A compound (particularly useful for inhibiting cancer) according to formula I:or a pharmaceutically acceptable salt thereof, wherein: x is 0 or 1 R1-R6 are each independently H, —CN, —NO2, —NO, —OH, halogen, hydroxyalkyl, carboxyl, substituted carboxyl, aminocarbonyl, alkoxy, carbonyl or substituted carbonyl R7 is H, alkyl, alkyl amino, aminoacyl, hydroxyacyl, heteroaryl, heterocycloalkyl, alkyl heteroaryl or alkyl heterocycloalkyl R8 is H or alkyl A is O or N and Ar is an aryl, substituted aryl, heteroaryl, or substituted heteroaryl, provided that if R7 is H then Ar is aryl substituted with alkyl amino.
