Synthesis of Further Lichen Depsides

Abstract

The unambiguous total synthesis of 18 lichen depsides has been achieved by the condensation of an appropriately substituted orsellinic acid and protected phenol in the key step, followed by subsequent deprotection and/or secondary reduction. The natural occurrence of the first meta-depside involving substitution at the 5𔉮-position of the B-ring has been confirmed. The intermediacy of such compounds has previously been invoked to account for the probable biosynthetic interconversion of orcinol para-depsides to depsidones.