Synthesis of (S)‐cyano(3‐phenoxyphenyl)methyl (1R,3R)‐ 3‐[(1Z)‐2‐chloro‐3,3,3‐trifluoro‐1‐propenyl]‐2,2‐dimethylcyclopropanecarboxylate‐1‐14C

γ‐Cyhalothrin ( 1a ), (S)‐cyano(3‐phenoxyphenyl)methyl (1R,3R)‐3‐[(1Z)‐2‐chloro‐3,3,3‐trifluoro‐1‐propenyl]‐2,2‐dimethylcyclopropanecarboxylate, is a single‐isomer, synthetic pyrethroid insecticide marketed by Pytech Chemicals GmbH, a joint venture between Dow AgroSciences and Cheminova A/S. As a part of the registration process there was a need to incorporate a carbon‐14 label into the cyclopropyl ring of this molecule. A high yielding radiochemical synthesis of γ‐cyhalothrin was developed from readily available carbon‐14 labeled N‐t‐Boc protected glycine. This seven step synthesis, followed by a preparative normal phase HPLC separation of diastereomers, provided 21.8 mCi of γ‐cyhalothrin‐1‐¹⁴C ( 1b ) with >98% radiochemical purity. Copyright © 2007 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 of tritium‐labelled 3′‐azido‐3′‐deoxythymidine

New approaches to the synthesis of 3′‐azido‐3′‐deoxythymidine labelled with tritium in the heterocyclic base have been developed. With this aim, enzymatic transribosylation with [³H]thymine using the enzyme preparation from rat liver and a three‐step chemical synthesis with use of the tritium labelled precursor were studies. The enzyme preparation did not catalyse the transfer of the 3′‐azido‐3′‐deoxyribosyl fragment to the [³H]thymine residue. 5′‐O‐Benzoyl‐2,3′‐anhydrothymidine was taken as a precursor for the tritium labelling by the chemical methods. The resulting [³H]3′‐azido‐3′‐deoxythymidine was obtained with a specific radioactivity of 18.3 Ci/mmol, the tritium is located in the C‐6 position of the thymine residue. Copyright © 2003 John Wiley & Sons, Ltd.     

Synthesis of [2‐13C, 4‐13C]‐(2R,3S)‐catechin and [2‐13C, 4‐13C]‐(2R,3R)‐epicatechin

The first synthesis of doubly labeled, [2‐¹³C, 4‐¹³C]‐(2R,3S)‐catechin 15 and [2‐¹³C, 4‐¹³C]‐(2R,3R)‐epicatechin 18 starting from labeled 2‐hydroxy‐4, 6‐bis(benzyloxy)acetophenone 3 and labeled 3, 4‐bis(benzyloxy)‐benzaldehyde 7 are described. Copyright © 2010 John Wiley & Sons, Ltd.     

Synthesis of [3‐3H]20(S)‐protopanaxadiol

[3‐³H]20(S)‐Protopanaxadiol (PPD) was prepared via selective reduction of PPD dioxide with sodium borotritide in N,N‐dimethyl acetamide. A radiochemical yield of 22% was obtained. The radiochemical purity of the final product was 99% and the ratio of C‐3/C‐12 tritium labeling was 97:3. Copyright © 2009 John Wiley & Sons, Ltd.     

A novel asymmetric synthesis of tritium and carbon‐14 labeled (R)‐ibuprofen

An efficient asymmetric synthesis of tritium and carbon‐14 labeled R‐ibuprofen was achieved in good overall yield (15% and 47%, respectively) and excellent enantiomerical excess (>98% e.e.), using (4R, 5S)‐4‐methyl‐5‐phenyl‐2‐oxazolidinone as a chiral auxiliary. Copyright © 2006 John Wiley & Sons, Ltd.     

Labelling of anilines,benzylamines and some N‐heterocyclics using cycloocta‐1,5‐dienyliridium(I)‐1,1,1,5,5,5‐hexafluoro‐pentan‐2,4‐dionate and isotopic hydrogen gas in DMF or DMA

A wide range of anilines, benzylamines and some N‐heterocyclics can be ortho‐deuterated at room temperature using deuterium gas and cycloocta‐1,5‐dienyliridium(I)‐1,1,1,5,5,5‐hexafluoropentan‐2,4‐dionate in DMF or DMA. The method is applicable to labelling with tritium. Copyright © 2004 John Wiley & Sons, Ltd.     

Synthesis of [3α‐3H] 17α‐Hydroxy pregnenolone and [3α‐3H] Pregnenolone

For the first time, [3α‐³H] 17α‐hydroxy pregnenolone (1) was synthesized through a multiple step sequence. The presence of [3β‐³H] isomer in RP‐HPLC purified product was identified by tritium NMR. The [3β‐³H] isomer was then separated from [3α‐³H] 17α‐hydroxy pregnenolone with chiralPAK AD‐H column. [3α‐³H] pregnenolone (2) was synthesized from commercial available 5‐pregnen‐3,20‐dione in one step with an improved procedure.     

Synthesis and radioiodination of 7‐(3′‐ammoniopropyl)‐7,8‐dicarba‐nido‐undecaborate(‐1), (ANC)

Derivatives of nido‐carborate have potential use in tumour targeting as hydrophilic boron‐rich compounds for boron neutron capture therapy (BNCT) and as pendant groups for attachment of radiohalogens to tumour‐seeking molecules. For this purpose, functionalized derivatives of nido‐carborates that can be conjugated to biomolecules should be synthesized and evaluated. In this study, racemic 1 , 7‐(3′‐ammoniopropyl)‐7,8‐dicarba‐nido‐undecaborate(‐1) (acronym ANC ) was obtained by degradation of the corresponding aminopropyl‐o‐carborane, which was synthesized in three steps from 1‐tert‐butyldimethylsilyl‐2‐(3‐bromopropyl)‐o‐carborane, with sodium hydroxide in absolute ethanol. The racemate 1 was radioiodinated (¹²⁵ I ) using the Chloramine‐T method. Radio‐TLC results showed that radiolabelling with ¹²⁵ I was achieved in a yield greater than 95%. Copyright © 2004 John Wiley & Sons, Ltd.     

Synthesis of all‐trans‐[10′‐3H]‐8′‐apo‐β‐carotenoic acid

The enzyme, 15,15′‐β‐carotene dioxygenase (BCDOX), facilitates the oxidation of β‐carotene to yield retinal. This is a remarkable process in which one of 11 double bonds in β‐carotene is selectively oxidized. To further probe the mechanistic aspects of BCDOX, the synthesis of all‐trans‐[10′‐³H]‐8′‐apo‐β‐carotenoic acid is reported. This compound will be used as a photoaffinity labeling reagent to probe the β‐carotene binding pocket within BCDOX. The synthesis outlines a simple and efficient route for the incorporation of tritium at the 10′ olefinic carbon of 8′‐apo‐β‐carotenoic acid. Copyright © 2002 John Wiley & Sons, Ltd.     

3‐butyl‐6‐fluoro‐1(3H)‐isobenzofuranone (6‐F‐NBP), a derivative of dl‐n‐butylphthalide,inhibits glutamate‐induced cytotoxicity in PC12 cells

It is widely recognized that glutamate (Glu)‐induced cytotoxicity, intracellular calcium overload and the excessive free radical production are key events in the development and progression of ischemic brain injury. dl‐3‐n‐butylphthalide (NBP), an anti‐ischemic agent, has therapeutic effects in animal models of vascular dementia. The aim of the present study was to investigate the protective effect of 3‐butyl‐6‐fluoro‐1(3H)‐isobenzofuranone (6‐F‐NBP), a derivative of NBP on Glu‐induced cytotoxicity in rat pheochromocytoma (PC12) cells, and to compare this action with NBP. The results showed that after 24‐h incubation with Glu (5 mM), cell viability and mitochondrial membrane potential (MMP) were decreased. In contrast, the content of reactive oxygen species (ROS), activity of nitric oxide synthase (NOS), and apoptosis rate, as well as intracellular accumulation of [Ca²⁺]_i, were increased, 6‐F‐NBP inhibited the damage induced by Glu in a dose‐dependent manner and exerted a more potent effect than NBP, indicating that 6‐F‐NBP exhibited a protective effect against Glu‐induced cytotoxicity in cultured PC12 cells. Drug Dev Res 73: 11–17, 2012. © 2011 Wiley Periodicals, Inc.     

1‐[(2,3‐Dihydro‐1‐benzofuran‐2‐yl) methyl]piperazines as novel anti‐inflammatory compounds: Synthesis and evaluation on H3R/H4R

The histamine receptors (HRs) are members of G‐protein‐coupled receptor superfamily and traditional targets of huge therapeutic interests. Recently, H₃R and H₄R have been explored as targets for drug discovery, including in the search for dual‐acting H₃R/H₄R ligands. The H₄R, the most recent histamine receptor, is a promising target for novel anti‐inflammatory agents in several conditions such as asthma and other chronic inflammatory diseases. Due to similarity with previously reported ligands of HRs, a set of 1‐[(2,3‐dihydro‐1‐benzofuran‐2‐yl)methyl]piperazines were synthesized and evaluated in competitive binding assays as H₃R/H₄R ligands herein. The results showed the compounds presented affinity (K_i) for H₃R/H₄R in micromolar range, and they are more selective to H₃R. All the compounds showed no important cytotoxicity to mammalian cells. The phenyl‐substituted compound LINS01005 has shown the higher affinity of the set for H₄R, but no considerable selectivity toward this receptor over H₃R. LINS01005 showed interesting anti‐inflammatory activity in murine asthma model, reducing the eosinophil counts in bronchoalveolar lavage fluid, as well as the COX‐2 expression. The presented compounds are valuable prototypes for further improvements to achieve better anti‐inflammatory agents.     

Synthesis of 2H‐ and 3H‐labeled N‐cyclopropylmethyl‐7α‐[(R)‐1‐hydroxy‐1‐methyl‐3‐(2thienyl)‐propyl]‐6,14‐endoethano‐6,7,8,14‐tetrahydro nororipavine

A procedure for deuterium and tritium labeling of the titled compound, an analgesic agent, was developed. A secondary amine intermediate was acylated to an acylamide, then the carbonyl function was reduced by LiAlD₄ to yield the tertiary amine. In the tritium‐labeled synthesis, the process utilized a bromo‐substituted precursor, which was subsequently reduced with ³H₂ in the presence of a Pd/C catalyst. The labeled compounds were successfully applied in pharmacokinetic and pharmacological studies. Copyright © 2005 John Wiley & Sons, Ltd.     

Synthesis of tritium‐labeled (R,R)‐4‐methoxyfenoterol

The preparation of 2′,4′,6′‐[³H₃]‐(R,R)‐4‐methoxyfenoterol, a tritium‐labeled derivative of (R,R)‐4‐methoxyfenoterol was demonstrated on a 15 mCi scale providing material with a specific activity of 57 Ci/mmol. Copyright © 2009 John Wiley & Sons, Ltd.     

A facile synthesis of 5,5‐dideutero‐4‐dimethyl(phenyl)silyl‐6‐undecyl‐tetrahydropyran‐2‐one as a deuterium labeled synthon for (−)‐tetrahydrolipstatin and (+)‐δ‐hexadecanolide

Deuterium‐labeled biologically active compounds are gaining importance because they can be utilized as tracers or surrogate compounds to understand the mechanism of action, absorption, distribution, metabolism, and excretion. Deuterated drug molecules (heavy drugs) become novel as well as popular because of better stability and bioavailability compared with their hydrogen analogs. Labeling of organic molecules with deuterium at specific positions is thus gaining popularity. In this work, we have exploited a highly regioselective and enantioselective direct Michael addition of methyl‐d₃ alkyl ketones to dimethyl(phenyl)silylmethylene malonate that was catalyzed by (S)‐N‐(2‐pyrrolidinylmethyl)pyrrolidine/trifluoroacetic acid/ D₂O combination with high yield and isotopic purity. The 5,5‐dideutero‐4‐dimethyl(phenyl)silyl‐6‐undecyl‐tetrahydropyran‐2‐one was obtained from the adduct of methyl‐d₃ undecanyl ketone and dimethyl(phenyl)silylmethylene malonate by a silicon controlled diastereoselective ketone reduction, lactonization, and deethoxycarbonylation. The dideuterated silylated tetrahydropyran‐2‐one is the precursor for geminal ²H₂‐labeled (+)‐4‐hydroxy‐6‐undecyl‐tetrahydropyran‐2‐one, an advanced intermediate for gem‐dideutero (–)‐tetrahydrolipstatin and (+)‐δ‐hexadecanolide syntheses.     

High specific activity (+)‐amphetamine and (+)‐methamphetamine

High specific activity (+)‐amphetamine and (+)‐methamphetamine were prepared by reductive dechlorination of (S)‐(3′,5′‐dichlorophenyl)‐2‐propylazide and (S)‐2′6′‐dichloromethamphetamine, respectively. While the latter was readily obtained by resolution of racemic 2′6′‐dichloromethamphetamine using (+)‐dibenzoyltartaric acid, the analogous amphetamine resisted all efforts to resolve it. Hence, the required chiral precursor was prepared by stereospecific total synthesis following methodology that had been previously developed in our Laboratories. The tritium labeled compounds had specific activity 30.1 Ci/mmol and 38.3 Ci/mmol, respectively. Copyright © 2009 John Wiley & Sons, Ltd.     

The Structural and Functional Role of the B‐chain C‐terminal Arginine in the Relaxin‐3 Peptide Antagonist,R3(BΔ23‐27)R/I5

Relaxin‐3, a member of the insulin superfamily, is involved in regulating stress and feeding behavior. It is highly expressed in the brain and is the endogenous ligand for the receptor RXFP3. As relaxin‐3 also interacts with the relaxin receptor RXFP1, selective agonists and antagonists are crucial for studying the physiological function(s) of the relaxin‐3/RXFP3 pair. The analog R3(BΔ23‐27)R/I5, in which a C‐terminally truncated human relaxin‐3 (H3) B‐chain is combined with the INSL5 A‐chain, is a potent selective RXFP3 antagonist and has an Arg residue remaining on the B‐chain C‐terminus as a consequence of the recombinant protein production process. To investigate the role of this residue in the RXFP3 receptor binding and activation, the analogs R3(BΔ23‐27)R/I5 and R3(BΔ23‐27)R containing the B‐chain C‐terminal Arg as well as R3(BΔ23‐27)/I5 and R3(BΔ23‐27), both lacking the Arg, were chemically assembled and their secondary structure and receptor activity assessed. The peptides generally had a similar conformation but those with the extra Arg residue displayed a significantly increased affinity for the RXFP3. Interestingly, in contrast to R3(BΔ23‐27)R and R3(BΔ23‐27)R/I5, the peptide R3(BΔ23‐27) is a weak agonist. This suggests that the C‐terminal Arg, although increasing the affinity, alters the manner in which the peptide binds to the receptor and thereby prevents activation, giving R3(BΔ23‐27)R/I5 its potent antagonistic activity.     

Synthesis of tritium and carbon‐14 labelled NNC 61‐4655: a potent dual‐acting PPARα and PPARγ agonist

The synthesis of the potent dual‐acting PPARα and PPARγ agonist NNC 61‐4655 labelled with tritium and carbon‐14 is reported. Tritium labelled NNC 61‐4655 was obtained in three steps with introduction of tritium through catalytic tritium‐halogen exchange of an aryl bromide precursor. This provided [³H]NNC 61‐4655 in 39% overall radiochemical yield with a specific activity of 49 Ci/mmol. Carbon‐14 labelled NNC 61‐4655 was obtained in five steps starting from bromo[1‐¹⁴C]acetic acid. The synthetic sequence, which included a Horner–Wadsworth–Emmons olefination and a Mitsunobu alkylation, provided [¹⁴C]NNC 61‐4655 in 33% overall radiochemical yield with a specific activity of 57.4 mCi/mmol. Copyright © 2003 John Wiley & Sons, Ltd.     

Preparation of carbon‐14 labeled (3R)‐7‐hydroxy‐N‐(1S)‐1‐{[(3R,4R)‐4‐(3‐hydroxyphenyl)‐3,4‐dimethyl‐1‐piperidinyl]methyl}‐2‐methylpropyl‐1,2,3,4‐tetrahydroisoquinolinecarboxamide (JDTic)

Starting with [¹⁴C]‐D‐tyrosine, carbon‐14 labeled JDTic dihydrochloride with specific activity 15 mCi/mol was prepared in 5% radiochemical yield. Separation of the (3R)‐ and (3S)‐diastereomers was carried out via the 3‐phenyl‐2,3,10,10a‐tetrahydro‐5H‐imidazo[1,5‐b]isoquinolin‐1‐ones formed by reaction with benzaldehyde. Copyright © 2008 John Wiley & Sons, Ltd.     

Preparation of high specific activity tritium labeled 6α,9,‐difluoro‐11β,21‐dihydroxy‐16α,17‐[(1‐methylethylidene)bis(oxy)]pregna‐1,4‐diene‐3,20‐one,fluocinolone acetonide

Fluocinolone acetonide was tritiated by selective reduction of the 1,2‐double bond of the O‐protected analog under tritium, followed by re‐establishment of the 1,2‐double bond and deprotection. Protection of both hydroxyl functionalities was required. The product was obtained with specific activity 36.8 Ci/mmol. Copyright © 2009 John Wiley & Sons, Ltd.