Synthesis and biological activity of anticoccidial agents: 5,6-diarylimidazo[2,1-b][1,3]thiazoles

Novel 5,6-diarylimidazo[2,1-b][1,3]thiazoles bearing an amine substituent at the imidazothiazole 2-position have been synthesized and evaluated as anticoccidial agents in both in vitro and in vivo assays. Both subnanomolar in vitro activity and broad spectrum in vivo potency were detected for several compounds, particularly compound 10.     

Synthesis and glycosidase inhibitory activity of novel (2-phenyl-4H-benzopyrimedo[2,1-b]-thiazol-4-yliden)acetonitrile derivatives

A series of (2-phenyl-4H-benzopyrimodo[2,1-b][1,3]thiazol-4-yliden-4-yliden)acetonitrile derivatives have been prepared by ring transformation reaction of 4-(methylthio)-2-oxo-6-aryl-2H-pyrane-3-carbonitriles. The yield of ring transformation product is moderate to good. Furthermore the glycosidase inhibitory activities were tested by using α-amylase and α-glucosidase pancreatic, intestinal and liver enzymes, responsible for hyperglycemia in type II diabetes. The results revealed that all compounds exhibit significant glycosidase inhibitory activity.     

Synthesis and anti-tubercular activity of a series of 2-sulfonamido/trifluoromethyl-6-substituted imidazo[2,1-b]-1,3,4-thiadiazole derivatives

A series of 2-sulfonamido/trifluoromethyl-6-(4'-substituted aryl/heteroaryl)imidazo[2,1-b]-1,3,4-thiadiazole derivatives (II) have been synthesized by reaction of 2-amino-5-sulfonamido/trifluoromethyl-1,3,4-thiadiazoles and an appropriate alpha-haloaryl/heteroaryl ketones. Further 5-bromo (III), 5-thiocyanato (IV), 5-gaunylhydrazone (V) derivatives were synthesized in order to study the effect of these substituents on biological activity. Structures of these compounds were established by IR, (1)H NMR, (13)C NMR, Mass and HRMS. The selected compounds were evaluated for their preliminary in vitro anti-tuberculosis activity against Mycobacterium tuberculosis H37Rv strain using radiometric BACTEC and broth dilution assay methods. The results show that compounds 5, 7, 8, 10 and 12 exhibited moderate to good anti-tubercular activity with percentage inhibition of 29, 43, 58, 31 and 41, respectively, at a MIC of >6.25 microg/mL. Compound 18 showed a MIC of 20 microg/mL.     

Regioselectivity in Sonogashira synthesis of 6-(4-nitrobenzyl)-2-phenylthiazolo[3,2-b]1,2,4-triazole: a quantum chemistry study

In the present research, the experimentally observed regioselectivity in Sonogashira synthesis of 6-(4-nitrobenzyl)-2-phenylthiazolo[3,2-b]1,2,4triazole has been modeled by means of density functional theory (DFT) employed to investigate the structural and thermochemical aspects of this synthesis in the gas and solution phases. Comparison of our calculated structural parameters of the title compound with the available X-ray crystallographical data demonstrate a reliable agreement. Then, the effect of two different solvents, DMF and ethanol, are examined via polarized continuum model calculations, showing a significant decrease in the computed values of the reaction enthalpy and free energy changes compared with the gas phase results. We have also considered two tautomeric structures of the intermediate species that it seems the mode of its intermolecular cyclization has an important role in regioselectivity of the final products. Moreover, all obtained results in the gas and solution phases also confirm that the synthesis of the title compound is thermodynamically more favorable than the other regioisomeric product. We also discuss the thermodynamical feasibility of this reaction at higher temperatures. Finally, we concentrate on the survey of substituent effect by choosing electron-withdrawing and electron-donating groups on the aryl iodide. Our calculated thermochemical data in the gas and solution phases indicate that the use of electron-withdrawing moieties is more favorable thermodynamically than electron-donating ones which has been previously concluded via the experimental elucidations.

New derivatives of 11-methyl-6-[2-(dimethylamino)ethyl]-6H-indolo[2,3-b]quinoline as cytotoxic DNA topoisomerase II inhibitors

Novel indolo[2,3-b]quinoline derivatives substituted at N-6 and C-2 or C-9 positions with (dimethylamino)ethyl chains linked to heteroaromatic core by ether, amide or amine bonds, were manufactured and evaluated in vitro for their cytotoxic activity against several cell lines of different origin including multidrug resistant sublines and tested for their ability to influence the cell cycle and inhibit topoisomerase II activity. It was found, that all compounds show cytotoxic activity against cell lines tested, including multidrug resistant LoVo/DX, MES-SA/DX5 and HL-60 sublines. The tested compounds induce the G(2)M phase cell cycle arrest in Jurkat cells, and inhibit topoisomerase II activity.     

Synthesis and antitubercular activity of 7-(R)- and 7-(S)-methyl-2-nitro-6-(S)-(4-(trifluoromethoxy)benzyloxy)-6,7-dihydro-5H-imidazo[2,1-b][1,3]oxazines, analogues of PA-824

Nitroimidazoles such as PA-824 and OPC-67683 are currently in clinical development as members of a promising new class of therapeutics for tuberculosis. While the antitubercular activity of these compounds is high, they both suffer from poor water solubility thus complicating development. We determined the single crystal X-ray structure of PA-824 and found a close packing of the nitroimidazoles facilitated by a pseudoaxial conformation of the p-trifluoromethoxybenzyl ether. To attempt to disrupt this tight packing by destabilizing the axial preference of this side chain, we prepared the two diastereomers of the 7-methyl-nitroimidazo-oxazine. Determination of the crystal structure of the 7-(S)-methyl derivative (5, cis) revealed that the benzylic side chain remained pseudoaxial while the 7-(R)-methyl derivative (6, trans) adopted the desired pseudoequatorial conformation. Both derivatives displayed similar activities against Mycobacterium tuberculosis, but neither showed improved aqueous solubility, suggesting that inherent lattice stability is not likely to be a major factor in limiting solubility. Conformational analysis revealed that all three compounds have similar energetically accessible conformations in solution. Additionally, these results suggest that the nitroreductase that initially recognizes PA-824 is somewhat insensitive to substitutions at the 7-position.     

Synthesis and pharmacological characterization of 5-phenyl-2-[2-(1-piperidinylcarbonyl)phenyl]-2,3-dihydro-1H-pyrrolo[1,2-c]imidazol-1-ones: a new class of Neuropeptide S antagonists

A new class of selective NPS antagonist was developed starting from a commercially available product identified by screening activities. Experimental NMR observations and computational experiments allowed the discovery of a new class of derivatives. 5-Phenyl-2-[2-(1-piperidinylcarbonyl)phenyl]-2,3-dihydro-1H-pyrrolo[1,2-c]imidazol-1-one represents a new lead compound in the NPS antagonist field.     

Analogs of 4-(3-bromo-8-methyl-10-methoxy-6,11-dihydro-5H-benzo[5,6]-cyclo hepta[1,2-b]pyridin-11-yl)-1-(4-pyridinylacetyl)piperidine N-oxide as inhibitors of farnesyl protein transferase.

A series of 3-substituted analogs 3 of 4-(3-bromo-8-methyl-10-methoxy-6,11-dihydro-5H-benzo[5,6]-cyclohepta[1,2 b]pyridin-11-yl)-1-(4-pyridinylacetyl)piperidine N-oxide 2 was prepared and evaluated as FPT inhibitors. The objective of this study was to identify other substituents at C3 in this series of FPT inhibitors that would have the FPT potency enhancement similar to that found for a C3 bromo substituent. The 3-methyl analog 17b was found to be tenfold less active than 2, and other C3 substituents having more steric bulk were found to cause a further reduction in activity.     

Synthesis and cytotoxicity of 3,4-disubstituted-5-(3,4,5-trimethoxyphenyl)-4H-1,2,4-triazoles and novel 5,6-dihydro-[1,2,4]triazolo[3,4-b][1,3,4]thiadiazole derivatives bearing 3,4,5-trimethoxyphenyl moiety

A series of 3,4-disubstituted-5-(3,4,5-trimethoxyphenyl)-4H-1,2,4-triazoles and some novel 5,6-dihydro-[1,2,4]triazolo[3,4-b][1,3,4]thiadiazoles bearing 3,4,5-trimethoxyphenyl moiety were synthesized and screened for their anticancer activity. The preliminary bioassay results indicated that compounds 14 and 16 showed much stronger cytotoxicity than Doxorubicin against HepG2 cell lines with IC(50) values of 0.58 and 3.17 μM, respectively. Meanwhile compound 16 also exhibited a broad spectrum of antitumor activity against MCF-7 and MKN45 with IC(50) values of 10.92 and 13.79 μM, respectively.     

6-Bicycloaryl substituted (S)- and (R)-5,6-dihydro-2H-pyran-2-ones: Asymmetric synthesis,and anti-proliferative properties

(R)-Goniothalamin, is a member of styryl lactones, possesses selective cytotoxicity against cancer cell lines. In this work, replacement of styryl substituent with 2-naphthyl and 3-quinoyl gave new analogues which may have less conformational changes compared to the lead compound. Anti-proliferative tests indicated that 2-naphthyl substituted (R)-5,6-dihydro-2H-pyran-2-one has slightly better cytotoxicity than (R)-goniothalamin. To clarify the effect of 2-naphthyl substituent additional aryl substituted (R)-5,6-dihydro-2H-pyran-2-ones have been synthesized enantioselectively and tested against PC-3 and MCF-7 cell lines.     

Identification and characterization of 4-[4-(3-phenyl-2-propen-1-yl)-1-piperazinyl]-5H-pyrimido[5,4-b]indole derivatives as Salmonella biofilm inhibitors

A screening of a small-molecule library was conducted, in search of Salmonella biofilm inhibitors active in a broad temperature range, both in prevention and in eradication of biofilms. Moreover, the inhibitors were selected not to influence the planktonic growth of Salmonella to diminish the selective pressure and to prevent or slow down resistance development. Out of the 20,014 compounds screened at 16 and 37 °C, 140 hits were identified. After characterization of the most promising hits at a broader set of temperatures (16, 25, 30 and 37 °C), we identified 7-methoxy-4-[4-(3-phenyl-2-propen-1-yl)-1-piperazinyl]-5H-pyrimido[5,4-b]indole as an interesting preventive anti-biofilm compound. A first structure-activity relationship of this compound was delineated, revealing 8-fluoro-4-[4-(3-phenyl-2-propen-1-yl)-1-piperazinyl]-5H-pyrimido[5,4-b]indole as a promising analogue in the prevention of Salmonella biofilms.     

Novel and potent transforming growth factor beta type I receptor kinase domain inhibitor: 7-amino 4-(2-pyridin-2-yl-5,6-dihydro-4H-pyrrolo[1,2-b]pyrazol-3-yl)-quinolines

A novel series of 7-amino 4-(2-pyridin-2-yl-5,6-dihydro-4H-pyrrolo[1,2-b]pyrazol-3-yl)-quinolines was synthesized and their TbetaR-1 inhibitory, p38 MAPK inhibitory, and TbetaR-1-dependent cellular activity were evaluated. Compound 5a was found to be a highly potent in the enzyme assay and TbetaR-1-dependent cellular assays. In addition, dimer (4g), with a urea linker, shows a similar enzyme and cellular activity despite a bulky substitution.     

Equilibrium and dynamic structure of large, unilamellar, unsaturated acyl chain phosphatidylcholine vesicles. Higher order analysis of 1,6-diphenyl-1,3,5-hexatriene and 1-[4-(trimethylammonio)phenyl]- 6-phenyl-1,3,5-hexatriene anisotropy decay

Equilibrium and dynamic structural properties of minimally to highly unsaturated acyl chain, large, unilamellar phosphatidylcholine (PC) vesicles have been characterized by the dynamic fluorescence properties of 1,6-diphenyl-1,3,5-hexatriene (DPH) and 1-[4-(trimethylammonio)phenyl]-6-phenyl-1,3,5-hexatriene (TMA-DPH). Fluorescence lifetimes and equilibrium and dynamic rotational properties of these probes were analyzed by limited-frequency phase-modulation fluorometry in egg PC, palmitoyloleoyl-PC (POPC), dioleoyl-PC (DOPC), palmitoylarachidonoyl-PC (PAPC), and palmitoyldocosahexaenoyl-PC (P-22:6-PC) vesicles over a temperature range from 5 to 37 degrees C. DPH equilibrium orientational distributions were derived according to a model permitting bimodal orientational distributions in which the parallel probability maximum was aligned parallel to the bilayer normal and the orthogonal probability maximum was oriented parallel to the plane of the bilayer. TMA-DPH orientational distributions were derived according to the same model except that all probability was constrained to the parallel orientation. TMA-DPH fluorescence lifetimes were much more sensitive than those of DPH to variations in acyl chain composition and temperature although the same qualitative behavior was generally observed with both probes. Greater acyl chain unsaturation and higher sample temperatures each gave rise to shorter lifetimes consistent with increased water penetrability into the bilayers. Equilibrium order of the hydrocarbon core (as probed by DPH) and of the interfacial and head group regions of the bilayers (as probed by TMA-DPH) was reduced by increasing levels of unsaturation and by higher sample temperatures.(ABSTRACT TRUNCATED AT 250 WORDS)     

Acyl chain orientational order in large unilamellar vesicles: comparison with multilamellar liposomes: a 2H and 31P nuclear magnetic resonance study.

Large unilamellar vesicles (LUVs) composed of 1-[2H31]palmitoyl-2-oleoyl phosphatidylcholine (POPC-d31), with diameters of approximately 117 +/- 31 and 180 +/- 44 nm, were prepared by extrusion through polycarbonate filters with pore sizes of 0.1 and 0.2 microns, respectively. The 2H nuclear magnetic resonance (NMR) spectra obtained at 21 degrees C contain two components: a broad component (approximately 17 kHz linewidth) corresponding to the methylene groups and a narrower component originating from the methyl groups. Spectra with increasing powder pattern characteristics were obtained by reducing the rate of phospholipid reorientations by addition of glycerol (to increase the solvent viscosity) and by lowering the temperature. Full powder spectra, characteristic of liquid-crystalline bilayers, were obtained for both LUV samples at 0 degrees C in the presence of 50 wt% glycerol. Individual quadrupolar splittings were not resolved in these spectra, due to broader linewidths in the LUVs, which have significantly shorter values for spin-spin relaxation time T2 measured from the decay of the quadrupolar echo (90 microseconds) than the multilmellar vesicles (MLVs; 540 microseconds). Smoothed order parameter profiles (OPPs) were obtained for these samples by integration of the dePaked spectra. The OPPs were very similar to the OPP of POPC-d31 MLVs in 50 wt% glycerol at the same temperature, indicating that orientational order in MLVs and LUVs with a diameter of > or = 100 nm is essentially the same. The presence of 80 wt% glycerol was found to have a disordering effect on the vesicles.     

Synthesis,antidepressant evaluation and QSAR studies of novel 2-(5H-[1,2,4]triazino[5,6-b]indol-3-ylthio)-N-(substituted phenyl)acetamides

In search for novel antidepressants, a series of 2-(5H-[1,2,4]triazino[5,6-b]indol-3-ylthio)-N-(substituted phenyl)acetamides was synthesized and screened for potential antidepressant activity by tail suspension test (TST) in mice. Number of synthesized compounds exhibited impressive antidepressant activity, measured in terms of percentage decrease in immobility duration (%DID). QSAR analysis was also undertaken which correlated three parameters FOSA, PISA, and glob with biological activity.     

Synthesis of (8Z,11Z,14Z)-eicosatrien-5-ynoic (5,6-dehydroarachidonic) acid and its transformation into [5,6-3H]arachidonic acid and [5,6-3H]prostaglandins E2 and F2 alpha

8Z,11Z,14Z-Eicosatriene-5-ynoic acid and its tritium-labelled analogue, [5,6-3H]arachidonic acid, have been synthesized on the basis of acetylenic compounds. [5,6-3H]Arachidonic acid has been used as substrate for the enzymatic synthesis of [5,6-3H]PGE2 and [5,6-3H]PGF2 alpha.     

Benzoxaborole antimalarial agents. Part 2: Discovery of fluoro-substituted 7-(2-carboxyethyl)-1,3-dihydro-1-hydroxy-2,1-benzoxaboroles

A series of new boron-containing benzoxaborole compounds was designed and synthesized for a continuing structure-activity relationship (SAR) investigation to assess the antimalarial activity changes derived from side-chain structural variation, substituent modification on the benzene ring and removal of boron from five-membered oxaborole ring. This SAR study demonstrated that boron is required for the antimalarial activity, and discovered that three fluoro-substituted 7-(2-carboxyethyl)-1,3-dihydro-1-hydroxy-2,1-benzoxaboroles (9, 14 and 20) have excellent potencies (IC(50) 0.026-0.209 μM) against Plasmodium falciparum.     

Synthesis and biological activity of N(alpha)-[4-[N-[(3,4-dihydro-2-methyl-4-oxo-6-quinazolinyl)methyl]-N-propargylamino]phenylacetyl]-L-glutamic acid

2-Deamino-2-methyl-N10-propargyl-5,8-dideazafolic acid (ICI 198583) is a potent inhibitor of thymidylate synthase. Its analogue, N(alpha)-[4-[N-[(3,4-dihydro-2-methyl-4-oxo-6-quinazolinyl)methyl]-N-propargylamino]phenylacetyl]-L-glutamic acid, containing p-aminophenylacetic acid residue substituting p-aminobenzoic acid residue, was synthesized. The new analogue exhibited a moderately potent thymidylate synthase inhibition, of linear mixed type vs. the cofactor, N(5,10)-methylenetetrahydrofolate. The Ki value of 0.34 microM, determined with a purified recombinant rat hepatoma enzyme, was about 30-fold higher than that reported for inhibition of thymidylate synthase from mouse leukemia L1210 cells by ICI 198583 (Hughes et al., 1990, J. Med. Chem. 33, 3060). Growth of mouse leukemia L5178Y cells was inhibited by the analogue (IC50 = 1.26 mM) 180-fold weaker than by ICI 198583 (IC50 = 6.9 microM).     

The fidelity of response by 1-[4-(trimethylammonio)phenyl]-6-phenyl-1,3,5-hexatriene in time-resolved fluorescence anisotropy measurements on lipid vesicles

Time-resolved fluorescence anisotropy measurements on 1⁰-[4-(tri-methylammonio)phenyl]-6-phenyl-1,3,5-hexatriene (TMA-DPH) molecules in lipid vesicles of palmitoyloleoylphosphatidylcholine (POPC), PC extracted from egg yolk (EggPC), dioleoyl-PC (DOPC), dilinoleoyl-PC (DLPC), phosphatidylglycerol extracted from egg yolk (EggPG), dioleoyl-PG (DOPG), sulfoquinovosyldiacylglycerol (SQDG) and digalactosyl-DG (DGDG) with and without cholesterol are presented. The observed intensity decay curves are analyzed simultaneously in terms of the Brownian rotational diffusion model. The analysis thus yields the isotropic fluorescence decay, the initial anisotropy r (0), the order parameters P ₂ and P ₂ as well as the diffusion coefficient of the long molecular axis. It is shown that increasing unsaturation in the acyl chains of the PC lipids results in an increase in the rotational diffusion rates of the probes and a decrease in the order parameter P ₂. However, the value of P ₂ remains unchanged. The corresponding orientational distribution function of the probes is bimodal, with fractions lying preferentially parallel and perpendicular to the local vesicle surface. Surprisingly, the fraction of probe molecules lying with their long axes parallel to the bilayer surface increases with increasing unsaturation with a concomitant narrowing in the width of the distribution of the fraction lying perpendicular to it. As expected, cholesterol is found to increase the order parameters in all the systems and to suppress the tendency of the molecules to lie parallel to the bilayer surface. Furthermore, the rotational diffusion coefficients of the probes is found to increase in all the systems except for DLPC. Interestingly, the effects of unsaturation on the reorientational dynamics of TMA-DPH molecules in the vesicle systems are opposite to those found in the corresponding planar multibilayers (Deinum et al. 1988), whereas the same cholesterol effect is observed for the two systems. Nevertheless, the TMA-DPH molecules exhibit higher diffusion coefficients in the vesicle than in the planar multibilayer systems. In addition, a unimodal distribution of the probe molecules is found in the multibilayer systems. The differences between the two systems are ascribed to the differences in the radius of curvature and the hydration of the bilayers. Lastly we rationalize the bimodal distribution of the TMA-DPH molecules in the vesicles in terms of their observed partition between the lipid and aqueous phases.Abbreviations DPH 1,6-diphenyl-1,3,5-hexatriene - TMA-DPH 1-[4-(trimethylammonio)-phenyl]-6-phenyl-1,3,5-hexatriene - POPC palmitoyloleoylphosphatidylcholine - EggPC PC extracted from egg yolk - DOPC dioleoyl-PC - DLPC dilinoleoyl-PC - EggPG phosphatidylglycerol extracted from egg yolk - DOPG dioleoyl-PG - SQDG sulfoquinovosyldiacylglycerol - DGDG di-galactosyl-DG - HPTLC high performance thin layer chromatography     

Discovery of N-[5-({2-[(cyclopropylcarbonyl)amino]imidazo[1,2-b]pyridazin-6-yl}oxy)-2-methylphenyl]-1,3-dimethyl-1H-pyrazole-5-carboxamide (TAK-593), a highly potent VEGFR2 kinase inhibitor

Vascular endothelial growth factor (VEGF) plays important roles in tumor angiogenesis, and the inhibition of its signaling pathway is considered an effective therapeutic option for the treatment of cancer. In this study, we describe the design, synthesis, and biological evaluation of 2-acylamino-6-phenoxy-imidazo[1,2-b]pyridazine derivatives. Hybridization of two distinct imidazo[1,2-b]pyridazines 1 and 2, followed by optimization led to the discovery of N-[5-({2-[(cyclopropylcarbonyl)amino]imidazo[1,2-b]pyridazin-6-yl}oxy)-2-methylphenyl]-1,3-dimethyl-1H-pyrazole-5-carboxamide (23a, TAK-593) as a highly potent VEGF receptor 2 kinase inhibitor with an IC₅₀ value of 0.95 nM. The compound 23a strongly suppressed proliferation of VEGF-stimulated human umbilical vein endothelial cells with an IC₅₀ of 0.30 nM. Kinase selectivity profiling revealed that 23a inhibited platelet-derived growth factor receptor kinases as well as VEGF receptor kinases. Oral administration of 23a at 1 mg/kg bid potently inhibited tumor growth in a mouse xenograft model using human lung adenocarcinoma A549 cells (T/C = 8%).