Cyanobenzyl heterocyclic aromatase-inhibiting compounds.

Compounds of the formula wherein R1 is H, CH3, OCH3, NO2, NH2, CN, CF3, CHF2, CH2F or halogen, R2 is a heterocyclyl radical selected from 1-imidazolyl, triazolyl, tetrazolyl, pyrazolyl, pyrimidinyl, oxazolyl, thiazolyl, isoxazolyl and isothiazolyl, R3 is H or OH, R4 is H, R5 is H or OH; or R4 is H and R3 and R5 combined form a bond; or R3 is H and R4 and R5 combined form =O; R6 is methylene, ethylene, -CHOH-, -CH2-CHOH-, -CHOH-CH2-, -CH=CH- or C(=O) or R4 is H and R5 and R6 combined is =CH- or =CH-CH2-; stereoisomers thereof and non-toxic pharmaceutically acceptable acid addition salts thereof exhibit selective aromatase inhibiting properties, compared with their desmolase inhibiting properties. The compounds of the invention are valuable in the treatment of estrogen dependent diseases, e.g. breast cancer or benign prostatic hyperplasia (BPH).