Update on thiopyran-fused heterocycle synthesis (2013-2024)

Thiopyrans and their fused derivatives have significant synthetic relevance owing to their biological importance and occurrence in natural products. The current article provides an overview of synthetic strategies employed for the construction of thiopyran-fused heterocycles. In particular, this article discusses synthetic methods for the fusion of thiopyran with heterocycles such as indole, quinoline, pyrimidine, pyridine, thiophene, chromene, oxazole, pyrazole, pyran and furan and covers the literature from 2013 to 2024. The most common precursors for thiopyrano[2,3-b]indoles, thiopyranoquinolines and thiopyranothiazoles are indoline-2-thione, 2-mercaptoquinoline-3-carbaldehyde and thiazolidinone, respectively, and various reactions involving these are described in detail here. Asymmetric syntheses of thiopyranoindoles achieved using chiral catalysts based on thiourea, proline and metal complexes are also included. The biological activity associated with some compounds is also discussed.

Synthesis, anticancer evaluation, molecular docking and ADME study of novel pyrido[4',3':3,4]pyrazolo[1,5-a]pyrimidines as potential tropomyosin receptor kinase A (TrKA) inhibitors

The starting compound 3-amino-1,7-dihydro-4H-pyrazolo[4,3-c]pyridine-4,6(5H)-dione (1) is reacted with each of diketone and β-ketoester, forming pyridopyrazolo[1,5-a]pyrimidines 4a,b and 14a,b, respectively. The compounds 4 and 14 reacted with each of aromatic aldehyde and arenediazonium salt to give the respective arylidenes and arylhydrazo derivatives, respectively. The structure of the new products was established using spectroscopic techniques. The cytotoxic activity of selected targets was tested in vitro against three cancer cell lines MCF7, HepG2 and HCT116. The data obtained from enzymatic assays of TrKA indicated that compounds 7b and 16c have the strongest inhibitory effects on TrKA with IC50 = 0.064 ± 0.0037 μg/ml and IC50 = 0.047 ± 0.0027 μg/ml, respectively, compared to the standard drug Larotrectinib with IC50 = 0.034 ± 0.0021 μg/ml for the HepG2 cancer cell line. In cell cycle analysis, compounds 7b, 15b, 16a and 16c caused the greatest arrest in cell cycle at the G2/M phase. In addition, compound 15b has a higher apoptosis-inducing effect (36.72%) than compounds 7b (34.70%), 16a (21.14) and 16c (26.54%). Compounds 7b, 16a and 16c were shown fit tightly into the active site of the TrKA kinase crystal structure (PDB: 5H3Q). Also, ADME study was performed on some selected potent anticancer compounds described in this study.

Design, Synthesis, Anticancer Evaluation and Molecular Modeling Studies of New Thiazolidinone-Benzoate Scaffold as EGFR Inhibitors, Cell Cycle Interruption and Apoptosis Inducers in HepG2

Synthesis of new anticancer candidates with protein kinases inhibitory potency is a major goal of pharmaceutical science and synthetic research. This current work represents the synthesis of a series of substituted benzoate-thiazolidinones. Most prepared thiazolidinones were evaluated in vitro for their potential anticancer activity against three cell lines by MTT assay, and they found to be more effective against cancer cell lines with no harm toward normal cells. Thiazolidinones 5 c and 5 h were further evaluated to be kinase inhibitors against EGFR showing effective inhibitory impact (with IC50 value; 0.2±0.009 and 0.098±0.004 μM, for 5 c and 5 h, respectively). Furthermore, 5 c and 5 h have effects on cell cycle and apoptosis induction capability in HepG2 cell lines by DNA-flow cytometry analysis and annexin V-FITC apoptosis assay, respectively. The results showed that they have effect of disrupting the cell cycle and causing cell mortality by apoptosis in the treated cells. Moreover, molecular docking studies showed better binding patterns for 5 c and 5 h with the active site of the epidermal growth factor receptor (EGFR) protein kinase (PDB code 1M17). Finally, toxicity risk and physicochemical characterization by Osiris method was performed on most of the compounds, revealing excellent properties as possible drugs.

Novel Thiopyrano[2,3-d]thiazole-pyrazole Hybrids as Potential Nonsulfonamide Human Carbonic Anhydrase IX and XII Inhibitors: Design, Synthesis, and Biochemical Studies

In recent years, molecular hybridization strategies have developed into a potent strategy for drug discovery. A series of novel thiopyrano[2,3-d]thiazoles linked to the pyrazole moiety was designed and developed as anticancer agents by a molecular hybridization. Target compounds were synthesized and characterized by spectroscopic tools as well as X-ray crystallography analysis as in the case of thiopyrano[2,3-d]thiazole derivative 5a. The MTT assay was used to demonstrate the in vitro efficacy of compounds 5a-g and 7a-j on MCF-7 and HePG-2. The results showed that some cycloadducts such as bromophenyl-4-thioxo-2-thiazolidinone 3e, 4-methylphenyl derivative of thiopyrano[2,3-d]thiazole 5d, and 6-substituted-thiopyrano[2,3-d]thiazoles 7e-j displayed good to excellent IC₅₀ in the range of 10.08 ± 1.5 to 25.95 ± 2.8 μg/mL against the MCF-7 cell line and from 7.83 ±2.1 to 13.37 ± 1.2 μg/mL against the HePG-2 cell line. To explore the enzymatic tests for isozymes hCAIX and hCAXII, the most promising eight compounds 3e, 5d, and 7e-j with IC₅₀ ranging from 7.83 ± 2.1 to 25.95 ± 2.8 μM were chosen. Compound 7e exhibited an IC₅₀ (0.067 ± 0.003 μM) similar to that of the standard drug AZA against CAIX (0.059 ± 0.003 μM)). For CAXII, the compound 7i had an IC₅₀ equal to 0.123 ± 0.007 μM compared to that of AZA (0.083 ± 0.005 μM). In addition, using flow cytometry, cell cycle analysis and apoptosis studies in HePG-2 were performed for the two potent anticancer and selective carbonic anhydrase agents (7e and 7i). An enzymatic assay of these two compounds against caspase-9 was also examined. Interestingly, the molecular docking studies revealed that compounds 7e and 7i successfully embedded themselves in the active pockets of the CAIX and CAXII enzymes through different interactions. Overall, the novel thiopyrano[2,3-d]thiazole-pyrazole hybrids (7e and 7i) were suggested to be potent and selective inhibitors of CAIX and CAXII.

Theoretical and molecular mechanistic investigations of novel (3-(furan-2-yl)pyrazol-4-yl) chalcones against lung carcinoma cell line (A549)

A new chalcone series has been developed that may be useful in the treatment of lung cancer. The new series was confirmed by the different spectral tools. MTT assay was used to detect the cytotoxic effect of the novel chalcones against lung cancer cell line (A549). Molecular docking studies were performed on the most two effective chalcones 7b and 7c. Different molecular techniques were utilized to study the activity and the effect of two chalcones 7b and 7c on apoptosis of A549 cell line.

1,4-Naphthoquinone Motif in the Synthesis of New Thiopyrano[2,3-d]thiazoles as Potential Biologically Active Compounds

A series of 11-substituted 3,5,10,11-tetrahydro-2H-benzo[6,7]thiochromeno[2,3-d][1,3]thiazole-2,5,10-triones were obtained via hetero-Diels-Alder reaction of 5-alkyl/arylallylidene/-4-thioxo-2-thiazolidinones and 1,4-naphthoquinones. The structures of newly synthesized compounds were established by spectral data and a single-crystal X-ray diffraction analysis. According to U.S. NCI protocols, compounds 3.5 and 3.6 were screened for their anticancer activity; 11-Phenethyl-3,11-dihydro-2H-benzo[6,7]thiochromeno[2,3-d]thiazole-2,5,10-trione (3.6) showed pronounced cytotoxic effect on leukemia (Jurkat, THP-1), epidermoid (KB3-1, KBC-1), and colon (HCT116wt, HCT116 p53-/-) cell lines. The cytotoxic action of 3.6 on p53-deficient colon carcinoma cells was two times weaker than on HCT116wt, and it may be an interesting feature of the mechanism action.

rel-2-[4-Chloro-2-[(5R,6R,7S)-6-[5-(4-methoxyphenyl)-3-(2-naphthyl)-3,4-dihydropyrazole-2-carbonyl]-5-methyl-2-oxo-3,5,6,7-tetrahydrothiopyrano[2,3-d]thiazol-7-yl]phenoxy]acetic Acid

The hetero-Diels–Alder reaction is the main synthetic tool for obtaining pharmacological agents with a thiopyrano[2,3-d]thiazole motif. In the present work, an efficient method for the synthesis of pyrazoline-containing thiopyrano[2,3-d]thiazole is described. The pyrazoline-bearing dienophile was proposed and used as effective building block for the synthesis of the title compound. The structure of the synthesized rel-2-[4-chloro-2-[(5R,6R,7S)-6-[5-(4-methoxyphenyl)-3-(2-naphthyl)-3,4-dihydropyrazole-2-carbonyl]-5-methyl-2-oxo-3,5,6,7-tetrahydrothiopyrano[2,3-d]thiazol-7-yl]phenoxy]acetic acid (3) was confirmed by 1H, 13C, 2D NMR, and LC-MS spectra. Anticancer activity in “60 lines screening” (NCI DTP protocol) was studied in vitro for the title compound.

Anticancer activity of novel 3-(furan-2-yl)pyrazolyl and 3-(thiophen-2-yl)pyrazolyl hybrid chalcones: Synthesis and in vitro studies

Twelve novel chalcone derivatives were prepared using the Claisen-Schmidt condensation reaction. The reaction of 4-acetyl-5-furan/thiophene-pyrazole derivatives 5 with the corresponding aldehydes 6 afforded the targeted chalcone derivatives 7a-l in good yields. The newly synthesized chalcones were fully characterized by spectrometric and elemental analyses. The in vitro anticancer activities of the novel compounds 7a-l were evaluated against four human cancer cell lines: HepG2 (human hepatocellular carcinoma), MCF7 (human Caucasian breast adenocarcinoma), A549 (lung carcinoma), and BJ1 (normal skin fibroblasts). Compound 7g emerged as the most promising compound, with IC₅₀  = 27.7 µg/ml against A549 cells compared to the reference drug doxorubicin (IC₅₀  = 28.3 µg/ml), and IC₅₀  = 26.6 µg/ml against HepG2 cells compared to the reference drug doxorubicin (IC₅₀  = 21.6 µg/ml). The gene expression and DNA damage values and the DNA fragmentation percentages for compound 7g were determined on the lung and liver cell lines. The expression levels of the AMY2A and FOXG1 genes increased significantly (p < 0.01) in the negative samples of lung cancer cells compared with treated cells. Also, the expression values of the PKM and PSPH genes improved significantly (p < 0.01) in the negative samples compared with treated samples of liver cancer cells. The DNA damage values increased significantly (p < 0.01) in treated lung cell line samples (7g) and the positive control. The results showed a significant decrease (p < 0.05) in DNA damage values in the negative samples of liver cancer cells compared to those treated with 7g. However, the DNA fragmentation values increased significantly (p < 0.01) in the treated lung and liver cell line samples compared with the negative control.

Expedition of sulfur-containing heterocyclic derivatives as cytotoxic agents in medicinal chemistry: A decade update

This review article proposes a comprehensive report of the design strategies engaged in the development of various sulfur-bearing cytotoxic agents. The outcomes of various studies depict that the sulfur heterocyclic framework is a fundamental structure in diverse synthetic analogs representing a myriad scope of therapeutic activities. A number of five-, six- and seven-membered sulfur-containing heterocyclic scaffolds, such as thiazoles, thiadiazoles, thiazolidinediones, thiophenes, thiopyrans, benzothiazoles, benzothiophenes, thienopyrimidines, simple and modified phenothiazines, and thiazepines have been discussed. The subsequent studies of the derivatives unveiled their cytotoxic effects through multiple mechanisms (viz. inhibition of tyrosine kinases, topoisomerase I and II, tubulin, COX, DNA synthesis, and PI3K/Akt and Raf/MEK/ERK signaling pathways), and several others. Thus, our concise illustration explains the design strategy and anticancer potential of these five- and six-membered sulfur-containing heterocyclic molecules along with a brief outline on seven-membered sulfur heterocycles. The thorough assessment of antiproliferative activities with the reference drug allows a proficient assessment of the structure-activity relationships (SARs) of the diversely synthesized molecules of the series.

Synthetic and Medicinal Perspective of Fused-Thiazoles as Anticancer Agents

BACKGROUND

Cancer is second leading disease after cardiovascular disease. Presently, Chemotherapy, Radiotherapy and use of chemicals are some treatments available these days. Thiazole and its hybrid compounds extensively used scaffolds in drug designing and development of novel anticancer agents due to their wide pharmacological profiles. Fused thiazole scaffold containing drugs are available in market as a promising group of anticancer agents.

METHODS

The detailed study has been done using different database that focused on potent thiazole hybrid compounds with anticancer activity. The literature included in this review is focused on novel fused thiazole derivatives exhibiting anticancer potency in last decade.

RESULTS

Literature suggested that thiazoles and its fused and linked congener serve excellent pharmacological profile as an anticancer agent. Various synthetic strategies for fused thiazole are also summarized in this article. Novel thiazole and its fused congener showed anticancer activity against various cancer cell lines.

INTERPRETATION

Thiazole is a promising scaffold reported in literature with broad range of biological activities. This article covers the thiazole compounds fused with other carbocyclic/heterocycle including benzene, imidazole, pyridine, pyrimidine, quinoline, phenothiazine, thiopyrano, steroids, pyrrole etc. with anticancer activity from last decades. Several inhibitors for breast cancer, colon cancer, melanoma cancer, ovarian cancer, tubulin cancer etc. were reported in this review. Thus, this review will definitely aid to develop a lead for the new selective anticancer agents in future.

Design, green one-pot synthesis and molecular docking study of novel N,N-bis(cyanoacetyl)hydrazines and bis-coumarins as effective inhibitors of DNA gyrase and topoisomerase IV

A novel, quick, environmentally safe, and one-pot synthesis of a series of N,N-bis(cyanoacetyl)hydrazine derivatives, bis-imino-2H-chromenes and bis-2-oxo-2H-chromene derivatives have been designed. Some selected newly synthesized compounds were investigated in vitro for their antibacterial activity. Compound 5j is the most toxic compound against Staphylococcus aureus with activity index 171%, followed by compound 15b with activity index 136% compared to standard drug ampicillin. Moreover, compound 15a is the most toxic compound against Escherichia coli with activity index 111% compared to standard drug gentamicin. Minimum inhibitory concentration (MIC) was carried out for compounds with high antibacterial activity. Compound 5j has good MIC (7.8 μg/ml) against Staphylococcus aureus while 15a has good MIC (31.25 μg/ml) against Streptococcus mutans which is better than MIC of the standard drug ampicillin (MIC = 62.5 μg/ml). Compounds 5j, 5k, 15a, 15b and 15e which have good MIC values were introduced to enzyme assay against DNA gyrase and topoisomerase IV. The results showed that compound 15a can strongly inhibit DNA gyrase and topoisomerase IV (IC₅₀ = 27.30 and 25.52 μM respectively), compared to methotrexate as the standard drug (IC₅₀ = 29.01 and 23.55 μM respectively). Structure-activity relationships were also discussed based on the biological and docking simulation results.

2-(3,5-Dimethyl-1H-pyrazol-1-yl)thiazolo[4,5-b]pyridine

The compound 2-(3,5-dimethyl-1H-pyrazol-1-yl)thiazolo[4,5-b]pyridine (1) was synthesized with a yield of 71% by the reaction of 1-(thiazolo[4,5-b]pyridine-2-yl)hydrazine and acetylacetone. The structure was characterized by a single-crystal X-ray structure determination as well as 1H and 13C{1H} NMR spectroscopy. X-ray crystallography on 1 confirms the molecule consists of a pyridine–thiazole moiety and the pyrazole ring, and all non-hydrogen atoms are planar.

Design, synthesis, anticancer evaluation, molecular docking and cell cycle analysis of 3-methyl-4,7-dihydropyrazolo[1,5-a]pyrimidine derivatives as potent histone lysine demethylases (KDM) inhibitors and apoptosis inducers

A novel series of pyrazolo[1,5-a]pyrimidines were synthesized and proved by their spectral and elemental analysis, some elected of the newly synthesized compounds were examined for their cytotoxic activity employing MTT assay on two cancer cell lines (Breast and Hela cancers). Compounds 5, 7e and 7i showed the higher cytotoxicity against two cancer cell lines with (IC₅₀ = 13.91 ± 1.4 and 22.37 ± 1.8 μM/L), (IC₅₀ = 6.56 ± 0.5 and 8.72 ± 0.9 μM/L) and (IC₅₀ = 4.17 ± 0.2 and 5.57 ± 0.4 μM/L) for two cancer cell lines breast and hela respectively, using doxorubicin as a reference drug. The most potent cytotoxic active compounds 5, 7e and 7i presented inhibitory activity against KDM (histone lysine demethylases) with IC₅₀ = 4.05, 1.91 and 2.31 μM, respectively. The most potent KDM inhibitor 7e (IC₅₀ = 1.91 μM) showed to cause cell cycle arrest at G2/M phase by 4 folds than control and induce total apoptotic effect by 10 folds more than control. In silico studies performed on the more potent cytotoxic active compounds 5, 7e and 7i included lipinisk's rule of five. Moreover, molecular docking study was utilized to explore the binding mode of the most active compounds to the target enzyme (PDB-ID: 5IVE). Also, some bioinformatics studies were carried out for compounds 7e and 7i using Swiss ADME (Swiss Institute of bioinformatics 2018).

Tandem hetero-Diels–Alder-hemiacetal reaction in the synthesis of new chromeno[4′,3′:4,5]thiopyrano[2,3-d]thiazoles

Novel rel-(5aR,6R,11bS)-6-hydroxy-3,5a,6,11b-tetrahydro-2H,5H-chromeno[4′,3′:4,5]thiopyrano[2,3-d][1,3]thiazole-2-ones were synthesized via tandem hetero-Diels-Alder-hemiacetal reaction of 5-(2-hydroxybenzylidene)-4-thioxo-2-thiazolidinones and α,β-unsaturated aldehydes. The stereochemistry of cycloadditions was confirmed by NMR spectra and a single crystal X-ray diffraction analysis.