Four new ß-orcinol meta-depsides from Pertusaria and Siphula lichens

The new depsides decarboxyhypothamnolic acid [3-(2′,4′-dihydroxy-3′,6′-dimethylphenyloxycarbonyl)-2- hydroxy-6-methoxy-4-methylbenzoic acid] (4) and cryptothamnolic acid [3-(3′-formyl-2′-hydroxy-4′-methoxy6′-methylbenzoyloxy)- 4,6-dihydroxy-2,5-dimethylbenzoic acid] (6) have been detected in extracts of a Chinese Pertusaria species together with hypothamnolic acid (3) and their structures implied by means of Chromatographic and spectroscopic comparisons with synthetic materials. Two further new depsides, neothamnolic acid [3-(5′,7′-dihydrdxy-6′-methyl-1′-oxo-1′,3′- dihydroisobenzofuran-4′-yloxycarbonyl)-2-hydroxy-6-methoxy-4-methylbenzoic acid] (8) and lactothamnolic acid [3-(6′-formyl-5′,7′-dihydroxy-1′-oxo-1′,3′- dihydroisobenzofuran-4′-yloxycarbonyl)-2-hydroxy-6-methoxy-4-methylbenzoic acid] (9), have been isolated from the lichen Siphula ramalinoides, and the structure of these compounds followed from a combination of spectroscopic data, derivatization and degradation experiments.