Quinonaphthothiazines, syntheses, structures and anticancer activities

NaOAc-Promoted [3+1+2] Annulation of O-Pivaloyl Oximes, Aldehydes, and 2-Methylbenzothiazole Salts: Synthesis of 1-Azaphenothiazines

This paper presents an efficient strategy for constructing 1-azaphenothiazines through the NaOAc-promoted [3+1+2] annulation of O-pivaloyl oximes, aldehydes, and 2-methylbenzothiazole salts. The reaction is conducted in ethanol and employs oxygen as the oxidant under catalyst-free conditions. The process is amenable to various O-pivaloyl oximes, 2-methylbenzothiazole salts, and aldehydes, affording the target products in satisfactory yields.

Evaluation of the Lipophilicity of Angularly Condensed Diquino- and Quinonaphthothiazines as Potential Candidates for New Drugs

Lipophilicity is one of the most important properties of compounds required to estimate the absorption, distribution, and transport in biological systems, in addition to solubility, stability, and acid-base nature. It is crucial in predicting the ADME profile of bioactive compounds. The study assessed the usefulness of computational and chromatographic methods (thin-layer chromatography in a reversed-phase system, RP-TLC) for estimating the lipophilicity of 21 newly synthesized compounds belonging to diquinothiazines and quinonaphthiazines. In order to obtain reliable values of the relative lipophilicities of diquinothiazines and quinonaphthiazines, the partition coefficients obtained using different algorithms such as AlogPs, AClogP, AlogP, MLOGP, XLOGP2, XLOGP3, logP, and ClogP were compared with the chromatographic RM0 values of all the tested compounds measured by the experimental RP-TLC method (logPTLC). Additionally, logPTLC values were also correlated with other descriptors, as well as the predicted ADME and drug safety profiling parameters. The linear correlations of logPTLC values of the tested compounds with other calculated molecular descriptors such as molar refractivity, as well as ADME parameters (Caco-2 substrates, P-gp inhibitors, CYP2C19, and CYP3A4) generally show poor predictive power. Therefore, in silico ADME profiling can only be helpful at the initial step of designing these new candidates for drugs. The compliance of all discussed diquinothiazines and naphthoquinothiazines with the rules of Lipiński, Veber, and Egan suggests that the tested pentacyclic phenothiazine analogs have a chance to become therapeutic drugs, especially orally active drugs.

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.

Synthesis of new hybrid 1,4-thiazinyl-1,2,3-dithiazolyl radicals via Smiles rearrangement

The condensation reaction of 2-aminobenzenethiols and 3-aminopyrazinethiols with 2-amino-6-fluoro-N-methylpyridinium triflate afforded thioether derivatives that were found to undergo Smiles rearrangement and cyclocondensation with sulphur monochloride to yield new hybrid 1,4-thiazine-1,2,3-dithiazolylium cations. The synthesized cations were readily reduced to the corresponding stable neutral radicals with spin densities delocalized over both 1,4-thiazinyl and 1,2,3-dithiazolyl moieties.

Azaphenothiazines - promising phenothiazine derivatives. An insight into nomenclature, synthesis, structure elucidation and biological properties

For the last two decades, classical phenothiazines have attracted attention of researchers, as the hitherto investigations have revealed many significant biological activities within this class of compounds, other than originally discovered neuroleptic ones. Important, new pharmaceutical results on phenothiazines, as 10-substituted dibenzothiazines, were recently highlighted in several reviews. Azaphenothiazines are structurally modified phenothiazines by substitution of one or both benzene rings in the phenothiazine ring system with the azine rings, such as: pyridine, pyridazine, pyrimidine, pyrazine, 1,2,4-triazine, quinoline, quinoxaline, benzoxazine and benzothiazine. They form over 50 different heterocyclic systems, of tri-, tetra-, penta- and hexacyclic structures, and contain from one to even four azine nitrogen atoms. This review summarizes the methodical knowledge on azaphenothiazines, referring to their nomenclature, synthesis, structure analysis and above all significant varied biological activities, examined in vitro and in vivo. It describes, in addition, current trends in the synthesis of azaphenothiazines. The influence of the azaphenothiazine ring system, the nature of the substituents, predominantly at the thiazine nitrogen atom, as well as at the azine nitrogen atom and carbon atom, on the biological activities, were also discussed.

Synthesis and biological evaluation of novel propargylquinobenzothiazines and their derivatives as potential antiproliferative, anti-inflammatory, and anticancer agents

Azaphenothiazines containing the quinoline ring, 8-10-substituted 6H-quinobenzothiazines and 6H-diquinothiazine were transformed into new 6-propargyl and 6-dialkylaminobutynyl derivatives containing the triple bond. Most of them displayed strong antiproliferative actions against human peripheral blood mononuclear cells (PBMC) stimulated with phytohemagglutinin A (PHA), strongly suppressed lipopolysaccharide (LPS)-induced TNF-α production by whole blood human cell cultures, and exhibited low cytotoxicity. Three propargylquinobenzothiazines with the bromine, trifluoromethyl, and methylthio groups at position 9 and propargyldiquinothiazine exhibited comparable actions to cisplatin against the L-1210 and SW-948 tumor lines. 6-Propargyl-9-trifluoromethylquinobenzothiazine was shown to block caspase 3 expression and inhibit expression of caspase 8 and 9 in Jurkat cells indicating its possible mechanism of action. These derivatives could be promising, potential therapeutics for treatment of neoplastic diseases and autoimmune disorders.