Synthesis and antitrypanosomal activity of new 6,6,7-trisubstituted thiopyrano[2,3-d][1,3]thiazoles

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.

Molecular design, synthesis and anticancer activity of new thiopyrano[2,3-d]thiazoles based on 5-hydroxy-1,4-naphthoquinone (juglone)

A series of 11-substituted 9-hydroxy-3,5,10,11-tetrahydro-2H-benzo[6,7]thiochromeno[2,3-d][1,3]thiazole-2,5,10-triones 3.1-3.13 were synthesized via hetero-Diels-Alder reaction of 5-ene-4-thioxo-2-thiazolidinones and 5-hydroxy-1,4-naphthoquinone (juglone). The structure of newly synthesized compounds was established by means of spectral data and a single-crystal X-ray diffraction analysis. The synthesized compounds were tested on a panel of cell lines representing different types of cancer as well as normal and pseudonormal cells and peripheral human blood lymphocytes. Compound 3.10 was found to be the most active derivative, exhibiting a cytotoxic effect similar to doxorubicin's one (IC₅₀ ranged from 0.6 to 5.98 μM), but less toxic to normal and pseudonormal cells. All synthesized compounds were able to interact with DNA, although their anticancer activity did not correlate with the potency of interaction with DNA. The status of p53 in colorectal cancer cells correlated with the activity of the synthesized derivatives 3.1, 3.7, and 3.10. Compound 3.10 did not have an acute toxic effect on the body of С57BL/6 mice, unlike the well-known anticancer drug doxorubicin, which was used as a positive control. The injection of 3.10 (20 mg/kg) to mice had no effect on the counts of leukocytes, erythrocytes, platelets and hemoglobin level in their blood, in contrast to doxorubicin, which caused anemia and leukopenia, indicating bio-tolerance of 3.10in vivo.

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.

Synthesis of Thiazole-2(3H)-ones via [3,3]-Sigmatropic Rearrangement/5-exo-dig Cyclization of N-Propargylamines

An efficient methodology has been developed for the synthesis of both di- and trisubstituted thiazol-2(3H)-ones from N-propargylamines and silver(I) trifluoromethanethiolate (AgSCF₃) in good yields. The reaction proceeds via [3,3]-sigmatropic rearrangement/5-exo-dig cyclization of N-propargylamines. The starting material can be easily prepared from the A³-coupling reaction of amines, aldehydes, and alkynes. The methodology can be extended for the synthesis of thiozole-2(3H)-thione derivatives, and photophysical properties have been studied for some synthesized compounds.

Synergistic effects of dual antimicrobial combinations of synthesized N-heterocycles or MgO nanoparticles with nisin against the growth of Aspergillus fumigatus: In vitro study

Introduction of new inhibitory agents such as peptides, heterocyclic derivatives and nanoparticles (NPs) along with preventive proceedings are effective ways to deal with standard and drug-resistant strains of microorganisms. In this regard, inhibitory activities of some recently synthesized 4-thiazolylpyrazoles, imidazolidine- and tetrahydropyrimidine-2-thiones and magnesium oxide (MgO) NPs alone and in combination with nisin have been assessed against Aspergillus fumigatus. Antimicrobial susceptibility tests were done via broth microdilution, disk diffusion and streak plate methods according to the modified Clinical and Laboratory Standards Institute (CLSI) guidelines. Synergistic effects were also determined as fractional inhibitory concentration (FIC) and fractional fungicidal concentration (FFC) values. Inhibitory potentials of all heterocycles and NPs against A. fumigatus were proved based on inhibition zone diameter (IZD) values in the range of 7.72 - 16.85 mm, minimum inhibitory concentration (MIC) values in the range of 64.00 - 512 µg mL^-1 and minimum fungicidal concentration (MFC) values in the range of 256 - 2048 µg mL^-1. Tetrahydropyrimidine derivative 3f showed the best inhibitory properties. Inhibitory activity was not significant with nisin. While antifungal effects of major derivatives were improved by combination with it. The results indicated that the combined treatment of heterocycles used in the present study with nisin might be efficient for mold prevention and removal in foodstuffs or other products.

Study of in vitro biological activity of thiazoles on Leishmania (Leishmania) infantum

OBJECTIVES

In the prospection of possible agents against neglected diseases, thiazole compounds are presented as promising candidates and are known to have activity against trypanosomatid parasites. Thus, this work aimed to evaluate the effects of thiazole compounds on Leishmania infantum, the aetiological agent of visceral leishmaniasis.

METHODS

Thiazole compounds (five thiazoacetylpyridines [TAPs-01, -04, -05, -06, -09) and five thiazopyridines [TPs-01, -04, -05, -06, -09]) were tested regarding their leishmanicidal activity on both promastigote and amastigote forms of L. infantum. Cytotoxicity was tested using peritoneal macrophages of BALB/c mice. Ultrastructural analyses were performed to identify possible intracellular targets of the most effective compound on promastigote forms. To observe routes that can clarify the possible mechanism of action of the compounds on the intracellular amastigote forms, the nitrite dosage was performed.

RESULTS

All compounds inhibited the growth of promastigote and presented low cytotoxicity, being more selective to the parasite than to mammalian cells. All compounds tested were able to decrease macrophage infection. There was a significant decrease in the survival rate of the amastigote when compared with the untreated cells, with TAP-04 presenting the best index. TAP-04 induced ultrastructural changes that are related to cell death by apoptosis. None of the macrophage groups infected with L. infantum and subsequently treated showed increased nitrite release.

CONCLUSIONS

The low toxicity to mammalian cells and the leishmanicidal activity observed demonstrate that the synthesis of drugs based in thiosemicarbazone nucleus, thiazole and pyridine derivatives are promising for the treatment of visceral leishmaniasis.

Recent Advances in the Discovery of Novel Antiprotozoal Agents

Parasitic diseases have serious health, social, and economic impacts, especially in the tropical regions of the world. Diseases caused by protozoan parasites are responsible for considerable mortality and morbidity, affecting more than 500 million people worldwide. Globally, the burden of protozoan diseases is increasing and is been exacerbated because of a lack of effective medication due to the drug resistance and toxicity of current antiprotozoal agents. These limitations have prompted many researchers to search for new drugs against protozoan parasites. In this review, we have compiled the latest information (2012-2017) on the structures and pharmacological activities of newly developed organic compounds against five major protozoan diseases, giardiasis, leishmaniasis, malaria, trichomoniasis, and trypanosomiasis, with the aim of showing recent advances in the discovery of new antiprotozoal drugs.

A Brief Literature and Review of Patents on Thiazole Related Derivatives

Background:

Thiazole is widely investigated bioactive scaffold and dynamic tool in medicinal chemistry research. Significance of thiazole compounds are well documented as thiazole is an obligatory structure of number of currently available therapeutics. In spite of that, thiazole derivatives are endowed with myriad biological activities, such as antiviral, anticancer, antibacterial, antifungal, antimalarial, antiparkinsonian, anti-inflammatory activities and many more.

Methods:

In recent past, different approaches have been introduced for synthesis of thiazole and related compounds. Intrinsic molecular interaction between newly synthesized thiazole compounds and plethora of drug targets/enzymes has rendered discovery of new drug molecules with advances in modes of action. A renewed interest in therapeutic use of thiazole derivatives has been seen among the prospective researchers as exemplified by influx of huge scientific articles and patents. Some important patents of anti-infective and anticancer interest have been addressed appropriately and are presented in tables.

Results:

This review paper is a contemporary approach on therapeutic/applications of thiazole derivatives by summarizing important patents filed from 2000-2017. The main focus of these patents is on anti-infective and anticancer potential of thiazole based compounds.

Conclusion:

These approaches may provide valuable information for the further design of more active biological agents through various modifications and derivatizations.

Thiazolidinone/thiazole based hybrids - New class of antitrypanosomal agents

Different compounds have been investigated as potent drugs for trypanosomiasis treatment, but no new drug has been marketed in the past 3 decades. 4-Thiazolidinone/thiazole as privileged structures and thiosemicarbazides cyclic analogs are well known scaffolds in novel antitrypanosomal agent design. We present here the design and synthesis of new hybrid molecules bearing thiazolidinone/thiazole cores linked by the hydrazone group with various molecular fragments. Structure optimization led to compounds with phenyl-indole or phenyl-imidazo[2,1-b][1,3,4]thiadiazole moieties showing excellent antitrypanosomal activity towards Trypanosoma brucei brucei and Trypanosoma brucei gambiense. Biological study allowed identifying compounds with the submicromolar levels of IC₅₀, good selectivity indexes and relatively low cytotoxicity upon human primary fibroblasts as well as low acute toxicity.

Thiopyrano[2,3-d]Thiazoles as New Efficient Scaffolds in Medicinal Chemistry

This review presents the up to date development of fused thiopyranothiazoles that comprise one of the thiazolidine derivatives classes. Thiazolidine and thiazolidinone-related compounds belong to the widely studied heterocycles from a medicinal chemistry perspective. From the chemical point of view, they are perfect heterodienes to undergo hetero-Diels–Alder reaction with a variety of dienophiles, yielding regio- and diastereoselectively thiopyranothiazole scaffolds. The annealing of thiazole and thiopyran cycles in condensed heterosystem is a precondition for the “centers conservative” creation of the ligand-target binding complex and can promote a potential selectivity to biotargets. The review covers possible therapeutic applications of thiopyrano[2,3-d]thiazoles, such as anti-inflammatory, antibacterial, anticancer as well as aniparasitic activities. Thus, thiopyrano[2,3-d]thiazoles may be used as powerful tools in the development of biologically active agents and drug-like molecules.

Development of Predictive QSAR Models of 4-Thiazolidinones Antitrypanosomal Activity Using Modern Machine Learning Algorithms

This paper presents novel QSAR models for the prediction of antitrypanosomal activity among thiazolidines and related heterocycles. The performance of four machine learning algorithms: Random Forest regression, Stochastic gradient boosting, Multivariate adaptive regression splines and Gaussian processes regression have been studied in order to reach better levels of predictivity. The results for Random Forest and Gaussian processes regression are comparable and outperform other studied methods. The preliminary descriptor selection with Boruta method improved the outcome of machine learning methods. The two novel QSAR-models developed with Random Forest and Gaussian processes regression algorithms have good predictive ability, which was proved by the external evaluation of the test set with corresponding Q²_ext =0.812 and Q²_ext =0.830. The obtained models can be used further for in silico screening of virtual libraries in the same chemical domain in order to find new antitrypanosomal agents. Thorough analysis of descriptors influence in the QSAR models and interpretation of their chemical meaning allows to highlight a number of structure-activity relationships. The presence of phenyl rings with electron-withdrawing atoms or groups in para-position, increased number of aromatic rings, high branching but short chains, high HOMO energy, and the introduction of 1-substituted 2-indolyl fragment into the molecular structure have been recognized as trypanocidal activity prerequisites.

5-Ene-4-thiazolidinones - An efficient tool in medicinal chemistry

The presented review is an attempt to summarize a huge volume of data on 5-ene-4-thiazolidinones being a widely studied class of small molecules used in modern organic and medicinal chemistry. The manuscript covers approaches to the synthesis of 5-ene-4-thiazolidinone derivatives: modification of the C5 position of the basic core; synthesis of the target compounds in the one-pot or multistage reactions or transformation of other related heterocycles. The most prominent pharmacological profiles of 5-ene derivatives of different 4-thiazolidinone subtypes belonging to hit-, lead-compounds, drug-candidates and drugs as well as the most studied targets have been discussed. Currently target compounds (especially 5-en-rhodanines) are assigned as frequent hitters or pan-assay interference compounds (PAINS) within high-throughput screening campaigns. Nevertheless, the crucial impact of the presence/nature of C5 substituent (namely 5-ene) on the pharmacological effects of 5-ene-4-thiazolidinones was confirmed by the numerous listed findings from the original articles. The main directions for active 5-ene-4-thiazolidinones optimization have been shown: i) complication of the fragment in the C5 position; ii) introduction of the substituents in the N3 position (especially fragments with carboxylic group or its derivatives); iii) annealing in complex heterocyclic systems; iv) combination with other pharmacologically attractive fragments within hybrid pharmacophore approach. Moreover, the utilization of 5-ene-4-thiazolidinones in the synthesis of complex compounds with potent pharmacological application is described. The chemical transformations cover mainly the reactions which involve the exocyclic double bond in C5 position of the main core and correspond to the abovementioned direction of the 5-ene-4-thiazolidinone modification.

Synthesis, antioxidant and antimicrobial activities of novel thiopyrano[2,3-d]thiazoles based on aroylacrylic acids

Here it is described the synthesis, antioxidant and antimicrobial activity determination of novel rel-([Formula: see text])-6-benzoyl-7-phenyl-2-oxo-3,5,6,7-tetrahydro-2H-thiopyrano[2,3-d]thiazole-5-carboxylic acids. The target compounds were obtained in good yields from 5-arylidene-4-thioxo-2-thiazolidinones and [Formula: see text]-aroylacrylic acids via regio- and diastereoselective hetero-Diels-Alder reaction. The stereochemistry of the cycloaddition was confirmed by NMR spectra. The antioxidant and antimicrobial activity screening identified 7 compounds (3c, 3e, 3f, 3g, 3k, 3l, 3p) with a high level of free radical scavenging (43-77% DPPH assay), and compounds with significant influence on Staphylococcus aureus, Bacillus subtilis and Candida albicans (MIC 3.13-6.25 [Formula: see text]), but slight effect on Escherichia coli.

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.

Enantioselective organocatalytic Michael addition of isorhodanines to α,β-unsaturated aldehydes

The Michael reaction of substituted isorhodanines with α,β-unsaturated aldehydes in the presence of a catalytic amount of a chiral secondary amine is presented. This transformation proceeds in good to high yields furnishing the corresponding 4,5-disubstituted isorhodanine adducts in good to excellent enantioselectivities.

Synthesis and Anticancer Activity of New Thiopyrano[2,3-d]thiazoles Based on Cinnamic Acid Amides

Novel rel-(5R,6S,7S)-2-oxo-5-phenyl-7-aryl(hetaryl)-3,7-dihydro-2H-thiopyrano [2,3-d]thiazole-6-carboxylic acid amides were synthesized in a hetero-Diels-Alder reaction with a series of cinnamic acid amides. The synthesized compounds were tested for their anticancer activity in vitro in the standard National Cancer Institute 60 cancer cell line assay. Promising compounds 3e, 3g, and 3h with moderate antitumor activity were identified among the synthesized series.