Substituted 2-(3',4',5'-trimethoxybenzoyl)-benzo[b]thiophene derivatives as potent tubulin polymerization inhibitors

Construction of 3-Methyl-2-Substituted Benzo[b]furans and 3-Methyl-2-Substituted Benzo[b]thiophenes Using Solid Calcium Carbide as a Substitute for Gaseous Acetylene

A concise method for the facile construction of 3-methyl-2-substituted benzo[b]furans and 3-methyl-2-substituted benzo[b]thiophenes using low-cost, abundant, and easy-to-use solid calcium carbide instead of flammable and explosive gaseous acetylene as an original alkyne source, o-bromophenyl ethers or o-bromophenyl thioethers as substrates through an intramolecular carbanion-yne cyclization in a 5-exo-dig manner, and subsequent double-bond isomerization is described. The simultaneous formation of two C-C bonds is realized in a one-step route. The wide substrate scope, high yield, and simple workup manipulations are also merits of this method. The synthetic strategy can also be suitable for the gram scale.

Palladium-Catalyzed Direct Selanylation of Chalcogenophenes and Arenes Assisted by 2-(Methylthio)amide

The direct and selective conversion of a C-H bond into a C-Se bond remains a significant challenge, which is even more intricate with substrates having an innate regioselectivity under several reaction conditions, such as chalcogenophenes. We overrode their selectivity toward selanylation using palladium, copper, and the 2-(methylthio)amide directing group. This chelation-assisted direct selanylation was also suitable for mono and double ortho functionalization of arenes. The mechanistic studies indicate high-valent Pd(IV) species in the catalytic cycle, a reversible C-H activation step, and Cu(II) as a sequestering agent for organoselenide byproducts.

Recent developments in decarboxylative C(aryl)-X bond formation from (hetero)aryl carboxylic acids

Decarboxylative coupling reactions using readily available (hetero)aryl carboxylic acids are a highly efficient approach for the formation of new C-C and C-X bonds. These decarboxylative coupling reactions eliminate CO2 as a by-product, resulting in a greener and environmentally more benign approach than conventional coupling reactions. In this review, we summarize the recent developments in ipso-decarboxylative C-X (X = O/N/halo/S/Se/P/CN) bond formations using (hetero)aryl carboxylic acids. Furthermore, we highlight the current limitations and future research opportunities of aryl-decarboxylative coupling reactions.

Virtual and experimental high throughput screening of substituted hydrazones on β-Tubulin polymerization

Microtubule targeting agents that disrupt the dynamic functioning of the mitotic spindle are some of the best chemotherapeutic agents. Interruption of microtubule dynamics through polymerization or depolymerization causes cell arrest leading to apoptosis. We report a novel class of aroylhydrazones with anticancer properties. Tubulin inhibition studies were performed using both computational and biological methods. Docking and pharmacophore mapping showed efficient binding between the ligands and the protein. Tubulin inhibition assay showed the aroylhydrazones to be inhibitors of tubulin polymerization. DFT studies explains the geometrical and electronic properties of the compounds. Furthermore, anticancer studies using lung and liver cancer cell lines gave low IC₅₀ values with the methyl substituted hydrazone MH-2 being the most potent. (IC₅₀ of 0.0896 and 0.1040 µM respectively). The methyl group is responsible for the effective binding to the protein. Thus, a new class of tubulin binding agents have been identified as potential agents in cancer therapy.

A Review on Anticancer Activities of Thiophene and Its Analogs

Cancer is the world's second-largest cause of mortality and one of the biggest global health concerns. The prevalence and mortality rates of cancer remain high despite significant progress in cancer therapy. The search for more effective, as well as less toxic treatment methods for cancer, is at the focus of current studies. Thiophene and its derivatives have surged as an influential scaffold, which, because of their appreciable diversity in biological activities, has drawn the concerned interest of the researchers in the field of medicinal chemistry. By the affluent introduction of its derivatives, which have antioxidant, anti-inflammatory, antimicrobial, and anticancer activities, the adaptability of the thiophene moiety has been displayed. The nature and positioning of the substitutions significantly impacted thiophene moiety activity. This decent array in the living response account about this moiety has picked plentiful researcher's consideration to inquire about it to its peculiar potential across certain activities. In the field of cancer therapy against different cancer cells, the structure-activity relationship for each of the derivatives showed an excellent understanding of thiophene moiety. Information from the various articles revealed the key role of thiophene moiety and its derivatives to develop the vital lead compound. The essential anticancer mechanisms identified include inhibition of the topoisomerase, inhibition of tyrosine kinase, tubulin interaction and apoptosis induction through the activation of reactive oxygen species. This review is an endeavor to promote the anticancer potential of the derivatives, whether having thiophene or condensed thiophene as a core moiety or as a substituent that can lead in the future to synthesize varieties of chemotherapeutic entities in the field of cancer treatment.

Combretastatin A-4 sulfur-containing heterocyclic derivatives: Synthesis, antiproliferative activities and molecular docking studies

Combretastatin A-4 inspired heterocyclic derivatives were synthesized and evaluated for their biological activities on tubulin polymerization and cell proliferation. Among the 19 described sulfur-containing compounds, derivatives (Z)-4h and (Z)-4j exhibited interesting in cellulo tubulin polymerization inhibition and antiproliferative activities with IC₅₀ values for six different cell lines between 8 and 27 nM. Furthermore, in silico docking studies within the colchicine/CA-4 binding site of tubulin were carried out to understand the interactions of our products with the protein target. The effects on the cell cycle of follicular lymphoma cells were also investigated at 1-10 nM concentrations showing that apoptotic processes occurred.

Syntheses, quantum mechanical modeling, biomolecular interaction and in vitro anticancer - Tubulin activity of thiosemicarbazones

A new series of thiosemicarbazones were designed and synthesized. Their structures were confirmed by spectral characterization and single crystal XRD studies. Compounds MTSC-2 and ETSC-3 crystallized in the orthorhombic crystal system with space group Pbc2₁ andPca2₁respectively. Density functional theory computational studies were performed on MTSC-2 and ETSC-3 along with natural bond orbital analysis and Mulliken population analysis to study the structural and electronic properties of the thiosemicarbazones. The HOMOs of the two thiosemicarbazones are -5.2943 and -5.1133 eV respectively while the LUMOs are -1.6879 and -1.6398 eV respectively. The energy gap is 3.6064 and 3.4736 eV respectively. Molecular docking studies were performed to determine the binding mode of the thiosemicarbazones against β-tubulin. The theoretical studies were further supplemented with tubulin polymerization inhibition assay. All the four thiosemicarbazones proved effective in inhibiting the polymerization of α- and β-tubulin heterodimers into microtubules. The anticancer activity of these compounds showed their extreme potency against A549 and HepG2 cancer cell lines with IC₅₀ values of 0.051 - 0.189 µm and 0.042 - 0.136 µm respectively. Compound PTSC-4 showed the highest activity both against tubulin and the two cancer cell lines. This was in correlation with the theoretical studies. Hence, these four compounds, specifically PTSC-4, can be considered to be potential leads in the development of non-metallic anticancer agents.

Synthesis, crystal structure and conformational analysis of an unexpected [1,5]dithiocine product of aminopyridine and thiovanillin

The condensation reaction of 2-mercapto-3-methoxybenzaldehyde with 3-aminopyridine afforded an unexpected N-alkylated [1,5]dithiocine instead of the N-salicylideneaniline. The proposed mechanism for this condensation involves a strong intramolecular hydrogen bond between the thiol and the amine groups, leading to a second condensation. The corresponding product, i.e. 4,10-dimethoxy-13-(pyridin-3-yl)-6H,12H-6,12-epiminodibenzo[b,f][1,5]dithiocine methanol 0.463-solvate, C₂₁H₁₈N₂O₂S₂·0.463CH₃OH, was characterized by single-crystal X-ray diffraction analysis. The supramolecular structure shows π-π stacking and S...S interactions in the crystal packing. Within the asymmetric unit, two geometries of the N atom are observed. Although a planar geometry should be expected, a pyramidal one is observed due to the crystal packing. The presence of the two geometries was further supported by density functional theory (DFT) calculations that show an electronic energy difference of less than 2 kJ mol^-1 between the two conformers.

Copper-catalyzed synthesis of 2-acylbenzo[b]thiophenes from 3-(2-iodophenyl)-1-arylpropan-1-ones and potassium sulfide under aerobic conditions

A method was developed for the synthesis of 2-acylbenzo[b]thiophenes via a copper-catalyzed sulfuration of 3-(2-iodophenyl)-1-arylpropan-1-ones with K2S under aerobic conditions. Mechanistically, this procedure was proved to involve the formation of a dihydrobenzo[b]thiophene intermediate.

Cobalt-catalyzed carbon–sulfur/selenium bond formation: synthesis of benzo[b]thio/selenophene-fused imidazo[1,2-a]pyridines

An efficient cobalt-catalyzed C–S/C–Se bond formation method for the synthesis of benzo[b]thio/selenophene-fused imidazo[1,2-a]pyridines has been developed.

An overview of benzo[b]thiophene-based medicinal chemistry

Among sulfur containing heterocycles, benzothiophene and its derivatives are at the focus as these candidates have structural similarities with active compounds to develop new potent lead molecules in drug design. Benzo[b]thiophene scaffold is one of the privileged structures in drug discovery as this core exhibits various biological activities allowing them to act as anti-microbial, anti-cancer, anti-inflammatory, anti-oxidant, anti-tubercular, anti-diabetic, anti-convulsant agents and many more. Further, numerous benzothiophene-based compounds as clinical drugs have been extensively used to treat various types of diseases with high therapeutic potency, which has led to their extensive developments. Due to the wide range of biological activities of benzothiophene, their structure activity relationships (SAR) have generated interest among medicinal chemists, and this has culminated in the discovery of several lead molecules against numerous diseases. The present review is endeavoring to highlight the progress in the various pharmacological activities of benzo[b]thiophene derivatives. It is hoped that this review will be helpful for new thoughts in the quest for rational designs of more active and less toxic benzothiophene-based medicinal drugs, as well as more effective diagnostic agents and pathologic probes. Also, SAR studies that highlight the chemical groups responsible for evoking the potential activities of benzothiophene derivatives are studied and compared.

Design and in vitro biological evaluation of substituted chalcones synthesized from nitrogen mustards as potent microtubule targeted anticancer agents

Six chalcones were synthesized and their structures determined by single crystal X-ray diffraction studies. They exhibited enhanced anticancer activity and tubulin inhibition.

Microwave-mediated Newman–Kwart rearrangement in water

For the first time the unimolecular Newman–Kwart rearrangement is performed in pure water.

Synthesis and biological evaluation of novel 3,4-diaryl-1,2,5-selenadiazol analogues of combretastatin A-4

A set of novel selenium-containing heterocyclic analogues of combretastatin A-4 (CA-4) have been designed and synthesised using a rigid 1,2,5-selenadiazole as a linker to fix the cis-orientation of ring-A and ring-B. All of the target compounds were evaluated for their in vitro anti-proliferative activities. Among these compounds, compounds 3a, 3i, 3n and 3q exhibited superior potency against different tumour cell lines with IC50 values at the nanomolar level. Moreover, compound 3n significantly induced cell cycle arrest in the G2/M phase, inhibited tubulin polymerisation into microtubules and caused microtubule destabilisation. A molecular modelling study of compound 3n was performed to elucidate its binding mode at the colchicine site in the tubulin dimer and to provide a basis for the further structure-guided design of novel CA-4 analogues.

Tubulin inhibitors: pharmacophore modeling, virtual screening and molecular docking

AIM

To construct a quantitative pharmacophore model of tubulin inhibitors and to discovery new leads with potent antitumor activities.

METHODS

Ligand-based pharmacophore modeling was used to identify the chemical features responsible for inhibiting tubulin polymerization. A set of 26 training compounds was used to generate hypothetical pharmacophores using the HypoGen algorithm. The structures were further validated using the test set, Fischer randomization method, leave-one-out method and a decoy set, and the best model was chosen to screen the Specs database. Hit compounds were subjected to molecular docking study using a Molecular Operating Environment (MOE) software and to biological evaluation in vitro.

RESULTS

Hypo1 was demonstrated to be the best pharmacophore model that exhibited the highest correlation coefficient (0.9582), largest cost difference (70.905) and lowest RMSD value (0.6977). Hypo1 consisted of one hydrogen-bond acceptor, a hydrogen-bond donor, a hydrophobic feature, a ring aromatic feature and three excluded volumes. Hypo1 was validated with four different methods and had a goodness-of-hit score of 0.81. When Hypo1 was used in virtual screening of the Specs database, 952 drug-like compounds were revealed. After docking into the colchicine-binding site of tubulin, 5 drug-like compounds with the required interaction with the critical amino acid residues and the binding free energies < -4 kcal/mol were selected as representative leads. Compounds 1 and 3 exhibited inhibitory activity against MCF-7 human breast cancer cells in vitro.

CONCLUSION

Hypo1 is a quantitative pharmacophore model for tubulin inhibitors, which not only provides a better understanding of their interaction with tubulin, but also assists in discovering new potential leads with antitumor activities.

Synthesis of 2,5-asymmetrically substituted 3,4-diaminothieno[2,3-b]thiophenes by domino reaction

A convenient one pot synthesis of 2,5-asymmetrically substituted thieno[2,3-b]thiophenes is developed. The method is based on consecutive domino reactions (SN2 reaction → Thorpe-Ziegler reaction) using malononitrile and carbon disulfide as starting materials with the generation of potassium 2,2-dicyanoethene-1,1-bis(thiolate) in a solution. The high yield of the target thienothiophenes was achieved using the Ziegler dilution effect.

B-ring-modified isocombretastatin A-4 analogues endowed with interesting anticancer activities

A novel class of isocombretastatin A-4 (isoCA-4) analogues with modifications at the 3'-position of the B-ring by replacement with C-linked substituents was studied. Exploration of the structure-activity relationships of theses analogues led to the identification of several compounds that exhibit excellent antiproliferative activities in the nanomolar concentration range against H1299, MDA-MB231, HCT116, and K562 cancer cell lines; they also inhibit tubulin polymerization with potency similar to that of isoCA-4. 1,1-Diarylethylenes 8 and 17, respectively with (E)-propen-3-ol and propyn-3-ol substituents at the 3'-position of the B-ring, proved to be the most active in this series. Both compounds led to the arrest of various cancer cell lines at the G(2) /M phase of the cell cycle and strongly induced apoptosis. Docking of compounds 8 and 17 in the colchicine binding site indicated that their C3' substituents guide the positioning of the B-ring in a manner different from that observed for isoCA-4.

Discovery of 7-hydroxy-6-methoxy-2-methyl-3-(3,4,5-trimethoxybenzoyl)benzo[b]furan (BNC105), a tubulin polymerization inhibitor with potent antiproliferative and tumor vascular disrupting properties

A structure-activity relationship (SAR) guided design of novel tubulin polymerization inhibitors has resulted in a series of benzo[b]furans with exceptional potency toward cancer cells and activated endothelial cells. The potency of early lead compounds has been substantially improved through the synergistic effect of introducing a conformational bias and additional hydrogen bond donor to the pharmacophore. Screening of a focused library of potent tubulin polymerization inhibitors for selectivity against cancer cells and activated endothelial cells over quiescent endothelial cells has afforded 7-hydroxy-6-methoxy-2-methyl-3-(3,4,5-trimethoxybenzoyl)benzo[b]furan (BNC105, 8) as a potent and selective antiproliferative. Because of poor solubility, 8 is administered as its disodium phosphate ester prodrug 9 (BNC105P), which is rapidly cleaved in vivo to return the active 8. 9 exhibits both superior vascular disrupting and tumor growth inhibitory properties compared with the benchmark agent combretastatin A-4 disodium phosphate 5 (CA4P).