Carbocation rearrangements in aspernomine biosynthesis

Quantum chemical calculations (B3LYP/6-31G(d)) on carbocation rearrangements that are proposed to occur in the biosynthesis of aspernomine are described. Based on these calculations, a pathway involving a concerted but asynchronous [4+2] cycloaddition that avoids the formation of a secondary carbocation is proposed for small model systems.