Asymmetric Construction of the Core of C 6 , C 7 -Epoxy Daphnane Diterpenoid Orthoesters.

Asymmetric construction of the core of C 6 , C 7 -epoxy daphnane diterpenoid orthoesters is developed through a convergent synthetic strategy. The salient features include a diastereoselective nucleophilic assembly of two bulky cyclic fragments, an oxidative cleavage/transesterification/aldol cascade to fashion the seven-membered ring, and a base-mediated transesterification/retro-aldol/aldol/epoxidation cascade to install the epoxy moiety with proper stereochemistry.