New pyrazole derivative 5‐[1‐(4‐fluorophenyl)‐1H‐pyrazol‐4‐yl]‐2H‐tetrazole: synthesis and assessment of some biological activities

The molecular modification and synthesis of compounds is vital to discovering drugs with desirable pharmacological and toxicity profiles. In response to pyrazole compounds' antipyretic, analgesic, and anti‐inflammatory effects, this study sought to evaluate the analgesic, anti‐inflammatory, and vasorelaxant effects, as well as the mechanisms of action, of a new pyrazole derivative, 5‐[1‐(4‐fluorophenyl)‐1H‐pyrazol‐4‐yl]‐2H‐tetrazole. During the acetic acid‐induced abdominal writhing test, treatments with 5‐[1‐(4‐fluorophenyl)‐1H‐pyrazol‐4‐yl]‐2H‐tetrazole reduced abdominal writhing, while during the formalin test, 5‐[1‐(4‐fluorophenyl)‐1H‐pyrazol‐4‐yl]‐2H‐tetrazole reduced licking times in response to both neurogenic pain and inflammatory pain, all without demonstrating any antinociceptive effects, as revealed during the tail flick test. 5‐[1‐(4‐fluorophenyl)‐1H‐pyrazol‐4‐yl]‐2H‐tetrazole also reduced carrageenan‐induced paw edema and cell migration during the carrageenan‐induced pleurisy test. As demonstrated by the model of the isolated organ, 5‐[1‐(4‐fluorophenyl)‐1H‐pyrazol‐4‐yl]‐2H‐tetrazole exhibits a vasorelaxant effect attenuated by Nω‐nitro‐l ‐arginine methyl ester, 1H‐[1,2,4]oxadiazolo[4,3‐alpha]quinoxalin‐1‐one, tetraethylammonium or glibenclamide. 5‐[1‐(4‐fluorophenyl)‐1H‐pyrazol‐4‐yl]‐2H‐tetrazole also blocked CaCl₂‐induced contraction in a dose‐dependent manner. Suggesting a safe toxicity profile, 5‐[1‐(4‐fluorophenyl)‐1H‐pyrazol‐4‐yl]‐2H‐tetrazole reduced the viability of 3T3 cells at higher concentrations and was orally tolerated, despite signs of toxicity in doses of 2000 mg/kg. Lastly, the compounds' analgesic activity might be attributed to the involvement of the NO/cGMP pathway and K⁺ channels observed in the vasorelaxant effect.     

Synthesis of deuterium labeled standards of 5‐methoxy‐N,N‐dimethyltryptamine (5‐Meo‐DMT)

The Batcho‐Leimgruber strategy was employed to synthesize 5‐[²H₃]‐methoxy‐1 H‐indole 4 from commercially available 5‐hydroxy‐2‐nitrotoluene 1 and CD₃I. Compound 4 was treated with oxalyl chloride, dimethylamine and lithium aluminum hydride to yield 5‐[²H₃]‐methoxy‐N,N‐dimethyltryptamine 6 . Copyright © 2006 John Wiley & Sons, Ltd.     

Synthesis of a highly potent leukocyte function‐associated antigen‐1 antagonist and its metabolite labeled with stable isotopes and carbon‐14, part 2

(S)‐2‐[(R)‐7‐(3,5‐Dichlorophenyl)‐5‐methyl‐6‐oxo‐5‐(4‐trifluoromethoxybenzyl)‐6,7‐dihydro‐5H‐imidazo[1,2‐a]imidazole‐3‐sulfonylamino]‐proprionamide (1), a potent lymphocyte function‐associated antigen‐1 antagonist and its sulfonamide metabolite (2) labeled with stable isotopes and carbon‐14 were prepared for Drug Metabolism and PharmacoKinetics and other studies. A long linear route was used to prepare [¹³C₂, ²H₃]‐(1) using [3,3,3‐²H]‐D‐alanine and [¹³C₂]‐glycine in 15 steps and 2.5% overall yield. With the availability of [¹³C₆]‐3,5‐dichloroaniline, the sulfonamide [¹³C₆]‐(2) was prepared in 12 steps and in 5.6% overall yield. For the carbon‐14 synthesis, a six‐step synthesis gave both compounds [¹⁴C]‐(1) and [¹⁴C]‐(2) from the common sulfonyl chloride intermediate [¹⁴C]‐(15) in 18% and 4% radiochemical yields and specific activities of 44 and 40.5 mCi/mmol, respectively. Copyright © 2011 John Wiley & Sons, Ltd.     

Synthesis of deuterium‐labeled 3‐O‐methyldopa and 4‐O‐methyldopa

Concise methods for the synthesis of 4‐hydroxy‐3‐[²H₃]‐methoxyphenylalanine (3‐O‐[²H₃]‐methydopa) and 3‐hydroxy‐4‐[²H₃]‐methoxyphenylalanine (4‐O‐[²H₃]‐methydopa) are described. The 3‐O‐[²H₃]‐methydopa is a valuable internal standard for the tandem MS quantification of 3‐O‐methyldopa, a metabolite of value in the diagnosis of aromatic l‐amino acid decarboxylase (AADC) deficiency. Copyright © 2003 John Wiley & Sons, Ltd.     

Synthesis of isotope‐labeled HSP90 inhibitor: [13CD3] and [14C]‐TAK‐459

[¹³CD₃]‐TAK‐459 (1A), an HSP90 inhibitor, was synthesized from [¹³CD₃]‐sodium methoxide in three steps in an overall yield of 29%. The key intermediate [¹³CD₃]‐2‐methoxy‐6‐(4,4,5,5‐tetramethyl‐1,3,2‐dioxaborolan‐2‐yl)pyridine was synthesized in two steps from 2,6‐dibromopyridine and stable isotope‐labeled sodium methoxide. [¹⁴C]‐TAK‐459 (1B) was synthesized from [¹⁴C(U)]‐guanidine hydrochloride in five steps in an overall radiochemical yield of 5.4%. The key intermediate, [¹⁴C]‐(R)‐2‐amino‐7‐(2‐bromo‐4‐fluorophenyl)‐4‐methyl‐7,8‐dihydropyrido[4,3‐d]pyrimidin‐5(6H)‐one, was prepared by microwave‐assisted condensation.     

Synthesis of doubly 13C‐labelled antalarmin isotopomers for pharmacokinetic studies

Antalarmin (butyl‐ethyl‐[2,5,6‐trimethyl‐7‐(2,4,6‐trimethyl‐phenyl)‐7H‐pyrrolo[2,3‐d]pyrimidin‐4‐yl]‐amine) was doubly labelled with carbon‐13. The synthesized butyl‐[¹³C₂]ethyl‐[2,5,6‐trimethyl‐7‐(2,4,6‐trimethyl‐phenyl)‐7H‐pyrrolo[2,3‐d]pyrimidin‐4‐yl]‐amine ( 1 ) and butyl‐ethyl‐[2‐¹³C]‐[2,5,6‐trimethyl‐7‐(2,4,6‐trimethyl‐phenyl)‐7H‐pyrrolo[2,3‐d]‐[2‐¹³C] pyrimidin‐4‐yl]‐amine, ( 2 ) were prepared for use as substrates for pharmacokinetic studies. These compounds were obtained in fair overall yield in a 5 and 6 step synthesis (20–24.5%, respectively) and high isotopic purity (about 99 at% ¹³C). Copyright © 2002 John Wiley & Sons, Ltd.     

Synthesis of a deuterium‐labelled standard of bufotenine (5‐HO‐DMT)

The Batcho–Leimgruber strategy was employed to synthesize 3‐(2‐dimethylamino‐[²H₄]‐ethyl)‐1H‐indol‐5‐ol (bufotenine, 5‐HO‐DMT) ( 8 ) from commercial 3‐methyl‐4‐nitro‐phenol ( 1 ), benzyl bromide and N,N–dimethylformamide–dimethylacetal. Compound 4 was synthesized from compound 3 using the Batcho–Leimgruber strategy in the presence of Raney nickel and hydrazine hydrate. Compound 4 was treated with oxalyl chloride, dimethylamine and lithium aluminum [²H₄]‐hydride to yield [2‐(5‐benzyloxy‐1H‐indol‐3‐yl)‐[²H₄]‐ethyl]‐dimethyl‐amine ( 7 ). The benzyl ether in compound 7 was cleaved by hydrogenolysis to give bufotenine 8 . Copyright © 2007 John Wiley & Sons, Ltd.     

Synthesis of highly potent lymphocyte function‐associated antigen‐1 antagonists labeled with carbon‐14 and with stable isotopes,part 3

The drug candidates ( 2 ) and ( 3 ) are highly potent LFA‐1 inhibitors. They were efficiently prepared labeled with carbon‐14 using a palladium‐catalyzed carboxylation of an iodo‐precursor ( 5 ) and sodium formate‐¹⁴C to afford acid [¹⁴C]‐( 6 ), which was coupled via an amide bond to chiral amines ( 7 ) and ( 8 ) in 52% and 48% overall yield, respectively, and with specific activities higher than 56 mCi/mmol and radiochemical purities of 99%. For stable isotopes synthesis, the amine [²H₈]‐( 7 ) was synthesized in three steps from 2‐cyanopyridine‐²H₄ using Kulinkovich‐Szymonik aminocyclopropanation, followed by coupling to L ‐alanine‐2,3,3,3‐²H₄‐N‐t‐BOC, and then removal of the BOC‐protecting group. Amide bond formation with acid ( 6 ) gave [²H₈]‐( 2 ) in 36% overall yield. The amine [¹³C₄,¹⁵N]‐( 8 ) was obtained in two steps using L‐threonine‐¹⁴C₄,¹⁵N and then coupled to acid [¹³C]‐( 6 ) to give [¹³C₅,¹⁵N]‐( 3 ) in 56% overall yield.     

Isotope labeled ‘HEA/HEE’ moiety in the synthesis of labeled HIV‐protease inhibitors—Part II

[²H₅]‐Amprenavir and [²H ₅]‐saquinavir have been prepared from a common labeled precursor (1S, 2S)‐(1‐oxiranyl‐2‐[²H₅]phenylethyl)‐carbamic acid tert‐butyl ester, 1 . Both of these compounds are in the ‘HEA’ class of HIV protease inhibitors. [²H₅]‐Indinavir, a representative of the ‘HEE’ group of protease inhibitors, has also been synthesized. In the case of indinavir, 1S‐(2,2‐dimethyl‐8, 8a‐dihydro‐3aH‐indeno‐[1,2‐d]‐oxazol‐3R‐yl)‐2‐oxiranylmethyl‐3‐[²H₅]phenylpropan‐1‐one, 11 , provided the [phenyl‐²H₅]‐HEE core structure for synthesis of the desired labeled compound. Copyright © 2005 John Wiley & Sons, Ltd.     

Isotope labeled ‘HEA Moiety’ in the synthesis of labeled HIV‐protease inhibitors – Part 1

[(S)‐1′‐((N‐tert‐Butyloxycarbonyl)amino)‐2S‐[²H₅]phenyl‐ethyl]oxirane 11 , made from [²H₅]‐bromobenzene, was transformed into the HIV‐protease inhibitors [²H₅]‐DPH 153893 and [²H₅]‐DPH 140662. Both compounds are members of the hydroxyethylamine class of protease inhibitors (HIV‐PIs). The method of synthesis is applicable to members of this class and the HEE group of HIV‐PIs. Copyright © 2004 John Wiley & Sons, Ltd.     

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.     

Synthesis of deuterium labelled 2‐bromobenzylamine by directed ortho‐metalation chemistry

Directed ortho‐metalation (DoM) strategy has been applied for the development of a short procedure for the regiospecific synthesis of [phenyl‐²H₄]‐2‐bromo‐benzylamine 6 starting from commercially available [phenyl‐²H₅]‐benzoyl chloride 1 . A strong isotope effect was observed during the ortho‐substitution. Copyright © 2005 John Wiley & Sons, Ltd.     

A gram‐scale synthesis of [3,4‐13C2,1α,7‐2H2]cortisone

A gram‐scale synthesis of [3,4‐¹³C₂,1α,7‐²H₂]cortisone from prednisone was developed. The deuterium atom at the C‐1 position was introduced through a regioselective and stereoselective deuteration of the 1,2‐double bond of the 1,4‐diene‐3‐one using Wilkinson's catalyst. After the oxidative cleavage of the A‐ring, two carbon‐13 atoms were introduced via acetylation of an A‐ring enol lactone with [1,2‐¹³C₂]acetyl chloride. The steroidal A‐ring was then reconstructed to incorporate the carbon‐13 atoms into the C‐3 and C‐4 positions. The deuterium atom at C‐7 was introduced through a regioselective deuteration of the 6,7‐double bond of a 4,6‐diene‐3‐one intermediate using palladium on strontium carbonate. The M + 4 stable isotope labeled cortisone was thus prepared in ca. 4% overall yield. In addition, [3,4‐¹³C₂,1α,7‐²H₂]‐11‐dehydrocorticosterone, [3,4‐¹³C₂,1α,7‐²H₂]cortisol, and [3,4‐¹³C₂,1α,7‐²H₂]corticosterone were also prepared. Copyright © 2011 John Wiley & Sons, Ltd.     

Synthesis of C‐14 and C‐13, H‐2‐labeled IKK inhibitor: [14C] and [13C4,D3]‐N‐(6‐chloro‐7‐methoxy‐9H‐pyrido[3,4‐b]indol‐8‐yl)‐2‐methyl‐3‐pyridinecarboxamide

[¹⁴C]‐N‐(6‐Chloro‐7‐methoxy‐9H‐pyrido [3,4‐b]indol‐8‐yl)‐2‐methyl‐3‐pyridinecarboxamide (5B ), an IKK inhibitor, was synthesized from [¹⁴C]‐barium carbonate in two steps in an overall radiochemical yield of 41%. The intermediate, [carboxyl‐¹⁴C]‐2‐methylnicotinic acid, was prepared by the lithiation and carbonation of 3‐bromo‐2‐methylpyridine. [¹³C₄,D₃]‐N‐(6‐chloro‐7‐methoxy‐9H‐pyrido [3,4‐b]indol‐8‐yl)‐2‐methyl‐3‐pyridinecarboxamide (5C ) was synthesized from [1,2,3,4‐¹³C₄]‐ethyl acetoacetate and [D₄]‐methanol in six steps in an overall yield of 2%. [¹³C₄]‐2‐methylnicotic acid, was prepared by condensation of [¹³C₄]‐ethyl 3‐aminocrotonate and acrolein, followed by hydrolysis with lithium hydroxide. Copyright © 2006 John Wiley & Sons, Ltd.     

Synthesis of N‐(2‐chloro‐5‐methylthiophenyl)‐ N′‐(3‐methyl‐thiophenyl)‐ N′‐[3H3]methylguanidine, {[3H3]CNS‐5161}

The preparation of the title compound, [³H₃]CNS‐5161, was accomplished in three steps starting with the production of [³H₃]iodomethane (CT₃I). The intermediate N‐[³H₃]methyl‐3‐(thiomethylphenyl)cyanamide was prepared in 77% yield by the addition of CT₃I to 3‐(thiomethylphenyl)cyanamide, previously treated with sodium hydride. Reaction of this tritiated intermediate with 2‐chloro‐5‐thiomethylaniline hydrochloride formed the guanidine compound [³H₃]CNS‐5161. Purification by HPLC gave the desired labeled product in an overall yield of 9% with >96% radiochemical purity and a final specific activity of 66 Ci mmol^?1. Copyright © 2002 John Wiley & Sons, Ltd.     

Synthesis of two potent glucocorticoid receptor agonists labeled with carbon‐14 and stable isotopes

Two potent glucocorticoid receptor agonists were prepared labeled with carbon‐14 and with stable isotopes to perform drug metabolism, pharmacokinetics, and bioanalytical studies. Carbon‐14 labeled (1) was obtained from an enantiopure alkyne (5) via a Sonogashira coupling to a previously reported 5‐amino‐4‐iodo‐[2‐¹⁴C]pyrimidine [¹⁴C]‐(6), followed by a base‐mediated cyclization (1) in 72% overall radiochemical yield. Carbon‐14 labeled (2) was prepared in five steps employing a key benzoic acid intermediate [¹⁴C]‐(13), which was synthesized in one pot from enolization of trifluoromethylketone (12), followed by bromine–magnesium exchange and then electrophile trapping reaction with [¹⁴C]‐carbon dioxide. A chiral auxiliary (S)‐1‐(4‐methoxyphenyl)ethylamine was then coupled to this acid to give [¹⁴C]‐(15). Propargylation and separation of diastereoisomers by crystallizations gave the desired diastereomer [¹⁴C]‐(17) in 34% yield. Sonogashira coupling to iodopyridine (10) followed by cyclization to the azaindole [¹⁴C]‐(18) and finally removal of the chiral auxiliary gave [¹⁴C]‐(2) in 7% overall yield. For stable isotope syntheses, [¹³C₆]‐(1) was obtained in three steps using [¹³C₄]‐(6) and trimethylsilylacetylene‐[¹³C₂] in 26% yield, while [²H₅]‐(2) was obtained by first preparing the iodopyridine [²H₅]‐(10) in five steps. Then, Sonogashira coupling to chiral alkyne (24) and cyclization gave [²H₅]‐(2) in 42% overall yield.     

An overview of radio or stable isotope‐labeled cis‐neonicotinoid analogs

To support the metabolism and toxicology study of cis‐neonicotinoids, radio or stable isotope was introduced into different sites of the key intermediate 2‐chloro‐5‐((2‐(nitromethylene)imidazolidin‐1‐yl)methyl)pyridine (6‐Cl‐PMNI). [³H₂]‐ and [¹⁴C]‐label were successively prepared from initial materials NaB³H₄ and [¹⁴C]‐nitromethane, respectively. Similarly, [D₂]‐6‐Cl‐PMNI was prepared from NaBD₄ in four steps, with 52.6% overall isotopic yield, and dual‐labeled [D₂, ¹³C]‐target was obtained from NaBD₄ and [¹³C]‐nitromethane, affording overall isotopic yield of 42.5%. Moreover, [¹⁴C₂] was introduced from [U‐¹⁴C]‐ethylenediamine dihydrochloride in three steps, with a 58.3% overall chemical yield. Finally, typical labeled cis‐neonicotinoids paichongding and cycloxaprid were prepared and characterized. The methods were proved to have good generality in the synthesis of other cis‐neonicotinoids, and all results would be useful in metabolism studies of new cis‐neonicotinoids. Copyright © 2012 John Wiley & Sons, Ltd.     

Ring‐chain tautomerism in 2,2‐bis(2‐thienyl)tetrahydrofurans: preparation of [butene‐2H5]‐tiagabine

A concise preparation of [butene‐²H₅]‐tiagabine hydrochloride starting from [²H₆]‐γ‐butyrolactone is described. It was necessary to ring‐open the labeled γ‐butyrolactone precursor before the addition of 2‐thienyllithium to avoid cyclisation of the intermediate to a 2,2‐bis(2‐thienyl)tetrahydrofuran. Copyright © 2010 John Wiley & Sons, Ltd.     

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.     

Syntheses of perdeuterated indoles and derivatives as probes for the biosyntheses of crucifer phytoalexins

A simple two‐step preparation of [²H₄]indole, a starting material necessary for the synthesis of various crucifer metabolites, starting with readily available ¹H NMR solvent [²H₅]nitrobenzene (99% deuterated) was developed. [4,5,6,7‐²H₄]Indole 99% deuterated at the specified positions was then used to synthesize [4′,5′,6′,7′‐²H₄]indolyl‐3‐acetaldoxime, [4′,5′,6′,7′‐²H₄]1‐methoxyindolyl‐3‐acetaldoxime, [1″,1″,1″,4′,5′,6′,7′‐²H₇]1‐methoxyindolyl‐3‐acetaldoxime, [4′,5′,6′,7′‐²H₄]1‐methoxybrassinin, and [3,3,3,4′,5′,6′,7′‐²H₇]1‐methoxybrassinin. Copyright © 2005 John Wiley & Sons, Ltd.