Synthesis and antitumor activity of heteroatom-substituted azulenes derivatives of 1,2-benzothiazine

Using methylated pyrroloxicam as a starting material and following the principles of drug design such as bioisosterism and active site binding, we designed and synthesized ten structurally novel target compounds, whose structures were characterized by ¹H NMR and MS analysis. The in vitro antitumor activity of these title compounds was evaluated by measuring their inhibitory activity against pancreatic cancer cells Capan-1, leukemia cells L1210, and human liver cancer cells SMMC-7721. The results showed that compound 6f (IC₅₀=4.8±0.5 μmol/L) exhibited good inhibitory activity against Capan-1 pancreatic cancer cells, that compound 6b (IC₅₀=2.6±0.3 μmol/L) showed good inhibitory activity against L1210 leukemia cells, and that compound 6c (IC₅₀=2.1±0.2 μmol/L) displayed good inhibitory activity against SMMC-7721 human liver cancer cells. These preliminary results from the antitumor activity experiments suggest that the introduction of benzothiazine derivatives plays a certain role in enhancing the antitumor activity of this class of compounds.