Construction of the Tetracyclic Skeleton of Polycyclic Norcembranoids Sinudenoids B–D Via Ireland-Claisen Rearrangement

Sinudenoids B–D represent a biologically significant
and
structurally intricate family of natural products distinguished by
their unique [5–5–6–6] tetracyclic skeleton.
Herein, we present an efficient strategy for the asymmetric synthesis
of their [5–5–6–6] tetracyclic framework. Key
features of our approach include a convergent synthetic strategy driven
by esterification, a pivotal Ireland-Claisen rearrangement to construct
a C11–C12 bond, followed by efficient lactonization and isomerization,
and a ring-closing metathesis to complete the [5–5–6–6]
tetracyclic skeleton.