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.