Graham J. Bennett

Xanthones from guttiferae

Abstract Since the last review in 1980, over eighty new xanthones have been isolated from the Guttiferae. These are listed with reference to structure elucidation and synthesis. The distribution of xanthones is examined in relation to the taxonomic divisions of the Guttiferae. Xanthone biosynthesis is discussed in the light of new biosynthetic results and the various pharmacological properties of xanthones are summarized.

Triterpenoids, tocotrienols and xanthones from the bark of Cratoxylum Cochinchinense

Abstract A novel bicyclic triterpenoid, polypoda-8(26),13,17,21-tetraen-3β-ol, as well as friedelin, three known tocotrienols, four known xanthones (mangostin, β-mangostin, garcinone D and tovophyllin A) and the previously unreported 2-geranyl-1,3,6-trihydroxy-4-(3,3-dimethylallyl)-xanthone and cratoxylone (1,3,6-trihydroxy-2-(3-hydroxy-3-methylbutyl)-7-methoxy-8-(3,3-dimethylallyl)-xanthone) have been isolated from the bark of Cratoxylum cochinchinense . The structures of the new compounds were determined using a combination of spectroscopic and chemical methods.

Minor xanthones from the bark of cratoxylum cochinchinense

Abstract Three new xanthone derivatives, 11-hydroxy-1-isomangostin, a xanthonolignoid (5′-demethoxycadensin G) and a bisxanthone, as well as the known compound 1,3,5,6-tetrahydroxyxanthone, were isolated from the bark of Cratoxylum cochinchinense. Their structures were elucidated mainly by a combination of high-field NMR spectroscopic techniques.

A dihydrochalcone from Lindera lucida

Abstract A new dihydrochalcone, 3′,5′-dihydroxy-2′,4′,6′-trimethoxydihydrochalcone and five known compounds, methyl linderone, 5-hydroxy-6,7,8-trimethoxyflavone (alnetin), 2′-hydroxy-3′,4′,5′,6′-tetramethoxydihydrochalcone (dihydrokanakugiol), 2′-hydroxy-3′,4′,5′,6′-tetramethoxychalcone (kanakugiol) and 2′,3′,4′,5′,6′-pentamethoxychalcone (pedicellin) were isolated from twigs of Lindera lucida. The structures of these compounds were determined by spectral analyses and chemical correlations.

Biosynthesis of mangostin. Part 1. The origin of the xanthone skeleton

The biosynthesis of mangostin (3) has been studied by wick-feeding of 14C- and 13C-labelled precursors to young Garcinia mangostana plants. Radioactive mangostin was isolated as 3,6-di-O-methylmangostin (4), which was subsequently degraded to phloroglucinol and isovaleric acid to aid location of the label. Although results from feeding of 14C-labelled precursors suggested two alternative malonate–shikimate routes to compound (3), experiments with 13C-labelled compounds clearly demonstrated that mangostin (3) originates from a C6C1 unit (benzoate) and three C2 units (malonates). [1,2,3-13C3]malonic acid was incorporated solely into ring A of compound (4) and two different arrangements of C2 units in compounds (17a and b) were evident, indicating that mangostin (3) derives via ring closure of a symmetrical intermediate (18).

The biosynthesis of mangostin: the origin of the xanthone skeleton

Cinnamic, benzoic, and m-hydroxybenzoic acids and benzophenone (1) are efficient precursors to mangostin (3).

Halenia elliptica xanthone: A structural revision

Abstract The 1,3,6,8-tetraoxygenated xanthone structure assigned to a compound from Halenia elliptica is incorrect. Based on published evidence, the xanthone appears to be 1-hydroxy-2,3,7-trimethoxyxanthone.

Geranyl anthraquinones from the bark of Ploiarium alternifolium

Abstract Two geranylated anthraquinones have been isolated from the bark of Ploiarium alternifolium. Their structures were elucidated by spectroscopic methods.

Oleanane benzoates from the bark of Ploiarium alternifolium

Abstract Two triterpenoid benzoates, 3β-benzoyloxyoleana-11,13(18)-dien-28-oic acid, characterized as its methyl ester, and 3β- benzoyloxyolean-11-en-13β,28-olide have been isolated from the bark of Ploiarium alternifolium . Their structures were determined by spectroscopic methods and by chemical correlation with known compounds.

Rearrangement of 1,3,5,8-tetraoxygenated xanthones in hot aqueous morpholine

Abstract Aqueous morpholine demethylation of 2-prenyl-1-hydroxy-3,5,8-trimethoxyxanthone leads to a mixture of 1,3,5,8- and 1,3,7,8-tetraoxygenated xanthones.