Au-Catalyzed 1,3 Acyloxy Migration/Cyclization Cascade: A Direct Strategy toward the Synthesis of Functionalized Abietane-Type Diterpenes

A direct strategy toward the synthesis of functionalized abietane-type diterpenes and related polycyclic molecules was developed through an Au-catalyzed 1,3-acyloxy migration/cyclization/electrophilic aromatic substitution cascade. Unlike the known polyene-type cyclization strategies for the construction of abietane-type diterpene skeletons, propargylic ester groups were used for the cyclization process, which can readily lead to the key skeleton with C2 and C3 functionalization. As a demonstration of the potential application of this tandem reaction, a collective total synthesis of (+/-)-2-ketoferruginol, (+/-)-fleuryinol B, (+/-)-salviol, (+)-2 beta-acetoxyferruginol, and (+/-)-2 beta-acetoxysugiyl methyl ether was achieved. Among these molecules, (+/-)-fleuryinol B and (+/-)-2 beta-acetoxyferruginol were synthesized for the first time.