An intramolecular Heck reaction (<
B>90
91)serves as the key step in the total synthesis of thetitledcompounds. The synthetic route is
based on utilizing theWieland-Miescher ketone (
5) as a matrix to providetheC and D rings of the targets and to provide functionality implementsfor joining this sector to an A ring precursor(
6). Catalytically induced enantiotopic control andearly emplacement of the oxetane are other features of theroute.