Synthesis of stable isotope‐labeled metabolites of asenapine

The stable isotope‐labeled synthesis of four of the major metabolites of asenapine is described. The synthesis of [¹³CD₃]‐asenapine N‐oxide proceeded in two synthetic steps. Preparation of [¹³CD₃]‐asenapine 11‐hydroxysulfate and [¹³C₆]‐N‐desmethylasenapine paralleled established synthetic protocols with effective utilization of labeled precursors. The synthesis of [¹³CD₃]‐asenapine N⁺‐glucuronide was achieved in three chemical steps followed by purification.     

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.     

Expeditious syntheses of stable and radioactive isotope‐labeled anticonvulsant agent,JNJ‐26990990, and its metabolites

Syntheses of stable and radioactive isotope‐labeled anticonvulsant agent, JNJ‐26990990, that is, N‐(benzo[b]thien‐3‐ylmethyl)‐sulfamide and its metabolites are described. [¹³C¹⁵N]Benzo[b]thiophene‐3‐carbonitrile was first prepared by coupling of 3‐bromo‐benzo[b]thiophene with [¹³C¹⁵N]‐copper cyanide. The resultant [¹³C¹⁵N]benzo[b]thiophene‐3‐carbonitrile was reduced with lithium aluminum deuteride to give [¹³CD₂¹⁵N]benzo[b]thiophen‐3‐yl‐methylamine; which was then coupled with sulfamide to afford [¹³CD₂¹⁵N]‐N‐(benzo[b]thien‐3‐ylmethyl)‐sulfamide, the stable isotope‐labeled compound with four stable isotope atoms. Direct oxidation of [¹³CD₂¹⁵N]‐N‐(benzo[b]thien‐3‐ylmethyl)‐sulfamide with hydrogen peroxide and peracetic acid gave the stable isotope‐labeled sulfoxide and sulfone metabolites. On the other hand, radioactive ¹⁴C‐labeled N‐(benzo[b]thien‐3‐ylmethyl)‐sulfamide was prepared conveniently by sequential coupling of 3‐bromo‐benzo[b]thiophene with [¹⁴C]‐copper cyanide, reduction of the carbonitrile to carboxaldehyde, and reductive amination with sulfamide.     

Facile synthesis of stable isotope‐labeled antibacterial agent RWJ‐416457 and its metabolite

Synthesis of multiple stable isotope‐labeled antibacterial agent RWJ‐416457, (N‐{3‐[3‐fluoro‐4‐(2‐methyl‐2,6‐dihydro‐4H‐pyrrolo[3,4‐c]pyrazol‐5‐yl)‐phenyl]‐2‐oxo‐oxazolidin‐5‐ylmethyl}‐acetamide), and its major metabolite, N‐{3‐[4‐(2,6‐dihydro‐4H‐pyrrolo[3,4‐c]pyrazol‐5‐yl)‐3‐fluoro‐phenyl]‐2‐oxo‐oxazolidin‐5‐ylmethyl}‐acetamide, is described. The stable isotope‐labeled [¹³CD₃]RWJ‐416457 was prepared readily by acetylation of the precursor amine, 5‐aminomethyl‐3‐[3‐fluoro‐4‐(2‐methyl‐2,6‐dihydro‐4H‐pyrrolo[3,4‐c]pyrazol‐5‐yl)‐phenyl]‐oxazolidin‐2‐one with CD₃¹³COCl in pyridine. Synthesis of the stable isotope‐labeled metabolite involved a construction of multiple isotope‐labeled pyrazole ring. N,N‐dimethyl(formyl‐¹³C,D)amide dimethyl acetal was first prepared by treating N,N‐dimethyl(formyl‐¹³C,D)amide with dimethyl sulfate, followed by sodium methoxide. Then, N‐{3‐[3‐fluoro‐4‐(3‐oxo‐pyrrolidin‐1‐yl)‐phenyl]‐2‐oxo‐oxazolidin‐5‐ylmethyl}‐acetamide was condensed with N,N‐dimethyl(formyl‐¹³C,D)amide dimethyl acetal, and the resultant β‐ketoenamine intermediate underwent pyrazole ring formation with hydrazine‐¹⁵N₂, to give the [¹³C¹⁵N₂D]‐labeled metabolite. Copyright © 2012 John Wiley & Sons, Ltd.     

Synthesis of deuterium‐labelled coenzyme Q10

Deuterium‐labelled coenzyme Q₁₀ ([2‐CD₃‐1′‐CD₂]coenzyme Q₁₀, coenzyme Q₁₀‐d₅ ) was synthesized by condensation of 2,3‐dimethoxy‐[5‐CD₃]methyl‐1, 4‐hydroquinone with [1‐CD₂]decaprenol. Five positions were selected for deuteration as replacement at these positions allowed examination of every step of the synthesis. This examination was carried out by a combination of ¹H‐ and ¹³C‐nuclear magnetic spectrometry and mass spectrometry. Further, these positions have been proved to be metabolically stable. This reagent makes simultaneous quantification of the source of coenzyme Q₁₀ (exogenously supplied or endogenously supplied) possible in biological samples by measurements on gas chromatography–mass spectrometry. Copyright © 2002 John Wiley & Sons, Ltd.     

The synthesis of 14C‐labeled, 13CD2‐labeled saxagliptin,and its 13CD2‐labeled 5‐hydroxy metabolite

¹⁴C‐labeled saxagliptin, ¹³CD₂‐labeled saxagliptin, and its ¹³CD₂‐labeled 5‐hydroxy metabolite were synthesized to further support development of the compound for biological studies. This paper describes new syntheses leading to the desired compounds. A total of 3.0 mCi of ¹⁴C‐labeled saxagliptin was obtained with a specific activity of 53.98 μCi/mg (17.13 mCi/mmol). The radiochemical purity determined by HPLC was 99.29%, and the overall radiochemical yield was 3.0% based upon 100 mCi of [¹⁴C]CH₂I₂ starting material. By following similar synthetic routes, 580.0 mg of ¹³CD₂‐labeled saxagliptin and 153.1 mg of ¹³CD₂‐labeled 5‐hydroxysaxagliptin metabolite were prepared. Copyright © 2014 John Wiley & Sons, Ltd.     

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.     

A practical laboratory route to the synthesis of trideuteriomethyl‐[13C] iodide

A practical synthetic laboratory route for the synthesis of trideuteriomethyl‐[¹³C] iodide (¹³CD₃I) (from tetradeuterio‐[¹³C]‐methanol and hydriodic acid) is described. We comment on the experimental protocol, and the use of water as an ‘additive’ to improve the synthetic yield. Copyright © 2003 John Wiley & Sons, Ltd.     

Synthesis of [phenyl‐13C6]lachnanthocarpone and other 13C‐labelled phenylphenalenones

[phenyl‐¹³C₆]Lachnanthocarpone ([phenyl‐¹³C₆]2,6‐dihydroxy‐9‐phenylphenalen‐1‐one), a hypothetical intermediate in the biosynthesis of various natural phenylphenalenones, was prepared in four steps using [U‐¹³C]bromobenzene to introduce the label. Based on related methodologies further native phenylphenalenones such as [phenyl‐¹³C₆]anigorufone, [1‐¹³C]anigorufone and [4′‐O¹³CH₃]4′‐methoxyanigorufone were synthesized in labelled form. 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.     

The synthesis of [3,4,1′‐13C3]genistein

A facile synthesis is described for [3,4,1′‐¹³C₃]genistein for use as an internal standard in isoflavone analysis by mass spectrometric methods. Ethyl 4‐hydroxy[1‐¹³C]benzoate was first prepared from the reaction of diethyl [2‐¹³C]malonate and 4H‐pyran‐4‐one. Two further ¹³C atoms were incorporated using potassium [¹³C]cyanide as the source to give 4′‐benzyloxy‐[1,2,1′‐¹³C₃]phenylacetonitrile. [3,4,1′‐¹³C₃]Genistein was then constructed through coupling of the isotopically labelled phenylacetonitrile with phloroglucinol under Hoesch conditions, followed by formylation and cyclization. Copyright © 2007 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.     

Efficient syntheses of benzyl and n‐octyl [1,3‐13C2]acetoacetates,and their application to syntheses of 13C‐labelled pyrrole and 13C‐labelled hymecromone

Benzyl [1‐¹³C]acetate (2a) was prepared via esterification of sodium [1‐¹³C]acetate (1) with benzyl bromide in the presence of 18‐crown‐6‐ether in 97% yield. n‐Octyl [1‐¹³C]acetate (2b) was rapidly obtained by microwave irradiation of 1‐bromooctane and potassium [1‐¹³C]acetate (obtained by salt exchange of 1) absorbed on Al₂O₃ in 82% yield. Solvent‐free Claisen condensation of benzyl or n‐octyl [1‐¹³C]acetate (2a or 2b) in the presence of potassium tert‐butoxide efficiently gave benzyl or n‐octyl [1,3‐¹³C₂]acetoacetate (3a or 3b) in 51 or 68% yield, respectively. Dibenzyl 2,4‐dimethyl[2,4‐¹³C₂]pyrrole‐3,5‐di[¹³C]carboxylate (4) was synthesized from benzyl [1,3‐¹³C₂]acetoacetate (3a) in 54% yield. [2,4‐¹³C₂]Hymecromone (6) (7‐hydroxy‐4‐methyl[2,4‐¹³C₂]coumarin) was obtained from n‐octyl [1,3‐¹³C₂]acetoacetate (3b) and 1,3‐benzenediol (5) in 73% yield. Copyright © 2008 John Wiley & Sons, Ltd.     

Synthesis of 3H‐, 14C‐, and stable‐isotope‐labelled galantamine

Reminyl^® is a newly approved drug, used in the treatment of mild to moderate Alzheimer disease. The active compound, galantamine, was initially isolated from the bulbs of certain Narcissus species, but is at the moment also produced synthetically. In the process leading to the final approval, the synthesis of tritium‐, carbon‐14‐ and stable‐isotope‐labelled galantamine for pharmacokinetic studies was required. Racemic (±)‐1‐bromonarwedine, a compound available as intermediate from the commercial synthesis, was transformed to racemic 1‐bromo‐galantamine. Catalytic bromo‐tritium exchange, followed by HPLC purification and resolution afforded tritium‐labelled galantamine. The [¹⁴C]‐label was introduced on the nitrogen as well as on the oxygen‐methyl position. This was achieved by N‐ and O‐demethylation of galantamine and reaction of the thoroughly purified intermediate with [¹⁴C]‐methyl iodide. Stable‐isotope‐labelled galantamine was obtained likewise by ¹³CD₃OD‐methylation of O‐demethylated galantamine under Mitsunobu conditions. Copyright © 2002 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.     

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.     

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 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 13C and 15N labeled 2,4‐dinitroanisole

Syntheses of [¹³C₆]‐2,4‐dinitroanisole (ring‐¹³C₆) from [¹³C₆]‐anisole (ring‐¹³C₆) and [¹⁵N₂]‐2,4‐dinitroanisole from anisole using in situ generated acetyl nitrate and [¹⁵N]‐acetyl nitrate, respectively, are described. Treatment of [¹³C₆]‐anisole (ring‐¹³C₆) with acetyl nitrate generated in 100% HNO₃ gave [¹³C₆]‐2,4‐dinitroanisole (ring‐¹³C₆) in 83% yield. Treatment of anisole with [¹⁵N]‐acetyl nitrate generated in 10 N [¹⁵N]‐HNO₃ gave [¹⁵N₂]‐2,4‐dinitroanisole in 44% yield after two cycles of nitration. Byproducts in the latter reaction included [¹⁵N]‐2‐nitroanisole and [¹⁵N]‐4‐nitroanisole.     

The synthesis of isotopically labeled (+)‐2‐aminobicyclo[3.1.0]hexane‐2,6‐carboxylic acid and its 2‐oxa‐ and 2‐thia‐analogs

As part of a program aimed at the design of conformationally constrained analogs of glutamic acid, (+)‐2‐aminobicyclo[3.1.0]hexane‐2,6‐carboxylic acid ( 1 ), identified as a highly potent, selective, group II metabotropic glutamate receptor agonist has been synthesized and studied clinically. Heterocyclic analogs of 1 were subsequently synthesized in which the C‐2 methylene has been replaced by an oxygen atom ( 2 ) or a sulfur atom ( 3 ). C‐14 labeled isotopomers of 1 , 2 and 3 have been synthesized to facilitate pre‐clinical ADME studies. A tritium labeled isotopomer of 1 was also synthesized for use in in vitro experiments. A stable labeled isotopomer of rac‐1 was prepared for use as an internal standard for bioanalytical assays. The key step in each of these syntheses was the reaction of chiral ketone 4 , 5 or 6 with K¹⁴CN/(NH₄)₂CO₃ using the Bucherer–Berg protocol. In the preparation of the stable labeled isotopomer, rac‐4 ‐[¹³ C ₂] was prepared in two steps from ethyl bromoacetate‐[UL‐¹³C₂]; subsequent reaction of rac‐4 ‐[¹³ C ₂] with K¹³CN/¹⁵NH₄Cl/Na₂CO₃, followed by hydrolysis of the hydantoin yielded rac‐1 ‐[¹³ C ₃,¹⁵ N ]. Copyright © 2005 John Wiley & Sons, Ltd.