Antitumor agents. 166. Synthesis and biological evaluation of 5,6,7,8-substituted-2-phenylthiochromen-4-ones

Progress on the Cu-Catalyzed 1,4-Conjugate Addition to Thiochromones

Carbon-carbon bond formation is one of the most important tools in synthetic organic chemists' toolbox. It is a fundamental transformation that allows synthetic chemists to synthesize the carbon framework of complex molecules from inexpensive simple starting materials. Among the many synthetic methodologies developed for the construction of carbon-carbon bonds, organocopper reagents are one of the most reliable organometallic reagents for this purpose. The versatility of organocuprate reagents or the reactions catalyzed by organocopper reagents were demonstrated by their applications in a variety of synthetic transformations including the 1,4-conjugate addition reactions. Sulfur-containing heterocyclic compounds are a much less studied area compared to oxygen-containing heterocycles but have gained more and more attention in recent years due to their rich biological activities and widespread applications in pharmaceuticals, agrochemicals, and material science. This paper will provide a brief review on recent progress on the synthesis of an important class of sulfur-heterocycles-2-alkylthiochroman-4-ones and thioflavanones via the conjugate additions of Grignard reagents to thiochromones catalyzed by copper catalysts. Recent progress on the synthesis of 2-substituted thiochroman-4-ones via alkynylation and alkenylation of thiochromones will also be covered in this review.

Recent advances in the synthesis of pharmaceutically active 4-quinolone and its analogues: a review

4-Quinolone and its analogs are heterocyclic classes of organic compounds displaying biologically active and a broad spectrum of pharmaceutical drug scaffolds. 4-Quinolone is the first-line chemotherapeutic treatment for a wide spectrum of bacterial infections. Recently, 4-quinolone and its derivatives have been shown to have the potential to cure and regulate various acute and chronic diseases, including pain, ischemia, immunomodulation, inflammation, malarial, bacterial infection, fungal infection, HIV, and cancer, based on several reports. This review highlights and provides brief information to better understand the development of experimental progress made to date in the synthetic protocol towards 4-quinolone and its analogs. Thus, classical synthesis protocol, metal-free reaction protocol, and transition metal-catalyzed reaction procedures are briefly discussed along with the pharmaceutical activities of selected 4-quinolone derivatives.

Visible-Light-Promoted Transition-Metal-Free Construction of 3-Perfluoroalkylated Thioflavones

A visible-light-promoted transition-metal-free perfluoroalkylation/cyclization reaction was developed with 9-mesityl-10-methylacridinium perchlorate (Acr⁺-Mes·ClO₄⁻) as the photocatalyst, by which various perfluoroalkyl-substituted heterocycles including thioflavones, oxindoles, and quinoline-2,4(1H,3H)-diones were prepared at room temperature. Moreover, the potential of this sustainable method is demonstrated by the excellent in vitro anti-lymphoma and cervical carcinoma activity of the novel 3-perfluoroalkylated thioflavone 3m.

Chemical repair of damaged leucine and tryptophane by thiophenols at close to diffusion-controlled rates: Mechanisms and kinetics

Thiophenols are chemical species with multiple desirable biological properties, including their primary and secondary antioxidant capacity. In this work, the repairing antioxidant activity of eight different thiophenols has been investigated for damaged leucine and tryptophane. The investigation was carried out employing quantum mechanical and transition state methods to calculate the thermodynamic and kinetic data of the reactions involved, while simulating the biological conditions at physiological pH and aqueous and lipidic medium. The analysis of the atomic charges and the spin densities at each of the points on the potential energy surface was the tool that allowed the elucidation of the reaction mechanisms through which thiophenols repair the oxidative damage caused to the amino acids leucine and tryptophan. It was found that thiophenols can repair leucine via a hydrogen atom transfer mechanism in a manner which is similar to the one used by glutathione to repair the carbon-centered radicals of guanosine. In addition, thiophenols can also restore tryptophane, a nitrogen-centered radical, via proton-coupled electron transfer and single electron transfer mechanisms. Moreover, both processes occur at close to diffusion-controlled rates.

Nickel-Catalyzed One-Pot Carbonylative Synthesis of 2-Mono- and 2,3-Disubstituted Thiochromenones from 2-Bromobenzenesulfonyl Chlorides and Alkynes

A nickel-catalyzed one-pot carbonylation reaction of 2-bromobenzenesulfonyl chlorides with alkynes for the synthesis of thiochromenones has been established. Both terminal and internal alkynes were suitable substrates in this carbonylative transformation, and a broad range of 2-mono- and 2,3-disubstituted thiochromenone products were obtained in moderate to good yields with quite high functional group compatibility. Notably, this procedure presents the first example of nickel-catalyzed carbonylative synthesis of thiochromenones with 2-bromobenzenesulfonyl chlorides as a promising sulfur precursor.

Synthesis of 2-Aryl-4H-thiochromen-4-one Derivatives via a Cross-Coupling Reaction

A concise and efficient cross-coupling synthetic strategy has been developed to construct 2-aryl-4H-thiochromen-4-one derivatives from 2-sulfinyl-thiochromones and arylboronic acids. This reaction proceeds via a catalyst system of Lewis acid and palladium(II) combined with XPhos as an optimal ligand in moderate to good yields. Besides, this flexible methodology provides a wide scope for the synthesis of different functionally substituted thiochromone scaffolds and can be further exploited to construct diverse thioflavone libraries for pharmaceutical research.

Conjugate Addition of Grignard Reagents to Thiochromones Catalyzed by Copper Salts: A Unified Approach to Both 2-Alkylthiochroman-4-One and Thioflavanone

Grignard reagents undergo conjugate addition to thiochromones catalyzed by copper salts to afford 2-substituted-thiochroman-4-ones, both 2-alkylthiochroman-4-ones and thioflavanones (2-arylthiochroman-4-ones), in good yields with trimethylsilyl chloride (TMSCl) as an additive. The best yields of 1,4-adducts can be attained with CuCN∙2LiCl as the copper source. Excellent yields of 2-alkyl-substituted thiochroman-4-ones and thioflavanones (2-aryl substituted) are attained with a broad range of Grignard reagents. This approach works well with both alkyl and aromatic Grignard reagents, thus providing a unified synthetic approach to privileged 2-substituted thiochroman-4-ones and a potential valuable precursor for further synthetic applications towards many pharmaceutically active molecules. The use of commercially available and/or readily prepared Grignard reagents will expedite the synthesis of a large library of both 2-alkyl substituted thiochroman-4-ones and thioflavanones for additional synthetic applications.

Transition-metal-free sulfonylations of methylthiolated alkynones to synthesize 3-sulfonylated thioflavones

A set of transition-metal-free NaI/TBHP-mediated sulfonylation cyclization reactions of methylthiolated alkynones with sulfonyl hydrazides was developed, by which various 3-sulfonylated thioflavones were prepared under mild reaction conditions.

Thiophenols, Promising Scavengers of Peroxyl Radicals: Mechanisms and kinetics

The activity of 12 thiophenols as primary antioxidants in aqueous solution has been studied using density functional theory. Twelve different substituted thiophenols were tested as peroxyl radicals scavengers. Single electron transfer (SET) and formal hydrogen transfer (FHT) were investigated. The SET mechanism was found to be the main mechanism, with rate constants that are close to the diffusion limit, which means that these thiophenolic compounds have the capacity to scavenge peroxyl radicals before they can damage biomolecules. All 12 thiophenolic compounds react faster with methylperoxyl than with hydroperoxyl radicals. In addition, it was found that pH plays an important role in the reactivity of these compounds. © 2019 Wiley Periodicals, Inc.

Thioether-based 2-aminobenzamide derivatives: Novel HDAC inhibitors with potent in vitro and in vivo antitumor activity

Previously, we focused on a series of 2-aminobenzamide-based histone deacetylase (HDAC) inhibitors, compound 9 of which displayed potent HDAC inhibitory activity against HDAC1 and HDAC2, and moderate anti-proliferative activity against several cancer cell lines. In the current study, we have designed and synthesized a series of novel HDAC inhibitors based on thioether moiety with 9 as a lead compound. Representative compounds12 g and 12 h showed apparently potent anti-proliferative activities against five solid cancer cell lines: A549, HCT116, Hela, A375 and SMMC7721, and low cytotoxicity against NIH 3T3 normal cells. Especially, 12 g and 12 h also revealed potent HDAC inhibitory activity against HDAC1, 2 and 3. In addition, the two compounds could arrest cell cycle in G2/M phase and promote cell apoptosis. Moreover, they showed extended inhibition of colony formation and effectively blocked cell migration towards A549 cancer cells. Furthermore, 12 g and 12 h possessed better pharmacokinetic properties than the lead compound 9. Benefiting from these results, we also explored 12 g and 12 h in the A549 xenografts model for in vivo antitumor activity. The in vivo experiment indicated that 12 g and 12 h could evidently augment antitumor activity (TGI = 56.9% and 62.7% respectively).

Development of Conjugate Addition of Lithium Dialkylcuprates to Thiochromones: Synthesis of 2-Alkylthiochroman-4-ones and Additional Synthetic Applications

Lithium dialkylcuprates undergo conjugate addition to thiochromones to afford 2-alkylthiochroman-4-ones in good yields. This approach provide an efficient and general synthetic approach to privileged sulfur-containing structural motifs and valuable precursors for many pharmaceuticals, starting from common substrates-thiochromones. Good yields of 2-alkyl-substituted thiochroman-4-ones are attained with lithium dialkylcuprates, lithium alkylcyanocuprates or substoichiometric amount of copper salts. The use of commercially available inexpensive alkyllithium reagents will expedite the synthesis of a large library of 2-alkyl substituted thiochroman-4-ones for additional synthetic applications.

Retracted: Novel spiro-thiazolidin-4-one and thioether derivatives of benzylidene flavanones: New leads in cancer and microbial chemotherapy

The above article from Archiv der Pharmazie, published online on 12 March 2018 in Wiley Online Library (wileyonlinelibrary.com), has been retracted by agreement between the authors, the journal Editor-in-Chief, Prof. Holger Stark, and Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim. The retraction has been agreed due to errors in the spectroscopic data of the investigated new compounds.

REFERENCE TO RETRACTION

S. Mukhtar, M. A. Alsharif, M. I. Alahmdi, H. Parveen, A. U. Khan, Arch. Pharm. Chem. Life Sci. 2018;1-12. DOI: 10.1002/ardp.201700397.

Modulating the reactivity of functionalized N,S-ketene acetal in MCR: selective synthesis of tetrahydropyridines and thiochromeno[2,3-b]pyridines via DABCO-catalyzed tandem annulation

An efficient and straightforward three-component synthetic protocol was developed to synthesize 1,2,3,4-tetrahydropyridine derivatives or thiochromeno[2,3-b]pyridine derivatives from β-aroylthioacetanilides or β-(2-haloaroyl)thioacetanilides, aldehydes, and aroyl acetonitriles via DABCO-catalyzed tandem [3 + 2 + 1] annulation and S(N)Ar reaction. This synthetic approach has the prominent features of high chemo-, stereo- (or enantio-), and unusual regioselectivity. In the domino processes, at least seven reactive sites were involved, and up to three covalent bonds and one functionalized pyridine ring were generated. This facile and efficient reaction is a quite general for the preparation of tetrahydropyridine derivatives or thiochromeno[2,3-b]pyridine derivatives.

The role of polyphenolic antioxidants in health, disease, and aging

Polyphenolic antioxidants from dietary sources are frequently a topic of interest due to widespread scientific agreement that they may help lower the incidence of certain cancers, cardiovascular and neurodegenerative diseases, and DNA damage and even may have antiaging properties. On the other hand, questions still remain as to whether some antioxidants could be potentially harmful to health, because an increase in glycation-mediated protein damage (carbonyl stress) has been reported in some cases. Nevertheless, the quest for healthy aging has led to the extensive use of phytochemically derived antioxidants to disrupt age-associated deterioration in physiological function and to prevent many age-related diseases. Although a diet rich in the polyphenolic forms of antioxidants does seem to offer hope in delaying the onset of age-related disorders, it is still too early to define their exact clinical benefit for treating age-related disease. This review critically examines polyphenolic antioxidants, such as flavonoids, curcumene, and resveratrol in health, disease, and aging with the hope that a better understanding of the many mechanisms involved with these diverse compounds may lead to better health and novel treatment approaches for age-related diseases.

Heterocyclic analogs of thioflavones: synthesis and NMR spectroscopic investigations

The synthesis of several hitherto unknown heterocyclic ring systems derived from thioflavone is described. Coupling of various o-haloheteroarenecarbonyl chlorides with phenylacetylene gives 1-(o-haloheteroaryl)-3-phenylprop-2-yn-1-ones, which were treated with NaSH in refluxing ethanol to yield the corresponding bi- and tricyclic annelated 2-phenylthiopyran-4-ones. Detailed NMR spectroscopic investigations of the ring systems and their precursors are presented.

New developments in natural products-based anti-AIDS research

This review discusses anti-HIV natural products from several compound classes, including terpenoids, coumarins, alkaloids, polyphenols, tannins, and flavonoids. Natural products can provide novel anti-AIDS chemotherapeutic leads that are structurally unique or have new mechanisms of action. The drug discovery and development process proceeds from bioactivity-directed isolation and identification of a promising lead natural product, followed by rational design-based structural modification and structure-activity relationship analyses to optimize the lead compound as a drug candidate. This process is notably exemplified by the discovery of the modified betulinic acid derivative, DSB [PA-457], which is currently in Phase II clinical trial and is the first-in-class HIV maturation inhibitor (MI).

Electrolytic Partial Fluorination of Organic Compounds. 79. Anodic Fluorination of Spiropyrazoline-5,3‘-chroman-4-ones and Thiochromanone Analogues. A Route to Aroyl Fluoride Derivatives

[reaction: see text] Anodic fluorination of spiropyrazole-5,3'-chroman-4-ones and their thiochromanone analogues in dimethoxyethane containing Et4NF x 4HF resulted in ring opening of spiroheterocycles, which led to the formation of (5-pyrazolyl)methyl o-carbomethoxyphenyl ethers and their thioether analogues via benzoyl fluoride derivatives.

Synthesis and structure–activity relationships of thioflavone derivatives as specific inhibitors of the ERK-MAP kinase signaling pathway

Condensation of nitrobenzaldehydes 3 and alpha-[o-(p-methoxybenzylthio)benzoyl] sulfoxide 4 gave alpha-sulfinyl enones 5. Treatment of 5 with formic acid caused cyclization followed by debenzylation to afford 3-(methylsulfinyl)thioflavanones 6. Double-bond formation with elimination of methanesulfenic acid was performed by refluxing 6 in benzene, and, finally, the nitro group of 2-phenyl-4H-1-benzothiopyran-4-one (thioflavones) 7 was reduced with tin in tetrafluoroboric acid. Various 2'-aminothioflavones 8 thus prepared were evaluated for their inhibitory effects on the ERK-MAP kinase pathway. In a cell-based assay, 2-(2'-amino-3'-methoxyphenyl)-4H-1-benzothiopyran-4-one (8b) showed a more potent inhibitory effect than the corresponding oxygen compound (PD98059, 1) on the Raf-induced activation of the ERK-MAP kinase pathway as well as cell proliferation. Furthermore, compound 8b selectively and potently inhibited the proliferation of tumor cells in which the ERK-MAP kinase pathway is constitutively activated.