Synthesis, spectroscopic characterization, and anticancer activity of new 10-substituted 1,6-diazaphenothiazines

New phenothiazine derivatives as 10-substituted dipyridothiazines of the 1,6-diazaphenothiazine structure were obtained in the cyclization reaction of 3-amino-3′-nitro-2,2′-dipyridinyl sulfide and 3,3′-dinitro-2,2′-dipyridinyl disulfide, and in the reaction of 2-chloro-3-ntropyridine with sodium 3-amino-2-pyridinethiolate followed by various alkylation and arylation reactions. The reaction of the thiazine ring formation ran via the Smiles rearrangement of the S-N type. As the alkylation reactions could proceed at the thiazine, azine or both nitrogen atoms, the product structure elucidation was based on the 2D NMR (Rotating-frame Overhauser Effect Spectroscopy, Correlated Spectroscopy, Heteronuclear Single Quantum Coherence, and Heteronuclear Multiple Bond Correlation) spectra of the N-methylated product. Some 10-substituted 1,6-diazaphenothizines (5, 10, 12, 13) were at least anticancer active against melanoma C-32 and breast cancer MCF-7 cell lines as a reference drug – cisplatin. The monoazaphenothiazine drug, prothipendyl, turned out to be less active than least 6 derivatives of the 1,6-diazaphenothiazine structure.