Oxadiazole-substituted naphtho[2,3- b ]thiophene-4,9-diones as potent inhibitors of keratinocyte hyperproliferation. Structure−activity relationships of the tricyclic quinone skeleton and the oxadiazole substituent
3-b]thiophene-4,9-diones were synthesized in which the tricyclic quinone skeleton was systematically replaced with simpler moieties, such as structures with fewer rings and open-chain forms, while the oxadiazole ring was maintained. In addition, variants of the original 1,2,4-oxadiazole ring were explored. Overall, the complete three-ring quinone was essential for potent suppression of human keratinocyte