Synthesis of (−)-Chamobtusin A from (+)-Dehydroabietylamine

Chamobtusin A, a unique diterpene alkaloid isolated from Chamaecyparis obtusa cv. tetragon, is considered to be biosynthesized from an abietane diterpenoid. On the basis of this biosynthetic hypothesis, ferruginol (15) was synthesized from (+)-dehydroabietylamine and then biomimetically transformed into (−)-chamobtusin A in 6 steps (12 steps from (+)-dehydroabietylamine).