Synthesis and biodistribution studies of two novel radioiodinated areno‐annelated estra‐1,3,5(10),16‐tetraene‐3‐ols as promising estrogen receptor radioligands

Two novel radioiodinated areno‐annelated estra‐1,3,5(10),16‐tetraenes, [¹²⁵I]2‐iodo‐1′‐methoxybenzo[4′,3′:16,17]estra‐1,3,5(10),16‐tetraene‐3‐ol ( 2 ‐[ ¹²⁵ I ]‐ MEBE ) and [¹²⁵I]4‐iodo‐1′‐methoxybenzo[4′,3′:16,17]estra‐1,3,5(10),16‐tetraene‐3‐ol, ( 4 ‐[ ¹²⁵ I ]‐ MEBE ) were synthesized for evaluation as potential ligands for the estrogen receptor. Radioiodination of 1′‐methoxybenzo[4′,3′:16,17]estra‐1,3,5(10),16‐tetraene‐3‐ol at the A ring was accomplished by electrophilic aromatic substitution using [¹²⁵I] sodium iodide and chloramine‐T as oxidant. After purification by reverse phase HPLC, the two radioisomers ( 2 ‐[ ¹²⁵ I ]‐ MEBE and 4 ‐[ ¹²⁵ I ]‐ MEBE ) were obtained in a radiochemical yield of 42 and 48%, respectively, in a radiochemical purity of greater than 95% and a high specific activity. The effect of the site of radioiodination (C₂ vs C₄) on the biological behaviour of the molecules was evaluated through biodistribution studies in immature female Sprague‐Dawley rats. Both 2 ‐[ ¹²⁵ I ]‐ MEBE and 4 ‐[ ¹²⁵ I ]‐ MEBE are stable in vivo and are mainly excreted through the hepatobiliary pathway. Both localize in the uterus and ovaries via a receptor‐mediated process, where the 2 ‐[ ¹²⁵ I ]‐ MEBE isomer has the higher specific ER binding and uterus selectivity. The favourable in vitro/in vivo stability and biodistribution profiles suggest that these radioligands are good candidates for further exploration of their potential clinical application. Copyright © 2006 John Wiley & Sons, Ltd.     

Preparation of the iodine‐124 derivative of the Bolton–Hunter reagent ([124I]I‐SHPP) and its use for labelling a VEGF antibody as a PET tracer

This study describes the radioiodination of an antibody specific to the vascular endothelial growth factor (VEGF), VG76e, with [¹²⁴I]iodine to obtain a novel PET tracer for measurement of angiogenesis. In vitro binding assays showed a significantly higher immunoreactive fraction with the protein labelling reagent N‐succinimidyl 3‐(4‐hydroxy‐5‐[¹²⁵I]iodophenyl) propionate ([¹²⁵I]Bolton–Hunter reagent, [¹²⁵I]I‐SHPP) (34.0±4.0%) as compared with N‐succinimidyl 3‐[¹²⁵I]iodobenzoate (10.9±6.4%) or direct radioiodination using [¹²⁵I]iodide and IodoGen (3.1±3.0%). Consequently, the cyclotron–produced positron–emitting [¹²⁴I]iodine (T_1/2=4.2 days) was employed to prepare [¹²⁴I]I‐SHPP. Using an improved radioiodination methodology, [¹²⁴I]I‐SHPP was prepared from sodium [¹²⁴I]iodide with IodoGen at pH 6.5. The [¹²⁴I]Bolton–Hunter reagent was isolated with 25–58% (n=3) radiochemical yield and 88–95% (n=3) radiochemical purity by the conventional extraction procedure. The conjugate of VG76e with [¹²⁴I]I‐SHPP was prepared with 17–18% (n=3) labelling efficiency and 98% radiochemical purity. The immunoreactive fraction was determined to be 33.5% (n=2). Copyright © 2002 John Wiley & Sons, Ltd.     

Synthesis and preliminary characterization of radioiodinated benzofuran‐3‐yl‐(indol‐3‐yl)maleimide derivatives as potential SPECT imaging probes for the detection of glycogen synthase kinase‐3β (GSK‐3β) in the brain

We report on the synthesis and preliminary characterization of two radioiodinated benzofuran‐3‐yl‐(indol‐3‐yl)maleimides, 3‐(benzofuran‐3‐yl)‐4‐(5‐[¹²⁵I]iodo‐1‐methyl‐1H‐indol‐3‐yl)‐1H‐pyrrole‐2,5‐dione ([¹²⁵I]5), and 3‐(5‐[¹²⁵I]iodo‐1‐methyl‐1H‐indol‐3‐yl)‐4‐(6‐methoxybenzofuran‐3‐yl)‐1H‐pyrrole‐2,5‐dione ([¹²⁵I]6), as the first potential SPECT imaging probes targeting glycogen synthase kinase‐3β (GSK‐3β). In this study, we used ¹²⁵I as a surrogate of ¹²³I because of its ease of use. The radioiodinated ligands were prepared from the corresponding tributyltin precursors through an iododestannylation reaction using hydrogen peroxide as an oxidant with a radiochemical yield of 10–30%. In vitro binding experiments suggested that both compounds show high affinity for GSK‐3β at a level similar to a known GSK‐3β inhibitor. Biodistribution studies with normal mice revealed that the radioiodinated compounds display sufficient uptake into (1.8%ID/g at 10 min postinjection) and clearance from the brain (1.0%ID/g at 60 min postinjection). These preliminary results suggest that the further optimization of radioiodinated benzofuran‐3‐yl‐(indol‐3‐yl)maleimide derivatives may facilitate the development of clinically useful SPECT imaging probes for the in vivo detection of GSK‐3β.     

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.     

A tin precursor for the synthesis of no‐carrier‐added [*I]MIBG and [211At]MABG

Radioiodinated MIBG has shown considerable promise as an imaging agent for cardiac and oncologic applications, and also as a targeted radiotherapeutic for treating patients with neuroendocrine tumors. This radiolabeled agent, synthesized at a no‐carrier‐added level, has demonstrated advantages over the carrier‐added preparation in preliminary clinical studies. Earlier we developed a silicon precursor from which both radioiodinated MIBG and the α‐particle‐emitting ²¹¹At analog [²¹¹At]MABG could be synthesized at a no‐carrier‐added level. In order to increase the practicality of this approach, we have developed a synthesis of a tin precursor in two steps from a readily available starting material. This tin precursor, N, N′‐bis(tert‐butyloxycarbonyl)‐3‐(trimethylstannyl)benzylguanidine (Bis‐Boc MTMSBG) was evaluated for the synthesis of n.c.a. [*I]MIBG and [²¹¹At]MABG via halodestannylation. The radiochemical yields were 83 ± 9% (n=7), 30 ± 21% (n=2), 77 ± 2% (n=2), and 66 ± 7% (n=4) for labeling with ¹³¹I, ¹²⁴I, ¹²⁵I, and ²¹¹At, respectively. Copyright © 2007 John Wiley & Sons, Ltd.     

A Novel Antifungal Agent with Broad Spectrum: 1‐(4‐Biphenylyl)‐3‐(1H‐imidazol‐1‐yl)‐1‐propanone

A series of (1‐substituted aryl)‐3‐(1H‐imidazol‐1‐yl)‐1‐propanones was synthesized through the N‐alkylation of imidazole with 3‐dimethylamino‐1‐(substituted aryl)‐1‐propanone hydrochlorides (ketonic Mannich bases). A second series of N¹‐substituted imidazoles was obtained by the reduction of the carbonyl function of the imidazole–ketones in the previous series by means of NaBH₄. All of the compounds were evaluated for antifungal activity against 16 strains of Candida, and 3‐(1H‐imidazol‐1‐yl)‐1‐(4‐biphenylyl)‐1‐propanone emerged as a broad‐spectrum antifungal agent. Several 3‐(1H‐imidazol‐1‐yl)‐1‐(2′‐(substituted benzyl)oxyphenyl)‐1‐propanones were also active towards Candida kefyr.     

Synthesis and Antimicrobial Activity of Some Novel 2‐[4‐(Substituted Piperazin‐/Piperidin‐1‐ylcarbonyl)phenyl]‐1H‐benzimidazole Derivatives

In this study, we report the synthesis and antimicrobial evaluation of several new 4‐(1H‐benzimidazol‐2‐yl)benzamides ( 11 – 30 ) and 5‐chloro‐1‐(p‐fluorobenzyl)‐2‐{4‐[(4‐methylpiperazin‐1‐yl)carbonyl]phenyl}‐1H‐benzimidazole ( 33 ). Compound 20 exhibited the best antibacterial activity with MIC value of 6.25 μg/mL against Staphylococcus aureus and methicillin‐resistant Staphylococcus aureus (MRSA). Significant antifungal activities were obtained with the compounds 13 , 14, 18 , 19, and 33 with MIC values of 3.12 μg/mL which are close to fluconazole.     

1‐[(Imidazolidin‐2‐yl)imino]‐1H‐indoles as new hypotensive agents: synthesis and in vitro and in vivo biological studies

A series of 1‐[(imidazolidin‐2‐yl)imino]‐1H‐indole analogues of hypotensive α₂‐AR agonists, 1‐[(imidazolidin‐2‐yl)imino]‐1H‐indazoles, was synthesized and tested in vitro for their activities at α₁‐ and α₂‐adrenoceptors as well as imidazoline I₁ and I₂ receptors. The most active 1‐[(imidazolidin‐2‐yl)imino]‐1H‐indoles displayed high or moderate affinities for α₁‐ and α₂‐adrenoceptors and substantial selectivity for α₂‐adrenoceptors over imidazoline‐I₁ binding sites. The in vivo cardiovascular properties of indole derivatives 3 revealed that substitution at C‐7 position of the indole ring may result in compounds with high cardiovascular activity. Among them, 7‐fluoro congener 3g showed the most pronounced hypotensive and bradycardic activities in this experiment at a dose as low as 10 μg/kg i.v. Metabolic stability of the selected compounds of type 3 was determined using both in vitro and in silico approaches. The results indicated that these compounds are not vulnerable to rapid first‐phase oxidative metabolism.     

Synthesis and biological evaluation of 125I/123I‐labelled analogues of citalopram and escitalopram as potential radioligands for imaging of the serotonin transporter

Two novel radioligands for the serotonin transporter (SERT), [¹²⁵I]{3‐[5‐iodo‐1‐[4‐fluorophenyl)‐1,3‐dihydroisobenzofuran‐1‐yl]‐propyl}‐dimethylamine ([¹²⁵I]‐2) and S‐[¹²⁵I]{3‐[5‐iodo‐1‐(4‐fluorophenyl)‐1,3‐dihydroisobenzofuran‐1‐yl]‐propyl}‐dimethylamine ([¹²⁵I]‐(S)‐2) were synthesized in a Br/¹²⁵I exchange reaction. Binding experiments in rats yielded K_d values of 0.7 ± 0.06 and 0.52 ± 0.02 nM for [¹²⁵I]‐2 and [¹²⁵I]‐(S)‐2, respectively. One hour after intravenous injection of [¹²⁵I]‐2, 0.34% of the injected dose had accumulated in the brain. The highest hypothalamus‐to‐cerebellum ratio was reached 2 h after injection of [¹²⁵I]‐(S)‐2 and amounted to 2.4. Pre‐treatment experiments with paroxetine resulted in effective reduction of the target‐to‐cerebellum ratios. The corresponding iodine‐123 labelled compound S‐[¹²³I]{3‐[5‐Iodo‐1‐(4‐fluorophenyl)‐1,3‐dihydroisobenzofuran‐1‐yl]‐propyl}‐dimethylamine [¹²³I]‐S‐ 2 was investigated in a pig single photon emission computed tomography (SPECT) study. Between 60 and 110 min after IV injection, the midbrain‐to‐cerebellum ratio was 1.2. However, the uptake did not differ between high‐density and medium‐density regions questioning the feasibility of the radioligand in imaging cortical SERT distribution in vivo. These data suggest that the iodine‐labelled derivatives of citalopram and escitalopram are not superior to another SPECT tracer for the SERT, namely [¹²³I]ADAM. Copyright © 2010 John Wiley & Sons, Ltd.     

Conformationally Constrained Analogs of N‐Substituted Piperazinylquinolones: Synthesis and Antibacterial Activity of N‐(2,3‐Dihydro‐4‐hydroxyimino‐4H‐1‐benzopyran‐3‐yl)‐piperazinylquinolones

A series of novel quinolone agents bearing a particular bulky and conformationally constrained bicyclic substituent (2,3‐dihydro‐4‐hydroxyimino‐4H‐1‐benzopyran‐3‐yl‐ moiety) on the piperazine ring of 7‐piperazinyl quinolones (norfloxacin, enoxacin, ciprofloxacin, and levofloxacin) were synthesized and evaluated against a panel of Gram‐positive and Gram‐negative bacteria. Among these derivatives, ciprofloxacin counterpart 9c , highly inhibited the tested Gram‐positive bacteria, superior to that of the reference drugs, and displayed antibacterial activity at non‐cytotoxic concentrations.     

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.     

Syntheses,calcium channel modulation effects,and nitric oxide release studies of O2‐alkyl‐1‐(pyrrolidin‐1‐yl) diazen‐1‐ium‐1,2‐diolate 4‐aryl(heteroaryl)‐1,4‐dihydro‐2,6‐dimethyl‐3‐nitropyridine‐5‐carboxylates

A group of racemic 4‐aryl(heteroary)‐1,4‐dihydro‐2,6‐dimethyl‐3‐nitropyridine‐5‐carboxy‐lates possessing a potential nitric oxide donor C‐5 O²‐alkyl‐1‐(pyrrolidin‐1‐yl)diazen‐1‐ium‐1,2‐diolate ester [alkyl=(CH₂)_n, n=1–4] substituent were synthesized using a modified Hantzsch reaction. Compounds having a C‐4 2‐trifluoromethylphenyl ( 16 ), 2‐pyridyl ( 17 ), or benzofurazan‐4‐yl ( 20 ) substituent generally exhibited more potent smooth‐muscle calcium channel antagonist activity (IC₅₀ values in the 0.55 to 38.6 μM range) than related analogs having a C‐4 3‐pyridyl ( 18 ), or 4‐pyridyl ( 19 ) substituent with IC₅₀ values > 29.91 μM, relative to the reference drug nifedipine (IC₅₀=0.0143 μM). The point of attachment of C‐4 isomeric pyridyl substituents was a determinant of antagonist activity where the relative potency profile was 2‐pyridyl > 3‐pyridyl and 4‐pyridyl. Subgroups of compounds 16a–d , 17a–d , and 20a–d having alkyl spacer groups of variable chain length [–CO₂(CH₂)_nO–, n=1–4] exhibited small differences in calcium channel antagonist potency. Replacement of the ester “methyl” moiety of Bay K 8644 by an O²‐alkyl‐1‐(pyrrolidin‐1‐yl)diazen‐1‐ium‐1,2‐diolate group provided the Bay K 8644 group of analogs 16a‐d that retained the desired cardiac positive inotropic effect. The most potent compound in this group, O²‐ethyl‐1‐(pyrrolidin‐1‐yl)diazen‐1‐ium‐1,2‐diolate 1,4‐dihydro‐2,6‐dimethyl‐3‐nitro‐4‐(2‐trifluoromethylphenyl)pyridine‐5‐carboxylate ( 16b , EC₅₀=0.096 μM) is about eightfold more potent positive inotrope (cardiac calcium channel agonist) than the reference compound Bay K 8644 (EC₅₀=0.77 μM). A similar replacement of the ester “isopropyl” group in the C‐4 benzofurazan‐4‐yl group of compounds by an O²‐alkyl‐1‐(pyrrolidin‐1‐yl)diazen‐1‐ium‐1,2‐diolate ester substituent provided compounds 20 (n=1 and 4) that were approximately equipotent cardiac positive inotropes with the parent reference compound PN 202‐791 ( 3 , EC₅₀=9.40 μM). The O²‐alkyl‐1‐(pyrrolidin‐1‐yl)diazen‐1‐ium‐1,2‐diolate ester moiety present in 1,4‐dihydropyridine calcium channel modulating compounds 16–20 is not a suitable ?NO donor moiety because the percent nitric oxide released upon in vitro incubation with either l ‐cysteine, rat serum, or pig liver esterase was less than 1%. Drug Dev. Res. 60:204–216, 2003. © 2003 Wiley‐Liss, Inc.     

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.     

Synthesis of N‐(piperidin‐1‐yl)‐5‐(4‐methoxyphenyl)‐1‐(2‐chlorophenyl)‐4‐[18F]fluoro‐1H‐pyrazole‐3‐carboxamide by nucleophilic [18F] fluorination: a PET radiotracer for studying CB1 cannabinoid receptors

The feasibility of nucleophilic displacement of bromide in the 4‐bromopyrazole ring with [¹⁸F]fluoride has been demonstrated by the synthesis of two radiolabeled compounds: N‐(piperidin‐1‐yl)‐5‐(4‐methoxyphenyl)‐1‐(2‐chlorophenyl)‐4‐[¹⁸F]fluoro‐1H‐pyrazole‐3‐carboxamide, ([¹⁸F] NIDA‐42033) 1b and 1‐(2‐chlorophenyl)‐4‐[¹⁸F]fluoro‐5‐(4‐methoxyphenyl)‐1H‐pyrazole‐3‐carboxylic acid, ethyl ester 4 . The radiochemical yields were in the range of 1–6%. [¹⁸F]NIDA‐42033, a potential radiotracer for the study of CB₁ cannabinoid receptors in the animal brain by positron emission tomography, has been synthesized in sufficient quantities with specific radioactivity greater than 2500 mCi/μmol and radiochemical purity >95%. Copyright © 2002 John Wiley & Sons, Ltd.     

A potent IκB kinase‐β inhibitor labeled with carbon‐14 and deuterium

3‐Amino‐4‐(1,1‐difluoro‐propyl)‐6‐(4‐methanesulfonyl‐piperidin‐1‐yl)‐thieno[2,3‐b]pyridine‐2‐carboxylic acid amide (1) is a potent IκB Kinase‐β (IKK‐β) inhibitor. The efficient preparations of this compound labeled with carbon‐14 and deuterium are described. The carbon‐14 synthesis was accomplished in six radiochemical steps in 25% overall yield. The key transformations were the modified Guareschi–Thorpe condensation of 2‐cyano‐¹⁴C‐acetamide and a keto‐ester followed by chlorination to 2,6‐dichloropyridine derivative in one pot. The isolated dichloropyridine was then converted in three steps in one pot to [¹⁴C]‐ (1) . The carbon‐14 labeled (1) was isolated with a specific activity of 54.3 mCi/mmol and radiochemical purity of 99.8%. The deuterium labeled (1) was obtained in eight steps and in 57% overall chemical yield using 4‐hydroxypiperidine‐2,2,3,3,4,5,5,6,6‐²H₉. The final three steps of this synthesis were run in one pot.     

Design,synthesis, and biological evaluation of 5‐(4‐(pyridin‐4‐yl)‐1H‐1,2,3‐triazol‐1‐yl)benzonitrile derivatives as xanthine oxidase inhibitors

A series of 5‐(4‐(pyridin‐4‐yl)‐1H‐1,2,3‐triazol‐1‐yl)benzonitrile derivatives ( 1a–p ) was designed, synthesized, and identified as xanthine oxidase inhibitors with micromolar level potencies. Among them, the most promising compounds 1j and 1k were obtained with IC₅₀ values of 8.1 and 6.7 μm , respectively. The Lineweaver–Burk plot revealed that compound 1k acted as a mixed‐type xanthine oxidase inhibitor. SAR analysis revealed that a carbon atom occupying the X³ position is not as effective as a nitrogen atom, and an iso‐pentyloxy or a cyclopentyloxy at the 2‐position of benzonitrile moiety will benefit the inhibitory potency. The basis of xanthine oxidase inhibition by 1k was rationalized by molecular modeling studies.     

2‐Aryl‐3‐(1H‐Azol‐1‐yl)‐1H‐Indole Derivatives: A New Class of Antimycobacterial Compounds – Conventional Heating in Comparison with MW‐Assisted Synthesis

2‐Aryl‐3‐(1H‐imidazol‐1‐yl and 1H‐1,2,4‐triazol‐1‐yl)‐1H‐indole derivatives were synthesized and tested for their in‐vitro antifungal and antimycobacterial activities. These indole derivatives were devoid of antifungal activity against the tested strains of Candida spp. Yet, they exhibited an interesting antitubercular activity against Mycobacterium tuberculosis reference strain H₃₇Rv.     

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.     

Radiosynthesis of 2‐exo‐(2′‐[18F]Fluoro‐3′‐(4‐fluorophenyl)‐pyridin‐5′‐yl)‐7‐azabicyclo[2.2.1]heptane ([18F]F2PhEP), a potent epibatidine‐based radioligand for nicotinic acetylcholine receptor PET imaging

2‐exo‐(2′‐Fluoro‐3′‐(4‐fluorophenyl)‐pyridin‐5′‐yl)‐7‐azabicyclo[2.2.1]heptane (F₂PhEP), a novel, epibatidine‐based, α4β2‐selective nicotinic acetylcholine receptor antagonist of low toxicity, as well as the corresponding N‐Boc‐protected chloro‐ and bromo derivatives as precursors for labelling with fluorine‐18 were synthesized from 7‐tert‐butoxycarbonyl‐7‐azabicyclo[2.2.1]hept‐2‐ene in 13, 19 and 8% overall yield, respectively. [¹⁸F]F₂PhEP was prepared in 8–9% overall yield (non‐decay‐corrected) using 1 mg of the bromo derivative in the following two‐step radiochemical process: (1) no‐carrier‐added nucleophilic heteroaromatic ortho‐radiofluorination with the activated K[¹⁸F]F‐Kryptofix^®₂₂₂ complex in DMSO using microwave activation at 250 W for 90 s, followed by (2) quantitative TFA‐induced removal of the N‐Boc protective group. Radiochemically pure (>95%) [¹⁸F]F₂PhEP (1.48–1.66 GBq, 74–148 GBq/µmol) was obtained after semi‐preparative HPLC (Symmetry^® C18, eluent aqueous 0.05 M NaH₂PO₄ CH₃CN: 78/22 (v:v)) in 75–80 min starting from an 18.5 GBq aliquot of a cyclotron‐produced [¹⁸F]fluoride production batch. Copyright © 2006 John Wiley & Sons, Ltd.     

Synthesis of the tritiated isotopomers of enzastaurin and its N‐des‐pyridylmethyl metabolite for use in ADME studies

Enzastaurin (3‐(1‐methyl‐1H‐indol‐3‐yl)‐4‐[1‐[1‐(2‐pyridinylmethyl)‐4‐piperidinyl]‐1H‐indol‐3‐yl]‐1H‐pyrrole‐2,5‐dione, 1), an agent with potential utility in the treatment of solid tumors, is currently in phase II clinical trials. Enzastaurin undergoes metabolism in vitro and in vivo to several products of oxidative metabolism, the major one of which is 3‐(1‐methyl‐1H‐indol‐3‐yl)‐4‐(1‐piperidin‐4‐yl‐1H‐indol‐3‐yl)‐1H‐pyrrole‐2,5‐dione (2). In a model study, the attempted synthesis 1‐[²H] by reaction of 1 with deuterium gas in the presence of Ir[(COD)(Cy₃P)pyr]PF₆ (Crabtree's catalyst) was unsuccessful. Alternatively, it was decided to prepare tritiated 2 as both a final product and the starting material for the tritiation of 1. We have reported herein a route that was developed for use in the preparation of tritium‐labeled 2‐[³H] and its successful conversion to 1‐[³H]. Copyright © 2008 John Wiley & Sons, Ltd.