An efficient ligand-free ferric chloride catalyzed synthesis of annulated 1,4-thiazine-3-one derivatives

Anti-lung Cancer Activity of Synthesized Substituted 1,4-Benzothiazines: An Insight from Molecular Docking and Experimental Studies

BACKGROUND

Thiazine, a 6-membered distinctive heterocyclic motif with sulfur and nitrogen atoms, is one of the heterocyclic compounds that functions as a core scaffold in a number of medicinally significant molecules. Small thiazine-based compounds may operate simultaneously on numerous therapeutic targets and by employing a variety of methods to halt the development, proliferation, and vasculature of cancer cells. We have, herein, reported a series of substituted 1,4 benzothiazines as potential anticancer agents for the treatment of lung cancer.

METHODS

In order to synthesize 2,3-disubstituted-1,4 benzothiazines in good yield, a facile green approach for the oxidative cycloaddition of 2-amino benzenethiol and 1,3-dicarbonyls employing a catalytic amount of ceric ammonium nitrate has been devised. All the molecules have been characterized by spectral analysis and tested for anticancer activity against the A-549 lung cancer cell line using various functional assays. Further in silico screening of compound 3c against six crucial inflammatory molecular targets, such as Il1-α (PDB ID: 5UC6), Il1- β (PDB ID: 6Y8I), Il6 (PDB ID: 1P9M), vimentin (PDB ID: 3TRT), COX-2 (PDB ID: 5KIR), Il8 (PDB ID: 5D14), and TNF-α (PDB ID: 2AZ5), was done using AutoDock tool.

RESULTS

Among the synthesized compounds, propyl 3-methyl-3,4-dihydro-2H-benzo[b][1,4]thiazine-2- carboxylate (3c) was found to be most active based on cell viability assays using A-549 lung cancer cell line and was found to effectively downregulate various pro-inflammatory genes, like Il1-α, Il1-β, Il6, vimentin, COX-2, Il8, and TNF-α in vitro. The ability of the molecule to effectively suppress the proliferation and migration of lung cancer cells in vitro has been further demonstrated by the colony formation unit assay and wound healing assay. Molecular docking analysis showed the maximal binding affinity (- 7.54 kcal/mol) to be exhibited by compound 3c against IL8.

CONCLUSION

A green unconventional route for the synthesis of 2,3-disubstituted-1,4 benzothiazines has been developed. All the molecules were screened for their activity against lung cancer and the data suggested that the presence of an additional unbranched alkyl group attached to the thiazine ring increased their activity. Also, in vitro and in silico modeling confirmed the anti-cancer efficiency of compound 3c, encouraging the exploration of such small molecules against cancer.

Tunable Synthesis of Disulfide-Functionalized Enaminones and 1,4-Thiazines via the Reactions of Enaminones and β-Aminoethanethiol

The reactions of β-aminoethanethiol with N,N-dimethyl enaminones are performed to selectively provide disulfide-functionalized enaminones and 1,4-thiazines. By performing the reaction in water and catalyst-free conditions, the transamination and oxidative S-S coupling between the two substrates take place to give disulfide-functionalized enaminones. On the other hand, by using identical starting materials, the employment of the CuI catalyst in dimethyl sulfoxide enables the selective generation of 1,4-thiazines via tandem transamination and C(sp2)-H bond thiolation.

Fe-promoted oxidative cyclization of α-benzoylthioformanilides for the synthesis of 2-benzoylbenzothiazoles

This protocol has the advantages of short reaction times, moderate to good yields, convenient manipulation, and high selectivities.