Wikipedia
Pentagestrone
Pentagestrone ( INN), also known as progesterone 3-cyclopentyl enol ether, is a steroidal progestin of the 17α-hydroxyprogesterone group that was never marketed. It acts as a prodrug to 17α-hydroxyprogesterone. An acetate ester, pentagestrone acetate (Gestovis, Gestovister), has been marketed for clinical use.