Novel retinoidal tropolone derivatives. Bioisosteric relationship of tropolone ring with benzoic acid moiety in retinoid structure

Several tropolone derivatives (4-7) were designed as novel retinoids on the assumption that the tropolone ring may mimic the benzoic acid moiety in retinoid structures, such as Am80 (2). Among the synthesized compounds, 5-[2-(5,6,7,8-tetrahydro-5,5,8,8-tetramethyl-2-naphthyl)ethynyl]tropolone (7a) showed moderate potency as a differentiation-inducer of HL-60 cells. The activities of the tropolones were greatly enhanced in the presence of HX630, an RXR agonist (retinoid synergist).