Biomimetic Skeleton Conversion from Tiglianes into Three <i>Euphorbia</i> Diterpenoid Skeletons via Regioselective Cyclopropane Ring-Opening

Structurally complex <i>Euphorbia</i> diterpenoids represent a synthetic challenge. Here, we report a divergent strategy that biomimetically converts abundant tiglianes into three <i>Euphorbia</i> skeletons via regioselective cyclopropane ring-opening. The high utility of this approach was demonstrated in the semisynthesis of two rhamnofolane-type natural products, langduin A (<b>4</b>) and fischerianin A (<b>5</b>), via a single transformation. This work provides not only rapid access to these diverse diterpenoid frameworks but also chemical evidence of their potential biosynthetic relationship.