Synthesis and biological evaluation of (2S)- and (2R)-2-(3'-phosphonobicyclo[1.1.1]pentyl)glycines as novel group III selective metabotropic glutamate receptor ligands

The synthesis of (2S)- and (2R)-2-(3'-phosphonobicyclo[1.1.1]pentyl)glycine isomers (10 and 11), characterized by the bioisosteric replacement of the distal carboxylic group of 2-(3'-carboxybicyclo[1.1.1]pent-1-yl)glycine by the phosphonate moiety, was accomplished by a stereoselective Ugi condensation. The two isomers were tested for their activity against an array of metabotropic glutamate receptors, and the S-isomer (10) turned out to be a moderately potent and selective mGluR4 agonist.     

Discovery and in vitro and in vivo profiles of 4-fluoro-N-[4-[6-(isopropylamino)pyrimidin-4-yl]-1,3-thiazol-2-yl]-N-methylbenzamide as novel class of an orally active metabotropic glutamate receptor 1 (mGluR1) antagonist

We identified 4-fluoro-N-[4-[6-(isopropylamino)pyrimidin-4-yl]-1,3-thiazol-2-yl]-N-methylbenzamide 27 as a potent mGluR1 antagonist. The compound possessed excellent subtype selectivity and good PK profile in rats. It also demonstrated relatively potent antipsychotic-like effects in several animal models. Suitable for development as a PET tracer, compound 27 would have great potential for elucidation of mGluR1 functions in human.     

Dual neurokinin NK(1)/NK(2) antagonists: N-[(R,R)-(E)-1-arylmethyl-3-(2-oxo-azepan-3-yl)carbamoyl]allyl-N-methyl-3,5-bis(trifluoromethyl)benzamides and 3-[N'-3,5-bis(trifluoromethyl)benzoyl-N-arylmethyl-N'-methylhydrazino]-N-[(R)-2-oxo-azepan-3-yl]propionamides.

Based on the structure of N-[(R,R)-(E)-1-(4-chlorobenzyl)-3-(2-oxoazepan-3-yl)carbamoyl]allyl-N-methyl-3,5-bis(trifluoromethyl)benzamide (1), attempts to improve the NK(2) affinity have resulted in the discovery of N-[(R,R)-(E)-1-(3,4-dichlorobenzyl)-3-(2-oxoazepan-3-yl)carbamoyl]allyl-N-methyl-3,5-bis(trifluoromethyl)benzamide (9, DNK333) exhibiting a 5-fold improved affinity to the NK(2) receptor in comparison to 1. Simplification of the structure via elimination of a chiral centre led to 3-[N'-3,5-bis(trifluoromethyl)benzoyl-N-(3,4-dichlorobenzyl)-N'-methylhydrazino]-N-[(R)-2-oxo-azepan-3-yl]propionamide (22), a potent and fairly balanced NK(1)/NK(2) antagonist.     

1-[4-(1H-Benzoimidazol-2-yl)-phenyl]-3-[4-(1H-benzoimidazol-2-yl)-phenyl]-urea derivatives as small molecule heparanase inhibitors

A novel class of 1-[4-(1H-benzoimidazol-2-yl)-phenyl]-3-[4-(1H-benzoimidazol-2-yl)-phenyl]-ureas are described as potent inhibitors of heparanase. Among them are 1,3-bis-[4-(1H-benzoimidazol-2-yl)-phenyl]-urea (7a) and 1,3-bis-[4-(5,6-dimethyl-1H-benzoimidazol-2-yl)-phenyl]-urea (7d), which displayed good heparanase inhibitory activity (IC(50) 0.075-0.27 microM). Compound 7a showed good efficacy in a B16 metastasis model.     

A novel synthesis of acyclonucleosides via allylation of 3-[1-(phenylhydrazono)-L-threo-2,3,4-trihydroxybut-1-yl]quinoxalin-2(1H)one

The allylation of 3-[1-(phenylhydrazono)-L-threo-2,3,4-trihydroxybut-1-yl]quinoxalin-2(1H)one (1) gave, in addition to the anticipated 1-N-allyl derivative (2), a dehydrative cyclized product, 1-N-allyl-3-[5-(hydroxymethyl)-1-phenylpyrazol-3-yl]quinoxalin-2-one (4) and its isomeric O-allyl derivative 3. The O-allyl group in 3 underwent acetolysis under acetylation conditions, in addition to the acetylation of the hydroxyl group, to afford 2-acetoxy-3-[5-(acetoxymethyl)-1-phenylpyrazol-3-yl]quinoxaline (8) instead of the O-acetyl derivative of 3. Allylation of the tri-O-acetyl derivative of 1 caused the elimination of a molecule of acetic acid in addition to N-allylation to give 1-N-allyl-3-[3,4-di-O-acetyl-2-deoxy-1-(phenylhydrazono)but-2-en-1-yl]quinoxalin-2-one (11). Hydroxylation of the allyl group gave a glycerol-1-yl acyclonucleoside which can be alternatively obtained by a displacement reaction of the tosyloxy group in 2,3-O-isopropylidene-1-O-(p-tolylsulfonyl)glycerol (14), followed by deisopropylidenation. 1-N-(2,3-Dibromopropyl)-3-[5-(hydroxymethyl)-1-(4-bromophenyl)pyrazol-3-yl]quinoxalin-2-one (15) underwent azidolysis to give a 2,3-diazido derivative. The assigned structures were based on spectral analysis. The activity of compounds 2, 4, 6, and 15 against hepatitis B virus was studied.     

3-(Cyclopropylmethyl)-7-((4-(4-[11C]methoxyphenyl)piperidin-1-yl)methyl)-8-(trifluoromethyl)-[1,2,4]triazolo[4,3-a]pyridine: Synthesis and preliminary evaluation for PET imaging of metabotropic glutamate receptor subtype 2

Selective metabotropic glutamate receptor 2 (mGluR2) inhibitors have been demonstrated to show therapeutic effects by improving alleviating symptoms of schizophrenic patients in clinical studies. Herein we report the synthesis and preliminary evaluation of a ¹¹C-labeled positron emission tomography (PET) tracer originating from a mGluR2 inhibitor, 3-(cyclopropylmethyl)-7-((4-(4-methoxyphenyl)piperidin-1-yl)methyl)-8-(trifluoromethyl)-[1,2,4]triazolo[4,3-a]pyridine (CMTP, 1a). [¹¹C]CMTP ([¹¹C]1a) was synthesized by O-[¹¹C]methylation of desmethyl precursor 1b with [¹¹C]methyl iodide in 19.7 ± 8.9% (n = 10) radiochemical yield (based on [¹¹C]CO₂) with >98% radiochemical purity and >74 GBq/μmol molar activity. Autoradiography study showed that [¹¹C]1a possessed moderate in vitro specific binding to mGluR2 in the rat brain, with a heterogeneous distribution of radioactive accumulation in the mGluR2-rich brain tissue sections, such as the cerebral cortex and striatum. PET study indicated that [¹¹C]1a was able to cross the blood–brain barrier and enter the brain, but had very low specific binding in the rat brain. Further optimization for the chemical structure of 1a is necessary to increase binding affinity to mGluR2 and then improve in vivo specific binding in brain.     

Optically active antifungal azoles: synthesis and antifungal activity of (2R,3S)-2-(2,4-difluorophenyl)-3-(5-[2-[4-aryl-piperazin-1-yl]-ethyl]-tetrazol-2-yl/1-yl)-1-[1,2,4]-triazol-1-yl-butan-2-ol

A series of (2R,3S)-2-(2,4-difluorophenyl)-3-(5-[2-[4-aryl-piperazin-1-yl]-ethyl]-tetrazol-2-yl)-1-[1,2,4]-triazol-1-yl-butan-2-ol (11a-n) and (2R,3S)-2-(2,4-difluorophenyl)-3-(5-[2-[4-aryl-piperazin-1-yl]-ethyl]-tetrazole-1-yl)-1-[1,2,4]-triazol-1-yl-butan-2-ol (12a-n) has been synthesized. The antifungal activity of compounds was evaluated by in vitro agar diffusion and broth dilution assay. Compounds 11d and its positional isomer 12d having 3-trifluoromethyl substitution on the phenyl ring of piperazine demonstrated significant antifungal activity against variety of fungal cultures (Candida spp. C. neoformans and Aspergillus spp.). The compound 12d showed MIC value of 0.12 microg/mL for C. albicans, C. albicans V-01-191A-261 (resistant strain); 0.25 microg/mL for C. tropicalis, C. parapsilosis ATCC 22019 and C. krusei and MIC value of 0.5 microg/mL for C. glabrata, C. krusei ATCC 6258, which is comparable to itraconazole and better than fluconazole. Further, compound 11d showed significant activity (MIC; 0.25-0.5 microg/mL) against Candida spp. and strong anticryptococcal activity (MIC; 0.25 microg/mL) against C. neoformans.     

Side chain modifications of (indol-3-yl)glyoxamides as antitumor agents

New series of analogues of N-(pyridin-4-yl)-2-[1-(4-chlorobenzyl)-indol-3-yl]glyoxamide D-24851 were synthesized, characterized and tested for their in vitro anticancer properties. In the first series, an amino acid spacer was introduced in the glyoxamide chain of D-24851. In the second series, the glyoxamide chain was moved to positions 4 and 5 of indole skeleton. These new compounds were tested on four cancer cell lines (KB, SK-OV-3, NCI-H460 and SF-268), with promising activity for the glycine derivative.     

Novel 2-(2-(benzylthio)-1H-benzo[d]imidazol-1-yl)acetic acids: discovery and hit-to-lead evolution of a selective CRTh2 receptor antagonist chemotype

Hit-to-lead evolution of 2-(2-((2-(4-chlorophenoxy)ethyl)thio)-1H-benzo[d]imidazol-1-yl)acetic acid (1), discovered in a high-throughput screening campaign as a novel chemotype of CRTh2 receptor antagonist, is presented. SAR development as well as in vitro and in vivo DMPK properties of selected representatives of substituted 2-(2-(benzylthio)-1H-benzo[d]imidazol-1-yl)acetic acids are discussed.     

Side chain modifications of (indol-3-yl)glyoxamides as antitumor agents

New series of analogues of N-(pyridin-4-yl)-2-[1-(4-chlorobenzyl)-indol-3-yl]glyoxamide D-24851 were synthesized, characterized and tested for their in vitro anticancer properties. In the first series, an amino acid spacer was introduced in the glyoxamide chain of D-24851. In the second series, the glyoxamide chain was moved to positions 4 and 5 of indole skeleton. These new compounds were tested on four cancer cell lines (KB, SK-OV-3, NCI-H460 and SF-268), with promising activity for the glycine derivative.     

Synthesis and anticonvulsant activity of new 1-[2-oxo-2-(4-phenylpiperazin-1-yl)ethyl]pyrrolidine-2,5-diones

Twenty-two new 1-[2-oxo-2-(4-phenylpiperazin-1-yl)ethyl]pyrrolidine-2,5-diones were synthesized and tested for anticonvulsant activity. Initial anticonvulsant screening was performed using standard maximal electroshock (MES) and subcutaneous pentylenetetrazole (scPTZ) screens in mice. Several compounds were tested additionally in the 6-Hz psychomotor seizure model. The neurotoxicity was determined applying the rotarod test. Excluding one compound, all other molecules were found to be effective in at least one seizure model. The most active were 1-(2-oxo-2-{4-[3-(trifluoromethyl)phenyl]piperazin-1-yl}ethyl)pyrrolidine-2,5-dione (14), 1-{2-[4-(4-chlorophenyl)piperazin-1-yl]-2-oxoethyl}-3-methylpyrrolidine-2,5-dione (17), 1-{2-[4-(4-chlorophenyl)piperazin-1-yl]-2-oxoethyl}-3,3-dimethylpyrrolidine-2,5-dione (23) and 3,3-dimethyl-1-(2-oxo-2-{4-[3-(trifluoromethyl)phenyl]piperazin-1-yl}ethyl)pyrrolidine-2,5-dione (26). These compounds showed high activity in the 6-Hz psychomotor seizure test as well as were active in the maximal electroshock and subcutaneous pentylenetetrazole (14 and 23) screens. Initial SAR studies for anticonvulsant activity have been discussed.     

Evolution of novel tricyclic CRTh2 receptor antagonists from a (E)-2-cyano-3-(1H-indol-3-yl)acrylamide scaffold

(E)-2-(3-(3-((3-Bromophenyl)amino)-2-cyano-3-oxoprop-1-en-1-yl)-1H-indol-1-yl)acetic acid (1) was discovered in a HTS campaign for CRTh2 receptor antagonists. An SAR around this hit could be established and representatives with interesting activity profiles were obtained. Ring closing tactics to convert this hit series into a novel 2,3,4,5-tetrahydro-1H-pyrido[4,3-b]indole based CRTh2 receptor antagonist series is presented.     

N-[1-(2-Phenylethyl)pyrrolidin-3-yl]-1-adamantanecarboxamides as novel 5-HT2 receptor antagonists

A series of 1-adamantanecarboxamides was synthesized and examined for their potency as a selective 5-HT2 receptor antagonist. We found (S)-N-[1-[2-(4-fluorophenyl)ethyl]pyrrolidin-3-yl]-1-adamantane carboxamide hydrochloride hydrate (10-(S), Y-39241) to have a high affinity and selectivity for 5-HT2 receptors, and this potent anti-platelet effect of Y-39241 was confirmed both in vitro and in vivo.     

Synthesis and positive inotropic activity of N-(4,5-dihydro-[1,2,4]triazolo[4,3-a]quinolin-7-yl)-2-(piperazin-1-yl)acetamide derivatives

A series of N-(4,5-dihydro-[1,2,4]triazolo[4,3-a]quinolin-7-yl)-2-(piperazin-1-yl)acetamide derivatives were synthesized and their positive inotropic activity was evaluated by measuring left atrium stroke volume on isolated rabbit heart preparations. Several compounds showed favorable activity compared with the standard drug, milrinone, among which N-(1-benzyl-4,5-dihydro-[1,2,4]triazolo[4,3-a]quinolin-7-yl)-2-(4-benzylpiperazin-1-yl)acetamide 6j was found to be the most potent with the 13.2% increased stroke volume (milrinone 4.7%) at concentration of 3x10(-5) M in our in vitro study. The chronotropic effects of those compounds having inotropic effects were also evaluated in this work.     

Synthesis and antiplatelet activity of ethyl 4-(1-benzyl-1H-indazol-3-yl)benzoate (YD-3) derivatives

Previously, ethyl 4-(1-benzyl-1H-indazol-3-yl)benzoate (YD-3) was identified by us as the first non-peptide protease-activated receptor 4 (PAR4) antagonist. To continue on our development of novel anti-PAR4 agents, YD-3 was used as a lead compound and a series of its derivatives were synthesized and evaluated for their selective anti-PAR4 activity. Through structure-activity relationship (SAR) study, we identified the important functional groups contributing to anti-PAR4 activity, and these functional groups were kept intact during subsequent structural modification. Several new compounds with anti-PAR4 activity comparable to YD-3 were identified. Among them, ethyl 4-[1-(3-chlorobenzyl)-1H-indazol-3-yl]benzoate (33) showed the most potent inhibitory effect on PAR4-mediated platelet aggregation, ATP release, and P-selectin expression. On the other hand, ethyl 4-(1-phenyl-1H-indazol-3-yl)benzoate (83) exhibited dual inhibitory effects on PAR4 and thromboxane formation from arachidonic acid. The above findings can be used as guidelines for development of novel antiplatelet drug candidates.     

Synthesis and evaluation of 6-[1-(2-[(18)F]fluoro-3-pyridyl)-5-methyl-1H-1,2,3-triazol-4-yl]quinoline for positron emission tomography imaging of the metabotropic glutamate receptor type 1 in brain

The purpose of this study was to synthesize 6-[1-(2-[¹⁸F]fluoro-3-pyridyl)-5-methyl-1H-1,2,3-triazol-4-yl]quinoline ([¹⁸F]FPTQ, [¹⁸F]7a) and to evaluate its potential as a positron emission tomography ligand for imaging metabotropic glutamate receptor type 1 (mGluR1) in the rat brain. Compound [¹⁸F]7a was synthesized by [¹⁸F]fluorination of 6-[1-(2-bromo-3-pyridyl)-5-methyl-1H-1,2,3-triazol-4-yl]quinoline (7b) with potassium [¹⁸F]fluoride. At the end of synthesis, 1280-1830 MBq (n = 8) of [¹⁸F]7a was obtained with >98% radiochemical purity and 118-237 GBq/??mol specific activity using 3300-4000 MBq of [¹⁸F]F⁻. In vitro autoradiography showed that [¹⁸F]7a had high specific binding with mGluR1 in the rat brain. Biodistribution study using a dissection method and small-animal PET showed that [¹⁸F]7a had high uptake in the rat brain. The uptake of radioactivity in the cerebellum was reduced by unlabeled 7a and mGluR1-selective ligand JNJ-16259685 (2), indicating that [¹⁸F]7a had in vivo specific binding with mGluR1. Because of a low amount of radiolabeled metabolite present in the brain, [¹⁸F]7a may have a limiting potential for the in vivo imaging of mGluR1 by PET.     

Synthesis and KCNQ2 opener activity of N-(1-benzo[1,3]dioxol-5-yl-ethyl, N-[1-(2,3-dihydro-benzofuran-5-yl)-ethyl, and N-[1-(2,3-dihydro-1H-indol-5-yl)-ethyl acrylamides

Bioisosteric replacement studies led to the identification of N-(1-benzo[1,3]dioxol-5-yl-ethyl)-3-(2-chloro-phenyl)-acrylamide ((S)-3) as a highly potent KCNQ2 opener, and 3-(2,6-difluoro-phenyl)-N-[1-(2,3-dihydro-benzofuran-5-yl)-ethyl]-acrylamide ((S)-4), and N-[1-(2,3-dihydro-1H-indol-5-yl)-ethyl]-3-(2-fluoro-phenyl)-acrylamide ((S)-5) as highly efficacious KCNQ2 openers. In contrast, their respective R enantiomers showed significantly less or no appreciable KCNQ2 opener activity even at the highest concentration tested (10 microM). Because of its high potency and moderate efficacy as well as its convenient synthesis, (+/-)-3 was selected as a reference compound for analyzing efficacies of KCNQ openers in electrophysiology studies. Compounds (S)-4 and (S)-5 demonstrated significant activity in reducing neuronal hyperexcitability in rat hippocampal slices. The synthesis and the KCNQ2 opener activity of these acrylamides are described.     

Synthesis, antimicrobial and antimycobacterial evaluation of [2-(substituted phenyl)-imidazol-1-yl]-pyridin-3-yl-methanones

A series of [2-(substituted phenyl)-imidazol-1-yl]-pyridin-3-yl-methanones (1-11) were synthesized and screened for their antimicrobial and antimycobacterial activities. Further, a series of [2-(substituted phenyl)-benzimidazol-1-yl]-pyridin-3-yl-methanones (12-20) reported in our earlier study was also screened for their antimycobacterial activity. The antimycobacterial activity results indicated that [2-(4-Nitro-phenyl)-imidazol-1-yl]-pyridin-3-yl-methanone (8, minimum inhibitory concentration [MIC]?=?3.13 μg) was equipotent as standard drug ciprofloxacin and [2-(4-Nitro-phenyl)-benzimidazol-1-yl]-pyridin-3-yl-methanone (16, MIC?=?1.56 μg) was equipotent as standard drug ethambutol. The results of antimicrobial screening demonstrated that 2-[1-(Pyridine-3-carbonyl)-1H-imidazol-2-yl]-benzoic acid (compound 11, MIC?=?0.002 μg) was two times more effective than standard drug ciprofloxacin (MIC?=?0.004 μg) against tested bacterial strains and [2-(2,5-Dimethyl-phenyl)-imidazol-1-yl]-pyridin-3-yl-methanone (compound 3, MIC?=?0.005 μg) was equipotent to the reference compound, fluconazole against tested fungal strains.     

1-(4-Phenylpiperazin-1-yl)-2-(1H-pyrazol-1-yl)ethanones as novel CCR1 antagonists

A novel series of CCR1 antagonists based on the 1-(4-phenylpiperazin-1-yl)-2-(1H-pyrazol-1-yl)ethanone scaffold was identified by screening a compound library utilizing CCR1-expressing human THP-1 cells. SAR studies led to the discovery of the highly potent and selective CCR1 antagonist 14 (CCR1 binding IC₅₀ = 4 nM using [¹²⁵I]-CCL3 as the chemokine ligand). Compound 14 displayed promising pharmacokinetic and toxicological profiles in preclinical species.     

Synthesis, pharmacological evaluation and docking studies of N-(benzo[d]thiazol-2-yl)-2-(piperazin-1-yl)acetamide analogs as COX-2 inhibitors

The existing NSAIDs having number of toxicities emphasises the need for discovery of new non-toxic anti-inflammatory agents. In this Letter, we present the simple two step chemical synthesis, in vivo pharmacological screening and docking study of few N-(benzo[d]thiazol-2-yl)-2-(piperazin-1-yl)acetamide analogs. Different amino benzothiazoles were chloroacetylated and further reacted with substituted piperazines in presence of a base to get N-(benzo[d]thiazol-2-yl)-2-(piperazin-1-yl)acetamide analogs (A1-C4). These compounds were evaluated for anti-inflammatory activity by carragenan induced paw oedema method. Promising compounds were screened for toxicity by evaluating the ulcerogenic potential. Molecular docking experiments were carried out against COX-2 enzyme using Surflex-Dock GeomX programme of Sybyl software on Dell T-1500 workstation to confirm the mechanism of action of active compounds among the series. In silico study reveal the binding interactions of N-(benzo[d]thiazol-2-yl)-2-(piperazin-1-yl)acetamide analogs with COX-2 protein and is in agreement with the in vivo anti-inflammatory activity.