Synthesis and biological evaluation of novel 2-amino-3-aroyl-4-neopentyl-5-substituted thiophene derivatives as allosteric enhancers of the A1 adenosine receptor.

2-Amino-3-benzoyl thiophenes have been widely reported to act as allosteric enhancers at the A1 adenosine receptor. Their activity can be increased considerably by appropriate substitutions at the 4- and 5-positions of the thiophene ring. Substituent size at the thiophene C-4 position seemed to be a factor closely related to activity, with the 4-neopentyl (2,2-dimethylpropyl) substitution showing the greatest enhanced activity. A wide series of 2-amino-3-aroyl-4-neopentylthiophene derivatives with general structure 3, characterized by the presence of different substituents (bromine, aryl and heteroaryl) at the 5-position of the thiophene ring, have been identified as potent AEs at the A1AR. With only one exception, all of the synthesized compounds proved to be superior to the reference compound PD 81,723 in a functional assay. Derivatives 3p, 3u, 3am, 3ap and 3ar were the most active compounds in binding (saturation and competition) and functional cAMP studies, being able to potentiate agonist [(3)H]CCPA binding to the A1 receptor.

Structure-activity relationships of 2-amino-3-aroyl-4-[(4-arylpiperazin-1-yl)methyl]thiophenes. Part 2: Probing the influence of diverse substituents at the phenyl of the arylpiperazine moiety on allosteric enhancer activity at the A1 adenosine receptor.

In a preliminary article, we reported the potent allosteric enhancer activity at the A(1) adenosine receptor of a small series of 2-amino-3-(4-chlorobenzoyl)-4-[4-(aryl)piperazin-1-yl)methyl]thiophene derivatives bearing electron-withdrawing or electron-releasing groups at the para-position of the phenylpiperazine moiety. In the present study, we report the development of the compounds previously studied by modifying both the number and position of substituents on the phenylpiperazine moiety, aimed at establishing a structure-activity relationship identifying additional compounds with improved activity. The nature and the position of substituents on the phenyl ring tethered to the piperazine seemed to exert a fundamental influence on the allosteric enhancer activity, with the 3,4-difluoro 4i, 3-chloro-4-fluoro 4o, and 4-trifluoromethoxy 4ak derivatives being the most active compounds in binding (saturation and competition experiments) and functional cAMP studies. This study shows that it is also possible to obtain a good separation between allosteric enhancement and antagonistic activity at the A(1) adenosine receptor.

Synthesis and Evaluation of Haloacetyl, α-Bromoacryloyl and Nitrooxyacetyl Benzo[b]furan and Benzo[b]thiophene Derivatives as Potent Antiproliferative Agents Against Leukemia L1210 and K562 Cells.

Identification of novel and selective anticancer agents remains an important and challenging goal in pharmacological research. In search of new compounds with strong antiproliferative activity and simple molecular structure, we have synthesized three different series of compounds in which different substituents were linked to the 3-amino position of the 2-(3', 4', 5'-trimethoxybenzoyl)-benzo[b]furan or benzo[b]thiophene ring system. These substituents, corresponding to acetyl/haloacetyl, α-bromoacryloyl and nitrooxyacetyl moieties had different electrophilic properties. The benzoheterocycle parent structures were selected because of their reported bioactivities. Compounds bearing a methoxy group at the 6-position of the benzo[b]furan skeleton, were identified as potent antiproliferative agents against the human chronic myelogenous K562 and murine L1210 leukemia cell lines. Comparison of positional isomers indicated that moving the methoxy group from the 6- to the 5- or 7-position yielded inactive compounds. The effects of a selected series of compounds on cell cycle progression correlated well with their strong antiproliferative activity and inhibition of tubulin polymerization. The analysis of structure-activity relationships observed in the series of compounds described here may represent a platform for the design of more active molecules.

Synthesis and evaluation of a thio analogue of duocarmycin SA.

The design, synthesis, and preliminary evaluation of methyl 1,2,8,8a-tetrahydrocyclopropa[c]thieno[3,2-e]indol-4-one-6-carboxylate (CTI) derivatives are detailed representing a single atom change (N to S) embedded in the duocarmycin SA alkylation subunit.

Hybrid alpha-bromoacryloylamido chalcones. Design, synthesis and biological evaluation.

Research into the anti-tumor properties of chalcones has received significant attention over the last few years Two novel large series of alpha-bromoacryloylamido chalcones 1a-m and 2a-k containing a pair of Michael acceptors in their structures, corresponding to the alpha-bromoacryloyl moiety and the alpha,beta-unsaturated ketone system of the chalcone framework, were synthesized and evaluated for antiproliferative activity against five cancer cell lines. Such hybrid derivatives demonstrated significantly increased anti-tumor activity compared with the corresponding amino chalcones. The most promising lead molecules were 1k, 1m and 2j, which had the highest activity toward the five cell lines. Flow cytometry with K562 cells showed that the most active compounds resulted in a large proportion of the cells entering in the apoptotic sub-G0-G1 peak. Moreover, compound 1k induced apoptosis through the mitochondrial pathway and activated caspase-3.

Design, synthesis and structure-activity relationship of 2-(3',4',5'-trimethoxybenzoyl)-benzo[b]furan derivatives as a novel class of inhibitors of tubulin polymerization.

The biological importance of microtubules in mitosis and cell division makes them an interesting target for the development of anticancer agents. Small molecules such as benzo[b]furans are attractive as inhibitors of tubulin polymerization. Thus, a new class of inhibitors of tubulin polymerization based on the 2-(3',4',5'-trimethoxybenzoyl)-benzo[b]furan molecular skeleton, with electron-donating (Me, OMe or OH) or electron-withdrawing (F, Cl and Br) substituents on the benzene ring, was synthesized and evaluated for antiproliferative activity, inhibition of tubulin polymerization and cell cycle effects. Adding a methyl group at the C-3 position resulted in increased activity. The most promising compound in this series was 2-(3',4',5'-trimethoxybenzoyl)-3-methyl-6-ethoxy-benzo[b]furan, which inhibits cancer cell growth at nanomolar concentrations and interacts strongly with tubulin by binding to the colchicine site.

Discovery of 8-methoxypyrazino[1,2-a]indole as a New Potent Antiproliferative Agent Against Human Leukemia K562 Cells. A Structure-Activity Relationship Study.

Identification of novel and selective anticancer agents remains an important and challenging goal in pharmacological research. The indole nucleus, frequently encountered as a molecular fragment in natural products and pharmaceutically active compounds, was employed as the initial building block for the synthesis of a series of pyrazino[1,2-a]indoles 1a-k, variably substituted at the 6, 7, 8 and 9-positions. Compound 1e, bearing the methoxy group at the 8-position of the pyrazino[1,2-a]indole nucleus was identified as a novel potent antiproliferative agent against the human chronic myelogenous leukemia K562 cell line, but it was much less active against several other cancer cell lines. Comparison of positional isomers indicated that moving the methoxy group from the 8- to the 7- or 6-position, to furnish compounds 1f and 1g, respectively, yielded inactive compounds. The analysis of structure-activity relationships observed in the series of investigated compounds may represent the basis for the design of more active molecules.

Synthesis and biological evaluation of 1-methyl-2-(3',4',5'-trimethoxybenzoyl)-3-aminoindoles as a new class of antimitotic agents and tubulin inhibitors.

The 2-(3,4,5-trimethoxybenzoyl)-2-aminoindole nucleus was used as the fundamental structure for the synthesis of compounds modified with respect to positions C-4 to C-7 with different moieties (chloro, methyl, or methoxy). Additional structural variations concerned the indole nitrogen, which was alkylated with small alkyl groups such as methyl or ethyl. We have identified 1-methyl-2-(3,4,5-trimethoxybenzoyl)-3-amino-7-methoxyindole as a new highly potent antiproliferative agent that targets tubulin at the colchicine binding site and leads to apoptotic cell death.

Synthesis and biological evaluation of 2-amino-3-(3',4',5'-trimethoxybenzoyl)-6-substituted-4,5,6,7-tetrahydrothieno[2,3-c]pyridine derivatives as antimitotic agents and inhibitors of tubulin polymerization.

Microtubules are among the most successful targets of compounds potentially useful for cancer therapy. A new series of inhibitors of tubulin polymerization based on the 2-amino-3-(3,4,5-trimethoxybenzoyl)-4,5,6,7-tetrahydrothieno[b]pyridine molecular skeleton was synthesized and evaluated for antiproliferative activity, inhibition of tubulin polymerization, and cell cycle effects. The most promising compound in this series was 2-amino-3-(3,4,5-trimethoxybenzoyl)-6-methoxycarbonyl-4,5,6,7-tetrahydrothieno[b]pyridine, which inhibits cancer cell growth with IC(50)-values ranging from 25 to 90 nM against a panel of four cancer cell lines, and interacts strongly with tubulin by binding to the colchicine site. In this series of N(6)-carbamate derivatives, any further increase in the length and in the size of the alkyl chain resulted in reduced activity.

Design, synthesis, and biological evaluation of thiophene analogues of chalcones.

Chalcones are characterized by possessing an enone moiety between two aromatic rings. A series of chalcone-like agents, in which the double bond of the enone system is embedded within a thiophene ring, were synthesized and evaluated for antiproliferative activity and inhibition of tubulin assembly and colchicine binding to tubulin. The replacement of the double bond with a thiophene maintains antiproliferative activity and therefore must not significantly alter the relative conformation of the two aryl rings. The synthesized compounds were found to inhibit the growth of several cancer cell lines at nanomolar to low micromolar concentrations. In general, all compounds having significant antiproliferative activity inhibited tubulin polymerization with an IC(50)<2microM. Several of these compounds caused K562 cells to arrest in the G2/M phase of the cell cycle.

Synthesis and biological evaluation of 2-aroyl-4-phenyl-5-hydroxybenzofurans as a new class of antitubulin agents.

Microtubules are among the most successful targets for development of compounds useful for anticancer therapy. Continuing our project to develop new small molecule antitumor agents, two new series of derivatives based on the 2-aroyl-4-phenylbenzofuran molecular skeleton were synthesized and evaluated for antiproliferative activity, inhibition of tubulin polymerization and cell cycle effects. SAR were elucidated with various substitutions on the benzoyl moiety at the 2-position of the benzofuran ring. The most promising compound in this series, the (5-hydroxy-4-phenylbenzofuran-2-yl)(4-methoxyphenyl)methanone derivative (3d), has significant growth inhibitory activity in the submicromolar range against the Molt4, CEM and HeLa cancer cell lines and interacts with tubulin by binding to the colchicine site. Exposure to 3d led to the arrest of K562 cells in the G2-M phase of the cell cycle and to the induction of apoptosis.

From tyrosine to glycine: synthesis and biological activity of potent antagonists of the purinergic P2X7 receptor.

The characterization of the native and recombinant P2X7 receptor continues to be hindered by the lack of specific and subtype-selective antagonists with a "druglike" profile. However, a tyrosine derivative named KN-62 exhibits selective P2X7 receptor-blocking properties. As a molecular simplification of KN-62, the present study was designed to evaluate the functional antagonistic properties of a novel series of glycine derivatives characterized by the presence of different phenyl-substituted piperazine moieties. Antagonistic activity of these glycine derivatives was tested on HEK293 cells transfected with the human P2X7 receptor. The most potent P2X7 receptor antagonist identified in this study (compound 4g) contains an o-fluorine substituent on the phenylpiperazine moiety and had an IC50 of 12.1 nM. The biological responses investigated were ATP-dependent Ca2+ influx across the plasma membrane and ethidium bromide uptake.

Allosteric enhancers for A1 adenosine receptor.

Allosteric enhancers at the adenosine A(1) receptor have received attention as anti-arrhythmic cardiac agents, and, more recently, as anti-lipolytic agents. In addition, allosteric modulators at the adenosine A(1) receptor have therapeutic potential as analgesics and neuroprotective agents. In particular, the compounds with improved potency as enhancers and reduced antagonist properties are mentioned.

Synthesis and biological evaluation of 2-amino-3-(3', 4', 5'-trimethoxy-phenylsulfonyl)-5-aryl thiophenes as a new class of antitubulin agents.

Bioisosterism represents one approach used by the medicinal chemist for the rational modification of lead compounds into safer and more clinically effective agents. Bioisosteres are substituents or groups that have chemical or physical similarities and that produce broadly similar biological effects. The sulfone moiety is recognized as a nonclassical bioisostere for replacement of the carbonyl group. When sulfonyl derivatives 5a-e were compared with carbonyl compounds 4a-e, the sulfone substitution dramatically decreased the antiproliferative activity of the series.

Synthesis and biological evaluation of 2-(3',4',5'-trimethoxybenzoyl)-3-amino 5-aryl thiophenes as a new class of tubulin inhibitors.

2-(3',4',5'-Trimethoxybenzoyl)-3-amino-5-aryl/heteroaryl thiophene derivatives were synthesized and evaluated for antiproliferative activity, inhibition of tubulin polymerization, and cell cycle effects. SARs were elucidated with various substitutions on the aryl moiety 5-position of the thienyl ring. Substituents at the para-position of the 5-phenyl group showed antiproliferative activity in the order of F=CH(3) > OCH(3)=Br=NO(2) > CF(3)=I > OEt. Several of these compounds led to arrest of HL-60 cells in the G2/M phase of the cell cycle and induction of apoptosis.

Synthesis and biological evaluation of 2-amino-3-(4-chlorobenzoyl)-4-[(4-arylpiperazin-1-yl)methyl]-5-substituted-thiophenes. effect of the 5-modification on allosteric enhancer activity at the A1 adenosine receptor.

We have recently reported a detailed structure-activity relationship study around a wide series of 2-amino-3-(4-chlorobenzoyl)-4-[(4-arylpiperazin-1-yl)methyl]thiophene derivatives as potent allosteric enhancers of the A(1) adenosine receptor. In the current study, we have continued to explore the potential of these molecules by synthesizing of a novel series of analogues that share a common 2-amino-3-(4-chlorobenzoyl)thiophene nucleus. Modifications were focused on varying the nature and the position of electron-withdrawing or electron-releasing groups on the phenyl of an arylpiperazine moiety attached at the 4-position of the thiophene ring by a methylene chain, combined with the presence of small alkyl groups (methyl or ethyl), bromine, or aryl moieties at the thiophene C-5 position. In this series of compounds, substitution at the 5-position had a fundamental effect on activity, with the 5-aryl group contributing additively to the allosteric enhancer activity. The thiophene C-5 aryl derivatives 4ad, 4ak, and 4al were the most active compounds in binding and functional experiments.

Synthesis and biological evaluation of 2-(3',4',5'-trimethoxybenzoyl)-3-aryl/arylaminobenzo[b]thiophene derivatives as a novel class of antiproliferative agents.

The biological importance of microtubules in mitosis, as well as in interphase, makes them an interesting target for the development of anticancer agents. Small molecules such as benzo[b]thiophenes are attractive as inhibitors of tubulin polymerization. Thus, a new class of compounds that incorporated the structural motif of the 2-(3',4',5'-trimethoxybenzoyl)-3-aryl/arylamino benzo[b]thiophene molecular skeleton, with electron-donating (Me, OMe, SMe or OEt) or electron-withdrawing (F and Cl) substituents on the B-ring, was synthesized and evaluated for antiproliferative activity, inhibition of tubulin polymerization and cell cycle effects. The most promising compound in this series was 2-(3',4',5'-trimethoxybenzoyl)-3-(4'-ethoxyphenyl)-benzo[b]thiophene (4e), which significantly inhibited cancer cell growth at submicromolar concentrations, especially against HeLa and Jurkat cells, and interacted with tubulin. As determined by flow cytometric analysis, 4e caused G2/M phase arrest and apoptosis in a time- and concentration-dependent manner. The block in G2/M was correlated with increased expression of cyclin B1 and phosphorylation of cdc25c. Moreover, 4e perturbed mitochondrial membrane potential and caused activation of caspase-3 and cleavage of poly(ADP-rybose)polymerase (PARP), events that are involved in 4e-induced apoptosis.

2-Arylamino-4-amino-5-aroylthiazoles. "One-pot" synthesis and biological evaluation of a new class of inhibitors of tubulin polymerization.

The essential role of microtubules in mitosis makes them a major target of compounds useful for cancer therapy. In our search for potent antitumor agents, a novel series of 2-anilino-4-amino-5-aroylthiazoles was synthesized and evaluated for antiproliferative activity, inhibition of tubulin polymerization, and cell cycle effects. SAR was elucidated with various substitutions on the phenylamino and aroyl moiety at the 2- and 5-positions, respectively, of the 4-aminothiazole skeleton. Tumor cell exposure to several of these compounds led to the arrest of HeLa cells in the G2/M phase of the cell cycle and induction of apoptosis.

Synthesis and biological evaluation of 2-amino-3-(4-chlorobenzoyl)-4-[N-(substituted) piperazin-1-yl]thiophenes as potent allosteric enhancers of the A1 adenosine receptor.

The synthesis and evaluation of a series of 2-amino-3-(4-chlorobenzoyl)-4-[4-(alkyl/aryl)piperazin-yl]thiophene derivatives as allosteric enhancers of the A 1-adenosine receptor are described. The nature of substituents on the phenyl ring tethered to the piperazine seem to exert a fundamental influence on the allosteric enhancer activity, with the 4-chlorophenyl 8f and 4-trifluoromethyl 8j derivatives being the most active compounds in binding (saturation and displacement experiments) and functional cAMP studies.

Microwave-assisted synthesis of thieno[2,3-c]pyridine derivatives as a new series of allosteric enhancers at the adenosine A(1) receptor.

The microwave-assisted aromatization method has been used for the synthesis of a series of novel thieno[2,3-c]pyridines. This rapid method produces compounds in good yield within minutes in comparison with conventional heating method. The synthesized molecules have been evaluated as a potential new series of allosteric enhancers acting at the adenosine A(1) receptor. In a functional assay, one compound (3h) showed activity comparable with that of reference compound PD 81,723.