Synthesis and Biological Activity of New Thiopyrano[2,3-d]thiazoles Containing a Naphthoquinone Moiety

Novel 11-substituted 3,11-dihydro-2H-benzo[6,7]thiochromeno[2,3-d][1,3]-thiazole-2,5,10-triones 4a–i were synthesized in 75–90% yields via the hetero-Diels-Alder reaction of 5-arylidene-4-thioxo-2-thiazolidinones with 1,4-naphthoquinone. The synthesized compounds were evaluated for their antineoplastic and antimycobacterial activities. A moderate selectivity against melanoma cancer cells (GI(50) (UACC-257-melanoma) = 0.22 μM) was demonstrated for 4i, whereas derivatives 4a, 4c, 4g, and 4h showed promising antimycobacterial activity at a low toxicity level.