Concise synthesis of carbazole-1,4-quinones and evaluation of their antiproliferative activity against HCT-116 and HL-60 cells.

We report a convenient synthesis of carbazole-1,4-quinone alkaloid koeniginequinones A and B using a tandem ring-closing metathesis with the dehydrogenation reaction sequence under an O2 atmosphere as an important step. Using this method, carbazole-1,4-quinones substituted at the 5-, 6-, 7-, and/or 8-positions have been synthesized. Moreover, 24 compounds, including koeniginequinones A and B, have been evaluated for their antiproliferative activity against HCT-116 and HL-60 cells, and the 6-nitro analog exhibited the most potent activity against both tumor cell types.