+/-)-5-acetoxy-3-(4-fluorophenyl)-2-phenylisoxazolidine

(+/-)-5-Acetoxy-3-(4-fluorophenyl)-2-phenylisoxazolidine has been synthesised by a highly diastereoselective [3+2] cycloaddition reaction between alpha-(4-fluorophenyl)-N-phenylnitrone and vinyl acetate in good yield. Candida rugosa lipase catalyses the deacetylation of this (+/-)-5-acetoxyisoxazolidine in a highly enantioselective fashion in diisopropyl ether containing n-butanol affording (-)-5-acetoxy-3-(4-fluorophenyl)-2-phenylisoxazolidine in 43% yield and >99% ee.     

Study on anti-proliferative effect of benzoxathiole derivatives through inactivation of NF-κB in human cancer cells

To investigate the anti-proliferative effect of a newly discovered NF-kB inhibitor, 6,6-dimethyl-2-(phenylimino)-6,7-dihydrobenzo[d][1,3]oxathiol-4(5H)-one (1a), a series of its analogs (1b-n) were prepared and evaluated for their NF-κB inhibition and anti-proliferative activity against various human cancer cell lines. Slight variation of hydrophobicity by replacement of dimethyl group of 1a at 6-position with bulky isopropyl group and introduction of para-fluoro substitution on 2-phenyl group showed good NF-κB inhibitory activity and anti-proliferative activity. However, excessive increase in hydrophobicity with 2,4,6-trichloro substituents on phenyl group resulted in the loss of both the activities. From the SAR results, 2-phenylimino-6,7-dihydrobenzo[d][1,3]oxathiol-4(5H)-one was identified as the lead scaffold for investigating new anticancer agent through inactivation of NF-κB.     

Synthesis of imidazoline and imidazo[2,1-c][1,2,4]triazole aryl derivatives containing the methylthio group as possible antibacterial agents

1-Arylimidazolidine-2-thiones (1a-g) were synthesized by the condensation reaction of N-arylethylenediamines with carbon disulfide in xylene medium. Their further alkylation with methyl iodide led to the formation of some biologically active 1-aryl-2-methylthio-imidazolines (2a-g). The 7-(4-methylphenyl)-3-methylthio-5H-6,7-dihydroimidazo[2,1-c][1,2,4]triazole (4b) was obtained by the alkylation of the respective 7-(4-methylphenyl)-2,5,6,7-tetrahydroimidazo[2,1-c][1,2,4]triazol-3(H)-thione (3b) with methyl iodide. Antimicrobial activities of 1-aryl-2-methylthio-imidazolines (2a-g) and the 7-(4-methylphenyl)-3- methylthio-5H-6,7-dihydroimidazo[2,1-c][1,2,4]triazole (4b) are presented. All tested compounds showed MIC in the range of 11.0-89.2 microM. Compounds 2a,e were found to be equipotent to chloramphenicol in vitro, whereas 2a,c,e-g and 4b showed superior activity (MIC) to ampicillin.     

Synthesis of novel GABA uptake inhibitors. Part 6: preparation and evaluation of N-Omega asymmetrically substituted nipecotic acid derivatives

In a previous series of potent GABA uptake inhibitors published from this laboratory, we noticed that asymmetry in the substitution pattern of the bis-aromatic moiety in known GABA uptake inhibitors such as 4 [1-(4,4-diphenyl-3-butenyl)-3-piperidinecarboxylic acid] and 5 [(R)-1-(4,4-bis(3-methyl-2-thienyl)-3-butenyl)-3-piperidinecarboxylic acid] was beneficial for high affinity. This led us to investigate asymmetric analogues of known symmetric GABA uptake inhibitors in which one of the aryl groups has been exchanged with an alkyl, alkylene or cycloalkylene moiety as well as other modifications in the lipophilic part. The in vitro values for inhibition of [(3)H]-GABA uptake in rat synaptosomes was determined for each compound, and it was found that several of the novel compounds inhibit GABA uptake as potently as their known symmetrical reference analogues. Several of the novel compounds were also evaluated for their ability to inhibit clonic seizures induced by a 15 mg/kg (ip) dose of methyl 6,7-dimethoxy-4-ethyl-beta-carboline-3-carboxylate (DMCM) in vivo. Some of the compounds, for example 18 [(R)-1-(2-(((1,2-bis(2-fluorophenyl)ethylidene)amino)oxy)ethyl)-3-piperidinecarboxylic acid], show a high in vivo potency and protective index comparable with that of our recently launched anticonvulsant product, 5 [(R)-1-(4,4-bis(3-methyl-2-thienyl)-3-butenyl)-3-piperidinecarboxylic acid], and may therefore serve as second-generation drug candidates.