Computationally Guided Organometallic Chemistry:  Preparation of the Heptacyclic Pyrazine Core of Ritterazine N

Diels−Alder cycloaddition of 10 followed by Wittig homologation and intramolecular diene cyclozirconation of the resulting triene under equilibrating conditions led to the tricyclic 6−6−5 ketone 5 with high diastereocontrol. The derived α-azido ketone 16 cyclized efficiently to the heptacyclic pyrazine core of ritterazine N.