Abstract: The invention is concerned with aromatase inhibiting compounds of formula I ##STR1## wherein R and Ro represent hydrogen or lower alkyl; or R and Ro located on adjacent carbon atoms and together when combined with the benzene ring to which they are attached form a naphthalene or tetrahydronaphthalene ring; R.sub.1 and R.sub.2 independently represent hydrogen, lower alkyl, (lower alkyl, aryl or aryl-lower alkyl)-thio, lower alkenyl, aryl, aryl-lower alkyl, C.sub.3 -C.sub.6 -cycloalkyl, or C.sub.3 -C.sub.6 -cycloalkyl-lower alkyl; or R.sub.1 and R.sub.2 combined represent lower alkylidene, mono- or di-aryl-lower alkylidene; R.sub.1 and R.sub.2 combined also represent C.sub.4 -C.sub.6 -straight chain alkylene, lower alkyl-substituted straight chain alkylene or ortho-phenylene bridged-C.sub.2 -C.sub.