One-Pot Synthesis of Benzopyran-4-ones with Cancer Preventive and Therapeutic Potential

A one-pot synthesis of novel benzopyran-4-ones is described. In a tandem reaction, organobase-catalysed Michael addition of R¹COCH₂COR² on chromone-3-carboxylic acid led to decarboxylation and pyran-4-one ring opening of the latter. This was followed by chromone-and/or chromanone ring closure of the resulting Michael adducts when R¹ is an ortho-hydroxyaryl group. Antioxidant testing of 14 derivatives identified strong antiradical properties of chromanones 3o-r (2.1-3.1 μmol Trolox equiv./μmol compound in the DPPH assay). Chromanones 3p and 3r and 2-styrylchromone 3k were also most potent in inducing the cytoprotective Keap1-Nrf2 signalling pathway in a reporter gene assay (fivefold induction at concentrations <3 μM). Of the seven compounds evaluated for antiproliferative activities, 3k and 3r were the most active, inhibiting leukaemia K562 cell proliferation by 50 % after 72 h at concentrations of 4.5 and 7.9 μM, whereas normal peripheral blood mononuclear cells were not affected. Chromanones 3p and 3r and 2-styrylchromones 3k potently activate the Nrf2 response in the AREc32 cell line at low micromolar concentrations (C5 <3 μM). Compounds 3k and 3r are also the most active in inhibiting cell proliferation by 50 % after 72 h incubation at concentrations of 4.5 and 7.7 μM, whereas normal peripheral blood mononuclear cells were not affected.