Synthesis and biological evaluation of 3-(trimethoxyphenyl)-2(3H)-thiazole thiones as combretastatin analogs

Multicomponent Reaction of CS2, Amines, and Sulfoxonium Ylides in Water: Straightforward Access to β-Keto Dithiocarbamates, Thiazolidine-2-thiones, and Thiazole-2-thiones

Simple, versatile, and catalyst-free synthetic methods for β-keto dithiocarbamates, thiazolidine-2-thiones, and thiazole-2-thiones via the multicomponent reaction of CS₂, amines, and sulfoxonium ylides have been described. The β-keto sulfoxonium ylides furnished β-keto dithiocarbamates in the presence of CS₂ and secondary amines, whereas primary amines afforded thiazolidine-2-thiones or thiazole-2-thiones after dehydration in an acidic environment. With simple procedures, the reaction has a wide substrate scope and excellent functional group tolerance.

Catalyst- and additive-free syntheses of rhodanine and S-alkyl dithiocarbamate derivatives from sulfoxonium ylides

An efficient catalyst- and additive-free facile access to rhodanine and S-alkyl dithiocarbamate derivatives via multi-component reaction of amines, CS₂ and α-ester sulfoxonium ylides in methanol has been described. The new synthetic methods offer excellent synthetic prospects for several functionalized rhodanines and S-alkyl dithiocarbamates with simple operational procedures.

Efficient, Recyclable, and Heterogeneous Base Nanocatalyst for Thiazoles with a Chitosan-Capped Calcium Oxide Nanocomposite

Calcium oxide (CaO) nanoparticles have recently gained much interest in recent research due to their remarkable catalytic activity in various chemical transformations. In this article, a chitosan calcium oxide nanocomposite was created by the solution casting method under microwave irradiation. The microwave power and heating time were adjusted to 400 watts for 3 min. As it suppresses particle aggregation, the chitosan (CS) biopolymer acted as a metal oxide stabilizer. In this study, we aimed to synthesize, characterize, and investigate the catalytic potency of chitosan–calcium oxide hybrid nanocomposites in several organic transformations. The produced CS–CaO nanocomposite was analyzed by applying different analytical techniques, including Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and field-emission scanning electron microscopy (FESEM). In addition, the calcium content of the nanocomposite film was measured using energy-dispersive X-ray spectroscopy (EDS). Fortunately, the CS–CaO nanocomposite (15 wt%) was demonstrated to be a good heterogeneous base promoter for high-yield thiazole production. Various reaction factors were studied to maximize the conditions of the catalytic technique. High reaction yields, fast reaction times, and mild reaction conditions are all advantages of the used protocol, as is the reusability of the catalyst; it was reused multiple times without a significant loss of potency.

Design, Synthesis, and Antipoliferative Activities of Novel Substituted Imidazole-Thione Linked Benzotriazole Derivatives

A new series of benzotriazole moiety bearing substituted imidazol-2-thiones at N1 has been designed, synthesized and evaluated for in vitro anticancer activity against the different cancer cell lines MCF-7(breast cancer), HL-60 (Human promyelocytic leukemia), and HCT-116 (colon cancer). Most of the benzotriazole analogues exhibited promising antiproliferative activity against tested cancer cell lines. Among all the synthesized compounds, BI9 showed potent activity against the cancer cell lines such as MCF-7, HL-60 and HCT-116 with IC₅₀ 3.57, 0.40 and 2.63 µM, respectively. Compound BI9 was taken up for elaborate biological studies and the HL-60 cells in the cell cycle were arrested in G₂/M phase. Compound BI9 showed remarkable inhibition of tubulin polymerization with the colchicine binding site of tubulin. In addition, compound BI9 promoted apoptosis by regulating the expression of pro-apoptotic protein BAX and anti-apoptotic proteins Bcl-2. These results provide guidance for further rational development of potent tubulin polymerization inhibitors for the treatment of cancer.

Design, synthesis, and cytotoxic screening of novel azole derivatives on hepatocellular carcinoma (HepG2 Cells)

Novel azole derivatives 3-30 were designed, synthesized, and screened for their antitumor activity on HepG2 cell line. The cytotoxicity screening demonstrated that imidazolone 8 and triazoles 25 and 29 exhibited more potent cytotoxic activities by 1.21-, 4.75-, and 1.8-fold compared to Sorafenib (SOR). Furthermore, vascular endothelial growth factor receptor-2 (VEGFR-2) enzyme inhibition assay declared that compounds 25 and 29 had inhibitory activity at the nanomolar concentration. Moreover, the tested compounds exhibited good β-tubulin (TUB) polymerization inhibition percentages. In addition, DNA flow cytometry analysis over HepG2 cells indicated that triazoles 25 and 29 demonstrated arrest at G₁ and G₂/M phase of the cell cycle and induced apoptotic activity by increasing sub-G₁ phase. Finally, mechanistic studies of the proapoptotic activities of compounds 8, 10, 11, 25, and 29 indicated that they induced upregulation of P53, Fas/Fas-ligand, and BAX/BCL-2 ratio expression that resulted in increasing the active caspase 3/7 percentages and trigger apoptosis.

Thiazole-containing compounds as therapeutic targets for cancer therapy

In the last few decades, considerable progress has been made in anticancer agents development, and several new anticancer agents of natural and synthetic origin have been produced. Among heterocyclic compounds, thiazole, a 5-membered unique heterocyclic motif containing sulphur and nitrogen atoms, serves as an essential core scaffold in several medicinally important compounds. Thiazole nucleus is a fundamental part of some clinically applied anticancer drugs, such as dasatinib, dabrafenib, ixabepilone, patellamide A, and epothilone. Recently, thiazole-containing compounds have been successfully developed as possible inhibitors of several biological targets, including enzyme-linked receptor(s) located on the cell membrane, (i.e., polymerase inhibitors) and the cell cycle (i.e., microtubular inhibitors). Moreover, these compounds have been proven to exhibit high effectiveness, potent anticancer activity, and less toxicity. This review presents current research on thiazoles and elucidates their biological importance in anticancer drug discovery. The findings may aid researchers in the rational design of more potent and bio-target specific anticancer drug molecules.

Design, synthesis and biological evaluation of flexible and rigid analogs of 4H-1,2,4-triazoles bearing 3,4,5-trimethoxyphenyl moiety as new antiproliferative agents

Several flexible and rigid analogs of 4H-1,2,4-triazoles (compounds 8a-g and 9a-g) bearing trimethoxyphenyl pharmacophoric unit, were designed and synthesized as potential anticancer agents. The in vitro cytotoxic assay indicated that both flexible and rigid analogs (8 and 9, respectively) can potentially inhibit the growth of cancerous cells (A549, MCF7, and SKOV3), with IC₅₀ values less than 5.0 µM. Furthermore, compounds 10a-l as regional isomers of compounds 9 exhibited remarkable cytotoxic activity with IC₅₀ values ranging from 0.30 to 5.0 µM. The rigid analogs 9a, 10h and 10k were significantly more potent than etoposide against MCF7, SKOV3 and A549 cells, respectively. These compounds showed high selectivity towards cancer cells over normal cells, as they had no significant cytotoxicity against L929 cells. In addition, the representative compounds 9a and 10h could inhibit the tubulin polymerization at micro-molar levels. By determining changes in the colchicine-tubulin fluorescence, it was suggested that compound 10h could bind to the tubulin at the colchicine pocket. The molecular docking study further confirmed the inhibitory activity of promising compounds 9a, 10h and 10k on tubulin polymerization through binding to the colchicine-binding site.

Thiazole in the targeted anticancer drug discovery

Cancer is known as one of the main causes of death in the world; and many compounds have been synthesized to date with potential use in cancer therapy. Thiazole is a versatile heterocycle, found in the structure of many drugs in use as well as anticancer agents. This review provides an overview of recent advances in thiazole-bearing compounds as anticancer agents with particular emphasis on their mechanism of action in cancerous cells. Chemical designs, structure–activity relationships and relevant preclinical properties have been comprehensively described.

Synthesis and characterisation of (Z)-styrylbenzene derivatives as potential selective anticancer agents

To identify anticancer agents with high potency and low toxicity, a series of (Z)-styrylbenzene derivatives were synthesised and evaluated for anticancer activities using a panel of nine cancer cell lines and two noncancerous cell lines. Most derivatives exhibited significant anti-proliferative activities against five cancer cell lines, including MGC-803 and BEL-7402. (Z)-3-(p-Tolyl)-2-(3,4,5-trimethoxyphenyl)acrylonitrile (6h) showed a strong inhibitory effect on MGC-803 cells (IC50 < 0.01 µM) and exhibited stronger anti-proliferative activity than taxol (IC50 < 0.06 ± 0.01 µM). The IC50 value of 6h in L-02 cells was 10,000-fold higher than in MGC-803 cells. Compound 6h inhibited proliferation of BEL-7402 cells by arresting at the G2/M phase through up-regulation of cyclin B1 expression, down-regulation of cyclin A and D1 expression, and induction of apoptosis. In addition, 6h inhibited the migration of BEL-7402 cells and the formation of cell colonies.

Atropisomerism in 3-arylthiazolidine-2-thiones. A combined dynamic NMR and dynamic HPLC study

Sterically hindered 3-arylthiazolidine-2-thiones were prepared by a solvent-free reaction with arylisothiocyanates and 1,4-dithiane-2,5-diol. Atropisomerism was observed in two compounds (3 and 4, aryl = 1-naphthyl and 2-methylnaphth-1-yl), whose rotational energy barriers were measured using dynamic NMR and dynamic HPLC. The experimental analyses were supported by DFT calculations. Thermally stable atropisomers were obtained by dehydration of compounds 3 and 4 and the absolute configuration of the atropisomers of compound 6 was determined by theoretical simulation of the ECD and VCD spectra.

Synthesis and biological evaluation of 4-amino-5-cinnamoylthiazoles as chalcone-like anticancer agents

A series of 4-amino-5-cinnamoylthiazoles 3a-p were designed and synthesized as chalcone-like anticancer agents. The synthesized derivatives 3a-p were evaluated for their in vitro antiproliferative activities against three different human cancer cell lines including MCF-7, HepG2 and SW480. Most of compounds could significantly prevent proliferation of tested cell lines. In particular, the pyrrolidine derivative 3e namely (E)-1-(4-amino-2-(pyrrolidin-1-yl)thiazol-5-yl)-3-(2,4-dichlorophenyl)prop-2-en-1-one showed promising activity, especially against HepG2 cells (IC₅₀ = 10.6 μg/ml). Flow cytometric analyses revealed that the prototype compound 3e can prevent the proliferation of HepG2 cells by blockade of the cell cycle at the G2 phase and induction of apoptosis.

Discovery and structure-activity relationship of novel 4-hydroxy-thiazolidine-2-thione derivatives as tumor cell specific pyruvate kinase M2 activators

Pyruvate kinase M2 isoform (PKM2) is a crucial protein responsible for aerobic glycolysis of cancer cells. Activation of PKM2 may alter aberrant metabolism in cancer cells. In this study, we discovered a 4-hydroxy-thiazolidine-2-thione compound 2 as a novel PKM2 activator from a random screening of an in-house compound library. Then a series of novel 4-hydroxy-thiazolidine-2-thione derivatives were designed and synthesized for screening as potent PKM2 activators. Among these, some compounds showed higher PKM2 activation activity than lead compound 2 and also exhibited significant anti-proliferative activities on human cancer cell lines at nanomolar concentration. The compound 5w was identified as the most potent antitumor agent, which showed excellent anti-proliferative effects with IC50 values from 0.46 μM to 0.81 μM against H1299, HCT116, Hela and PC3 cell lines. 5w also showed less cytotoxicity in non-tumor cell line HELF compared with cancer cells. In addition, Preliminary pharmacological studies revealed that 5w arrests the cell cycle at the G2/M phase in HCT116 cell line. The best PKM2 activation by compound 5t was rationalized through docking studies.

Design, synthesis and structure-activity relationship of 3,6-diaryl-7H-[1,2,4]triazolo[3,4-b][1,3,4]thiadiazines as novel tubulin inhibitors

A novel series of 3,6-diaryl-7H-[1,2,4]triazolo[3,4-b][1,3,4]thiadiazines were designed, synthesized and biologically evaluated as vinylogous CA-4 analogues, which involved a rigid [1,2,4]triazolo[3,4-b][1,3,4]thiadiazine scaffold to fix the configuration of (Z,E)-butadiene linker of A-ring and B-ring. Among these rigidly vinylogous CA-4 analogues, compounds 4d, 5b, 5i, 6c, 6e, 6g, 6i and 6k showed excellent antiproliferative activities against SGC-7901, A549 and HT-1080 cell lines with IC₅₀ values at the nanomolar level. Compound 6i showed the most highly active antiproliferative activity against the three human cancer cell lines with an IC₅₀ values of 0.011-0.015 µM, which are comparable to those of CA-4 (IC₅₀ = 0.009-0.013 µM). Interestingly, SAR studies revealed that 3,4-methylenedioxyphenyl, 3,4-dimethoxyphenyl, 3-methoxyphenyl and 4-methoxyphenyl could replace the classic 3,4,5-trimethoxyphenyl in CA-4 structure and keep antiproliferative activity in this series of designed compounds. Tubulin polymerization experiments showed that 6i could effectively inhibit tubulin polymerization, which was corresponded with CA-4, and immunostaining experiments suggested that 6i significantly disrupted microtubule/tubulin dynamics. Furthermore, 6i potently induced cell cycle arrest at G₂/M phase in SGC-7901 cells. Competitive binding assays and docking studies suggested that compound 6i binds to the tubulin perfectly at the colchicine binding site. Taken together, these results revealed that 6i may become a promising lead compound for new anticancer drugs discovery.

Novel Natural Product- and Privileged Scaffold-Based Tubulin Inhibitors Targeting the Colchicine Binding Site

Tubulin inhibitors are effective anticancer agents, however, there are many limitations to the use of available tubulin inhibitors in the clinic, such as multidrug resistance, severe side-effects, and generally poor bioavailability. Thus, there is a constant need to search for novel tubulin inhibitors that can overcome these limitations. Natural product and privileged structures targeting tubulin have promoted the discovery and optimization of tubulin inhibitors. This review will focus on novel tubulin inhibitors derived from natural products and privileged structures targeting the colchicine binding site on tubulin.

Synthesis of functionalized 5-substituted thiazolidine-2-thiones via adscititious xanthate-promoted radical cyclization of allyl(alkyl/aryl)dithiocarbamates

An adscititious radical precursor-promoted cyclization is designed and realized in efficient synthesis of functionalized 5-substituted thiazolidine-2-thiones from alkyl allyl(alkyl/aryl)dithiocarbamates.

Enantioselective construction of novel chiral spirooxindoles incorporating a thiazole nucleus

Enantioselective synthesis of novel thiazole-fused spirooxindoles has been realized via chiral thiourea catalyzed asymmetric cascade Michael addition/cyclization of thiazolones and 3-ylideneoxindoles.

Combretastatins: more than just vascular targeting agents?

Several prodrugs of the naturally occurring combretastatins have undergone extensive clinical evaluation as vascular targeting agents (VTAs). Their increased selectivity toward endothelial cells together with their innate ability to rapidly induce vascular shutdown and inhibit tumor growth at doses up to 10-fold less than the maximum tolerated dose led to the clinical evaluation of combretastatins as VTAs. Tubulin is well established as the molecular target of the combretastatins and the vast majority of its synthetic derivatives. Furthermore, tubulin is a highly validated molecular target of many direct anticancer agents routinely used as front-line chemotherapeutics. The unique vascular targeting properties of the combretastatins have somewhat overshadowed their development as direct anticancer agents and the delineation of the various cell death pathways and anticancer properties associated with such chemotherapeutics. Moreover, the ongoing clinical trial of OXi4503 (combretastatin-A1 diphosphate) together with preliminary preclinical evaluation for the treatment of refractory acute myelogenous leukemia has successfully highlighted both the indirect and direct anticancer properties of combretastatins. In this review, we discuss the development of the combretastatins from nature to the clinic. The various mechanisms underlying combretastatin-induced cell cycle arrest, mitotic catastrophe, cell death, and survival are also reviewed in an attempt to further enhance the clinical prospects of this unique class of VTAs.

Synthesis and biological evaluation of novel 4,5-disubstituted 2H-1,2,3-triazoles as cis-constrained analogues of combretastatin A-4

A series of combretastatin A-4 (CA-4) analogues have been prepared from (Z)-substituted diarylacrylonitriles (1a-1p) obtained in a two-step synthesis from appropriate arylaldehydes and acrylonitriles. The resulting 4,5-disubstituted 2H-1,2,3-triazoles were evaluated for their anti-cancer activities against a panel of 60 human cancer cell lines. The diarylacrylonitrile analogue 2l exhibited the most potent anti-cancer activity in the screening studies, with GI₅₀ values of <10 nM against almost all the cell lines in the human cancer cell panel and TGI values of <10 nM against cancer cell lines SF-539, MDA-MB-435, OVCAR-3 and A498. Furthermore, in silico docking studies of compounds 2l, 2e and 2h within the active site of tubulin were carried out in order to rationalize the mechanism of the anti-cancer properties of these compounds. From the in silico studies, compound 2e was predicted to have better affinity for the colchicine binding site on tubulin compared to compounds 2l and 2h. Analogue 2e was also evaluated for its anti-cancer activity by colony formation assay against 9LSF rat gliosarcoma cells and afforded an LD₅₀ of 7.5 nM. A cell cycle redistribution assay using analogue 2e was conducted to further understand the mechanism of action of these CA-4 analogues. From this study, analogues 2e and 2l were the most potent anti-cancer agents in this structural class, and were considered lead compounds for further development as anti-cancer drugs.

Synthesis and evaluation of a series of resveratrol analogues as potent anti-cancer agents that target tubulin

A series of novel diarylacrylonitrile and trans-stilbene analogues of resveratrol has been synthesized and evaluated for their anticancer activities against a panel of 60 human cancer cell lines. The diarylacrylonitrile analogues 3b and 4a exhibited the most potent anticancer activity of all the analogues synthesized in this study, with GI50 values of < 10 nM against almost all the cell lines in the human cancer cell panel. Compounds 3b and 4a were also screened against the acute myeloid leukemia (AML) cell line, MV4-11, and were found to have potent cytotoxic properties that are likely mediated through inhibition of tubulin polymerization. Results from molecular docking studies indicate a common binding site for 4a and 3b on the 3,3-tubulin heterodimer, with a slightly more favorable binding for 3b compared to 4a; this is consistent with the results from the microtubule assays, which demonstrate that 4a is more potent than 3b in inhibiting tubulin polymerization in MV4-11 cells. Taken together, these data suggest that diarylacrylonitriles 3b and 4a may have potential as antitubulin therapeutics for treatment of both solid and hematological tumors.

Recent applications of 1,3-thiazole core structure in the identification of new lead compounds and drug discovery

1,3-Thiazole is one of the most important scaffolds in heterocyclic chemistry and drug design and discovery. It is widely found in diverse pharmacologically active substances and in some naturally-occurring compounds. Thiazole is a versatile building-block for lead generation, and is easily access of diverse derivatives for subsequent lead optimization. In the recent years, many thiazole derivatives have been synthesized and subjected to varied biological activities. In this article we intended to review the most important biological effects of thiazole-based compounds and highlight their roles in new leads identification and drug discovery. This article is also intended to help researches for finding potential future directions on the development of more potent and specific analogs of thiazole-based compounds for various biological targets.

A solvent- and catalyst-free domino reaction for the efficient synthesis of 3-arylthiazolidine-2-thiones under microwave irradiation

A facile synthesis of 4-hydroxy-3-arylthiazolidine-2-thiones through novel domino reactions of aryl isothiocyanates and 1,4-dithiane-2,5-diol under solvent- and catalyst-free microwave irradiation is reported.

Synthesis, anticancer activity and molecular docking studies on a series of heterocyclic trans-cyanocombretastatin analogues as antitubulin agents

A series of heterocyclic combretastatin analogues have been synthesized and evaluated for their anticancer activity against a panel of 60 human cancer cell lines. The most potent compounds were two 3,4,5-trimethoxy phenyl analogues containing either an (Z)-indol-2-yl (8) or (Z)-benzo[b]furan-2-yl (12) moiety; these compounds exhibited GI50 values of <10 nM against 74% and 70%, respectively, of the human cancer cell lines in the 60-cell panel. Compounds 8, and 12 and two previously reported compounds in the same structural class, i.e. 29 and 31, also showed potent anti-leukemic activity against leukemia MV4-11 cell lines with LD50 values = 44 nM, 47 nM, 18 nM, and 180 nM, respectively. From the NCI anti-cancer screening results and the data from the in vitro toxicity screening on cultured AML cells, seven compounds: 8, 12, 21, 23, 25, 29 and 31 were screened for their in vitro inhibitory activity on tubulin polymerization in MV4-11 AML cells; at 50 nM, 8 and 29 inhibited polymerization of tubulin by >50%. The binding modes of the three most active compounds (8, 12 and 29) to tubulin were also investigated utilizing molecular docking studies. All three molecules were observed to bind in the same hydrophobic pocket at the interface of α- and β-tubulin that is occupied by colchicine, and were stabilized by van der Waals' interactions with surrounding tubulin residues. The results from the tubulin polymerization and molecular docking studies indicate that compounds 8 and 29 are the most potent anti-leukemic compounds in this structural class, and are considered lead compounds for further development as anti-leukemic drugs.

Crystal structure of 4,5-bis-(3,4,5-tri-meth-oxy-phen-yl)-2H-1,2,3-triazole methanol monosolvate

The title compound, C20H23N3O6·CH3OH, was synthesized by [3 + 2] cyclo-addition of (Z)-2,3-bis-(3,4,5-tri-meth-oxy-phen-yl)acrylo-nitrile with sodium azide and ammonium chloride in DMF/water. The central nitro-gen of the triazole ring is protonated. The dihedral angles between the triazole ring and the 3,4,5-tri-meth-oxy-phenyl ring planes are 34.31 (4) and 45.03 (5)°, while that between the 3,4,5-tri-meth-oxy-phenyl rings is 51.87 (5)°. In the crystal, the mol-ecules, along with two methanol solvent mol-ecules are linked into an R (4) 4(10) centrosymmetric dimer by N-H⋯O and O-H⋯N hydrogen bonds.