- Regioselective N-alkylation of some imidazole-containing heterocycles and their in vitro anticancer evaluation
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Imidazole-containing heterocycles: Imidazopyridines, imidazopyrimidines and imidazopyra-zines can exist more tautomeric forms than benzimidazoles. Their regioselectivities were determined for N-alkylations with 4-fluorobenzyl bromide under basic conditions (K2CO3) in DMF. We observed that, regioisomers were mainly formed as a mixture in this reaction and N-benzylation occurs at a higher ratio on six membered heterocycles. Their structural assignments were made with the use of two-dimensional 1H–1H NOE (nuclear overhauser effect spectroscopy, NOESY). Complementary structural information was provided by 2D-HMBC spectra of the compounds. Synthesized compounds were tested for in vitro cytotoxic activities against Human colon cancer cell line (HCT-116) and leukemia cell lines (K562 and HL-60) by MTT test. Among them, imidazopyridine analogue 10, bearing bromine atom at the C-6 position of the pyridine moiety, gave the lowest IC50 value with 6–7 μg/mL against all three cancer cell lines.
- Karaaslan, Cigdem,Doganc, Fatima,Alp, Mehmet,Koc, Asli,Karabay, Arzu Zeynep,G?ker, Hakan
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- Imidazopyridine- and purine-thioacetamide derivatives: Potent inhibitors of nucleotide pyrophosphatase/phosphodiesterase 1 (NPP1)
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Nucleotide pyrophosphatase/phosphodiesterase 1 (NPP1) belongs to the family of ecto-nucleotidases, which control extracellular nucleotide, nucleoside, and (di)phosphate levels. To study the (patho)physiological roles of NPP1 potent and selective inhibitors with drug-like properties are required. Therefore, a compound library was screened for NPP1 inhibitors using a colorimetric assay with p-nitrophenyl 5′-thymidine monophosphate (p-Nph-5′-TMP) as an artificial substrate. This led to the discovery of 2-(3H-imidazo[4,5-b]pyridin-2-ylthio)-N-(3,4-dimethoxyphenyl)acetamide (5a) as a hit compound with a Ki value of 217 nM. Subsequent structure-activity relationship studies led to the development of purine and imidazo[4,5-b]pyridine analogues with high inhibitory potency (Ki values of 5.00 nM and 29.6 nM, respectively) when assayed with p-Nph-5′-TMP as a substrate. Surprisingly, the compounds were significantly less potent when tested versus ATP as a substrate, with Ki values in the low micromolar range. A prototypic inhibitor was investigated for its mechanism of inhibition and found to be competitive versus both substrates.
- Chang, Lei,Lee, Sang-Yong,Leonczak, Piotr,Rozenski, Jef,De Jonghe, Steven,Hanck, Theodor,Müller, Christa E.,Herdewijn, Piet
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p. 10080 - 10100
(2015/02/05)
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- Metal-mediated inhibition of escherichia coli methionine aminopeptidase: Structure-activity relationships and development of a novel scoring function for metal-ligand interactions
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We report the discovery of thiabendazole as a potent inhibitor (K 1 = 0.4 μM) of Escherichia coli methionine aminopeptidase (ecMetAP) and the synthesis and pharmacological evaluation of thiabendazole congeners with activity in the upper nanomolar range, Elucidation of the X-ray structure of ecMetAP in complex with thiabendazole and an unrelated inhibitor that was independently described by another group showed that that both compounds bind to an additional CoII ion at the entrance of the active site. This unexpected finding explains the inactivity of the compounds under in vivo conditions. It also allows us to discuss the structure-activity relationships of this series of compounds in a meaningful way, based upon docking runs with an auxiliary metal ion, We describe a new scoring function for the evaluation of metal-mediated inhibitor binding that, unlike the previously used scoring function implemented in the docking program, allows us to distinguish between active and inactive compounds, Finally, conclusions for the structure-based design of in vivo-active inhibitors of ecMetAP are drawn.
- Schiffmann, Rolf,Neugebauer, Alexander,Klein, Christian D.
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p. 511 - 522
(2007/10/03)
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- Studies on Pyrazines. Part 33.1 Synthesis of 2,3-Diaminopyrazines via [1,2,5]Thiadiazolo[3,4-b] pyrazines
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The syntheses of [1,2,5]thiadiazolo[3,4-b]pyrazine (3) and its methyl and/or phenyl derivatives as well as their reduction to 2,3-diaminopyrazines 4 are described.
- Sato, Nobuhiro,Mizuno, Hajime
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p. 250 - 251
(2007/10/03)
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- Studies on pyrazines; part 30: Synthesis of aminopyrazines from azidopyrazines
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Azidopyrazines do not undergo reduction by reagents that are effective for the preparation of alkyl- or arylamines from the azides because the heterocyclic azides exist in the bicyclic form of tetrazolo[1,5-a]pyrazines. Nevertheless, the conversion into aminopyrazines was achieved by hydrogenolysis in the presence of ammonium hydroxide and palladium-on-carbon or particularly by reduction with tin(II) chloride in methanolic hydrochloric acid, in 34-87% yields. To elucidate the successful progress of the reaction, the equilibrium of azide-atetrazole was examined by 1H NMR spectroscopy in various solvents.
- Sato,Matsuura,Miwa
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p. 931 - 934
(2007/10/02)
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