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 [2H3]‐labelled sulfamethoxazole and its main urinary metabolites

Sulfamethoxazole was labelled at positions 3, 5, and 4′ by H/D exchange in a mixture of 5% ²H₂SO₄ and 95% ²H₂O (v/v) under reflux for 72h with good isotope incorporation and acceptable yield. Subsequently, [²H₃]‐sulfamethoxazole‐N₁‐glucuronide and [²H₃]‐N₄‐acetyl‐sulfamethoxazole were synthesized. Copyright © 2007 John Wiley & Sons, Ltd.     

Synthesis of deuterium‐labelled (−)‐galanthamine

The synthesis of deuterium‐labelled galanthamine is reported. 6‐[²H₃]methoxy‐N‐[²H₃]methyl‐(?)‐galanthamine was obtained in seven steps from galanthamine. The synthesis was carried out by selective O‐ and N‐demethylations. The [²H₃]‐N‐methyl and [²H₃]‐O‐methyl‐groups were introduced by selective aminoreduction and O‐methylation. Copyright © 2008 John Wiley & Sons, Ltd.     

Preparation of labelled 2‐methoxy‐3‐alkylpyrazines: synthesis and characterization of deuterated 2‐methoxy‐3‐isopropylyrazine and 2‐methoxy‐3‐isobutylpyrazine

Efficient synthetic routes for a number of deuterated analogues of 2‐methoxy‐3‐isopropylpyrazines and 2‐methoxy‐3‐isobutylpyrazines have been developed involving the condensation of glyoxal with an α‐amino acid amide followed by methylation with iodomethane. In this way [²H₃]2‐methoxy‐3‐isopropylpyrazine, 2‐methoxy‐3‐isopropyl‐[²H₂]pyrazine, [²H₃]2‐methoxy‐3‐isopropyl‐[²H₂]pyrazine, [²H₃]2‐methoxy‐3‐isobutylpyrazine; 2‐methoxy‐3‐isobutyl‐[²H₂]pyrazine and [²H₃]2‐methoxy‐3‐isobutyl‐[²H₂]pyrazine were prepared and characterized by NMR and MS. Copyright © 2002 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.     

An innovative and efficient synthesis of stable isotope labelled 1‐methyl‐5‐(4,4,5,5‐tetramethyl‐1,3,2‐dioxaborolan‐2‐yl)‐1H‐pyrazole via [13C42H3] N‐methylpyrazole

In support of a programme to develop a treatment for cancer, a stable isotope labelled version of the drug candidate was required. The key labelled intermediate was [¹³C₄²H₃] N‐methylpyrazole prepared by a novel bisacetal cyclisation. This was prepared from commercially available diethyl [¹³C₃] malonate and [¹³C²H₃] iodomethane. Copyright © 2012 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 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.     

The synthesis and structures of deuterium‐labeled 5‐substituted 1H‐tetrazoles

The synthesis and crystal structures of deuterium‐labeled 5‐substituted 1H‐tetrazoles, 5‐[²H₅]phenyl‐1H‐tetrazole (I), 5‐[²H₇]tolyl‐1H‐tetrazole (II), and 5‐[²H₇]benzyl‐1H‐tetrazole (III) are reported. All syntheses were carried out using simple, facile steps and the products were obtained in high yields. Copyright © 2008 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 [1,3, NH2‐15N3] (5′S)‐8,5′‐cyclo‐2′‐deoxyguanosine

To facilitate NMR studies and low‐level detection in biological samples by mass spectrometry, [1,3, NH₂‐¹⁵N₃] (5′S)‐8,5′‐cyclo‐2′‐deoxyguanosine was synthesized from imidazole‐4,5‐dicarboxylic acid in 21 steps. The three ¹⁵N isotopes were introduced during the chemo‐enzymatic preparation of [1,3, NH₂‐¹⁵N₃]‐2′‐deoxyguanosine using an established procedure. The ¹⁵N‐labeled 2′‐deoxyguanosine was converted to a 5′‐phenylthio derivative, which allowed the 8‐5′ covalent bond formation via photochemical homolytic cleavage of the C–SPh bond. SeO₂ oxidation of C‐5′ followed by sodium borohydride reduction and deprotection gave the desired product in good yield. The isotopic purity of the [1,3, NH₂‐¹⁵N₃] (5′S)‐8,5′‐cyclo‐2′‐deoxyguanosine was in excess of 99.94 atom% based on liquid chromatography–mass spectrometry measurements. Copyright © 2013 John Wiley & Sons, Ltd.     

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.     

Synthesis of 5‐[4,5‐13C2]‐ and 5‐[1,5‐13C2]aminolevulinic acid

5‐[4,5‐¹³C₂]‐ and 5‐[1,5‐¹³C₂]Aminolevulinic acid (ALA) have been synthesized by the Gabriel condensation of potassium phthalimide with ethyl bromo[1,2‐¹³C₂]acetate (derived from [1,2‐¹³C₂]acetic acid) or ethyl bromo[2‐¹³C]‐acetate (derived from sodium [2‐¹³C]acetate), followed by conversion to the chloride, coupling reaction with 2‐ethoxycarbonylethylzinc iodide derived from ethyl 3‐iodopropionate or 2‐methoxy[¹³C]carbonylethylzinc iodide derived from methyl 3‐iodo[1‐¹³C]propionate (generated from potassium [¹³C]cyanide), and hydrolysis. Copyright © 2002 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 deuterium‐labelled 6‐[5‐(4‐amidinophenyl)furan‐2‐yl]nicotinamidine and N‐alkoxy‐6‐{5‐[4‐(N‐alkoxyamidino)phenyl]‐ furan‐2‐yl}‐nicotinamidines

6‐[5‐(4‐Amidinophenyl)furan‐2‐yl]nicotinamidine‐d₄ ( 5 ) was synthesized from 6‐[5‐(4‐cyanophenyl)furan‐2‐yl]nicotinonitrile‐d₄ ( 3 ), through the bis‐O‐acetoxy‐amidoxime followed by hydrogenation. Compound 3 was prepared from 6‐(furan‐2‐yl)‐nicotinonitrile by a Heck coupling reaction with 4‐bromobenzonitrile‐d₄, a product of selective cyanation reaction of 1,4‐dibromobenzene‐d₄ with Cu(1)CN. Deuterium‐labelled N‐methoxy‐6‐{5‐[4‐(N‐methoxy‐amidinophenyl]‐furan‐2‐yl}‐nicotinamidines were prepared via methylation of their respective amidoximes with dimethyl sulfate‐d₆ in aqueous sodium hydroxide in good yields. Copyright © 2004 John Wiley & Sons, Ltd.     

Synthesis and radiosynthesis of N5‐[18F]fluoroethyl‐Pirenzepine and its metabolite N5‐[18F]fluoroethyl‐LS 75

The well established M₁ selective muscarinergic antagonist Pirenzepine 11‐[2‐(4‐methyl‐piperazin‐1‐yl)‐acetyl]‐5,11‐dihydro‐benzo[e]pyrido[3,2‐b][1,4]diazepin‐6‐one (1) exhibits an unusual behaviour in vivo, which cannot be explained with M₁ antagonism exclusively. One of the aspects discussed is a specific interaction with poly ADP‐ribose polymerase (PARP‐1). 1 undergoes metabolism to form LS 75 5,11‐dihydro‐benzo[e]pyrido[3,2‐b][1,4]diazepin‐6‐one (2). In order to study deviations in Pirenzepine efficacy from pure M₁ binding in vivo using PET, appropriate positron emitter labelled analogues of 1 and 2 were synthesised. Non‐radioactive reference compounds 3 and 4 were tested for PARP‐1 inhibition. The n‐octanol–water partition coefficients of compounds 1, 2, 3 and 4 at pH 7.4 (logD_7.4) were determined. Both, 3 and 4 were labelled with ¹⁸F via 2‐[¹⁸F]fluoroalkylation in position 5 of the benzodiazepinone moiety to obtain N⁵‐[¹⁸F]fluoroethyl Pirenzepine [¹⁸F]‐3 and N⁵‐[¹⁸F]fluoroethyl LS 75 [¹⁸F]‐4. Radiotracers [¹⁸F]‐3 and [¹⁸F]‐4 were obtained in radiochemical yields of 15±4 % and 30±5% after 120 and 110 min, respectively. Metabolism of both compounds was investigated in vitro in human and rat plasma, respectively. Compound 3 did not show activity as an inhibitor of PARP‐1. Contrary, 4 displays moderate PARP‐1 inhibition potency. The new radiotracer [¹⁸F]‐4 can be applied for molecular imaging using autoradiography and PET. Copyright © 2009 John Wiley & Sons, Ltd.     

Synthesis of 3H and 14C labeled (S)‐3‐(5‐chloro‐2‐methoxyphenyl)‐1,3‐dihydro‐3‐fluoro‐6‐(trifluoromethyl)‐2H‐indol‐2‐one,maxipost™. An agent for post‐stroke neuroprotection

The syntheses of tritium labeled (S)‐3‐(5‐chloro‐2‐[OC³H₃]methoxyphenyl‐1,3‐dihydro‐3‐fluoro‐6‐(trifluoromethyl)‐1H‐indol‐2‐one, and carbon‐14 (S)‐3‐(5‐chloro‐2‐methoxyphenyl)‐1,3‐dihydro‐3‐fluoro‐6‐(trifluoromethyl)‐2H‐[2,3‐¹⁴C₂] indol‐2‐one are reported. The ³H‐labeled compound was prepared in a two‐step synthesis from C³H₃I. The final product was purified via chiral HPLC to yield the desired enantiomer in a 4% radiochemical yield and a specific activity of 60 Ci/mmol. The ¹⁴C‐labeled compound was prepared in a four‐step synthesis from diethyl [carboxylate‐¹⁴C₁,₂] oxalate. The final product was purified via chiral HPLC to yield the desired enantiomer in a 20% radiochemical yield and a specific activity of 28.4 μCi/mg. Copyright © 2002 John Wiley & Sons, Ltd.     

Synthesis and evaluation of [123I]‐indomethacin derivatives as COX‐2 targeted imaging agents

A novel series of iodinated indomethacin derivatives was synthesized, and evaluated as selective inhibitors of COX‐2. Two candidate compounds N‐(p‐iodobenzyl)‐2‐(1‐(p‐chlorobenzoyl)‐5‐methoxy‐2‐methyl‐1H‐indol‐3‐yl)acetamide (3) and 1‐(p‐iodobenzyl)‐5‐methoxy‐2‐methyl‐3‐indoleacetic acid (9) possessed optimum properties suitable for potential in vivo imaging. Arylstannane precursors for radioiododestannylation were synthesized in 70–85% yield from the iodo compounds by reaction with hexabutylditin and tetrakis(triphenylphosphine)palladium(0) in refluxing dioxane. Radioiododestannylation was conducted by reaction with carrier‐added Na[¹²³I] in the presence of Chloramine‐T in an EtOAc/H₂O binary system under acidic conditions (pH 3.5), allowing direct isolation of the labeled products by separation of the organic phase. Radioiodinated products [¹²³I]3 and [¹²³I]9 were recovered in a decay‐corrected radiochemical yield of 86–87% and radiochemical purity of 98–99%. Copyright © 2009 John Wiley & Sons, Ltd.     

Caution in the use of 2‐iminothiolane (Traut's reagent) as a cross‐linking agent for peptides. The formation of N‐peptidyl‐2‐iminothiolanes with bombesin (BN) antagonist (d‐Trp6,Leu13‐ψ[CH2NH]‐Phe14)BN6−14 and d‐Trp‐Gln‐Trp‐NH2

Abstract: During a study aimed at generating a bispecific molecule between BN antagonist (d ‐Trp⁶,Leu¹³‐ψ[CH₂NH]‐Phe¹⁴)BN_6‐14 (Antag1) and mAb22 (anti‐FcγRI), we attempted to cross‐link the two molecules by introducing a thiol group into Antag1 via 2‐iminothiolane (2‐IT, Traut's reagent). We found that reaction of Antag1 with 2‐IT, when observed using HPLC, affords two products, but that the later eluting peptide is rapidly transformed into the earlier eluting peptide. To understand what was occurring we synthesized a model peptide, d ‐Trp‐Gln‐Trp‐NH₂ (TP1), the N‐terminal tripeptide of Antag1. Reaction of TP1 with 2‐IT for 5 min gave products 1a and 3a ; the concentration of 1a decreased with reaction time, whereas that of 3a increased. Thiol 1a , the expected Traut product, was identified by collecting it in a vial containing N‐methylmaleimide and then isolating the resultant Michael addition product 2a , which was confirmed by mass spectrometry. Thiol 1a is stable at acidic pH, but is unstable at pH 7.8, cyclizes and loses NH₃ to give N‐TP1‐2‐iminothiolane ( 3a ), ES‐MS (m/z) [602.1 (M+H)⁺], as well as regenerating TP1. Repeat reaction with Antag1 and 2‐IT allowed us to isolate N‐Antag1–2‐iminothiolane ( 3b ), FAB‐MS (m/z) [1212.8 (M+H)⁺] and trap the normal Traut product 1b as its N‐methylmaleimide Michael addition product 2b , ES‐MS (m/z) [1340.8 (M+H)⁺]. Thiol 1b is also stable at acidic pH, but when neutralized is unstable and cyclizes, forming 3b and Antag1.     

The preparation of [pentane‐5,5,5‐3H3]‐abnormal‐cannabidiol

A bromoalkane precursor was synthesized in six steps, and its copper catalysed coupling with methylmagnesium chloride to provide unlabelled abnormal‐cannabidiol (1a) was optimized. The methodology was used for an analogous coupling using [³H₃]‐methylmagnesium iodide to provide [pentane‐²H₃]‐abnormal‐cannabidiol (1b). Copyright © 2010 John Wiley & Sons, Ltd.