The structure of lividic acid. A depsidone from the lichen Parmelia formosana

Abstract

The depsidone, lividic acid [1'-carboxy-2',3-dihydroxy-4.methoxy-6-(2"-oxoheptyl)-6-pentyldepsidone](1) has been isolated from the lichen Parmelia formosana Zahlbr. The structure of this compound followed from a combination of spectroscopic properties and chemical interconversions. The overall substitution pattern of this depsidone was confirmed by methylation with excess diazomethane, whereupon methyl 3-methoxy-2',4,4'-tri-O-methylisophysodate was obtained. Further, lividic acid was synthesized from 3-hydroxyphysodic acid by methylation of the corresponding benzyl ester and subsequent hydrogenolysis.