Synthesis of Complex Stereoheptads en Route to Daphnane Diterpene Orthoesters

Tricyclic cores of the daphnane diterpene orthoesters (DDOs) are synthesized in 10 steps from readily available materials. Key to their assembly is the development of a stereocontrolled p-quinol functionalization sequence which enables rapid access to DDO C-ring stereopolyads from simple precursors. Problems encountered in stereo- and regioselectivity are highlighted and solved by exact changes in choreography, although it is shown that the undesired stereochemical outcomes also proceed with high selectivity.