Total Syntheses of Uncommon C₃₀ Terpenoids: Chamaecydin and Isochamaecydin

Abstract

(−)-Chamaecydin and (−)-isochamaecydin, two uncommon C30 terpenoids comprising abietane-type diterpenes and thujane-type monoterpenes, were achieved from β-pinene with (−)-sabinene in 18 and 20 steps, respectively. Key steps include a Claisen–Ireland rearrangement to establish the all-carbon quaternary center, a Rh catalyzed C–H bond insertion reaction to install a spiro-five-membered ring and a Lewis acid promoted cyclization of polyenes to construct the two six-membered rings.