Four New β-Orcinol meta-Depsides from Pertusaria and Siphula Lichens

Abstract

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′-methoxy- 6′-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′- dihydroxy-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′-dihydroisobenzo- furan-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.