Synthesis of the Tetracyclic Spiro-naphthoquinone Chartspiroton.

Chartspiroton is a recently discovered naphthoquinone natural product that features a spiro-fused benzofuran lactone. We report its first synthesis via an 11-step linear sequence. The sterically hindered tetra- ortho -substituted biaryl subunit was installed by base-induced ring expansion of a readily available 1,3-indandione. This step also liberated the fully substituted naphthalene core unit at the same time. The unique spiro-fused benzofuran lactone of the natural product was constructed via late-stage oxidation of an advanced naphthoquinone.