Synthesis of regioisomeric 17β-N-phenylpyrazolyl steroid derivatives and their inhibitory effect on 17α-hydroxylase/C17,20-lyase

The reaction of 3β-hydroxy-21-hydroxymethylidenepregn-5-en-3β-ol-20-one (1) with phenylhydrazine (2a) affords two regioisomers, 17β-(1-phenyl-3-pyrazolyl)androst-3-en-3β-ol (5a) and 17β-(1-phenyl-5-pyrazolyl)androst-5-en-3β-ol (6a). The direction of the ring-closure reactions of 1 with p-substituted phenylhydrazines (2b–e) depends strongly on the electronic features of the substituents. Oppenauer oxidation of 3β-hydroxy-17β-exo-heterocyclic steroids 5a–e and 6a–e yielded the corresponding Δ4-3-ketosteroids 9a–e and 10a–e. The inhibitory effects (IC50) of these compounds on rat testicular C17,20-lyase were investigated by means of an in vitro radioligand incubation technique.