Concise synthesis of spirocyclic, bridged γ-butyrolactones via stereospecific, dyotropic Rearrangements of β-lactones involving 1,2-acyl and δ-lactone migrations

Dyotropic processes involving unprecedented 1,2-acyl migrations provide access to novel spirocyclic, bridged keto-y-lactones from a series of fused, tricyclic-beta-lactones, available via biscyclization of ketoacids including a new asymmetric variant. In addition, a spirocyclic bis-y-lactone was generated via a dyotropic process involving a 1,2-beta-lactone/delta-lactone interchange. Overall, this sequence provides a simple, two-step process for conversion of diketoacids to complex spiro[5.n]alkanes bearing a contiguous tertiary carbon center, a quaternary carbon center, and a tertiary alcohol in the form of a bridging y-lactone.