A method of inhibiting cell proliferation or differentiation by exposing a cell to a compound of the formula ##STR1## or a pharmaceutically acceptable salt thereof. Q is selected from the group consisting of NH and S, n is 0 or 1; and R.sub.1-9 are independently selected from the group consisting of halo, trihalomethyl, alkyl, nitro, hydroxy, alkoxy, sulphoxy, sulphonyl, amide, sulfonamide, carboxamide, amino, and hydrogen. Also provided is a compound of the structure ##STR2##