9-Benzylidene-naphtho[2,3-b]thiophen-4-ones as Novel Antimicrotubule AgentsSynthesis, Antiproliferative Activity, and Inhibition of Tubulin Polymerization

Rh(III)-Catalyzed Oxidative C-2 Coupling of N-Pyridinylindoles with Benzo[b]thiophene 1,1-Dioxides via C-H Bond Activation

An efficient Rh(III)-catalyzed cross-dehydrogenative coupling of N-pyridinylindoles with benzo[b]thiophene 1,1-dioxides has been developed through directing-group-assisted C-H activation. This transformation constructs a new C-C bond from two inert C-H bonds in a one-pot reaction. The present reaction is compatible with various functional groups with respect to indoles and benzothiophene[b] 1,1-dioxides. Furthermore, the emission properties of synthesized compounds have been explored.

Tubulin inhibitors targeting the colchicine binding site: a perspective of privileged structures

The vital roles of microtubule in mitosis and cell division make it an attractive target for antitumor therapy. Colchicine binding site of tubulin is one of the most important pockets that have been focused on to design tubulin-destabilizing agents. Over the past few years, a large number of colchicine binding site inhibitors (CBSIs) have been developed inspired by natural products or synthetic origins, and many moieties frequently used in these CBSIs are structurally in common. In this review, we will classify the CBSIs into classical CBSIs and nonclassical CBSIs according to their spatial conformations and binding modes with tubulin, and highlight the privileged structures from these CBSIs in the development of tubulin inhibitors targeting the colchicine binding site.

Crystal structure of 6-(p-tol-yl)benzo[b]naphtho[2,3-d]thio-phene and of an ortho-rhom-bic polymorph of 7-phenyl-anthra[2,3-b]benzo[d]thio-phene

The title compounds, 6-(p-tol­yl)benzo[b]naphtho­[2,3-d]thio­phene and 7-phenyl­anthra[2,3-b]benzo[d]thio­phene, are benzo­thio­phene derivatives in which the benzo­thio­phene moiety is fused with a naphthalene ring system in the former and with an anthracene ring system in the latter. In the former, the 4-methyl­benzene ring substituent makes a dihedral angle of 71.40 (9)° with the mean plane of the naphthalene ring system, while the phenyl ring substituent in the latter makes a dihedral angle of 67.08 (12)° with the mean plane of the anthracene ring system.

The title compounds, C₂₃H₁₆S, (I), and C₂₆H₁₆S, (II), are benzo­thio­phene derivatives in which the benzo­thio­phene moiety is fused with a naphthalene ring system in (I), and with an anthracene ring system in (II). In (I), the mean plane of the benzo­thio­phene ring system makes a dihedral angle of 2.28 (6)° with the naphthalene ring system, and a dihedral angle of 1.28 (6)° with the anthracene ring system in (II), showing that the fused units are essentially planar. In (I), the 4-methyl­benzene ring substituent makes a dihedral angle of 71.40 (9)° with the naphthalene ring system, while the phenyl ring substituent in (II) makes a dihedral angle of 67.08 (12)° with the anthracene ring system. In the crystals of both compounds, mol­ecules are linked by C—H⋯π inter­actions, leading to the formation of slabs parallel to (001) in (I) and to zigzag chains along [001] in (II). There are also offset π–π inter­actions present within the slabs in (I). In the crystal of (II), they link the chains, forming sheets parallel to (010). The triclinic polymorph of compound (II) has been reported [Sivasakthikumaran et al., (2012 ▸). J. Org. Chem.77, 9053–9071].

4-(4-Meth-oxy-phen-yl)naphtho-[2,3-b]thio-phene

In the title compound, C₁₉H₁₄OS, the naphtho­thio­phene moiety is almost planar except for the S atom of the five-membered ring, which is situated 0.047 (6) Å out of the C₄ plane (with an r.m.s. deviation of fitted atoms = 0.0009 Å). The dihedral angle between the naphtho­thio­phene plane and the attached meth­oxy­phenyl ring is 67.6 (2)°. In the crystal, a C—H⋯π inter­action is observed between a meth­oxy­phenyl C—H group and the outer benzene ring of the naphtho­thio­phene moiety. The five-membered ring of the naphtho­thio­phene moiety is disordered, with the S and opposite non-fused C atom approximately exchanging positions, with a site-occupancy factors of 0.808 (3) and 0.187 (3).

Phenylimino-10H-anthracen-9-ones as novel antimicrotubule agents-synthesis, antiproliferative activity and inhibition of tubulin polymerization

A novel series of phenylimino-10H-anthracen-9-ones and 9-(phenylhydrazone)-9,10-anthracenediones were synthesized and evaluated for interaction with tubulin and for cytotoxicity against a panel of human tumor cell lines. The 10-(3-hydroxy-4-methoxy-phenylimino)-10H-anthracen-9-one 15h and its dichloro analog 16b were identified as potent inhibitors of tumor cell growth (16b, IC(50) K562 0.11 μM), including multidrug resistant phenotypes. Compound 15h had excellent activity as an inhibitor of tubulin polymerization. Concentration-dependent cell cycle analyzes by flow cytometry confirmed that KB/HeLa cells treated by 15h and 16b were arrested in the G2/M phases of the cell cycle. In competition experiments, 15h strongly displaced radiolabeled colchicine from its binding site on tubulin, showing IC(50) values similar to that of colchicine. The results obtained demonstrate that the antiproliferative activity is related to the inhibition of tubulin polymerization.

10-(2-oxo-2-phenylethylidene)-10H-anthracen-9-ones as highly active antimicrotubule agents: synthesis, antiproliferative activity, and inhibition of tubulin polymerization

A series of 10-(2-oxo-2-phenylethylidene)-10H-anthracen-9-ones were synthesized and evaluated for interactions with tubulin and for antiproliferative activity against a panel of human and rodent tumor cell lines. The 4-methoxy analogue 17b was most potent, displaying IC(50) values ranging from 40 to 80 nM, including multidrug resistant phenotypes, and had excellent activity as an inhibitor of tubulin polymerization (IC(50) = 0.52 microM). Concentration-dependent flow cytometric studies showed that KB/HeLa cells treated with 17b were arrested in the G2/M phases of the cell cycle (EC(50) = 90 nM). In competition experiments, 17b strongly displaced [(3)H]-colchicine from its binding site in the tubulin. The results obtained demonstrate that the antiproliferative activity is related to the inhibition of tubulin polymerization.

Sulfonate derivatives of naphtho[2,3-b]thiophen-4(9H)-one and 9(10H)-anthracenone as highly active antimicrotubule agents. Synthesis, antiproliferative activity, and inhibition of tubulin polymerization

Benzenesulfonate derivatives of naphtho[2,3-b]thiophen-4(9H)-one and 9(10H)-anthracenone were prepared and found to inhibit microtubule formation by an in vitro tubulin polymerization assay. Several analogues showed potent cytotoxic activity in an assay based on K562 leukemia cells with IC50 values of <100 nM. The methylamino analogue 14i was the most active compound in this assay (14i, IC50 K562: 0.05 muM). Antiproliferative activities of selected compounds were additionally evaluated against a panel of 12 tumor cell lines, including multi-drug-resistant phenotypes. All resistant cell lines were sensitive to these compounds. Concentration-dependent flow cytometric studies showed that KB/HeLa cells treated with selected compounds were arrested in the G2/M phases of the cell cycle. In competition experiments, these compounds strongly displaced radiolabeled colchicine from its binding site in the tubulin, showing IC50 values lower than that of colchicine. The results demonstrate that the antiproliferative activity is related to the inhibition of tubulin polymerization.

Microtubule inhibitors as a potential treatment for malaria

The spread of parasitic resistance has necessitated the development of new drugs and drug targets for the treatment of malaria. Microtubules, which have gained outstanding importance as target molecules for the development of anticancer drugs, are likely to be potent antimalarial targets. The clinical implementation of microtubule inhibitors has given rise to a detailed mechanistic understanding of their interaction with tubulin on the molecular level and their effects on the cellular level. By comparison, our knowledge on Plasmodium falciparum, the causative agent of the most severe form of malaria, is rather poor. This article gives an overview on the microtubule inhibitors that have been explored in the parasite, reviews their effects on parasite growth and assesses their potential as novel antimalarials.

9-Benzylidene-naphtho[2,3-b]thiophen-4-ones and benzylidene-9(10H)-anthracenones as novel tubulin interacting agents with high apoptosis-inducing activity

Tubulin-binding 9-benzylidene-naphtho[2,3-b]thiophen-4-ones 1a and 1b and benzylidene-9(10H)-anthracenone 2 were evaluated for their ability to induce cell death. We examined the effect of the molecules on cell cycle progression, organization of microtubule networks, and apoptosis induction. As determined by flow cytometry, cancer cells were predominantly arrested in metaphase with 4N DNA before cell death occurred. By using indirect immunofluorescence techniques we visualized microtubule depolymerization recognizable by short microtubule fragments scattered around the nucleus. The incubation with 1a and 2 resulted in chromatin condensation, nuclear fragmentation, and cell shrinkage, which are, among others, typical features of apoptotic cell death. Furthermore, time- and dose-dependent induction of apoptosis in SH-SY5Y cells was detected via cleavage of Ac-DEVD-AMC, a fluorigenic substrate for caspase-3. We observed a lower apoptotic activity in neuroblastoma cells overexpressing Bcl-xL, suggesting activation of the mitochondrial apoptosis pathway. Western blot analysis demonstrated that caspase-3, an apoptosis mediator, was activated in a time-dependent manner after exposure of SH-SY5Y cells to drugs 1a and 2. Taken together, the agents investigated in the present study display strong apoptosis-inducing activity and therefore show promise for the development of novel chemotherapeutics.