19-Oxygenated Derivatives of Androst-4-ene-6, 17-dione and Androst-5-ene-4, 17-dione as Catalytic Probes for the Active Site of Aromatase

Abstract

To gain insight into the binding manner of androst-4-ene-6, 17-dione (4) and its 5-en-4-one analog 9, good competitive inhibitors of aromatase, in the active site of the enzyme, their 19-oxygenated derivatives were evaluated as inhibitors of human placental aromatase. The 19-hydroxy steroids 6, 7, and 10 and the 19-oxo analogs 8 and 12 were much poorer competitive inhibitors than their corresponding parent 19-methyl steroids. Conversion of the 17-keto inhibitors, 4, 6, and 10 to the 17β-ols 5, 7, and 11, respectively, markedly decreased their affinity to the enzyme. The results suggest that steroids 4 and 9 would bind to the active site in a similar manner to that involved in the binding of the substrate androstenedione (1).