A new regiospecific synthesis of 1,4-dihydroxyxanthones

Abstract

Several methyl salicylates have been found to substitute halogenated benzoquinones regiospecifically in the presence of anhydrous potassium fluoride. The resultant phenoxybenzoquinones were reduced and cyclized to highly functionalized xanthones of unambiguous structure. A number of natural substances, including three which had not been obtained previously by synthesis, were prepared by application of this method, which also established that the structure proposed earlier for the naturally occurring product ‘1,4-dihydroxy-2,3,7-trimethoxyxanthone’ is indeed incorrect.