Showing papers on "Xanthone published in 1979"

Pharmacologically active sulfoximides: 5-hexyl-7-)S-methylsulfonimidoly) xanthone-2-carboxylic acid, a potent antiallergic agent.

Abstract: The antiallergic activity of some xanthone derivatives containing a sulfoximide substitutent has been investigated. While 2-(S-methylsulfonimidoyl)xanthone itself was found to be inactive, a series of 7-(S-methylsulfonimidoly)-xanthone-2-carboxylic acids showed good levels of activity in the passive cutaneous anaphylaxis screen. N-Substituted sulfoximide derivatives were, without exception, less active than the corresponding unsubstituted compounds. The activity of the 7-(S-methylsulfonimidoyl)xanthone-2-carboxylic acids could be enhanced by the introduction of an alkyl or alkoxy substituent at C-5. As a result of these studies, 5-hexyl-7(S-methylsulfonimidoyl)xanthone-2-carboxylic acid has been selected for further investigation as an antipasthmatic agent.

Synthesis utilising the β-carbonyl system. Part 5. A synthesis directed towards the fungal xanthone bikaverin

Abstract: 2-[3-(1-Oxo-3-aminobut-2-enyl)-7-methoxy-5-methyl-4-oxo-4H-benzopyran-2-ylmethyl]dioxolans, (7a and b), with an ethoxycarbonylmethyl or methyl substituent on the 2-position, have been synthesised starting with three precursors corresponding to β-tetra-, β-tri-, and β-di-carbonyl compounds. Acid treatment of the 2-ethoxycarbonylmethyl compound (7a) afforded ethyl 3-(1-hydroxy-6-methoxy-3,8-dimethyl-9-oxoxanthen-2-yl)-3-oxopropanoate (13a) as the major product together with three minor products, including ethyl 2-acetyl-1-hydroxy-6-methoxy-8-methyl-9-oxoxanthen-3-ylacetate (11); whereas the 2-methyl compound (7b) yielded 2-acetyl1-hydroxy-6-methoxy-3,8-dimethylxanthen-9-one (13b), exclusively. The structures of (13a) and (17) were cosnfirmed by 13C n.m.r. Spectroscopy using the long-range selective proton-decoupling (LSPD) method. Formation of (13a) from (7a) is explained in terms of a Wessely–Moser rearrangement of the intermediary benzopyranone (9a) or the xanthone (10a) under mild acidic conditions. Base-catalysed cyclisation of the xanthone3-acetate (11) gave 8,10,11-trihydroxy-3-methoxy-1-methyl-12H-benzo[b]xanthen-12-one (20) in excellent yield.

Photochemistry of 2-halogeno-1,1-diphenylethylenes. The photo-Fritsch–Buttenberg–Wiechell rearrangement

Abstract: Competing ionic and radical photobehaviour has been observed for 2-halogeno-1,1-diphenylethylenes. Irradiation of 2-fluoro-1,1-diphenylethylene in cyclohexane or ether afforded cis- and trans-fluorostilbene. Irradiation of the chloro, bromo, or iodo analogues gave a complex mixture of up to eight products, the three major products being diphenylacetylene, 1,1-diphenylethylene, and 1,1,4,4-tetraphenylbutadiene. The product distribution proved to depend on the halogen and on the solvent. Benzophenone or xanthone sensitised irradiation of 2-fluoro-1,1-diphenylethylene in cyclohexane gave 1-cyclohexyl-1-fluoro-2,2-diphenylethane, while irradiation of 2-chloro 1,1-diphenylethylene gave 2-cyclohexyl-1,1-diphenylethylene.

Synthesis of Xanthone‐O‐Glycosides. II.. Synthesis of 1‐O‐β‐glycosides

Abstract: Several naturally occurring xanthone-1-O-glycosides have been synthesized in order to study monoamine oxidase (MAO) inhibition structure-activity relationships. The syntheses also confirmed the structures as 1-β-D-glucosyloxy-3-hydroxy-5-methoxyxanthone (Canscora decussataSCHULT.), 1-O-β-primeverosyl-3, 7, 8-trimethoxyxanthone (decussatin-1-O-primeveroside, Gentiana vernaL.) and 1-O-β-primeverosyl-3, 8-dimethoxy-7-hydroxyxanthone (gentiacaulein-1-O-β-primeveroside, Gentiana vernaL.).