George H. Stout

Xanthones of the Gentianaceae—I : Frasera caroliniensis Walt.☆

Abstract The root of Frasera caroliniensis Walt. has been shown to contain 1-hydroxy-2,3,4,7-tetramethoxyanthone ( 1 ), 1-hydroxy-2,3,4,5-tetramethoxyxanthone ( 6 ), 1-hydroxy-2,3,7-trimethoxyxanthone ( 9 ), 1-hydroxy-2,3,5-trimethoxyxanthone ( 11 ), swerchirin ( 15 ), a swerchirin glycoside ( 16 ), 1,3-dihydroxy-4,5-dimethoxyxanthone ( 18 ), and a compound that yields 1,2,3,5,8-pentamethoxyxanthone ( 19 ) on methylation. The new xanthones have been synthesized by a general method from suitable benzophenone precursors by elimination of a OMe group under strongly basic conditions. This method has also been used to prepare 1,2,3,4,8-pentamethoxyxanthone and 1,3,4,8-tetramethoxyxanthone.Abstract The root of Frasera caroliniensis Walt. has been shown to contain 1-hydroxy-2,3,4,7-tetramethoxyanthone ( 1 ), 1-hydroxy-2,3,4,5-tetramethoxyxanthone ( 6 ), 1-hydroxy-2,3,7-trimethoxyxanthone ( 9 ), 1-hydroxy-2,3,5-trimethoxyxanthone ( 11 ), swerchirin ( 15 ), a swerchirin glycoside ( 16 ), 1,3-dihydroxy-4,5-dimethoxyxanthone ( 18 ), and a compound that yields 1,2,3,5,8-pentamethoxyxanthone ( 19 ) on methylation. The new xanthones have been synthesized by a general method from suitable benzophenone precursors by elimination of a OMe group under strongly basic conditions. This method has also been used to prepare 1,2,3,4,8-pentamethoxyxanthone and 1,3,4,8-tetramethoxyxanthone.

Xanthones of the Gentianaceae—II : Frasera albicaulis Dougl. ex Griesb.

Abstract The root of Frasera albicaulis Dougl. ex Griesb. has been shown to contain fifteen xanthones, ten of which are previously unreported in nature. These compounds have been identified spectroscopically and in most cases by comparison with synthetic samples. They are shown to be based on the 1,3,5- and 1,3,7-trioxyxanthone systems with added oxygen atoms at 2 and/or 4, and represent a number of methylation patterns including 1,3-dihydroxy, 1-hydroxy, 2-hydroxy, and totally methylated materials.

Celebixanthone : A combined chemical and crystallographic structure proof

Abstract Celebixanthone is shown by both chemical and crystallographic methods to be 3,4,8-trihydroxy-2-methoxy-1-(3-methyl-2-butenyl)-xanthone (VIIIa).

The structure and synthesis of xanthomicrol

Abstract Xanthomicrol is shown to be 5,4′-dihydroxy-6,7,8-trimethoxyflavone by a combination of physical and degradative methods. Its synthesis from pentamethoxybenzene is described.

The xanthones of a Halenia species

Abstract Extracts of a Colombian species of Halenia (Gentianaceae) yielded three xanthones, 1-hydroxy-2,3,4,7-tetramethoxy-, 1-hydroxy-2,3,4,5-tetramethoxy-, and 1-hydroxy-2,3,5-tetramethoxyxanthone, which have also been found to be the major xanthones of Frasera caroliniensis

The xanthones of macrocarpaea glabra

Abstract Extracts of both roots and stem of Macrocarpaea glabra (L.f.) Gilg (Gentianaceae) have been shown to yield 1-hydroxy-3,7-dimethoxyxanthone (I) and 8-hydroxy-1,2,6-trimethoxyxanthone (IIb).

Xanthones of the Gentianaceae—III : The crystal and molecular structure of 2-hydroxy-1,3,4,7-tetramethoxyxanthone

Abstract One of the xanthones isolated from Frasera albicaulis Dougl. ex Griesb. is shown to have the structure 2-hydroxy-1,3,4,7-tetramethoxyxanthone (1) by X-ray crystallographic analysis using the symbolic addition method.

Polygalaxanthone A : A revised structure

Abstract Polygalaxanthone A has been shown by synthesis to have the structure 1,2,3-trimethoxy-6,7-methylenedioxyxanthone ( 2a ) and not that originally proposed. The previous evidence for the structure is discussed, and the material is shown also to be identical with another xanthone previously isolated from Polygala macradenia .