Novel Entry into 5-Decarboxydibenzofurans via Smiles Rearrangement of the Lichen Para-Depside, Erythrin

Erythrin, isolated in 7.3% yield from the lichen Roccella montagnei, was converted via a Smiles rearrangement to a series of diphenyl ethers. Those with a free carboxylic acid at C-1 underwent a novel decarboxylative oxidative cyclisation in the presence of Pd(OAc)2 to produce 5-decarboxydibenzofurans. All compounds were assayed for their antioxidant and ?-glucuronidase enzyme inhibitory activity.