Synthesis of new carbon-11 labeled benzoxazole derivatives for PET imaging of 5-HT(3) receptor

5-HT(3) receptor is an attractive target for the development of therapeutic agents for use in brain, heart and cancer diseases, and imaging agents for use in biomedical imaging technique PET. Benzoxazole derivatives are a novel class of 5-HT(3) receptor partial agonists with high binding affinity. Carbon-11 labeled benzoxazole derivatives have been synthesized as new potential PET radioligands for imaging 5-HT(3) receptor. The target tracers were prepared by N-[(11)C]methylation of their corresponding precursors using [(11)C]CH(3)OTf and isolated by HPLC purification procedure in 40-50% radiochemical yields, which were decay corrected to the end of bombardment (EOB), based on [(11)C]CO(2). The overall synthesis time was 20-25min from EOB. The radiochemical purity was >99%, and specific activity was in a range of 74-111 GBq/micromol at the end of synthesis (EOS).     

Synthesis of some new substituted triazolo [4,3-a][1,4] benzodiazepine derivatives as potent anticonvulsants

Novel 8-chloro-6-(2-fluorophenyl)-1-(aryl)-4H-[1,2,4]triazolo[4,3-a][1,4]benzodiazepines (5a-f) were prepared by treating 7-chloro-5-(2-fluorophenyl)-1,3-dihydro-2H-1,4-benzodiazepine-2-thione with various aromatic acid hydrazides. The newly prepared compounds were characterized by spectral analysis. Compounds were tested for anticonvulsant activity. Four of the tested compounds such as 5a, 5d, 5e and 5f exhibited excellent anticonvulsant activity in comparison with standard drug, diazepam.     

Synthesis and preliminary biological evaluation of new carbon-11 labeled tetrahydroisoquinoline derivatives as SERM radioligands for PET imaging of ER expression in breast cancer

The estrogen receptors (ERs) are attractive targets in the treatment of breast cancer and the development of receptor-based breast cancer imaging agents for diagnostic use in biomedical imaging technique positron emission tomography (PET). Tetrahydroisoquinoline derivatives are a class of selective estrogen receptor modulators (SERMs) with high binding affinity and specificity exhibiting up to 50 folds for ERalpha over ERbeta. New carbon-11 labeled tetrahydroisoquinoline derivatives, [11C]methyl 1-(2-(4-(2-(4-fluorophenyl)-6-hydroxy-1-methyl-1,2,3,4-tetrahydroisoquinolin-1-yl)phenoxy)ethyl)piperidine-4-carboxylate ([11C]10a) and [11C]methyl 1-(2-(4-(2-(4-chlorophenyl)-6-hydroxy-1-methyl-1,2,3,4-tetrahydroisoquinolin-1-yl)phenoxy)ethyl)piperidine-4-carboxylate ([11C]10b), have been first designed, synthesized and evaluated. The target tracers were prepared by O-[11C]methylation of their corresponding precursors using [11C]CH3OTf and isolated by solid-phase extraction (SPE) purification procedure in 40-60% radiochemical yields, which were decay corrected to the end of bombardment (EOB), based on [11C]CO2. The overall synthesis time was 15-20 min from EOB. The radiochemical purity was >99%, and specific activity was in a range of 74-111GBq/micromol at the end of synthesis (EOS). Preliminary findings from in vitro biological assay indicate that the synthesized derivatives displayed similar potencies in the MCF-7 human breast cancer cell line in comparison with 4-hydroxytamoxifen, a well-known potent SERM. These results encourage further in vivo evaluation of carbon-11 labeled tetrahydroisoquinoline derivatives as new potential SERM radioligands for PET imaging of ER expression in breast cancer.     

Differential expression of the peripheral benzodiazepine receptor and gremlin during adipogenesis

This study used the mRNA differential display technique to identify differentially expressed genes during the process of adipogenesis in the preadipocyte cell line, 3T3-L1. 3T3-L1 cells were treated with dexamethasone, isobutyl-1-methylxanthine, and insulin to induce differentiation into mature adipocytes. Cells were collected at three time-points during differentiation: Day 0 (d0), or nondifferentiated; Day 3 (d3), during differentiation; and Day 10 (d10), >90% of the cells had differentiated into mature adipocytes. Initial studies yielded 18 potentially differentially regulated cDNA candidates (8 down-regulated and 10 up-regulated). Reverse Northern and Northern blots confirmed differential expression of six of the candidates. Four of the candidates up-regulated on d3 and d10 were identified by sequence analysis to be lipoprotein lipase, a well-known marker of adipocyte differentiation. A fifth candidate that was expressed in d0, but not d3 or d10, was identified as DRM/gremlin, a bone morphogenetic protein antagonist. Finally, a sixth candidate that was increased at d3 and d10 was identified as the peripheral benzodiazepine receptor, which has been implicated in proliferation, differentiation, and cholesterol transport in cells. This study is the first to show that peripheral benzodiazepine receptor and DRM/gremlin are expressed in preadipocyte cell lines and that they are differentially regulated during adipogenesis.     

Synthesis and preliminary in vitro biological evaluation of new carbon-11-labeled celecoxib derivatives as candidate PET tracers for imaging of COX-2 expression in cancer

The enzyme cyclooxygenase-2 (COX-2) is overexpressed in a variety of malignant tumors. This study was designed to develop new radiotracers for imaging of COX-2 in cancer using biomedical imaging technique positron emission tomography (PET). Carbon-11-labeled celecoxib derivatives, [(11)C]4a-c and [(11)C]8a-d, were prepared by O-[(11)C] methylation of their corresponding precursors using [(11)C]CH(3)OTf under basic conditions and isolated by a simplified solid-phase extraction (SPE) method in 52 ± 2% (n = 5) and 57 ± 3% (n = 5) radiochemical yields based on [(11)C]CO(2) and decay corrected to end of bombardment (EOB). The overall synthesis time from EOB was 23 min, the radiochemical purity was >99%, and the specific activity at end of synthesis (EOS) was 277.5 ± 92.5 GBq/μmol (n = 5). The IC(50) values to block COX-2 for known compounds celecoxib (4d), 4a and 4c were 40, 290 and 8 nM, respectively, and preliminary findings from in vitro biological assay indicated that the synthesized new compounds 4b and 8a-d display similar strong inhibitory effectiveness in the MDA-MB-435 human cancer cell line in comparison with the parent compound 4d. These results encourage further in vivo evaluation of carbon-11-labeled celecoxib derivatives as new potential PET radiotracers for imaging of COX-2 expression in cancer.     

Cerebral uptake and regional distribution of [11C]-vinpocetin after intravenous administration to healthy men: a PET study

INTRODUCTION: Vinpocetine is a compound widely used in the prevention and treatment of cerebrovascular diseases. The exact mechanism of action of the drug is still not known. The objective of the present investigation was to determine the global uptake and regional distribution of radiolabelled vinpocetine in the human brain. Three healthy persons were examined with positron emission tomography (PET) and [11C]-vinpocetine. RESULTS: The uptake of [11C]-vinpocetine in brain was rapid and on average as a maximum 3.7% of the total radioactivity injected was in the brain 2 minutes after radioligand administration. The uptake was heterogeneously distributed among brain regions. When compared with the cerebellum, an a priori reference region, the highest regional uptake was in the thalamus, the upper brain stem, the striatum and the cortex. CONCLUSIONS: The brain regions showing increased uptake in the human brain correspond to those in which vinpocetine has previously been shown to induce elevated metabolism and blood flow by PET clinical studies in patients with chronic ischaemic post-stroke condition.     

Simple synthesis of carbon-11 labeled styryl dyes as new potential PET RNA-specific, living cell imaging probes

A new type of styryl dyes have been developed as RNA-specific, live cell imaging probes for fluorescent microscopy technology to study nuclear structure and function. This study was designed to develop carbon-11 labeled styryl dyes as new probes for biomedical imaging technique positron emission tomography (PET) imaging of RNA in living cells. Precursors (E)-2-(2-(1-(triisopropylsilyl)-1H-indol-3-yl)vinyl)quinoline (2), (E)-2-(2,4,6-trimethoxystyryl)quinoline (3) and (E)-4-(2-(6-methoxyquinolin-2-yl)vinyl)-N,N-diemthylaniline (4), and standards styryl dyes E36 (6), E144 (7) and F22 (9) were synthesized in multiple steps with moderate to high chemical yields. Precursor 2 was labeled by [(11)C]CH(3)OTf, trapped on a cation-exchange CM Sep-Pak cartridge following a quick deprotecting reaction by addition of (n-Bu)(4)NF in THF, and isolated by solid-phase extraction (SPE) purification to provide target tracer [(11)C]E36 ([(11)C]6) in 40-50% radiochemical yields, decay corrected to end of bombardment (EOB), based on [(11)C]CO(2). The target tracers [(11)C]E144 ([(11)C]7) and [(11)C]F22 ([(11)C]9) were prepared by N-[(11)C]methylation of the precursors 3 and 4, respectively, using [(11)C]CH(3)OTf and isolated by SPE method in 50-70% radiochemical yields at EOB. The specific activity of the target tracers [(11)C]6, [(11)C]7 and [(11)C]9 was in a range of 74-111GBq/mumol at the end of synthesis (EOS).     

Imidazo[2,1-b]thiazepines: synthesis, structure and evaluation of benzodiazepine receptor binding

As a continuation of our search for new ligands acting on benzodiazepine receptors among the fused 2-thiohydantoin derivatives, a series of 5-substituted imidazo[2,1-b]thiazepines was synthesized and investigated in radioligand binding studies at the benzodiazepine binding site of GABA(A) receptors in rat brain cortical membranes. Among ortho-substituted 5-arylidene-imidazo[2,1-b]thiazepines compounds could be identified which exhibit affinity for the benzodiazepine binding site at low micromolar concentrations. X-ray structure analyses for two compounds (6ae and 6ag) have been performed. In order to analyze the structure-activity relationships, 3D models of all compounds have been completed (using X-ray data). Physicochemical properties calculated (log P and log D) as well as experimental thin layer chromatography data were examined.     

Percutaneous absorption of [7.10-14C]benzo[a]pyrene and [7,12-14C]dimethylbenz[a]anthracene in mice

The percutaneous penetration, tissue distribution, and excretion of 14C-labeled benzo[a]pyrene (BaP) and dimethylbenz[a]anthracene (DMBA) were studied in mice. Both BaP and DMBA rapidly penetrated the skin and were excreted more in the feces than in the urine. The proportion of BaP or DMBA absorbed was less with increasing applied dose due to apparent saturation of the uptake process. Uptake from the dorsal skin of the nose was similar to uptake from the dorsal nuchal skin.     

Synthesis of some new 4-styryltetrazolo[1,5-a]quinoxaline and 1-substituted-4-styryl[1,2,4]triazolo[4,3-a]quinoxaline derivatives as potent anticonvulsants

4-Methyltetrazolo[1,5-a]quinoxaline (3) was prepared by the azide cyclocondensation of 2-chloro-3-methylquinoxaline (2). The reaction of 3 with aromatic aldehydes furnished 4-styryltetrazolo[1,5-a]quinoxalines (4a-f). Compound 2, on treatment with hydrazine hydrate gave 2-hydrazino-3-methylquinoxaline (5). The ring closure of 5 was achieved by the reaction of orthoesters and trifluoroacetic acid to yield 4-methyl-1-(substituted)[1,2,4]triazolo[4,3-a]quinoxalines (7a-c). Further, reaction of 7a-c with different aromatic aldehydes furnished the title compounds, 4-styryl-1-(substituted)[1,2,4]triazolo[4,3-a]quinoxalines (8a-i) in good yield. In another scheme, the hydrazino compound 5 was treated with different aromatic aldehydes to yield corresponding N-arylidenehydrazino quinoxalines (6a-d). Further, the oxidative cyclization of hydrazones by nitrobenzene yielded 1-aryl-4-methyl[1,2,4]triazolo[4,3-a]quinoxalines (7d-g), which on condensation with aromatic aldehydes gave the title compounds, 1-aryl-4-styryl[1,2,4]triazolo[4,3-a]quinoxalines (8j-u). The newly synthesized compounds have been characterized by FTIR, (1)H NMR, (13)C NMR and mass spectral data, followed by elemental analysis. Some of the compounds were screened for in vivo anticonvulsant activity. Few of them exhibited promising results.     

Cerebral uptake and metabolism of (11C) Vinpocetine in monkeys: PET studies]

Vinpocetine, a vinca alkaloid, is a therapeutic agent widely used in the treatment of acute and chronic stroke patients. To explore the uptake and distribution of vinpocetine in the primate brain, vinpocetine was labelled with 11C and positron emission tomography (PET) was used to measure the uptake and distribution of 11C-vinpocetine in the brain and the trunk of a cynomolgous monkey. HPLC was used to determine the concentration of vinpocetine and its labelled metabolites in blood and plasma. Following the radioligand's intravenous administration, after an initial peak, the total concentration of radioactivity in blood was relatively stable with time. The uptake of 11C-vinpocetine into the brain was rapid and about 5% of the total injected radioactivity was present in the brain two minutes after drug administration. These facts indicate that the compound passes the blood-brain barrier readily and enters the brain. The radioactivity uptake was heterogeneously distributed among brain regions. The highest concentrations were found in the thalamus, the basal ganglia and certain neocortical regions. In an earlier PET investigation on chronic stroke patients the highest increases in cerebral blood flow and glucose metabolism after intravenous vinpocetine treatment occurred in these anatomical structures. The heterogenous regional distribution of vinpocetine and the observation that the highest uptake values in brain structures go parallel with the greatest regional blood flow and glucose metabolic rate increases indicate that direct CNS effects of vinpocetine should be considered as an explanation for the therapeutic effects. The confirmation of this suggestion requires further investigations.     

Synthesis and biological evaluation of dihydroindeno and indeno [1,2-e] [1,2,4]triazolo [3,4-b] [1,3,4]thiadiazines as antimicrobial agents

Two series of compounds namely, dihydroindeno and indeno [1,2-e] [1,2,4]triazolo [3,4-b] [1,3,4]thiadizines (9a-l & 11a-l) were synthesized by cyclocondensation between α-bromoindanones (7a-b) or/and α,α-dibromoindanones (8a-b) and various 3-alkyl/aryl-4-amino-5-mercapto-1,2,4-s-triazoles (3a-f) in methanol with an aim to explore their effect on in vitro growth of microorganism causing microbial infection. In vitro antibacterial activity was performed against four strains namely, Staphylococcus aureus, Bacillus subtilis, Escherichia coli, Pseudomonas aeruginosa and antifungal activity against three fungal strains namely, Aspergillus niger, Aspergillus flavus, Penicillium species. Of all the compounds screened for activity some of the compounds were associated with considerably higher antibacterial and antifungal activity than commercial antibiotics.     

Synthesis and in vitro antimicrobial activity of new 2-[p-substituted-benzyl]-5-[substituted-carbonylamino]benzoxazoles

Some new 2-(benzyl/p-chlorobenzyl)-5-[(substituted-thienyl/phenyl/phenylthiomethyl/benzyl)carbonylamino]benzoxazole derivatives have been synthesized by reacting 5-amino-2-(benzyl/p-chlorobenzyl)benzoxazoles with appropriate carboxylic acid chlorides. The structures of the synthesized compounds were confirmed by IR, (1)H NMR and MASS spectral data. In vitro antimicrobial activities of the compounds were investigated using twofold serial dilution technique against different two Gram-positive, two Gram-negative bacteria and three Candida spp. in comparison with standard drugs. Microbiological results indicated that the newly synthesized 2-(benzyl/p-chlorobenzyl)-5-[(substituted-thienyl/phenyl/phenylthiomethyl/benzyl)carbonylamino]benzoxazole derivatives (3-12) possessed a broad spectrum of activity having MIC values of 6.25-100 microg/ml against the tested microorganisms. Especially, with an MIC value of 6.25 microg/ml, 2-(p-chlorophenyl)-5-[(2,5-dimethylphenyl)carbonylamino]benzoxazole 4 displayed the same activity against Candida albicans as the standard drug clotrimazole.     

Synthesis and biological evaluation of N-substituted benzo[c]phenanthrolines and benzo[c]phenanthrolinones as antiproliferative agents

Benzo[c]phenanthrolines and benzo[c]phenanthrolinones substituted by dialkylaminoalkyl side chains at position N5 and C6, respectively, were synthesised and their biological activity evaluated. They displayed interessant cytotoxicity associated with some DNA interactions. However, the low topoisomerase 1 affinity suggests that other cellular targets are responsible for the antiproliferative activity.     

Synthesis of thieno[3,2-g]quinoxalines as potential amoebicides

A route for the synthesis of thieno[3,2-g]quinoxalines and their derivatives is described. The anti-amoebic activity of these compounds has been preliminaly assayed against Entamoeba histolytica. Compounds 1a, b, g, l, m, n, o displayed activity against hepatic amoebiasis and compounds 1 a, b, l showed activity against intestinal amoebiasis in animal models.     

Synthesis and primary cytotoxicity evaluation of new imidazo[2,1-b]thiazole derivatives

A series of arylidenehydrazides (3a-3i) were synthesized from [6-(4-bromophenyl)imidazo[2,1-b]thiazol-3-yl]acetic acid hydrazide. The structures of new compounds were determined by analytical and spectral (IR, (1)H NMR, (13)C NMR, EIMS) methods. The synthesized compounds (3a-3i) were evaluated in the National Cancer Institute's 3-cell line, one dose in vitro primary cytotoxicity assay. Compounds 3a-3c, 3h and 3i which passed the criteria for activity in this assay were scheduled automatically for evaluation against the full panel of 60 human tumour cell lines at a minimum of five concentrations at 10-fold dilutions. Compounds 3c demonstrated the most marked effects on a prostate cancer cell line (PC-3, log(10)GI(50) value<-8.00).     

Discovery of a new anilino-3H-pyrrolo[3,2-f]quinoline derivative as potential anti-cancer agent

The newly synthesized 1-[4-(3H-pyrrolo[3,2-f]quinolin-9-ylamino)-phenyl]-ethanone hydrochloride showed high antiproliferative activity by mixed mechanisms of action. The compound acts by forming an intercalative complex with DNA and inhibiting DNA topoisomerase II (topo II) and by blocking the cell cycle in G(2)/M phase. Probable cell death by apoptosis is also suggested by flow cytometry analysis.     

Synthesis and biological activity of new 2-amino-8-chloro-5,5-dioxo[1,2,4]triazolo[2,3-b][1,4,2]benzodithiazines

Two series of 1-(6-chloro-1,1-dioxo-1,4,2-benzodithiazin-3-yl)-4-arylsemicarbazides 6-17 and 2-arylamino-8-chloro-5,5-dioxo[1,2,4]triazolo[2,3-b][1,4,2]benzodithiazines 18-26 were prepared in order to evaluate their biological activity. Compounds 6 and 18-26 were tested for their in vitro cytotoxic potency against 12 human cancer cell lines. The compounds 6 and 19 were inactive, whereas triazolobenzodithiazines 18, 20-26 possess tumor growth inhibitory properties. The prominent methyl 8-chloro-2-(4-chlorophenylamino)-5,5-dioxo[1,2,4]triazolo[2,3-b][1,4,2]benzodithiazine-7-carboxylate (21) exhibited potency higher or comparable to cisplatin. Moreover, compounds 6, 9, 19 and 23-25 with structure similar to other chemotherapeutic agents were tested for their antibacterial activity and exhibited MIC and MBC against Staphylococcus aureus (3.9-31.5 microg ml).     

Design, synthesis and biological evaluation of substituted 11H-benzo[a]carbazole-5-carboxamides as novel antitumor agents

A series of novel 11H-benzo[a]carbazole-5-carboxamide derivatives were designed, synthesized and evaluated for their antitumor activity against human cancer A549 and HCT-116 cell lines. Most of the compounds showed potent antitumor activities, and compound 8 displayed remarkable in vitro and in vivo anticancer activity comparable to that of amonafide.