ChemInform Abstract: A Novel Synthesis of the Lichen Depsidones Divaronic Acid and Stenosporonic Acid, and the Biosynthetic Implications.

Abstract

345ChemInform Abstract The title compounds (Va) (divaronic acid) and (Vb) (stenosporonic acid) are shown to cooccur with colensoic acid, atranorin, and chloroatranorin in the lichen Paraparmelia mongaensis. A novel biomimetic-type approach to (Va) and (Vb) starts with the readily accessible educts (I) and (II) and involves a Smiles rearrangement of the depside esters (III) to the ethers (IVa), (IVb) as the key step. This rearrangement has important biosynthetic implications and may account for the natural occurrence of isostructural depside-depsidone pairs. Smiles rearrangements of unactivated meta-depsides are reported as model reactions.