Synthesis of [thiazolium‐2,2′‐14C2]‐SAR97276A from [14C]‐thiourea

[thiazolium‐2,2′‐¹⁴C₂]‐SAR97276A, a bis(thiazolium) antimalarial development candidate, was synthesized from [¹⁴C]‐thiourea with an overall radiochemical yield of 15%. The synthetic route involves a modified procedure for the synthesis of [¹⁴C]‐sulfurol, also a key intermediate in thiamine synthesis, which was developed due to unlabelled chemistry proving irreproducible with the radiolabelled substrate. Copyright © 2010 John Wiley & Sons, Ltd.     

Synthesis of [4‐14C]‐pelargonidin chloride and [4‐14C]‐delphinidin chloride

The synthesis of [4‐¹⁴C]‐pelargonidin chloride and [4‐¹⁴C]‐delphinidin chloride via [formyl‐¹⁴C]‐2‐(benzoyloxy)‐4,6‐dihydroxybenzaldehyde, ω,4‐diacetoxyacetophenone and ω,3,4,5‐tetraacetoxyacetophenone is described. The first step comprised labelling of the carbonyl group of 2‐(benzoyloxy)‐4,6‐dihydroxybenzaldehyde, verifying that the coupling with ω,4‐diacetoxyacetophenone or ω,3,4,5‐tetraacetoxyacetophenone under hydrogen chloride atmosphere resulted in the formation of [4‐¹⁴C] labelled anthocyanidins. Copyright © 2006 John Wiley & Sons, Ltd.     

An improved synthesis of [2‐14C]2, 5‐dichloropyrimidine

A previously described, five‐step synthesis of [2‐¹⁴C]2, 5‐dichloropyrimidine was based on condensation of [¹⁴C]urea with an acetal, followed by bromination, chlorination, boronic acid formation, and finally chlorination. This improved synthesis also started from readily available [¹⁴C]urea, which was condensed with 2‐chloromalonaldehyde, followed by chlorination with POCl₃ yielding [2‐¹⁴C]2, 5‐dichloropyrimidine with a radiochemical purity of 99% in an overall radiochemical yield of 72%. Copyright © 2012 John Wiley & Sons, Ltd.     

[125I], [127I]‐and [14C]‐Labelling of the GLP‐1‐(7‐37) derivative NN2211

Arg³⁴Lys²⁶(N^ε‐(γ‐L ‐glutamyl(N^α‐palmitoyl)))‐GLP‐1(7‐37) (NN2211) is currently in development as a diabetes type 2 drug. The fatty acid attached to the GLP‐1(7‐37) ensures a long and controlled duration of action. The synthesis of [¹²⁵I]NN2211, [¹²⁷I]NN2211 and [¹⁴C]NN2211 used for preclinical ADME studies are described. NN2211 was iodinated using the lactoperoxidase/hydrogen peroxide method, and [¹⁴C]NN2211 was synthesized in 4 steps by two routes both starting from an α‐protected [U‐¹⁴C]glutamic acid. Copyright © 2003 John Wiley & Sons, Ltd.     

[5‐14C]‐4‐methyltriazolepyridines via facile preparation of methyl‐[14C]‐isothiocyanate

A fast and convenient microwave assisted one‐pot synthesis of methyl‐[¹⁴C]‐isothiocyanate 4 was shown. The continued one‐pot synthesis with 4 to a highly refined material like [5‐¹⁴C]‐dimethylsulfanyltriazolepyridines 8 and 13 without any intermediate purification, six steps in the same pot from [¹⁴C]KCN. Oxidation of the sulfur provided access to triazole‐ethers upon reaction with alcohols. The triazole‐ethers, 15, were obtained at fair to good yields and specific activities above 2 GBq/mmol. Copyright © 2008 John Wiley & Sons, Ltd.     

The synthesis of [1‐14C]2‐(1H‐tetrazol‐5‐yl)acetic acid

Tetrazoles are a common heterocyclic functionality in many biologically active molecules. [1‐¹⁴C]2‐(1H‐Tetrazol‐5‐yl)acetic acid was required as an intermediate in the synthesis of a development candidate as part of a discovery phase program to complete metabolic profiling studies. [1‐¹⁴C]2‐(1H‐Tetrazol‐5‐yl)acetic acid was prepared in 4 steps overall and in 3 radiochemical steps from K¹⁴CN in an overall 32% radiochemical yield.     

Synthesis of [14C]‐l‐tryptophan and [14C]‐5′‐hydroxy‐l‐tryptophan labeled in the carboxyl group

The synthesis of selectively ¹⁴C‐labeled l ‐tryptophan and its derivative 5‐hydroxy‐l ‐tryptophan using chemical and multienzymatic methods is reported. The mixture containing [1‐¹⁴C[‐dl ‐alanine, indole or 5‐hydroxyindole has been converted to [1‐¹⁴C]‐l ‐tryptophan or 5′‐hydroxy‐[1‐¹⁴C]‐l ‐tryptophan, respectively, in a one‐pot multienzymatic reaction using four enzymes: d ‐amino acid oxidase, catalase, glutamic‐pyruvic transaminase and tryptophanase. Copyright © 2003 John Wiley & Sons, Ltd.     

A novel synthesis of [2‐14C]2,5‐dichloropyrimidine

[2‐¹⁴ C]2,5‐dichloropyrimidine is a useful reagent for labeling biologically active compounds for use in hepatocyte transport studies, protein covalent binding, and metabolic profiling. This paper describes a novel five‐step synthesis of [2‐¹⁴ C]2,5‐dichloropyrimidine from readily available [¹⁴C]urea by way of a boronic acid intermediate. A total of 4.34 mCi of [2‐¹⁴ C]2,5‐dichloropyrimidine was obtained with a specific activity of 226.0 μCi/mg (33.7 mCi/mmol). The radiochemical purity was 95.8%, and the overall radiochemical yield was 22% based on 20 mCi of [¹⁴C]urea starting material. Copyright © 2011 John Wiley & Sons, Ltd.     

Synthesis of [14C]‐ and [13C6]‐labeled potent HIV non‐nucleoside reverse transcriptase inhibitor

5,11‐Dihydro‐11‐ethyl‐5‐methyl‐8‐{2‐{(1‐oxido‐4‐quinolinyl)oxy}ethyl}‐6H‐dipyrido[3,2‐b:2′,3′‐e][1,4]diazepin‐6‐one, (1), labeled with carbon‐14 in the quinoline–benzene ring, in one of the pyridine rings of the dipyridodiazepinone tricyclic moiety, and in the side chain, was prepared in three different syntheses with specific activities ranging from 44 to 47 mCi/mmol (1.63–1.75 GBq/mmol). In the first synthesis, 5,11‐dihydro‐11‐ethyl‐8‐(2‐hydroxyethyl)‐5‐methyl‐6H‐dipyrido[3,2‐b:2′,3′‐e][1,4]diazepin‐6‐one (2) was coupled to 4‐hydroxyquinoline, [benzene‐¹⁴C(U)]‐, using Mitsunobu's reaction conditions, followed by the oxidation of the quinoline nitrogen with 3‐chloroperoxybenzoic acid to give ([¹⁴C]‐(1a)) in 43% radiochemical yield. Second, 3‐amino‐2‐chloropyridine, [2,6‐¹⁴C]‐, was used to prepare 8‐bromo‐5,11‐dihydro‐11‐ethyl‐5‐methyl‐6H‐dipyrido[3,2‐b:2′,3′‐e][1,4]diazepin‐6‐one (8), and then Stille coupled to allyl(tributyl)tin followed by ozonolysis of the terminal double bond and in situ reduction of the resulting aldehyde to alcohol (10). Mitsunobu etherification and oxidation as seen before gave ([¹⁴C]‐(1b)) in eight steps and in 11% radiochemical yield. Finally, carbon‐14 potassium cyanide was used to prepare isopropyl cyanoacetate (12), which was used to transform bromide (8) to labeled aryl acetic acid (13) under palladium catalysis. Trihydroborane reduction of the acid gave alcohol (14) labeled in the side chain, which was used as described above to prepare ([¹⁴C]‐(1c)) in 4.3% radiochemical yield. The radiochemical purities of these compounds were determined by radio‐HPLC and radio‐TLC to be more than 98%. To prepare [¹³C₆]‐(1), [¹³C₆]‐4‐hydroxyquinoline was prepared from [¹³C₆]‐aniline and then coupled to (2) and oxidized as seen before. Copyright © 2008 John Wiley & Sons, Ltd.     

Synthesis of [7‐14C]bergapten

Bergapten (1) is a furocoumarin natural product and currently employed to treat skin disorders. Since past attempts to radiolabel 1 with ¹⁴C were limited to only its 5‐methoxy group, a synthesis of the required ring [7‐¹⁴C]1 is now described. The literature reported precursor 4‐methoxy‐6‐hydroxybenzofuran‐5‐carboxaldehyde (3) was Wittig reacted with stabilized [carbonyl‐¹⁴C]methoxycarbonylmethylenetriphenylphosphorane (4) to obtain [7‐¹⁴C]1 in 47% radiochemical yield, with the desired product being characterized by thin‐layer chromatography, HPLC, m.p. and proton NMR.     

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 multi‐labeled [14C]Aripiprazole

Development of Aripiprazole as an oral treatment of schizophrenia required the synthesis of a suitably labeled drug product for use in human metabolism and pharmacokinetic studies. Due to the potential metabolic degradation of the molecule, a multi‐labeled approach utilizing ¹⁴C was adopted. The synthesis of [¹⁴C]Aripiprazole was accomplished in separate syntheses from 2,3‐dichloro[U‐¹⁴C]aniline and [3‐¹⁴C]‐cinnamic acid, respectively. Labeled versions were combined on the basis of molar radioactivity giving a final product with a radiochemical purity of 99.9% and a specific activity of 15.5 µCi/mg. Copyright © 2005 John Wiley & Sons, Ltd.     

Synthesis of carbon‐14 labeled 4‐[4‐[2‐[2‐[bis(4‐chlorophenyl) methoxy]ethyl sulfonyl][1‐14C]ethoxy]phenyl]‐1,1,1‐trifluoro‐2‐butanone

Carbon‐14 labeled 4‐[4‐[2‐[2‐[bis(4‐chlorophenyl)methoxyethylsulfonyl] [1‐¹⁴C]ethoxy]phenyl]‐1,1,1‐trifluoro‐2‐butanone was prepared in a six step radioactive synthesis from 2‐bromo[1‐¹⁴C]acetic acid. The overall radiochemical yield was 2.2%. The specific activity of the final product was found to be 42μCi/mg with a radiochemical purity of >98%. Copyright © 2002 John Wiley & Sons, Ltd.     

Synthesis of [14C]‐imexon

A four‐step synthesis of [¹⁴C]‐imexon is described, starting from [¹⁴C]‐phosgene. The overall yield is 27% and the specific activity is 55 mCi/mmol. Copyright © 2005 John Wiley & Sons, Ltd.     

Synthesis of [14C]‐labelled repinotan hydrochloride and its major metabolite M‐6

For studies of pharmacokinetics and drug metabolism of the new 5‐HT_1A agonist repinotan, the ¹⁴C‐labelled version was synthesized. Starting from [U‐¹⁴C]phenol, a 10‐step synthesis led to 457 mg (1.58 GBq) of [U‐¹⁴C]repinotan hydrochloride, labelled uniformly in the aromatic ring of the chromane moiety. For a study in man, a mono‐carbon‐14 labelled substance was required. Therefore a 7‐step synthesis was performed starting from [carbonyl‐¹⁴C]2‐hydroxy‐acetophenone. The yield was 106 mg (0.396 GBq) of [4‐chromane‐¹⁴C]repinotan hydrochloride. The carbon‐14 labelled major metabolite, hydroxylated in the 6‐position of the chromane moiety, was synthesised as reference compound. Copyright © 2002 John Wiley & Sons, Ltd.     

Syntheses of [14C]‐labeled 2‐(3‐chlorophenyloxy)‐3‐[3‐(3‐hydroxy) pyridin‐4‐yl propoxy]pyridine,a phosphodiesterase 4 inhibitor and its metabolites

We describe here the synthesis of [¹⁴C]‐2‐(3‐chlorophenyloxy)‐3‐[3‐(3‐hydroxy)pyridin‐4‐yl propoxy]pyridine (1), a phosphodiesterase 4 inhibitor. [¹⁴C]‐Labeled 1 was prepared in three steps from [¹⁴C]‐2‐bromopyridin‐3‐ol in an overall yield of 32%. Preparation of [¹⁴C]‐labeled 2 and 3, two metabolites of 1, is also described. Copyright © 2014 John Wiley & Sons, Ltd.     

An efficient synthesis of carbon‐14‐labeled 6‐[2‐(dimethylamino)ethyl]‐14‐(1‐ethylpropyl)‐5,6,7,8‐tetrahydroindolo [2,1‐α] [2,5]benzodiazocine‐11‐carboxylic acid using Curtius rearrangement reaction as a key step

Here we report an efficient synthesis of ¹⁴C‐labeled 6‐[2‐(dimethylamino)ethyl]‐14‐(1‐ethylpropyl)‐5,6,7,8‐tetrahydroindolo‐[2,1‐α][2,5]benzodiazocine‐11‐carboxylic acid (1) using the Curtius rearrangement as a key step. The synthesis was initiated by converting the unlabeled aryl carboxylic acid to an aryl amine via Curtius rearrangement reaction. The resulting aryl amine was then converted to an aryl iodide which was coupled with zinc [¹⁴C]cyanide to form an aryl [¹⁴C]nitrile. Subsequent hydrolysis yielded the ¹⁴C‐labeled carboxylic acid [¹⁴C]‐1. This overall process represents a mild and potentially general approach for conversion of unlabeled carboxylic acids to isotopically labeled carboxylic acids. Copyright © 2010 John Wiley & Sons, Ltd.     

Synthesis of [14C]‐radiolabelled entecavir

Radiolabelled [¹⁴C]entecavir, ( 1 ), was prepared in 12 steps from (1S,2R,3S,5R)‐3‐(benzyloxy)‐2‐(benzyloxymethyl)‐6‐oxa‐bicyclo[3.1.0]hexane 2 . The chemical yield of [¹⁴C]entecavir was 14% from the epoxide 2 . Introduction of [¹⁴C] radiolabel was achieved by elaboration of 4,5‐diaminopyrimidine 8 with triethyl[¹⁴C]orthoformate to purine derivative 9 . The radiochemical yield of [¹⁴C]entecavir from triethyl[¹⁴C]orthoformate was 11.3%. Radiochemical purity of [¹⁴C]entecavir determined by HPLC was 99.8%. The specific activity of [¹⁴C]entecavir was 108 µCi/mg (29.9 mCi/mmol). Copyright © 2005 John Wiley & Sons, Ltd.     

An efficient large‐scale synthesis of 1H‐indazole‐[3‐14C]carboxylic acid

An efficient large‐scale carbon‐14 synthesis of 1H‐indazole‐[3‐¹⁴C]carboxylic acid starting from [¹⁴C]potassium cyanide is reported. Key transformations encountered during the synthesis include aromatic nucleophilic substitution of 2‐nitrofluorobenzene by ethyl [¹⁴C]cyanoacetate, a mild decarbethoxylation and an aniline nitrosation/cyclization. Copyright © 2007 John Wiley & Sons, Ltd.     

Microwave‐assisted synthesis of (RS) methyl‐2‐([2′‐14C]4,6‐dimethoxypyrimidin‐2′‐yloxy)‐2‐phenyl [1‐14C]ethanoate

We report here a facile synthesis of (RS) methyl‐2‐([2′‐¹⁴C]4,6‐dimethoxypyrimidin‐2′‐yloxy)‐2‐phenyl [1‐¹⁴C]ethanoate under microwave irradiation. Copyright © 2006 John Wiley & Sons, Ltd.