Showing papers on "Xanthone published in 1973"

Studies in the xanthone series. Part XII. A general synthesis of polyoxygenated xanthones from benzophenone precursors

Abstract: Various 2-mono-, 2,3- and 1,7-di-, 1,3,7-, 1,5,6-, 1,6,7- and 2,3,4-tri-, 1,3,4,7-, 1,3,5,6-, 1,3,6,7-, 1,5,6,7- and 2,3,4,5-tetra-, and 1,3,5,6,7-penta-oxygenated xanthones have been synthesised by preparation of 2-hydroxy-2′-methoxybenzophenones under Friedel–Crafts conditions, and subsequent base catalysed cyclisation to eliminate methanol. Acid or base catalysed selective demethylations of polymethoxyxanthones, and of benzophenones lead to efficient synthesis of natural hydroxymethoxyxanthones, and of hydroxymethoxybenzophenones. Selective methylation procedures are also given.

Mass spectrometry of xanthones‐I: The electron‐impact‐induced fragmentation of xanthone, monohydroxy‐ and monomethoxyxanthones

Abstract: With the aid of isotopic labelling (D and 18O) and the metastable defocusing technique the mass spectra of xanthone, the monohydroxyxanthones and the monomethoxyxanthones have been recorded and interpreted. The relative position of the hydroxy group exerts no direct effect on the fragmentation, whereas the decomposition of the methoxy compounds is clearly influenced by the position of the substituent. The 1-methoxy-group exhibits an ‘Ortho-effect’. The presence and significance of doubly-charged ions in the spectra are discussed.

Method of using substituted xanthone carboxylic acid

Abstract: Methods employing as the essential ingredient, novel substituted xanthone carboxylic acid compounds in the treatment of the symptons of the asthmatic condition resulting from an antigen-antibody reaction. Methods for preparing these compounds and compositions and intermediates therein are also disclosed - 7 - (methylthio) - xanthone - 2 - carbonylic acid is illustrated as representative of the class.

Aromatic cations from pyrones and similar compounds

Abstract: Various pyrones and flavone, xanthone, and diphenylcyclopropenone react with organic nucleophiles in the presence of phosphorus oxychloride in nitromethane with the formation of the corresponding aromatic cations, which have been isolated in the form of the perchlorates.

Heterocyclic analogs of xanthone: IV. Physicochemical properties of 9-oxochromeno-[3,2-d]pyrazoles, 9-oxothiochromeno[3,2-d]pyrazoles, and 8-oxodipyrazolopyrans

Abstract: A comparative investigation of the acid-base properties, the polarographic behavior, and the spectral characteristics of oxochromeno- and oxothiochromenopyrazoles, oxodipyrazolopyrans, and their electronic analogs xanthone and thioxanthone, has been performed. The difference in properties is due to the electron-accepting nature of the condensed pyrazole ring.

A method of inhibiting symptoms of asthma

Abstract: Compounds containing and method employing, as the essential ingredient, novel substituted xanthone carboxylic acid compound which are useful in the treatment of allergic conditions. Method for preparing these compounds and compositions and intermediates therein are also disclosed. 7-Trifluoromethylxanthone-2-carboxylic acid is illustrated as representative of the class.

Ditetrazole substituted acridone compounds

Abstract: Acridone and xanthone compounds substituted by at least one tetrazolyl group in one ring, and further substituted in the other ring, optionally for the acridones have antiallergic activity.