Synthesis of 13C6‐labeled,dual‐target inhibitor of cannabinoid‐1 receptor (CB1R) and inducible nitric oxide synthase (iNOS)

Cannabinoid‐1 receptor (CB₁R) antagonists/inverse agonists have great potential in the treatment of metabolic disorders like dyslipidemia, type 2 diabetes, and nonalcoholic steatohepatitis. Cannabinoid‐1 receptor inverse agonists have also been reported to be effective in mitigating fibrotic disorders in murine models. Inducible nitric oxide synthase is another promising target implicated in fibrotic and inflammatory disorders. We have disclosed MRI‐1867 as a potent and selective, peripherally acting dual‐target inhibitor of the CB₁R and inducible nitric oxide synthase (iNOS). Herein, we report the synthesis of [¹³C₆]‐MRI‐1867 as a racemate from commercially available chlorobenzene‐¹³C₆ as the starting, stable‐isotope label reagent. The racemic [¹³C₆]‐MRI‐1867 was further processed to the stable‐isotope‐labeled enantiopure compounds using chiral chromatography. Both racemic [¹³C₆]‐MRI‐1867 and S‐¹³C₆‐MRI‐1867 will be used to quantitate unlabeled S‐MRI‐1867 during clinical drug metabolism and pharmacokinetics studies and will be used as a liquid chromatography‐tandem mass spectrometry bioanalytical standard.     

Synthesis and characterization of tritium labeled N‐((R)‐1‐((S)‐4‐(4‐chlorophenyl)‐4‐hydroxy‐3,3‐dimethylpiperidin‐1‐yl)‐3‐methyl‐1‐oxobutan‐2‐yl)‐3‐sulfamoylbenzamide

N‐((R)‐1‐((S)‐4‐(4‐chlorophenyl)‐4‐hydroxy‐3,3‐dimethylpiperidin‐1‐yl)‐3‐methyl‐1‐oxobutan‐2‐yl)‐3‐sulfamoylbenzamide is a potent C‐C chemokine receptor 1 (CCR1) antagonist. The compound, possessing benzamide functionality, successfully underwent tritium/hydrogen (T/H) exchange with an organoiridium catalyst (Crabtree's catalyst). The labeling pattern in the product was studied with liquid chromatography–mass spectrometry, time‐of‐flight mass spectrometry, and ³H‐NMR. Overall, multiple labeled species were identified. In addition to the anticipated incorporation of tritium in the benzamide moiety, tritium labeling was observed in the valine portion of the molecule including substitution at its chiral carbon. Using authentic standards, liquid chromatography analysis of the labeled compound showed complete retention of stereochemical configuration.     

Radiolabeling of a high potency cannabinoid subtype‐1 receptor ligand,N‐(4‐fluoro‐benzyl)‐4‐(3‐(piperidin‐1‐yl)‐indole‐1‐sulfonyl)benzamide (PipISB), with carbon‐11 or fluorine‐18

PipISB [N‐(4‐fluoro‐benzyl)‐4‐(3‐(piperidin‐1‐yl)‐indole‐1‐sulfonyl)benzamide, 9] was identified as a selective high potency CB₁ receptor ligand. Here we describe the labeling of 9 with positron‐emitters to provide candidate radioligands for imaging brain CB₁ receptors with positron emission tomography (PET). The radiolabeling of 9 was achieved by two methods, method A with carbon‐11 and method B with fluorine‐18. In method A, [¹¹C]9 was prepared in one step from [¹¹C]carbon monoxide, itself prepared from cyclotron‐produced [¹¹C]carbon dioxide. In method B, [¹⁸F]9 was prepared from cyclotron‐produced [¹⁸F]fluoride ion in a two‐stage, four‐step synthesis with [¹⁸F]4‐fluoro‐benzyl bromide as a labeling agent. The radiosynthesis time for method A was 44 min; decay‐corrected radiochemical yields (RCYs) from [¹¹C]carbon monoxide ranged from 3.1 to 11.6% and specific radioactivities ranged from 21 to 67 GBq/µmol. The radiosynthesis time for method B was 115 min; RCYs from [¹⁸F]fluoride ion ranged from 1.5 to 5.6% and specific radioactivities ranged from 200 to 348 GBq/µmol. With these methods, [¹¹C]9 and [¹⁸F]9 may be prepared in adequate activity and quality for future evaluation as PET radioligands. Copyright © 2008 John Wiley & Sons, Ltd.     

Design and synthesis of 5‐(5‐nitrothiophen‐2‐yl)‐3‐phenyl‐4,5‐dihydro‐1H‐pyrazole derivatives with improved solubility and potential antituberculosis activity

We report the design‐synthesis of several nitrothiophene containing molecules as antituberculosis agents. The molecules were designed on the basis of previously reported nitrofuran molecules in our laboratory, and the α,β‐unsaturated linker was modified to cyclized linker in order to overcome the challenge of low solubility and possible toxicity. The stereo‐electronic properties such as HOMO, LUMO, and HOMO‐LUMO gap along with other properties such as aqueous solvation energies and QPLogS values were studied. The designed molecules were synthesized and tested for in vitro antituberculosis activity, and some molecules were found to be highly active comparable to standard drugs. Further, the aqueous solubility was determined using visual inspection method and the designed molecules were found to be more soluble than their chalcone counterparts. Cytotoxicity studies were performed and the molecules were found to be non‐cytotoxic. Electroanalytical studies proved nitro reduction as the mechanism of action for these molecules. Thus, this study provides potential nitrothiophene containing hits with improved solubility and reduced chances of toxicity.     

The synthesis of three isotopomers of 2‐methyl‐2‐(4‐[3‐[1‐(4‐methylbenzyl)‐5‐oxo‐4,5‐dihydro‐1H‐[1,2,4]triazol‐3‐yl]propyl]phenoxy)propionic acid,a potent and selective peroxisome proliferator‐activated receptor alpha agonist

Although fenofibrate ( 1a ) is commercially available and clinically effective in lowering serum triglycerides, its activity and sub‐type selectivity at the PPARα receptors are only moderate; therefore, there exists a need for more potent and sub‐type selective PPARα agonists. To that end, discovery efforts have identified 2‐methyl‐2‐(4‐[3‐[1‐(4‐methylbenzyl)‐5‐oxo‐4,5‐dihydro‐1H‐[1,2,4]triazol‐3‐yl]propyl]phenoxy)propionic acid ( 2 ), a potent and selective human PPARα receptor agonist. In support of pre‐clinical ADME studies and bioanalysis, three isotopomers of 2 have been synthesized. The results of these efforts are described below. Copyright © 2007 John Wiley & Sons, Ltd.     

Synthesis of N‐(piperidin‐1‐yl)‐5‐(4‐methoxyphenyl)‐1‐(2‐chlorophenyl)‐4‐[18F]fluoro‐1H‐pyrazole‐3‐carboxamide by nucleophilic [18F] fluorination: a PET radiotracer for studying CB1 cannabinoid receptors

The feasibility of nucleophilic displacement of bromide in the 4‐bromopyrazole ring with [¹⁸F]fluoride has been demonstrated by the synthesis of two radiolabeled compounds: N‐(piperidin‐1‐yl)‐5‐(4‐methoxyphenyl)‐1‐(2‐chlorophenyl)‐4‐[¹⁸F]fluoro‐1H‐pyrazole‐3‐carboxamide, ([¹⁸F] NIDA‐42033) 1b and 1‐(2‐chlorophenyl)‐4‐[¹⁸F]fluoro‐5‐(4‐methoxyphenyl)‐1H‐pyrazole‐3‐carboxylic acid, ethyl ester 4 . The radiochemical yields were in the range of 1–6%. [¹⁸F]NIDA‐42033, a potential radiotracer for the study of CB₁ cannabinoid receptors in the animal brain by positron emission tomography, has been synthesized in sufficient quantities with specific radioactivity greater than 2500 mCi/μmol and radiochemical purity >95%. Copyright © 2002 John Wiley & Sons, Ltd.     

Antimycobacterial evaluation of novel [4,5‐dihydro‐1H‐pyrazole‐1‐carbonyl]pyridine derivatives synthesized by microwave‐mediated Michael addition

The focus of this study is the synthesis and biological activity evaluation of a series of dibenzalaceton derivatives (3a‐3n) and novel [4,5‐dihydro‐1H‐pyrazole‐1‐carbonyl]pyridine derivatives (5a‐5g) against Mycobacterium bovis, Bacillus Calmette–Guerin (BCG). Dibenzalacetone derivatives were synthesized by benzaldehyde derivatives. The [4,5‐dihydro‐1H‐pyrazole‐1‐carbonyl]pyridine derivatives were synthesized by Michael addition reaction and using green chemistry microwave‐mediated method. All compounds were evaluated against BCG and the activity expressed as minimum inhibitory concentration (MIC) in μM. The result showed good activity for all the compounds especially compounds (3a), (3n), and (5a) illustrated high activity (7.03, 8.10 and 5.37 μM, respectively). Copyright © 2014 John Wiley & Sons, Ltd.     

Synthesis and Antitubercular Activity of 2‐(substituted phenyl/benzyl‐amino)‐6‐(4‐chlorophenyl)‐5‐(methoxycarbonyl)‐4‐methyl‐3,6‐dihydropyrimidin‐1‐ium Chlorides

A series of 2‐(substituted phenyl/benzyl‐amino)‐6‐(4‐chlorophenyl)‐5‐(methoxycarbonyl)‐4‐methyl‐3,6‐dihydropyrimidin‐1‐ium chlorides 7–13 and 15 was synthesized in their hydrochloride salt form. The title compounds were characterized by FT‐IR, NMR (¹H and ¹³C) and elemental analysis. They were evaluated for their in vitro antitubercular activity against Mycobacterium tuberculosis H37Rv, multidrug resistance tuberculosis and extensively drug resistance tuberculosis by agar diffusion method and tested for the cytotoxic action on peripheral blood mononuclear cells by MTT assay. Among all the tested compounds in the series, compounds 7 and 11 emerged as promising antitubercular agents at 16 μg/mL against multidrug resistance tuberculosis and over 64 μg/mL against extensively drug resistance tuberculosis. The conformational features and supramolecular assembly of the promising compounds 7 and 11 were determined by single crystal X‐ray study.     

Exploration of 5‐(5‐nitrothiophen‐2‐yl)‐4,5‐dihydro‐1H‐pyrazoles as selective,multitargeted antimycobacterial agents

We report the biological evaluation of 5‐(5‐nitrothiophen‐2‐yl)‐4,5‐dihydro‐1H‐pyrazole derivatives against bacteria, eukaryotic cell lines and the assessment of their mechanisms of action to determine their prospects of being developed into potent antituberculosis agents. The compounds were evaluated for their antibacterial property against Mycobacterium tuberculosis H37Rv, multidrug‐resistant M. tuberculosis, Mycobacterium bovis BCG, Mycobacterium aurum, Escherichia coli, and Staphylococcus aureus using high‐throughput spot‐culture growth inhibition assay. They were found to be selective toward slow‐growing mycobacteria and Gram‐positive bacteria. In M. bovis BCG, they exhibited a bactericidal mode of action. Cytotoxicity was assessed in human THP‐1 and murine RAW 264.7 cell lines, and the compounds showed a lower cytotoxicity potential when compared with their antibacterial activity. They were found to be excellent whole‐cell efflux pump inhibitors of the mycobacterial surrogate M. aurum, performing better than known efflux pump inhibitor verapamil. The 5‐nitrothiophene moiety was identified for the first time as a prospective inhibitor scaffold of mycobacterial arylamine N‐acetyltransferase enzyme, which is the key enzyme in metabolizing isoniazid, a first‐line antituberculosis drug. The two aforementioned findings make the compounds potential hits in the development of adjunctive tuberculosis therapy.     

Radiosynthesis of the α4β2 nicotinic acetylcholine receptor ligand: 5‐((1‐[11C]‐methyl‐2‐(S)‐pyrrolidinyl)methoxy)‐2‐chloro‐3‐((E)‐2‐(2‐fluoropyridin‐4‐yl)vinyl)pyridine

5‐((1‐[¹¹C]‐methyl‐2‐(S)‐pyrrolidinyl)methoxy)‐2‐chloro‐3‐((E)‐2‐(2‐fluoropyridin‐4‐yl)‐vinyl)pyridine ([¹¹C]‐FPVC) was synthesized from [¹¹C]‐methyl iodide and the corresponding normethyl precursor. The average time of synthesis, purification, and formulation was 42 min with an average non‐decay‐corrected radiochemical yield of 19%. The average specific radioactivity was 359 GBq/µmol (9691 mCi/µmole) at end of synthesis (EOS). Copyright © 2006 John Wiley & Sons, Ltd.     

Synthesis,Polymorphism, and Insecticidal Activity of Methyl 4‐(4‐chlorophenyl)‐8‐iodo‐2‐methyl‐6‐oxo‐1,6‐dihydro‐4H‐pyrimido[2,1‐b]quinazoline‐3‐Carboxylate Against Anopheles arabiensis Mosquito

Mosquitoes are the major vectors of pathogens and parasites including those causing malaria, the most deadly vector‐borne disease. The negative environmental effects of most synthetic compounds combined with widespread development of insecticide resistance encourage an interest in finding and developing alternative products against mosquitoes. In this study, pyrimido[2,1‐b]quinazoline derivative DHPM 3 has been synthesized by three‐step chemical reaction and screened for larvicide, adulticide, and repellent properties against Anopheles arabiensis, one of the dominant vectors of malaria in Africa. The title compound emerged as potential larvicide agent for further research and development, because it exerted 100% mortality, while adulticide activity was considered moderate.     

Anxiolytic‐like effect of 2‐(4‐((1‐phenyl‐1H‐pyrazol‐4‐yl)methyl)piperazin‐1‐yl)ethan‐1‐ol is mediated through the benzodiazepine and nicotinic pathways

In this study, we proposed the design, synthesis of a new compound 2‐(4‐((1‐phenyl‐1H‐pyrazol‐4‐yl)methyl)piperazin‐1‐yl)ethan‐1‐ol (LQFM032), and pharmacological evaluation of its anxiolytic‐like effect. This new compound was subjected to pharmacological screening referred to as Irwin test, prior to sodium pentobarbital‐induced sleep, open‐field and wire tests. The anxiolytic‐like effect of this compound was evaluated using elevated plus maze and light–dark box tests. In addition, the mnemonic activity was evaluated through step‐down test. In sodium pentobarbital‐induced sleep test, LQFM032 decreased latency and increased duration of sleep. In the open‐field test, LQFM032 altered behavioral parameter, that suggested anxiolytic‐like activity, as increased in crossings and time spent at the center of open field. In the plus maze test and light–dark box test, the LQFM032 showed anxiolytic‐like activity, increased entries and time spent on open arms, and increased in number of transitions and time spent on light area, respectively. Those effects was antagonized by flumazenil but not with 1‐(2‐Methoxyphenyl)‐4‐(4‐phthalimidobutyl)piperazine (NAN‐190). The LQFM032 did not alter mnemonic activity. Moreover, the anxiolytic‐like activity of LQFM032 was antagonized by mecamylamine. In summary, LQFM032 showed benzodiazepine and nicotinic pathways mediated anxiolytic‐like activity without altering the mnemonic activity.     

2‐Amino‐3‐(1‐(4‐(4‐(2‐methoxyphenyl) piperazine‐1‐yl)butyl)‐1H‐1,2,3‐triazol‐4‐yl) propanoic acid: synthesized, 99mTc‐tricarbonyl labeled,and bioevaluated as a potential 5HT1A receptor ligand

To develop a novel 5HT_1A receptor imaging agent, a new methoxyphenyl piperazine derivative was synthesized and radiolabeled with ^99mTc‐tricarbonyl precursor. We used the Cu (I)‐catalyzed cycloaddition of azide and terminal alkynes to synthesize 1, 2, 3 triazole as the metal chelating system. This synthesis provided reliable and reproducible method to attach technetium to the methoxyphenyl piperazine moiety. ^99mTc‐tricabonyl labeling of ligand was performed at high radiochemical purity (greater than 95%). The radiolabeled compound was stable at least 24 h in room temperature. In vitro stability study in human serum albumin showed more than 90% stability in 37 °C incubation for 6 h. Biodistribution studies in rat have shown brain hippocampus uptake of 0.31 ± 0.02 %ID/g at 5‐min post‐injection. The favorable in vitro/in vivo stability, lipophilicity, and biodistribution profiles suggest that this radioconjugate is a good candidate for further exploration of its potential clinical application. Copyright © 2012 John Wiley & Sons, Ltd.     

13C‐ and 14C‐labelling of N‐[1‐(4‐chlorophenyl)‐1H‐pyrrol‐2‐yl‐methyleneamino] guanidinium acetate

N‐[1‐(4‐chlorophenyl)‐1H‐pyrrol‐2‐yl‐¹³C₄‐methyleneamino]guanidinium acetate has been synthesized by a four‐step procedure. This involved reduction of the Weinreb amide N,N′‐dimethyl‐N,N′‐dimethyloxybutane‐1,4‐diamide‐1,2,3,4‐¹³C₄ by Dibal‐H to give the corresponding unstable dialdehyde which is reacted in situ with 4‐chloroaniline to form 1‐(4‐chlorophenyl)‐1H‐pyrrole‐¹³C₄. This pyrrole analogue underwent a Vilsmeyer acylation with POCl₃/DMF followed by final reaction with aminoguanidine bicarbonate to produce the desired labelled compound with 99% atom ¹³C. By using DMF [α‐¹⁴C] a radio‐labelled analogue was synthesized with a specific activity of 60 mCi/mmol. Copyright © 2005 John Wiley & Sons, Ltd.     

Radiosynthesis and validation of [5‐cyano‐N‐(4‐(4‐[11C]methylpiperazin‐1‐yl)‐2‐(piperidin‐1‐yl)phenyl) furan‐2‐carboxamide] ([11C]CPPC), a PET radiotracer for imaging CSF1R,a microglia‐specific marker

In this practitioner protocol, the radiochemical synthesis of [¹¹C]CPPC is described in detail, and a quality control summary of three validation productions is presented. The results indicate that the radiotracer product can be produced in good radiochemical yield (> 60 mCi (2.22 GBq) at end‐of‐synthesis (EOS)), at high specific activity (molar activity > 11,435 mCi/μmole (423 GBq/μmole) at EOS) and high chemical and radiochemical purity. The entire production conforms to current Good Manufacturing Practice (cGMP) requirements. The final product is formulated as a sterile, pyrogen‐free solution suitable for human injection.     

Synthesis,In Vitro Protoporphyrinogen Oxidase Inhibition,and Herbicidal Activity of N‐(Benzothiazol‐5‐yl)hexahydro‐1H‐isoindole‐1,3‐diones and N‐(Benzothiazol‐5‐yl)hexahydro‐1H‐isoindol‐1‐ones

Protoporphyrinogen oxidase ( EC 1.3.3.4 ) is one of the most significant targets for a large family of herbicides. As part of our continuous efforts to search for novel protoporphyrinogen oxidase‐inhibiting herbicides, N‐(benzothiazol‐5‐yl)tetrahydroisoindole‐1,3‐dione was selected as a lead compound for structural optimization, leading to the syntheses of a series of novel N‐(benzothiazol‐5‐yl)hexahydro‐1H‐isoindole‐1,3‐diones ( 1a – o ) and N‐(benzothiazol‐5‐yl)hexahydro‐1H‐isoindol‐1‐ones ( 2a – i ). These newly prepared compounds were characterized by elemental analyses, ¹H NMR, and ESI‐MS, and the structures of 1h and 2h were further confirmed by X‐ray diffraction analyses. The bioassays indicated that some compounds displayed comparable or higher protoporphyrinogen oxidase inhibition activities in comparison with the commercial control. Very promising, compound 2a , ethyl 2‐((6‐fluoro‐5‐(4,5,6,7‐tetrahydro‐1‐oxo‐1H‐isoindol‐2(3H)‐yl)benzo[d]thiazol‐2‐yl)‐sulfanyl)acetate, was recognized as the most potent candidate with K_i value of 0.0091 μm . Further greenhouse screening results demonstrated that some compounds exhibited good herbicidal activity against Chenopodium album at the dosage of 150 g/ha.