Four New β-Orcinol <i>meta</i> -Depsides from <i>Pertusaria</i> and <i>Siphula</i> 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.