The depsidone 2-methoxypsoromic acid (4-formyl-3-hydroxy-2,8-dimethoxy-1,9-
dimethyl-11-oxo-11H-dibenzo[b,e][1,4]dioxepin-6-carboxylic acid) (9) has be
en identified in several lichen species. The structure of compound (9) foll
owed from a combination of spectroscopic data.