Chemistry of Australian Lichens. II. A New Depsidone from Parmelia conspersa (Ehrh.) Ach

Abstract

A new compound, norlobaridone, from Parmelia conspersa is shown to have structure Ia by conversion of its monomethyl ether (lobaridone (Ib)) into lobariol (IIb). The depsidone ring is readily cleaved by basic reagents to give products containing a new cyclic system and including an isomeric γ-enol lactone (IIIa), norlobariol (IIa), and the oxime anhydride (IVa) of the latter. Ultraviolet and infra-red spectra support structural assignments. Norlobaridone (Ia) presents an exception to the acetate theory of biogenesis in the position of its ketonic oxygen atom.