(±)-Ganoapplanin, a Pair of Polycyclic Meroterpenoid Enantiomers from Ganoderma applanatum

(+/-) Ganoapplanin (1), a pair of novel meroterpenoid enantiomers featuring an unprecedented dioxaspiro cyclic skeleton constructed from a 6/6/6/6 tetracyclic system and an unusual tricyclo-. [4.3.3.0(3',7')]dodecane motif, were isolated from Ganoderma applanatum. Its structure and absolute configurations were determined by spectroscopic analyses, X-ray crystallography, and ECD (electronic circular dichroism calculations). A plausible biogenetic pathway, involving a key Gomberg Bachmann reaction, was also proposed for (+/-)-1. Biological studies showed that (+/-)-1 and its enantiomers exhibited different inhibitory activities on T-type voltage-gated calcium channels.