Showing papers on "Xanthone published in 1990"

A New Synthesis of Xanthones. 2,4,7-Trichloronorlichexanthone and 4,5,7-Trichloronorlichexanthone, Two New Lichen Xanthones

Abstract: A new synthetic route to norlichexanthone (1,3,6-trihydroxy-8-methyl- 9H-xanthen-9-one) derivatives has been developed by using a Smiles rearrangement of an appropriately substituted depside in the key step. 2,4,7-Trichloronorlichexanthone (22) and 4,5,7- trichloronorlichexanthone (29) have been prepared by this method. The former xanthone (22) was shown to be a constituent of the lichens Lecanora sulphurata and L. flavo-pallescens and the latter (29) a constituent of Micarea austroternaria var. isabellina.

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

Abstract: 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).

Structure and Synthesis of the Lichen Xanthone Isoarthothelin (2,5,7-Trichloronorlichexanthone)

Abstract: The structure of isoarthothelin (2,5,7-trichloro-1,3,6-trihydroxy-8-methyl-9H-xanthen-9-one or 2,5,7-trichloronorlichexanthone)(2), a metabolite of an Australian Buellia species and Lecanora broccha, was confirmed by total synthesis. Previous reports of the natural occurrence of (2) refer for the most part to an isomeric compound.

5,7-Dichloro-3-O-methylnorliche-xanthone, a New Xanthone From the Lichen Lecanora broccha

Abstract: 5,7-Dichloro-1,6-dihydroxy-3-methoxy-8-methyl-9H-xanthen-9-one (7) (5,7-dichloro-3-O-methylnorlichexanthone) has been synthesized and shown to cooccur with 2,5,7-trichloro-3-O-methylnorlichexanthone (6) in the lichen Lecanora broccha.

A Synthesis of the Lichen Xanthone Thiomelin

Abstract: A total synthesis of thiomelin (2,4-dichloro-1,8-dihydroxy-5-methoxy-6-methyl-9H-xanthen-9-one) (1) has been achieved.

Xanthone 1,4-dihydropyridine derivatives with a potent selective bradycardic effect.

Abstract: A series of xanthone 1,4-dihydropyridine derivatives were prepared. The compounds were evaluated for inotropic, chronotropic and calcium antagonistic properties. The tested compounds are weak calcium antagonists but exert potent selective bradycardic effects.

Notizen: A New Pentaoxygenated Xanthone from the Fern Cystopteris fragilis

Abstract: A new pentaoxigenated xanthone has been isolated from aerial parts of the fern Cystopteris fragilis. By spectroscopic and chemical methods this compound has been shown to be 1,6-dihydroxy-3,5,7-trimethoxyxanthone which is of biosynthetic interest in ferns.

Aldose reductase inhibitor comprising xanthones as active ingredient

Abstract: PURPOSE: To obtain an aldose reductase inhibitor useful for treating various complicating diseases in diabetes, comprising a specific xanthone as an active ingredient. CONSTITUTION: An aldose reductase inhibitor comprising a xanthone shown by the formula (R 1 and R 6 are OH, methoxyl or acetoxyl; R 2 and R 4 are H or methoxyl; R 3 and R 5 are H, OH, methoxyl or acetoxyl) as an active ingredient. The compound shown by the formula is obtained by extracting dried root of Polygala tenuifolia Willd., dried root of Polygala senega Linnaeus, Polygala tenuifolia Willd., Polygala senega Linnaeus, original plant thereof (Hirohasenega, Polygala senega L., var latifolida Torr. et Gray) or a homolugous plant thereof having expectorative action, hemolytic action and antiulcer action with an organic solvent such as ethanol or water at room temperature to the boiling point of the solvent and then partitioning the extract with water and a water- insoluble solvent such as benzene or n-hexane. COPYRIGHT: (C)1992,JPO&Japio

Synthesis of 2-Hydroxyacetyl-7-acetylxanthone, a New Xanthone Derivative Endowed with Antianaphylactic, Analgesic, and Antiinflammatory Activities.

Abstract: 2-Hydroxyacetyl-7-acetylxanthone (V), a new xanthone derivative, was synthesized in four steps starting from xanthene, by two synthetic approaches. The new compound displayed antianaphylactic activity in the PCA test and in the anaphylaxis shock test in rats. It also displayed analgesic activity in the writhing test in mice, and antiinflammatory activity in the carrageenin edema test in rats. The activity of the new compound has been tentatively interpreted on the basis of its chemical and structural analogy with known drugs.

A new pentaoxygenated xanthone from the fern cystopteris fragilis

Abstract: Pharmacological activity (e.g. antipsychotic ac­ tion [1]) and chemotaxonomic interest of xanthones may explain the increasing interest in these substances in recent years. It has been suggested [2] that Cystopteris fragilis complex is the most inter­ esting biosystematic problem in ferns. Xanthone analysis may be of interest in the study of relation­ ships of the taxa of this complex since previous work on the xanthones and flavonoids of Appala­ chian Asplenium complex [3] and Asplenium adiantum-nigrum complex [4] has shown that these two groups of ferns provide a classic example of addi­ tive inheritance of chemical characters. Earlier work on the chemical constituents of Cystopteris fragilis has led to the identification of two C-glycosylxanthones (mangiferin and isomangiferin) [5] and four flavonoids based on kaempferol (the 3-O-glucoside, the 3,4'-bis-glucoside, the 3-0-(3\"-sulphate)glucoside and the 3-0(6\"-sulphate)glucoside [6], In the present work a pentaoxygenated xanthone has been found for the first time in ferns and it has been shown that this compound (isolated from Cystopteris fragilis Bernh) is l,6-dihydroxy-3,5,7-trimethoxyxanthone (1) which is a new natural product o f biosynthetic interest in ferns.