Cycloaddition approaches to oxygen heterocycles applied to natural product synthesis

Diastereocontrol in the Synthesis of Models of Rings C and D of Phorbol: Directing Effect of an Ether Substituent on Lithium Carbenoid Mediated Cyclopropanation

“…The complex polycyclic structure of phorbol, together with an intense interest in structure–activity relationship studies to map the basis of the tumor‐promotion activity have fueled extensive efforts towards establishing efficient synthetic routes to phorbol ( 1 ) and its derivatives 7…”