Progress toward the Total Synthesis of Gukulenin A: Photochemically Triggered Two-Carbon Ring Expansion Key to α‑Tropolonic Ether Synthesis

The ex-chiral-pool synthesis of an advanced gukulenin A precursor from (−)-piperitone is revealed. Key C/C connecting maneuvers to the synthesis of a C₂ dissymmetric bis­(α-tropolonic) ether building block are a ring-contracting Meinwald rearrangement, a photochemically triggered two-carbon ring expansion, and a homodimerization by cross-metathesis.