The Smiles rearrangement in the syntheses of azaphenothiazines. Part I

14-Substituted Diquinothiazines as a New Group of Anticancer Agents

A series of novel double-angularly condensed diquinothiazines with aminoalkyl, amidoalkyl, sulfonamidoalkyl, and substituted phenyl groups was designed, synthesized, and evaluated for their anticancer activity against four selected human tumor cell lines (HTC116, SH-SY5Y, A549, and H1299). The cytotoxicity of the novel diquinothiazines was investigated against BEAS-2B cells. The activities of the compounds were compared to etoposide. Among them, compounds with aminoalkyl and phenyl groups showed excellent broad-spectrum anticancer activity. The most active 14-(methylthiophenyl)diquinothiazine, 3c, showed low cytotoxicity against BEAS-2B cells and high activity against tumor cell lines HTC116, SH-SY5Y, A549, and H1299, with IC50 values of 2.3 µM, 2.7 µM, 17.2 µM, and 2.7 µM, respectively (etopiside 8.6 µM, 3.9 µM, 44.8 µM, and 0.6, respectively). Live long-term microscopic observations of cell survival using the starting molecule M0 were also performed. Flow cytometry showed the proapoptotic effects of the studied diquinothiazines. Inhibition of the cell cycle in the S phase was observed, which is associated with damage to nucleic acids and connected to DNA replication arrest.

Tri- and Pentacyclic Azaphenothiazine as Pro-Apoptotic Agents in Lung Carcinoma with a Protective Potential to Healthy Cell Lines

The phenothiazine derivatives, tricyclic 10H-3,6-diazaphenothiazine (DPT-1) and pentacyclic 7-(3′-dimethylaminopropyl)diquinothiazine (DPT-2), have recently been shown to exhibit promising anticancer activities in vitro. In this report, we demonstrated that DPT-1 and DPT-2 could be pro-apoptotic agents in lung carcinoma, the human lung carcinoma A549 and non-small lung carcinoma H1299, in the range of IC50 = 1.52–12.89 µM, with a protective potential to healthy cell lines BEAS-2B and NHDF. The compounds showed higher activity in the range of the tested concentrations and low cytotoxicity in relation to normal healthy cells than doxorubicin, used as the reference drug. The cytostatic potential of DPT-1 and DPT-2 was demonstrated with the use of MTT assay. Cell cycle analysis via flow cytometry using Annexin-V assay showed the pro-apoptotic and pro-necrotic role of the studied diazaphenothiazines in the cell cycle. DPT-1 and DPT-2 initiated a biological response in the investigated cancer models with a different mechanism and at a different rate. Based on these findings, it can be concluded that DPT-1 and DPT-2 have potential as chemotherapeutic agents.

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.

High Chemo-/Stereoselectivity for Synthesis of Polysubstituted Monofluorinated Pyrimidyl Enol Ether Derivatives

A novel intramolecular Smiles rearrangement of α-fluoro-β-keto-pyrimidylsulfones (usually used as a carbon nucleophile) was developed, providing a versatile avenue for synthesis of tri/tetra-substituted monofluorinated pyrimidyl enol ethers. Among these, diverse (Z)-monofluorovinylsulfones and sulfinates were efficiently assembled by adding extra electrophile and fine-tuning reaction conditions. The process is triggered by a keto-enol tautomerism from enol oxyanion to pyrimidine 2-carbon, completely different from the classical carbon nucleophilic addition reaction approach.