Total Synthesis and Structural Revision of the Alkaloid Incargranine B

Seeing double: Consideration of the biosynthetic origins of incargranine B, which was originally assigned an unprecedented indolo[1.7]naphthyridine structure, led to the proposal of a dipyrroloquinoline framework as a more biosynthetically feasible structure (see scheme; Piv=pivaloyl). This hypothesis was validated by a short biomimetic synthesis of incargranine B.