3-Hydroxyphysodic acid. Chemical corroboration of the structure of this lichen depsidone

Abstract

The published structure of the lichen depsidone ?physodol? has been shown to be incorrect. This compound is in fact identical with 3- hydroxyphysodic acid (2) (1?-carboxy-2?,3,4-trihydroxy-6-(2?- oxoheptyl)-6?-pentyldepsidone).     Chemical evidence is presented to confirm the isocoumarin structure (10) for that of the key decarboxy anhydro derivative obtained by degradation of 3-hydroxyphysodic acid, and thus to disprove the alternative 5-hydroxy formulation suggested for this compound.