18F‐Labelled vorozole analogues as PET tracer for aromatase

One‐ and two‐step syntheses for the ¹⁸F‐labelling of 6‐[(S)‐(4‐chlorophenyl)(1H‐1,2,4‐triazol‐1‐yl)methyl]‐1‐(2‐[¹⁸F]fluoroethyl)‐1H‐benzotriazole, [¹⁸F]FVOZ, 1 and 6‐[(S)‐(4‐chlorophenyl)(1H‐1,2,4‐triazol‐1‐yl)methyl]‐1‐[2‐(2‐[¹⁸F]fluoroethoxy)ethyl]‐1H‐benzotriazole, [¹⁸F]FVOO, 2 were developed. In the two‐step synthesis, the nucleophilic fluorination step was performed by reacting (S)‐6‐[(4‐chlorophenyl)‐(1H‐1,2,4‐triazol‐1‐yl)methyl]‐1H‐benzotriazole (VOZ) with either the ¹⁸F‐labelled ethane‐1,2‐diyl bis(4‐methylbenzenesulfonate) or the oxydiethane‐2,1‐diyl bis(4‐methylbenzenesulfonate). The radiochemical yields were in the range of 9–13% after the 110–120 min total syntheses and the specific radioactivities were 175±7 GBq/µmol and 56 GBq/µmol for compounds 1 and 2, respectively. In the one‐step synthesis, the precursor 2‐{6‐[(4‐chlorophenyl)(1H‐1,2,4‐triazol‐1‐yl)methyl]‐1H‐1,2,3‐benzotriazol‐1‐yl}ethyl 4‐methylbenzenesulfonate (7) or 1‐[2‐(2‐bromoethoxy)ethyl]‐6‐[(4‐chlorophenyl)(1H‐1,2,4‐triazol‐1‐yl)methyl]‐1H‐benzotriazole (8) was directly labelled via an ¹⁸F nucleophilic substitution to give the corresponding tracer. The labelled compounds were obtained in 36–99% radiochemical yield after 75‐min syntheses. The specific radioactivities are 100 GBq/µmol for compound 1 and 80 GBq/µmol for compound 2. In vitro autoradiography using frozen rat brains illustrated specific binding in the medial amygdala, the bed nucleus of stria terminalis and the preoptic area, all of which corresponded well to the result of ¹¹C‐labelled vorozole. Copyright © 2008 John Wiley & Sons, Ltd.     

Synthesis and Anticonvulsant Properties of New Mannich Bases Derived from 3‐Aryl‐pyrrolidine‐2,5‐diones. Part 1

A series of new Mannich bases of N‐[(4‐arylpiperazin‐1‐yl)‐methyl]‐3‐(chlorophenyl)‐pyrrolidine‐2,5‐diones 10–23 have been synthesized and evaluated for their anticonvulsant activity in maximum electroshock (MES) and subcutaneous pentylenetetrazole (scPTZ) seizure threshold tests. Their neurotoxicity was determined using a rotorod screen. Several molecules showed a promising anticonvulsant profile especially in the MES‐test. In this model of seizures, the most active were N‐[{4‐(4‐chlorophenyl)‐piperazin‐1‐yl}‐methyl]‐3‐(3‐chlorophenyl)‐pyrrolidine‐2,5‐dione 16 and N‐[{4‐(3‐trifluoromethylphenyl)‐piperazin‐1‐yl}‐methyl]‐3‐(3‐chlorophenyl)‐pyrrolidine‐2,5‐dione 17 with ED₅₀ values of 21.4 mg/kg and 28.83 mg/kg, respectively. Selected derivatives 10 , 14 , and 16 were tested in the psychomotor seizure 6‐Hz test from which N‐[{4‐(2‐chlorophenyl)‐piperazin‐1‐yl}‐methyl]‐3‐(2‐chlorophenyl)‐pyrrolidine‐2,5‐dione 10 revealed the highest protection with an ED₅₀ of 78 mg/kg. Compounds 10 , 12 , and 17 were also tested in the pilocarpine‐induced status PIPS test. Furthermore, 17 was examined in the hippocampal kindling screen after i. p. administration to rats.     

Synthesis and Biological Evaluation of Kojic Acid Derivatives Containing 1,2,4‐triazole as Potent Tyrosinase Inhibitors

A series of 5‐substituted‐3‐[5‐hydroxy‐4‐pyrone‐2‐yl‐methymercapto]‐4‐amino‐1,2,4‐triazole derivatives were synthesized by nucleophilic substitution reaction of 5‐hydroxy‐2‐chloromethyl ‐4H‐pyran‐4‐one with 5‐substituted‐3‐mercapto‐4‐amino‐1,2,4‐triazole, and their inhibitory effects on mushroom tyrosinase were evaluated. The results indicated that most of the synthesized compounds exhibited significant inhibitory activity. Specifically, 5‐(4‐chlorophenyl)‐3‐[5‐hydroxy‐4‐pyrone‐2‐yl‐methymercapto]‐4‐amino‐1,2,4‐triazole ( 6j ) exhibited the most potent tyrosinase inhibitory activity with IC₅₀ value of 4.50 ± 0.34 μm . The kinetic studies of the compound ( 6j ) demonstrated that the inhibitory effects of the compound on the tyrosinase were belonging to competitive inhibitors. Meanwhile, the structure–activity relationship was also discussed.     

Efficient regioselective three-component domino synthesis of 3-(1,2,4-Triazol-5-yl)-1,3-thiazolidin-4-ones as potent antifungal and antituberculosis agents

In research for promising antibacterial and antifungal compounds, a series of 2‐aryl 3‐[1,2,4]triazol‐5‐yl 4‐thiazolidinones 1 were synthesized by a domino reaction of 5‐amino‐1H‐[1,2,4]triazoles 3 , aromatic aldehydes, and α‐mercaptoacids in boiling toluene in the presence of molecular sieves 4 Å. Of the twenty novel 3‐[1,2,4]triazol‐5‐yl 4‐thiazolidinone derivatives, four compounds 2‐benzo[d][1,3]dioxol‐6‐yl‐3‐[(3‐morpholin‐4‐yl)‐1H‐1,2,4‐triazol‐5‐yl)]‐1,3‐thiazolidin‐4‐one ( 1i ), 2‐(4‐chlorophenyl)‐5‐methyl‐3‐[3‐(4‐methylpiperazin‐1‐yl)‐1H‐1,2,4‐triazol‐5‐yl]‐1,3‐thiazolidin‐4‐one ( 1p ), 2‐benzo[d][1,3]dioxol‐6‐yl‐3‐[3‐(4‐methylpiperazin‐1‐yl)‐1H‐1,2,4‐triazol‐5‐yl]‐1,3‐thiazolidin‐4‐one ( 1s ), 2‐benzo[d][1,3]dioxol‐6‐yl‐5‐methyl‐3‐[3‐(4‐methylpiperazin‐1‐yl)‐1H‐1,2,4‐triazol‐5‐yl]‐1,3‐thiazolidin‐4‐one ( 1t ) exhibited MICs of 4 µg/mL or less versus Mycobacterium tuberculosis. Moreover, these compounds were screened against Candida albicans. Compounds 1p , 1s gave MICs of 1 µg/mL or less, and were fungicidal. Finally, compound 1s was evaluated against an expanded fungal panel and showed good activity against Cryptococcus neoformans. In addition, compound 1s also appeared to be fungicidal against Aspergillus arrhizus, with MIC <1 µg/mL.     

Characterization of cytochrome P450 enzymes and P‐glycoprotein involved in the metabolism and transport of a new anti‐angiogenic agent KR‐31831

The in vitro metabolism and the transport of a novel anti‐angiogenic agent KR‐31831, (2R,3R,4S)‐6‐amino‐4‐[N‐(4‐chlorophenyl)‐N‐(1H‐imidazol‐2‐ylmethyl)amino]‐3‐hydroxy‐2‐dimethyoxymethyl‐3,4‐dihydro‐2‐methyl‐2H‐1‐benzopyran were investigated. Liquid chromatography‐mass spectrometry and tandem mass spectrometry were used for qualitative and quantitative analysis. The bidirectional transport studies of KR‐31831 using Caco‐2 cell monolayers showed the efflux to be significantly higher than influx (29.1 × 10^?6 compared to 11.5 × 10^?6 cm/s). P‐glycoprotein inhibitors significantly increased the influx of KR‐31831 and decreased the efflux of KR‐31831. These data indicate that KR‐313831 is a substrate for an efflux pump, P‐glycoprotein. The incubations of KR‐31831 with human liver microsomes produced three metabolites, M1, M2, and M3. M1 and M2 were identified as N‐(4‐chlorophenyl)‐N‐(1H‐imidazol‐2‐ylmethyl)amine and (2R,3R,4S)‐6‐amino‐4‐[N‐(4‐chlorophenyl)‐N‐(1H‐imidazol‐2‐ylmethyl)amino]‐3‐hydroxy‐2‐hydroxymethyl‐3,4‐dihydro‐2‐methyl‐2H‐1‐benzopyran by comparison with the authentic standards. M3 was tentatively characterized as hydroxy‐KR‐31831. CYP3A4 was identified as the major enzyme responsible for KR‐31831 metabolism to a major metabolite M1 using the combination of correlation analysis, immuno‐inhibition, chemical inhibition in human liver microsomes, and metabolism by cDNA expressed CYP enzymes. There is the possibility of drug–drug interactions when prescribing KR‐31831 concomitantly with known inhibitors or inducers of CYP3A4 and P‐glycoprotein. KR‐31831 was found to inhibit potently the metabolism of CYP2D6 substrate, suggesting that coadministration of KR‐31831 with CYP2D6 substrates may have significant effects on the pharmacokinetics of CYP2D6 substrates. Drug Dev. Res. 66:40–49. 2006. © 2006 Wiley‐Liss, Inc.     

Synthesis of the lipid peroxidation product 4‐hydroxy‐2(E)‐nonenal with 13C stable isotope incorporation

The aim of this work was to synthesize ¹³C internal standards for the quantification of 4‐hydroxy‐2(E)‐nonenal (HNE), a lipid peroxidation product, and of the etheno‐adducts possibly formed by HNE damage to DNA nucleobases. We designed an eight‐step synthesis starting from ethyl 2‐bromoacetate and giving access to 4‐[(tetrahydro‐2H‐pyran‐2‐yl)oxy]‐2(E)‐nonenal. This compound is a precursor of HNE. The scheme was then used to produce the ¹³C precursor [1,2‐¹³C₂]‐4‐[(tetrahydro‐2H‐pyran‐2‐yl)oxy]‐2(E)‐nonenal. [1,2‐¹³C₂]‐HNE was obtained by acid deprotection. All the intermediary and final compounds were fully characterized by IR, HRMS, ¹H and ¹³C NMR. It is the first synthesis of HNE which enables the incorporation of two ¹³C labels at determined positions. Copyright © 2008 John Wiley & Sons, Ltd.     

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.     

Synthesis and Anticonvulsant Properties of New N‐Mannich Bases Derived from 3,3‐Diphenyl‐ and 3‐Ethyl‐3‐methyl‐pyrrolidine‐2,5‐diones. Part III

Twenty‐four new N‐[(4‐phenylpiperazin‐1‐yl)‐methyl] derivatives of 3,3‐diphenyl‐ ( 7 – 18 ) and 3‐ethyl‐3‐methyl‐pyrrolidine‐2,5‐dione ( 19 – 30 ) were synthesized and evaluated for their anticonvulsant activity in the maximum electroshock (MES) and subcutaneous pentylenetetrazole (scPTZ) seizure tests. The acute neurological toxicity was determined using the rotorod screen. Eleven compounds were active and revealed protection only in electrically induced seizures (MES). In the whole series the most effective compound was N‐[{4‐(3‐trifluoromethylphenyl)‐piperazin‐1‐yl}‐methyl]‐3,3‐diphenyl‐pyrrolidine‐2,5‐dione ( 14 ) with an ED₅₀ value of 30.3 mg/kg (p.o. rats) in the MES test. To explain the possible mechanism of action, for chosen active derivatives 7 , 8 , 9 , 11 , 14 , 23 , and 26 , their influence on Na_V1.2 sodium channel currents was evaluated in vitro. The crystallographic structures for several molecules ( 8 , 10 , and 11 ) were solved.     

Identification of NQO1 and ferrochelatase as interaction partners for neuroprotective N‐{[2‐(4‐phenyl‐piperazin‐1‐yl)‐ethyl]‐phenyl}‐arylamides

Affinity chromatography was used to identify potential cellular targets that are responsible for neuroprotective activity of N‐{[2‐(4‐phenyl‐piperazin‐1‐yl)‐ethyl]‐phenyl}‐arylamides. Active and inactive representatives of N‐{[2‐(4‐phenyl‐piperazin‐1‐yl)‐ethyl]‐phenyl}‐arylamides bearing an extended linker were synthesized and immobilized on an agarose‐based matrix. This was followed by the identification of specifically bound proteins isolated out of the whole rat brain extract. Inducible flavoprotein NAD(P)H:quinone oxidoreductase (NQO1) was identified as candidates for cellular targets.     

Synthesis and in‐vitro Cytotoxicity of Poly‐functionalized 4‐(2‐Arylthiazol‐4‐yl)‐4H‐chromenes

A new series of 4‐aryl‐4H‐chromenes bearing a 2‐arylthiazol‐4‐yl moiety at the 4‐position were prepared as potential cytotoxic agents. The in‐vitro cytotoxic activity of the synthesized 4‐aryl‐4H‐chromenes was investigated in comparison with etoposide, a well‐known anticancer drug, using MTT colorimetric assay. Among them, the 2‐(2‐chlorophenyl)thiazol‐4‐yl analog 4b showed the most potent activity against nasopharyngeal epidermoid carcinoma KB, medulloblastoma DAOY, and astrocytoma 1321N1, and compound 4d bearing a 2‐(4‐chlorophenyl)thiazol‐4‐yl moiety at the 4‐position of the chromene ring exhibited the best inhibitory activity against breast cancer cells MCF‐7, lung cancer cells A549, and colon adenocarcinoma cells SW480 with IC₅₀ values less than 5 μM. The ability of compound 4b to induce apoptosis was confirmed in a nuclear morphological assay by DAPI staining in the KB and MCF‐7 cells.     

Synthesis and Antimycobacterial Activity of Azetidine‐, Quinazoline‐, and Triazolo‐thiadiazole‐containing Pyrazines

The re‐emergence of tuberculosis (TB) as a global health problem over the past few decades, accompanied by the rise of drug‐resistant strains of Mycobacterium tuberculosis, emphasizes the need for the discovery of new therapeutic drugs against this disease. The emerging serious problem both in terms of TB control and clinical management prompted us to synthesize a novel series of N‐[2‐(substituted aryl)‐3‐chloro‐4‐oxoazetidin‐1‐yl]‐2‐(pyrazin‐2‐yloxy)acetamide, 6‐(substituted aryl)‐3‐[(pyrazin‐2‐yloxy)methyl][1,2,4]triazolo[3,4‐b][1,3,4]thiadiazole, and N‐[6‐({2‐[(pyrazin‐2‐yloxy)acetyl] hydrazino}sulfonyl)‐2‐methyl‐4‐oxo‐1,4‐dihydroquinazolin‐3(2H)yl]‐substituted aryl sulfonamides. The compounds were synthesized using the appropriate synthetic route. All synthesized compounds were assayed in vitro for antimycobacterial activity against the H37 Rv strain of Mycobacterium tuberculosis. The minimum inhibitory concentration (MIC) was determined for the test compounds as well as for the reference standards. The compound which exhibited good antimycobacterial activity contains the substituents fluorine and methoxy. These electron‐withdrawing or ‐donating substituents amend the lipophilicity of the test compounds which, in turn, alter the permeability across the bacterial cell membrane. Compounds 28 , 37 , and 43 showed good antimycobacterial activity while compound 51 showed a promising antimycobacterial activity.     

Synthesis and anticonvulsant activity of new n-mannich bases derived from 5-cyclopropyl-5-phenyl-hydantoins

Synthesis, physicochemical and anticonvulsant properties of new N‐Mannich bases 3–24 derived from 5‐cyclopropyl‐5‐phenyl‐ and 5‐cyclopropyl‐5‐(4‐chlorophenyl)‐hydantoins were described here. Initial anticonvulsant screening was performed using intraperitoneal (i.p.) maximal electroshock (MES) and subcutaneous pentylenetetrazole (scPTZ) seizures tests. Selected derivatives were also screened in the 6‐Hz test. The neurotoxicity was determined applying the rotorod test. The pharmacological results revealed that the majority of compounds were effective in MES and/or scPTZ tests. The quantitative studies after oral administration into rats showed that several molecules were more potent than phenytoin and ethosuximide which were used as reference antiepileptic drugs. From the whole series the most active was 3‐[(4‐phenylpiperazin‐1‐yl)‐methyl]‐5‐cyclopropyl‐5‐phenyl‐imidazolidine‐2,4‐dione ( 3 ) with the ED₅₀ value of 5.29 mg/kg in the MES test.     

Biscoumarin–pyrimidine conjugates as potent anticancer agents and binding mechanism of hit candidate with human serum albumin

In our continuing efforts to develop therapeutically active coumarin‐based compounds, a series of new C4–C4′ biscoumarin–pyrimidine conjugates ( 1a–l ) was synthesized via S_N2 reaction of substituted 4‐bromomethyl coumarin with thymine. All compounds were characterized using spectroscopic techniques, that is, attenuated total reflection infrared (ATR‐IR), CHN elemental analysis, and ¹H and ¹³C NMR (nuclear magnetic resonance). In addition, the structure of compound 1d (1,3‐bis[(7‐chloro‐2‐oxo‐2H‐chromen‐4‐yl)methyl]‐5‐methylpyrimidine‐2,4(1H,3H)‐dione) was established through X‐ray crystallography. Compounds 1a–l were screened for in vitro anticancer activity against C6 rat glioma cells. Among the screened compounds, 1,3‐bis[(6‐chloro‐2‐oxo‐2H‐chromen‐4‐yl)methyl]‐5‐methylpyrimidine‐2,4(1H,3H)‐dione ( 1c ) was identified as the best antiproliferative candidate, exhibiting an IC₅₀ value of 4.85 μM. All the compounds ( 1a – l ) were found to be nontoxic toward healthy human embryonic kidney cells (HEK293), indicating their selective nature. In addition, the most active compound ( 1c ) displayed strong binding interactions with the drug carrier protein, human serum albumin, and exhibited good solution stability at biological pH conditions. Fluorescence, UV–visible spectrophotometry and molecular modeling methodologies were employed for studying the interaction mechanism of compound 1c with protein.     

Synthesis of the tritiated isotopomers of enzastaurin and its N‐des‐pyridylmethyl metabolite for use in ADME studies

Enzastaurin (3‐(1‐methyl‐1H‐indol‐3‐yl)‐4‐[1‐[1‐(2‐pyridinylmethyl)‐4‐piperidinyl]‐1H‐indol‐3‐yl]‐1H‐pyrrole‐2,5‐dione, 1), an agent with potential utility in the treatment of solid tumors, is currently in phase II clinical trials. Enzastaurin undergoes metabolism in vitro and in vivo to several products of oxidative metabolism, the major one of which is 3‐(1‐methyl‐1H‐indol‐3‐yl)‐4‐(1‐piperidin‐4‐yl‐1H‐indol‐3‐yl)‐1H‐pyrrole‐2,5‐dione (2). In a model study, the attempted synthesis 1‐[²H] by reaction of 1 with deuterium gas in the presence of Ir[(COD)(Cy₃P)pyr]PF₆ (Crabtree's catalyst) was unsuccessful. Alternatively, it was decided to prepare tritiated 2 as both a final product and the starting material for the tritiation of 1. We have reported herein a route that was developed for use in the preparation of tritium‐labeled 2‐[³H] and its successful conversion to 1‐[³H]. Copyright © 2008 John Wiley & Sons, Ltd.     

Genotoxicity evaluation of two kinds of smoke‐water and 3,7‐dimethyl‐2H‐furo[2,3‐c]pyran‐2‐one

Smoke, smoke‐water and aerosols have a stimulatory effect on seed germination and growth vigour of many seedlings, making them potentially useful for different purposes, provided they do not pose a health risk. Therefore, the genotoxicity of two kinds of smoke‐water and 3,7‐dimethyl‐2H‐furo[2,3‐c]pyran‐2‐one, a variant of the most active smoke compound (3‐methyl‐2H‐furo[2,3‐c]pyran‐2‐one) was evaluated using the Vitotox? assay. Smoke‐water extracts were obtained from burning leaves: Themeda triandra (smoke‐water Tt) and a mix of Themeda triandra and Passerina vulgaris (smoke‐water Kb). No genotoxic effect was observed for any of the three samples. However, the three samples are toxic at the highest concentrations (3,7‐dimethyl‐2H‐furo[2,3‐c]pyran‐2‐one, 2 ppm; smoke‐water Tt, dilutions 1 : 1, 1 : 2, 1 : 4; smoke‐water Kb, dilution 1 : 1) without addition of S9 mix. Both the butenolide 3,7‐dimethyl‐2H‐furo[2,3‐c]pyran‐2‐one and smoke‐water Tt are also toxic at high doses in the presence of S9 (2 ppm and dilutions 1 : 1 and 1 : 2, respectively), but not smoke‐water Kb. Thus, from these results, no genotoxicity of these three samples can be assumed, which is accordance with the previous tests performed with 3‐methyl‐2H‐furo[2,3‐c]pyran‐2‐one and a smoke‐water. Copyright © 2010 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.     

A novel five‐lipoxygenase activity protein inhibitor labeled with carbon‐14 and deuterium

2‐[4‐(3‐{(1R)‐1‐[4‐(2‐Aminopyrimidin‐5‐yl)phenyl]‐1‐cyclopropylethyl}‐1,2,4‐oxadiazol‐5‐yl)‐1H‐pyrazol‐1‐yl]‐N,N‐dimethylacetamide (1), is a novel and selective five‐lipoxygenase activity protein (FLAP) inhibitor with excellent pharmacokinetics properties. The availability of a key chiral intermediate allowed the synthesis of [¹⁴C]‐(1) in six radiochemical steps and in 47% overall radiochemical yield with a specific activity of 51 mCi/mmol using carbon‐14 zinc cyanide. 2‐Chloro‐N,N‐dimethyl‐²H₆‐acetamide was prepared and condensed with a penultimate intermediate to give [²H₆]‐(1) in very high yield and in more than 99% isotopic enrichment.     

Potent and selective inhibitors of 11β‐hydroxysteroid dehydrogenase type 1 labeled with carbon‐13 and carbon‐14

(S )‐6‐(2‐Hydroxy‐2‐methylpropyl)‐3‐((S )‐1‐(4‐(1‐methyl‐2‐oxo‐1,2‐dihydropyridin‐4‐yl)phenyl)ethyl)‐6‐phenyl‐1,3‐oxazinan‐2‐one (1) and (4aR ,9aS )‐1‐(1H‐benzo[d]midazole‐5‐carbonyl)‐2,3,4,4a,9,9a‐hexahydro‐1‐H‐indeno[2,1‐b]pyridine‐6‐carbonitrile hydrochloride (2) are potent and selective inhibitor of 11β‐hydroxysteroid dehydrogenase type 1 enzyme. These 2 drug candidates developed for the treatment of type‐2 diabetes were prepared labeled with carbon‐13 and carbon‐14 to enable drug metabolism, pharmacokinetics, bioanalytical, and other studies. In the carbon‐13 synthesis, benzoic‐¹³C ₆ acid was converted in 7 steps and in 16% overall yield to [¹³C₆]‐(1). Aniline‐¹³C ₆ was converted in 7 steps to 1H‐benzimidazole‐1‐2,3,4,5,6‐¹³C₆‐5‐carboxylic acid and then coupled to a tricyclic chiral indenopiperidine to afford [¹³C₆]‐(2) in 19% overall yield. The carbon‐14 labeled (1) was prepared efficiently in 2 radioactive steps in 41% overall yield from an advanced intermediate using carbon‐14 labeled methyl magnesium iodide and Suzuki‐Miyaura cross coupling via in situ boronate formation. As for the synthesis of [¹⁴C]‐(2), 1H‐benzimidazole‐5‐carboxylic‐¹⁴C acid was first prepared in 4 steps using potassium cyanide‐¹⁴C , then coupled to the chiral indenopiperidine using amide bond formation conditions in 26% overall yield.     

Synthesis of deleobuvir,a potent hepatitis C virus polymerase inhibitor,and its major metabolites labeled with carbon‐13 and carbon‐14

Deleobuvir, (2E)‐3‐(2‐{1‐[2‐(5‐bromopyrimidin‐2‐yl)‐3‐cyclopentyl‐1‐methyl‐1H‐indole‐6‐carboxamido]cyclobutyl}‐1‐methyl‐1H‐benzimidazol‐6‐yl)prop‐2‐enoic acid (1), is a non‐nucleoside, potent, and selective inhibitor of hepatitis C virus NS5B polymerase. Herein, we describe the detailed synthesis of this compound labeled with carbon‐13 and carbon‐14. The synthesis of its three major metabolites, namely, the reduced double bond metabolite (2) and the acyl glucuronide derivatives of (1) and (2), is also reported. Aniline‐¹³C₆ was the starting material to prepare butyl (E)‐3‐(3‐methylamino‐4‐nitrophenyl‐¹³C₆)acrylate [¹³C₆]‐(11) in six steps. This intermediate was then used to obtain [¹³C₆]‐(1) and [¹³C₆]‐(2) in five and four more steps, respectively. For the radioactive synthesis, potassium cyanide‐¹⁴C was used to prepare 1‐cylobutylaminoacid [¹⁴C]‐(23) via Buchrer–Bergs reaction. The carbonyl chloride of this acid was then used to access both [¹⁴C]‐(1) and [¹⁴C]‐(2) in four steps. The acyl glucuronide derivatives [¹³C₆]‐(3), [¹³C₆]‐(4) and [¹⁴C]‐(3) were synthesized in three steps from the acids [¹³C₆]‐(1), [¹³C₆]‐(2) and [¹⁴C]‐(1) using known procedures.     

Antioxidant Potential of New Pyrazoline Derivatives to Prevent Oxidative Damage

Abstract: The antioxidant capacity of a series of six novel synthetic pyrazoline derivatives (i) 5‐hydroxy‐3‐methyl‐5‐trifluoromethyl‐4,5‐dihydro‐1H‐carbaldehyde‐pyrazole, (ii) 5‐hydroxy‐3‐methyl‐5‐trifluoromethyl‐4,5‐dihydro‐1H‐1‐acetyl‐pyrazole, (iii) 5‐hydroxy‐3‐methyl‐5‐trifluoromethyl‐4,5‐dihydro‐1H‐carboxyamide‐pyrazole, (iv) 5‐hydroxy‐3‐methyl‐5‐trifluoromethyl‐4,5‐dihydro‐1H‐1‐benzoyl‐pyrazole, (v) 5‐hydroxy‐3‐methyl‐5‐trifluoromethyl‐4,5‐dihydro‐1H‐1‐(2‐hydroxybenzoyl)‐pyrazole and (vi) 5‐hydroxy‐3‐methyl‐5‐trifluoromethyl‐4,5‐dihydro‐1H‐1‐(4‐methoxybenzoyl)‐pyrazole was evaluated as the capacity of compounds to transfer a hydrogen atom (protection against brain lipid peroxidation and glutathione oxidation) and their capacity to transfer a single electron [ferric‐reducing antioxidant power (FRAP) and 1,1‐diphenyl‐2‐picrylhydrazyl radical scavenging (DPPH) assays]. Compound 5 had the highest free radical scavenging capacity in the DPPH assay, while compound 2 had the highest FRAP value (P < 0.05). Only compounds 1, 4 and 5 protected against lipid peroxidation in rat brain homogenate. However, compound 5 was the most effective to prevent basal and iron‐, sodium nitroprusside‐ and H₂O₂‐stimulated lipid peroxidation (IC₅₀ < 15 µM) and the only one effective to block glutathione oxidation‐mediated by H₂O₂ (at 150 µM). Our results indicate that compound 5 has the greatest potential to prevent oxidative damage in brain homogenates.