The Structure of Chalybaeizanic Acid and Quaesitic Acid, Two New Lichen Depsidones Related to Salazinic Acid

Abstract

The depsidones chalybaeizanic acid (1,4,10-trihydroxy-8-methyl-3,7-dioxo-1,3-dihydro-7 H-isobenzofuro- [4,5-b][1,4]benzodioxepin-5,11-dicarbaldehyde) (4) and quaesitic acid (11-formyl-1,4,10-trihydroxy-8- methyl-3,7-dioxo-1,3-dihydro-7 H-isobenzofuro[4,5-b][1,4]benzodioxepin-5-methyl hydrogen fumarate) (5) have been isolated from the lichens Xanthoparmelia amphixanthoides and Hypotrachyna quaesita respectively, and their structures determined by a combination of spectroscopic evidence, partial synthesis, derivatization or degradation reactions.