Total Synthesis of Racemic Benzosceptrins via an Electrocyclization Cascade

Benzosceptrins are dimeric pyrrole-2-aminoimidazole alkaloids isolated from marine sponges of the genus <i>Agelas</i>, and they are characterized by the <i>C</i>₂ symmetric benzocyclobutane structure. Here, we report the total synthesis of (±)-benzosceptrins A, B, and C via sequential 8π and 6π electrocyclizations of nagelamide I and its structurally related analogues based on a Gibbs energy evaluation of the proposed biosynthetic pathway.