Synthesis of D-ring-substituted (5′R)- and (5′S)-17β-pyrazolinylandrostene epimers and comparison of their potential anticancer activities

► Steroidal 17β-pyrazolines were prepared from 21-benzalpregnenolone derivatives. ► The reaction afforded a mixture of 5′R and 5′S pyrazolinylandrostene epimers. ► The structures of epimers were determinated by NMR analysis. ► The two epimeric series possess different antiproliferative activity. Various steroidal benzylidenes were synthetized from pregnenolone with benzaldehyde and p-substituted benzaldehydes. The resulting 17β-chalconyl derivatives of pregnenolone were reacted with hydrazine hydrate in acetic acid solution. Regardless of the starting material, the ring-closure reaction afforded (in contrast with the literature data) a mixture of two steroidal pyrazoline epimers. The epimers were critical isomer pairs, which could be separated only in their acetylated form; their structures were investigated by NMR techniques. The in vitro inhibition of rat testicular C17,20-lyase activity and the antiproliferative effects on four human cancer cell lines were measured, and the results obtained from the two epimer series were compared.