Structure and synthesis of some lichen xanthones

Abstract

The xanthones 1-hydroxy-3,6-dimethoxy-(2), 2,4-dichloro-1,3-dihydroxy- 6-methoxy-(6), 2-chloro-1,3-dihydroxy-6-methoxy- (7), 4-chloro-1,3- dihydroxy-6-methoxy- (8) and 2-chloro-1-hydroxy-3,6-dimethoxy-8-methyl-9H-xanthen-9-one (11) were isolated from the lichen Pertusaria sulphurata Mull. Arg. The unambiguous synthesis of compounds (6), (7), (8), (11) and some other chloroxanthones, and the chlorination of 1,3- dihydroxy-6-methoxy-8-methyl-9H-xanthen-9-one (5), are described.