Design,stereoselective synthesis,configurational stability and biological activity of 7-chloro-9-(furan-3-yl)-2,3,3a,4-tetrahydro-1H-benzo[e]pyrrolo[2,1-c][1,2,4]thiadiazine 5,5-dioxide

Chiral 5-arylbenzothiadiazine derivatives have recently attracted particular attention because they exhibit an interesting pharmacological activity as AMPA receptor (AMPAr) positive modulators. However, investigations on their configurational stability suggest a rapid enantiomerization in physiological conditions. In order to enhance configurational stability, preserving AMPAr activity, we have designed the novel compound (R,S)-7-chloro-9-(furan-3-yl)-2,3,3a,4-tetrahydro-1H-benzo[e]pyrrolo[2,1-c][1,2,4]thiadiazine 5,5-dioxide bearing a pyrrolo moiety coupled with the 5-(furan-3-yl) substituent on benzothiadiazine core. A stereoselective synthesis was projected to obtain single enantiomer of the latter compound. Absolute configuration was assigned by X-ray crystal structure. Patch clamp experiments evaluating the activity of single enantiomers as AMPAr positive allosteric modulator showed that R stereoisomer is the active component. Molecular modeling studies were performed to explain biological results. An on-column stopped-flow bidimensional recycling HPLC procedure was applied to obtain on a large scale the active enantiomer with enantiomeric enrichment starting from the racemic mixture of the compound.     

Synthesis and antimycobacterial activity of 4-[5-(substituted phenyl)-4, 5-dihydro-3-isoxazolyl]-2-methylphenols

Compounds based on the isoxazoline moiety were screened for their antimycobacterial activity in vitro against Mycobacterium tuberculosis H37R (MTB), and INH (isoniazid) resistant Mycobacterium tuberculosis (INHR-MTB) using the agar dilution method and bactec 460. Among the synthesized compounds, 4-[5-(4-bromophenyl)-4,5-dihydro-3-isoxazolyl]-2-methylphenol (4l) was found to be the most active agent against MTB and INHR-MTB with minimum inhibitory concentration of 0.62 μM. When compared to INH, compound (4l) was 1.12 fold and 3.0 fold more active against MTB and INHR-MTB, respectively.     

Rational design, synthesis and evaluation of (6aR( *),11bS( *))-1-(4-fluorophenyl)-4-{7-[4-(4-fluorophenyl)-4-oxobutyl]1,2,3,4,6,6a,7,11b,12,12a(RS)-decahydropyrazino[2',1':6,1]pyrido[3,4-b]indol-2-yl}-butan-1-one as a potential neuroleptic agent

In our pursuit to prepare a potent antipsychotic compound, a novel 1,2,3,4,6,6a,7,11b,12,12a-decahydropyrazino[2',1':6,1]pyrido[3,4-b]indole derivative was synthesized which incorporates the butyrophenone substructure twice. This molecule has shown D(1), D(2) and 5-HT(2A) receptor blocking activity where the ratio pK(i) (5-HT(2A)) to pK(i) (D(2)) is 1.42 better than risperidone (1.15). It blocks amphetamine induced hyperactivity/stereotypy and secondary conditioned avoidance responses in rodents at lower doses than those required for the neuroleptic drugs haloperidol and centbutindole (biriperone).     

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.     

Antimycobacterial activity: synthesis of novel 3-(substituted phenyl)-6,7-dimethoxy-3a,4-dihydro-3H-indeno[1,2-c]isoxazole analogues

In this study, a series of novel 3-(substituted phenyl)-6,7-dimethoxy-3a,4-dihydro-3H-indeno[1,2-c]isoxazole analogues were synthesized and evaluated for antimycobacterial activity against Mycobacterium tuberculosis (MTB) H₃₇Rv and isoniazid resistant M. tuberculosis (INHR-MTB). All the newly synthesized compounds were showing moderate to high inhibitory activities. The compound 6,7-dimethoxy-3-(4-chloro phenyl)-4H-indeno[1,2-c]isoxazole (4b) was found to be the most promising compound, active against MTB H₃₇Rv and INHR-MTB with minimum inhibitory concentrations of 0.22 and 0.34 μM.     

Synthesis,antimicrobial, and mosquito larvicidal activity of 1-aryl-4-methyl-3,6-bis-(5-methylisoxazol-3-yl)-2-thioxo-2,3,6,10b-tetrahydro-1H-pyrimido[5,4-c]quinolin-5-ones

A series of 1-aryl-4-methyl-3,6-bis-(5-methylisoxazol-3-yl)-2-thioxo-2,3,6,10b-tetrahydro-1H-pyrimido[5,4-c]quinolin-5-ones (6a–h) have been synthesized by cyclization of ethyl-3-aryl-4-(2-chlorophenyl)-6-methyl-1-(5-methylisoxazol-3-yl)-2-thioxo-1,2,3,4-tetrahydropyrimidine-5-carboxylates 4a–h with 3-amino-5-methylisoxazole 5. Compounds 4a–h were obtained by Biginelli reaction, by condensation of aromatic aldehyde 1, ethyl acetoacetate 2, and isoxazolyl thioureas 3 in a one-pot reaction catalyzed by ceric ammonium nitrite (CAN). Compounds 6a–h were tested for their antibacterial and antifungal activities against various bacterial and fungal strains. The results showed that these compounds exhibited good antibacterial and antifungal activity compared with that of standard antibiotics. Mosquito larvicidal activity of the newly synthesized compounds 6a–h is also studied against fourth instar larvae Culex quinquefasciatus. Some of the compounds are proved to be lethal for mosquito larvae.     

Antimycobacterial activity: synthesis of novel 3-(substituted phenyl)-6,7-dimethoxy-3a,4-dihydro-3H-indeno[1,2-c]isoxazole analogues

In this study, a series of novel 3-(substituted phenyl)-6,7-dimethoxy-3a,4-dihydro-3H-indeno[1,2-c]isoxazole analogues were synthesized and evaluated for antimycobacterial activity against Mycobacterium tuberculosis (MTB) H(37)Rv and isoniazid resistant M. tuberculosis (INHR-MTB). All the newly synthesized compounds were showing moderate to high inhibitory activities. The compound 6,7-dimethoxy-3-(4-chloro phenyl)-4H-indeno[1,2-c]isoxazole (4b) was found to be the most promising compound, active against MTB H(37)Rv and INHR-MTB with minimum inhibitory concentrations of 0.22 and 0.34 μM.     

The effect of 3-(5-nitro-2-thienyl)-9-chloro-5-morpholin-4-yl[1,2,4]triazolo[4,3-c]quinazoline on cell growth, cell cycle, induction of DNA fragmentation, and activity of caspase 3 in murine leukemia L1210 cells and fibroblast NIH-3T3 cells

Quinazolines are multitarget agents, which have broad spectrum of biological activity, and some of them are now in cancer clinical testing. 3-(5-nitro-2-thienyl)-9-chloro-5-morpholin-4-yl[1,2,4]triazolo[4,3-c]quinazoline is a new synthetically prepared derivative, which in our previous study showed cytotoxic effects on cancer cell lines HeLa and B16. Quinazoline, at micromolar concentrations, induced morphological changes and necrosis of B16 cells, and at nanomolar concentrations it produced changes of F-actin cytoskeleton. It did not cause changes in the cell cycle, did not induce apoptotic cell death in B16 cells, did not have a mutagenic effect, and did not even behave as a typical intercalating agent. Little significant reduction of tumor volume in intramuscular transplanted B16 cells was observed. The aim of the present study was to examine the cytotoxic effect of 3-(5-nitro-2-thienyl)-9-chloro-5-morpholin-4-yl[1,2,4]triazolo[4,3-c]quinazoline on murine leukemia L1210 cells and fibroblast NIH-3T3 cells. Induction of cell morphology and cell cycle changes, induction of apoptosis and caspase 3 activity were studied. Quinazoline acted cytotoxically on both cell lines. The sensitivity of leukemia L1210 cells to the quinazoline was higher than that of fibroblast NIH-3T3. The IC(100) was 12 microM for L1210 cells and 24 microM for NIH-3T3 cells. No effect of quinazoline on the cell cycle profile of L1210 and NIH-3T3 was detected, however, quinazoline induced an increase of the sub-G(0) cell fraction, apoptotic DNA fragmentation, and apoptotic morphological changes at a concentration of 12 microM. This quinazoline concentration induced caspase 3 activity. Our results demonstrated that induction of apoptotic cell death via activation of caspase 3 contributed to the cytotoxic effects of 3-(5-nitro-2-thienyl)-9-chloro-5-morpholin-4-yl[1,2,4]triazolo[4,3-c]quinazoline in murine leukemia L1210 cells.     

Solution structure of a cis-opened (10R)-N6-deoxyadenosine adduct of (9S,10R)-9,10-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene in a DNA duplex

The solution structure of an 11-mer DNA duplex, d(CGGTCA*CGAGG) x d(CCTCGTGACCG), containing a 10R adduct at dA* that corresponds to the cis addition of the N(6)-amino group of dA(6) to (+)-(9S,10R)-9,10-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene was studied by 2D NMR methods. The NOESY cross-peak patterns indicate that the hydrocarbon is intercalated on the 5'-side of the modified base. This observation is the same as that observed for other oligonucleotides containing (10R)-dA adducts but opposite to that observed for the corresponding (10S)-dA adducts which are intercalated on the 3'-side of the modified base. The hydrocarbon is intercalated from the major groove without significant disruption of either the anti glycosidic torsion angle of the modified residue or the base pairing of the modified residue with the complementary residue on the opposite strand. The ensemble of 10 structures determined exhibits relatively small variations (6-15 degrees) in the characteristic hydrocarbon-base dihedral angles (alpha' and beta') as well as the glycosidic torsion angle chi. These angles are similar to those in a previously determined cis-opened benzo[a]pyrene diol epoxide-(10R)-dA adduct structure. Comparison of the present structure with the cis-opened diol epoxide adduct suggests that the absence of the 7- and 8-hydroxyl groups results in more efficient stacking of the aromatic moiety with the flanking base pairs and deeper insertion of the hydrocarbon into the helix. Relative to normal B-DNA, the duplex containing the present tetrahydroepoxide adduct is unwound at the lesion site, whereas the diol epoxide adduct structure is more tightly wound than normal B-DNA. Buckling of the adducted base pair as well as the C(5)-G(18) base pair that lies immediately above the hydrocarbon is much less severe in the present adducted structure than its cis-opened diol epoxide counterpart.     

Synthesis and bioactivity studies on new 4-(3-(4-Substitutedphenyl)-3a,4-dihydro-3H-indeno[1,2-c]pyrazol-2-yl) benzenesulfonamides

A series of new 4-(3-(4-substitutedphenyl)-3a,4-dihydro-3H-indeno[1,2-c]pyrazol-2-yl) benzenesulfonamides (7–12) was synthesized starting from 2-(4-substitutedbenzylidene)-2,3-dihydro-1H-inden-1-one (1–6) and 4-hydrazinobenzenesulfonamide. The substituted benzaldehydes from which the key intermediate was prepared by introducing 2- or 4-substituents such as fluorine, hydroxy, methoxy, or the 3,4,5-trimethoxy moieties. The compounds were tested for their cytotoxicity, tumor-specificity and potential as carbonic anhydrase (CA, EC 4.2.1.1) inhibitors. The 3,4,5-trimethoxy and the 4-hydroxy derivatives showed interesting cytotoxic activities, which may be crucial for further anti-tumor activity studies, whereas some of these sulfonamides strongly inhibited both human (h) cytosolic isoforms hCA I and II.     

Synthesis, structure, and antimycobacterial activity of 6-[1(3H)-isobenzofuranylidenemethyl]purines and analogs

6-Benzofuryl-, styryl, benzyl, and furfurylpurines as well as 6-[1(3H)-isobenzofuranylidenemethyl]purines have been synthesized and their activities against Mycobacterium tuberculosis (Mtb) determined. Several compounds displayed profound antimycobacterial activity in combination with low toxicity towards mammalian cells. NMR and X-ray crystallography were employed to determine the detailed structures and the results were supported by quantum chemical calculations.     

Synthesis, structure elucidation, determination of the lipophilicity and identification of antitumour activities in vitro of novel 3-(2-furanyl)-8-aryl-7,8-dihydroimidazo[2,1-c][1,2,4]triazin-4(6H)-ones with a low cytotoxicity towards normal human skin fibroblast cells

Eleven novel 3-(2-furanyl)-8-aryl-7,8-dihydroimidazo[2,1-c][1,2,4]triazin-4(6H)-ones (12-22) were designed and obtained from appropriate 1-aryl-2-hydrazonoimidazolidines (1-11) by condensation reaction with 2-oxo-2-furanacetic acid and subsequent cyclocondensation of intermediate chain derivatives. IR, (1)H NMR and (13)C NMR spectra and elemental analyses confirmed the chemical structure of all the synthesized compounds. The reversed-phase HPLC method was optimized and proved to be applicable and reliable for the analysis of these unknown small molecules (12-22). These compounds were chromatographed on octadecyl silica (ODS) stationary phase and their hydrophobic parameters expressed as the log k(w) values were determined by RP-HPLC, using mixtures of methanol and water as mobile phases with different methanol concentrations. Octane-1-sulfonic acid sodium salt (OSA-Na) and 20% acetate buffer (pH 3.5) was added to the mobile phase (eluent containing 0.01 M/L OSA-Na in organic modifier (MeOH)-buffered mobile phase). The high values of regression coefficients (r >0.9841) for all the compounds investigated proved the excellent fit between experimental data and the Snyder-Soczewiński equation. Results obtained from the reversed-phase HPLC were compared both with those theoretically calculated and with those obtained from an ALOGPS 2.1. software by the use of nine different computational methods for estimation of log P. The predicted values of log P by use of AB log P algorithm revealed the best correlation with the experimental log k(w) values for the investigated solutes, since a good correlation (r=0.7760) between these quantities was found. The majority of novel imidazotriazinones were found to be evidently effective in vitro against human cancerous cells (HeLa and T47D) in an effective concentration of 50 μg/mL. Five compounds (13, 15, 16, 18 and 22) revealed remarkable antiproliferative activities and selective cytotoxicities for cancer cells over normal HSF cells. Therefore these ones may be considered as a basis for the design of novel useful non-toxic (13, 15 and 16) and low toxic (18 and 22) anticancer agents.     

Discovery and activity of (1R,4S,6R)-N-[(1R)-2-[4-cyclohexyl-4-[[(1,1-dimethylethyl)amino]carbonyl]-1-piperidinyl]-1-[(4-fluorophenyl)methyl]-2-oxoethyl]-2-methyl-2-azabicyclo[2.2.2]octane-6-carboxamide (3, RY764), a potent and selective melanocortin subtype-4 receptor agonist

A novel isoquinuclidine containing selective melanocortin subtype-4 receptor small molecule agonist, 3 (RY764), is reported. Its in vivo characterization revealed mechanism-based food intake reduction and erectile activity augmentation in rodents.     

Synthesis and biological evaluation of novel 6, 7-dimethoxy-3-(4-pyridyl)-2,3,3a,4-tetrahydroindeno[1,2-c]pyrazol-2-yl-4-substituted phenylmethanone/ethanone derivatives

A series of 6,7-dimethoxy-3-(4-pyridyl)-2,3,3a,4-tetrahydroindeno[1,2-c]pyrazol-2-yl-4-substituted phenylmethanone/ethanone derivatives were synthesized and in vitro activity against mycobacterium tuberculosis (MTB) and INHR-MTB were carried out. Among the synthesized compounds, compound (4h) 6,7-dimethoxy-3-(4-pyridyl)-2,3,3a,4-tetrahydroindeno[1,2-c]pyrazol-2-yl-4-pyridyl methanone was found to be the most active agent against MTB and INHR-MTB with a minimum inhibitory concentration of 0.22 μM.     

Synthesis,structure elucidation and in vitro anticancer activities of novel derivatives of diethyl (2E)-2-[(2E)-(1-arylimidazolidin-2-ylidene)hydrazono]succinate and ethyl (4-oxo-8-aryl-4,6,7,8-tetrahydroimidazo[2,1-c][1,2,4]triazin-3-yl)acetate

The worked out and optimized synthesis routes and remarkable antitumour activities in vitro of novel polynitrogenated derivatives of diethyl (2E)-2-[(2E)-(1-arylimidazolidin-2-ylidene)hydrazono]succinate (7–10) and ethyl (4-oxo-8-aryl-4,6,7,8-tetrahydroimidazo[2,1-c][1,2,4]triazin-3-yl)acetate (11–16) are presented. Small molecules based on the privileged 7,8-dihydroimidazo[2,1-c][1,2,4]triazin-4(6H)-one scaffold (11–16) were obtained with fairly modest to good overall yields by very facile addition reactions of the nucleophilic centred 1-aryl-2-hydrazonoimidazolidine hydroiodides to diethyl acetylenedicarboxylate (DEAD) in the presence of triethylamine (TEA) and a subsequent cyclocondensation of the putative intermediate chain hydrazones. Heterobicyclic products 12 and 14–16 could also be prepared in high overall yields by an effective intramolecular cyclocondensation of the isolated stable and antiproliferative active heterocyclic hydrazones, namely, diethyl (2E)-2-[(2E)-(1-arylimidazolidin-2-ylidene)hydrazono]succinates (7–10), performed in refluxing DMF. These intermediates are the first products to be formed in the result of an addition of the nucleophilic reactants, namely, 1-aryl-2-hydrazonoimidazolidines of the 1–6 type, bearing the basic nitrogen atom of the hydrazono moiety (N–NH₂), to the carbon–carbon triple bond of the highly electrophilic alkyne, that is, DEAD. Molecular structures of the synthesized compounds (7–16) in the DMSO-d₆ solutions were verified by ¹H NMR and ¹³C NMR spectral data. These were finally confirmed based on the advanced 2D HMBC and HMQC NMR experiments, which were performed for the two representatives (8 and 11) of the two synthesized sets of the bioactive substances. Among the majority of antiproliferative active molecules, the disclosed herein ethyl [4-oxo-8-(3-chlorophenyl)-4,6,7,8-tetrahydroimidazo[2,1-c][1,2,4]triazin-3-yl]acetate (14) is proposed as a promising lead structure for the design of novel highly selective antitumour agents because of the distinctly marked lower cytotoxicity towards the primary cell line of normal HSF cells and several-fold higher against cancer cells used. A double fluorochrome mix-staining was performed in order to find out about the possible mode of action by which this novel small heterobicycle reveals remarkable antiproliferative effects in vitro. Taking into account the obtained double staining results, this small molecule was identified as capable of inducing significantly higher levels of necrotic cells in human cancer cell lines (T47D and HeLa) than in normal HSF cells. Furthermore, its cytotoxicity against cells was found to be connected to the predominant induction of necrosis over apoptosis.     

Synthesis and antiviral activity of cyclopropyl-spirocarbocyclic adenosine, (4R,5S,6R,7R)-4-(6-amino-9H-purin-9-yl)-7-(hydroxymethyl)spiro[2.4]heptane-5,6-diol against hepatitis C virus

An efficient method was developed for the synthesis of 6-exocyclic methylene carbocyclic intermediate 4. The Simmons-Smith cyclopropanation protocol was applied on the 6-exocyclic methylene of intermediate 4 and demonstrated its utility for the synthesis of novel class of a spiro-carbocyclic nucleoside analog 8. The titled compound 8 demonstrated a significant antiviral activity against HCV with EC₅₀ values of 0.273 and 0.368 μM in genotypes 1A and 1B, respectively.     

Synthesis and 5-hydroxytryptamine (5-HT) activity of 2,3,4,4a-tetrahydro-1H-pyrazino[1,2-a]quinoxalin-5-(6H)ones and 2,3,4,4a,5,6-hexahydro-1H-pyrazino[1,2-a]quinoxalines

A series of 2,3,4,4a-tetrahydro-1H-pyrazino[1,2-a]quinoxalin-5-(6H)ones and 2,3,4,4a,5,6-hexahydro-1H-pyrazino[1,2-a]quinoxalines was shown to exhibit 5-HT2C agonist binding and functional activity. Compound 21R inhibited food intake over 2 h in fasted, male Sprague Dawley rats with ED50 values of 2 mg/kg (i.p.) and 10 mg/kg (p.o.).     

Discovery of (1R,6S)-5-[4-(1-cyclobutyl-piperidin-4-yloxy)-phenyl]-3,4-diaza-bicyclo[4.1.0]hept-4-en-2-one (R,S-4a): Histamine H3 receptor inverse agonist demonstrating potent cognitive enhancing and wake promoting activity

A series of fused cyclopropyl-4,5-dihydropyridazin-3-one (3,4-diaza-bicyclo[4.1.0]hept-4-en-2-one) phenoxypiperidine analogs was designed and synthesized, leading to the identification of (1R,6S)-5-[4-(1-cyclobutyl-piperidin-4-yloxy)-phenyl]-3,4-diaza-bicyclo[4.1.0]hept-4-en-2-one (R,S-4a) as a second-generation pyridazin-3-one H₃R antagonist. Compound R,S-4a was a potent H₃R functional antagonist in vivo in the rat dipsogenia model, demonstrated potent wake activity in the rat EEG/EMG model, and enhanced short-term memory in the rat social recognition memory model at doses as low as 0.03–0.3 mg/kg po.