Lusitanic Acid, Peristictic Acid and Verrucigeric Acid. Three New β-Orcinol Depsidones from the Lichens Relicina sydneyensis and Xanthoparmelia verrucigera

Abstract

Three new β-orcinol depsidones belonging to the stictic acid chemosyndrome, namely peristictic acid (1,4-dihydroxy-10-methoxy-5,8-dimethyl-3,7-dioxo-1,3-dihydro-7H-isobenzofuro[4,5-b][1,4]benzodioxepin-11-carboxylic acid) (9), lusitanic acid (methyl 1,4-dihydroxy-10-methoxy-5,8-dimethyl-3,7-dioxo-1,3-dihydro-7H-isobenzofuro[4,5-b][1,4]benzodioxepin-11-carboxylate) (10) and verrucigeric acid (1,4-dihydroxy-11-hydroxymethyl-10-methoxy-5,8-dimethyl-3,7-dioxo-1,3-dihydro-7H-isobenzofuro[4,5-b][1,4]benzodioxepin-1,11-diyl hydrogen orthoacetate) (14) have been identified in the lichens Relicina sydneyensis and Xanthoparmelia verrucigera respectively. The structure of the new depsidones followed from a combination of partial syntheses, chromatographic comparisons and spectroscopic data.