Skeletal Rearrangements of Polycyclic α-Ketols

It has been proposed that prekinamycin and kinobscurinone may biogenetically isomerize to isoprekinamycin and prefluostatin, respectively, through the corresponding bridgehead α-ketol intermediates. In this transformation, the 6–5 ring system is converted into a 5–6 ring system via an α-ketol rearrangement. In this report, the skeletal rearrangement of polycyclic α-ketols inspired by this hypothetical biosynthetic transformation is reported. In addition, an unexpected rearrangement from dibenzo[b]fluorene to benzo[g]chromene is also reported.