SYNTHESIS OF DERIVATIVES OF XANTHENE-2-CARBOXYLIC ACID AND XANTHONE-2-CARBOXYLIC ACID

In the present paper, a series of xanthene-2-carboxylic acids and xanthone-2-carboxylic acids with electron withdrawing groups on the 7-position had been synthesized.Xanthone-2-carboxylic acid(Ⅷ) was converted to(Ⅸ) by Huang-Minlon reduction. A by-product, 2, 2'-dihydroxy-diphenylmethane(Ⅹ), was also obtained in this reaction.Elemental analysis and MS of Compound(Ⅻ_d) was consistent with the assigned structure, but its ¹HNMR spectrum in CF₃COOH solution was identical with that of(Ⅻ_e) obtained by refluxing compound(Ⅻ_d) in acetic anhydride. It follows that compound(Ⅻ_e) was formed through cyclization and dehydration of compound(Ⅻ_d) in CF₃COOH.The results of passive cutaneous anaphylaxis(PCA) assay in rats showed that compound(Ⅷ), (Ⅻ_b) and(Ⅻ_e) have 50～60% protective effect(po, 200mg/kg) and(Ⅻ_d) 54%(ⅳ, 10 mg/kg).