Naturally occurring 1,2,8-trimethoxyxanthone and biphenyl ether intermediates leading to 1,2-dimethoxyxanthone

In order to study structure-activity relationships, a series of mono-, di- and trioxygenated xanthones has been synthesized and the structures of methyl 2-(3,4-dimethoxyphenoxy)benzoate, C(16)H(16)O(5), 2-(3,4-dimethoxyphenoxy)benzoic acid, C(15)H(14)O(5), 1,2-dimethoxy-9H-xanthen-9-one, C(15)H(12)O(4), and 1,2,8-trimethoxy-9H-xanthen-9-one, C(16)H(14)O(5), have been determined. The first two compounds both assume skew conformations, the dihedral angles between the two phenyl rings being 80.04 (8) and 83.0 (1) degrees, respectively. The latter two compounds are essentially planar and their methoxy substituents assume orientations consistent with minimum steric interactions.