Total synthesis of spiro Ganoderma meroterpenoids spiroapplanatumines B, D, F, and H

The first total synthesis of spiroapplanatumines B (2), D (4), F (6), and H (8) as well as the possibly undiscovered natural product spiroapplanatumine R (10) has been realized in a linear sequence of 15-20 steps. The unusual [6-5-7] tricyclic core including a [5-7] spirocyclic system, found in the title molecules and some other naturally occurring spiro Ganoderma meroterpenoids, was efficiently synthesized through a Claisen rearrangement followed by an RCM reaction. The Pd-catalyzed methoxycarbonylation/regioselective epoxide opening cascade reaction efficiently installed the desired ester moiety at C3 ' and produced an allylic hydroxy group at C7 '. Further functional group transformations enabled the divergent synthesis of the final products.