Showing papers on "Xanthone published in 1971"

Extractives from Guttiferae. Part XIX. The isolation and structure of two benzophenones, six xanthones and two biflavonoids from the heartwood of Allanblackia floribunda Oliver

Abstract: Ten metabolites, hydrocotoin (2-hydroxy-4,6-dimethoxybenzophenone), 2,3′-dihydroxy-4,6-dimethoxybenzophenone, 1,3,5-trihydroxyxanthone, 4′,5′-dihydro-1,6,7-trihydroxy-4′,4′,5′-trimethylfurano(2′,3′ : 3,4)xanthone, volkensiflavone, morelloflavone; and from methylation of the crude extracts, 1,7-dimethoxyxanthone, 1-hydroxy-5-methoxyxanthone, 1-hydroxy-3,7-dimethoxy-2-(3,3-dimethylallyl)xanthone, and 1,3,6,7-tetramethoxyxanthone have been isolated from the heartwood of Allanblackia floribunda Oliver. The biogenetic significance of the co-occurrence of these compounds is discussed and syntheses of hydrocotoin, methylhydrocotoin, and 2,3′,4,6-tetramethoxybenzophenone are described.

Biogenesis of xanthones in Gentiana lutea

Abstract: Biogenetic studies indicate that gentisein and related xanthones are derived from a combination of both acetate and shikimate precursors, with the involvement of 2,3′,4,6-tetrahydroxybenzophenone in an oxidative coupling conversion into the xanthone.

The photosensitised decarboxylation of carboxylic acids by aromatic ketones

Abstract: Xanthone, fluorenone, 2-acetylnaphthalene, and acetophenone have been found to photosensitise the decarboxylation of acids of the type RX·CH2·CO2H (where X = O, S, or NH). Substituted hydrocarbons (RX·CH3) are formed in the reactions, and their yields are substantialy increased by the inclusion of benzenethiol in the reaction mixture.

Synthesis of sordidone and thiophanic acid, two chlorine-containing lichen metabolites

Abstract: Sordidone (IV) and thiophanic acid (XVI) are two metabolites isolated from the lichen Lecanora rupicola. Chlorination of 5,7-dihydroxy-2,6-dimethylchromone (III) with sulphuryl chloride gives sordidone. Condensation of dichloroeverninic acid (XIII) with phloroglucinol gave the xanthone (XIV), which by chlorination followed by demethylation, gave thiophanic acid (XVI).

Molecular polarisability. The conformations as solutes of 9,10-dihydroanthracene, anthrone, and xanthone

Abstract: Dipole moments and molar Kerr constants are reported for 9,10-dihydroanthracene, anthrone, and xanthone as solutes in non-polar media. The data are analysed to provide information on preferred solution-state conformations and on solute–benzene associations.

The photosensitised oxidation of amines. Part III. The use of xanthone, fluorenone, p-aminobenzophenone, and methyl β-naphthyl ketone as sensitisers

Abstract: Irradiation of oxygenated solutions of triethylamine, di-n-propylamine, and n-propylamine, containing xanthone, fluorenone, p-aminobenzophenone, and methyl β-naphthyl ketone, results in the amines being oxidised. The reactions are interpreted as occurring by initial hydrogen abstraction from the amine by the excited ketone, to give radicals of the amines which subsequently react with oxygen to give the observed products.

Extractives from Guttiferae. Part XXIII. An unambiguous synthesis of 6-deoxyjacareubin and related 3,3- and 1,1-dimethylallyl and annulated xanthones

Abstract: Unambiguous syntheses are described of 6-deoxyjacareubin (1) and ether derivatives of the related metabolite 1,3,5-trihydroxy-2-(3-methylbut-2-enyl)xanthone (4). In addition, related pyrano-, furo- and (3,3-, and 1,1-dimethylallyl)-xanthones derived from 1,3,5- and 1,3,7-trihydroxyxanthone have been prepared. The nuclear Over-hauser effect can differentiate a linear pyranoxanthone from its angular isomer.

Di(azidosulfonyl)xanthones

Abstract: Di(azidosulfonyl)xanthones are described of the formula: These compounds are prepared by reaction of the corresponding sulfonylhalides with sodium azide. The di(azidosulfonyl)xanthones are useful as cross-linking agents in photoresist systems, elastomers and the like. The sulfonylazido groups are sensitive to radiation particularly to ultraviolet light. This sensitivity is enhanced by the presence of the carbonyl groups of the xanthone, i.e., the compounds of the above formula have a built-in sensitizer.

Bis-basic esters and amides of xanthene and xanthone

Abstract: Novel bis-basic esters and amides of xanthene and xanthone of the formula WHEREIN: Z is oxygen or H2; each of R1 and R2 is hydrogen, (lower)alkyl of 1 to 6 carbon atoms, cycloalkyl of 3 to 6 ring carbon atoms, alkenyl of 3 to 6 carbon atoms having the vinyl unsaturation in other than the 1-position of the alkenyl group, or each set of R1 and R2 taken together with the nitrogen atom to which they are attached is pyrrolidino, piperidino, N(lower)alkylpiperazino, or morpholino; EACH A is alkylene of 2 to about 8 carbon atoms and separates its adjacent Y and amino nitrogen by an alkylene chain of at least 2 carbon atoms; and each Y is oxygen, or OR A PHARMACEUTICALLY ACCEPTABLE ACID ADDITION SALT THEREOF. These compounds can be used as pharmaceuticals for preventing or inhibiting a viral infection.

Water soluble khellin derivative

Abstract: The water-soluble khellin deriv. 1H, 3H-2-aza-4-methylene,5,8-dimethoxy-furo (2", 3", 6, 7)xanthone -2-spiro-1'-piperidinium chloride (I): permits parenteral application as spasmolytic and hypotensive. Obtd. by aminomethylation of khellin by reaction with piperidine and paraformaldehyde in benzene and nitrobenzene.