Indole Diterpene Synthetic Studies. Total Synthesis of (+)-Nodulisporic Acid F and Construction of the Heptacyclic Cores of (+)-Nodulisporic Acids A and B and (−)-Nodulisporic Acid D

A first-generation strategy for construction of (+)-nodulisporic acids A (1) and B (2) is described. The strategy entails union of the eastern and western hemisphere subtargets via the indole synthesis protocol developed in our laboratory. Subsequent elaboration of rings E and F, however, revealed the considerable acid instability of the C(24) hydroxyl, thereby preventing further advancement. Nonetheless, preparation of the heptacyclic core of (+)-nodulisporic acids A and B, the total synthesis of (+)-nodulisporic acid F, the simplest member of the nodulisporic acid family, and elaboration of the heptacyclic core of (−)-nodulisporic acid D were achieved.