Prostaglandins (PGs) exist in most mammalian tissues.'Isolation of PGs from natural biosynthetic sources cannot meet their medicinal demand. 2 Total synthesis thus remains the only means by which sufficient quantities of prostanoids can be made a~ ailable.~.~ Herein we report a novel biomimetic, cascade-type synthesis4 of various prostanoids via common 1 1 a, 9cr-epoxyimino-PGHs (ie, 25 and 27).