Hiok-Huang Lee

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.

Triterpenoid and other constituents from Sandoricum indicum

Abstract Bryononic and bryonolic acids, mesoinositol and mucic acid were identified in the fruits of Sandoricum indicum .

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).

1,3,6-Trihydroxy-7-methoxy-8-(3,7-dimethyl-2,6-octadienyl)xanthone from Garcinia cowa

Abstract 1,3,6-Trihydroxy-7-methoxy-8-(3,7-dimethyl-2,6-octadienylxanthone has been isolated from the stems of Garcinia cowa .

Constituents of Elephantopus scaber (compositae)

Abstract Elephantopus scaber has been found to contain epifriedelinol, lupeol, stigmasterol, potassium chloride, and a mixture of triacontan-1-ol and dotriacontan-1-ol.

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.

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.

13C NMR Chemical Shifts and CH Coupling Constants of Substituted 4-Ylidenebutenolides

Abstract The 13C chemical shifts and CH coupling constants for 6 substituted 4-ylidenebutenolides are reported. The CH coupling constants are useful in helping to determine the stereochemistry of the substituted exocyclic double bond.

Synthesis of lucidones

Reaction of 2-cinnamoyl-3-hydroxy-5-methoxy-1,4-benzoquinone (10) with acetic anhydride-dimethyl sulphoxide yielded (E)-4-(cinnamoylmethylene)-2-methoxybut-2-en-4-olide (4). Assignment of configuration of the exocyclic double bond in (4) is based on comparison of 1H n.m.r. shift data and 3J(C-3,5-H) value with those of 4-ylidenebutenolides (11)–(13).In the presence of sodium methoxide, (4) undergoes ready rearrangement affording lucidone (1a) and hence methyl-lucidone (1b).