3.5. Fusicoccane
In recent years, Zhang’s group has reported a serious of fusicoccane diterpenoids with unexpected carbon skeleton from the genusAlternaria and Talaromyces . Alterbrassicene A (97 ),[118] a fusicoccane diterpenoid bearing an unprecedented 5/9/4-fused carbocyclic skeleton, has been characterized from Alternaria brassicicola . 97 is the first fusicoccane derivative acting as a potent IKKβ inhibitor in the NF-κ B signaling pathway. Alterbrassicicene A (98 ),[119] a fusicoccane diterpenoid with a degradatived framework, has been also obtained from A. brassicicola . 98 reprents the first fusicoccane-derived diterpenoid functioning as a potent PPAR-γ agonist (EC50 = 744.1 nM). A plausible biosynthetic pathway for98 has been proposed and involved in a series of cyclizations and rearrangement by the function of enzymes (Fig. 15). Alterbrassinoids A−D (99102 ),[120] the first examples of fusicoccane dimers furnished by forming an undescribed C-12−C-18′ bond, have been isolated from the same fungus. Talaronoids A–D (103106 ), four diterpenoids with an unexpected tricyclic 5/8/6 carbon skeleton, have been isolated fromTalaromyces stipitatus . Talaromynoid A (107 ),[121] the first fusicoccane diterpenoid bearing an unexpected 5/7/5 tricyclic ring system, have been obtained from the endophytic fungus Talaromyces sp. DC-26.
Fig. 15. Proposed biosynthetic pathway for 98 .