547.814.5 I. V. Nagorichna, and A. S. OgorodniichukAmides of 5,7-dihydroxy-4-methylcoumaryl-3-ylacetic acid were synthesized by the activated ester method using N-hydroxysuccinimide and diisopropylcarbodiimide or by reaction with N,N-carbonylimidazole. The reactivity of 3-substituted 5,7-dihydroxy-4-methylcoumarins toward 2,2-diphenyl-1-picrylhydrazyl and superoxide radical was analyzed. The effect of the synthesized compounds on xanthineoxidase activity was studied.Natural coumarins and their synthetic structural analogs possess a broad spectrum of biological activity including antiinflammatory, antibacterial, and analgesic action [1,2]. The design of new derivatives of benzopyran-2-one is often based on research of the functions of these compounds in model systems. It has been found that simple natural coumarins containing two ortho hydroxyls (6,7-dihydroxycoumarins, 7,8-dihydroxycoumarins) are effective traps for the superoxide radical and alkylperoxyl radicals and are inhibitors of peroxide oxidation of lipids. However, these compounds in the presence of iron ions can also be prooxidants that are capable under certain conditions of stimulating undesired redox transformations involving molecular oxygen. Therefore, coumarin derivatives containing meta dihydroxyls are definitely interesting for constructing potential synthetic antioxidants. Thus, 5,7-dihydroxy-4-methylcoumarin is not a pro-oxidant, inhibits peroxide oxidation of lipids, and reacts with active oxygen species and hypochlorite [3]. Besides, it inhibits transformations catalyzed by cyclooxygenase and does not affect the activity of 5-lipoxygenase [2,4,5].Because of the importance of the 5,7-dihydroxy-4-methylcoumarin moiety in the structure of a potential antioxidant, we attempted to analyze certain properties of 5,7-dihydroxy-4-methylcoumarins containing 3-substituents. A series of structurally similar amides was synthesized using 5,7-dihydroxy-4-methylcoumarin-3-ylacetic acid as starting material. Their reactivity toward 2,2-diphenyl-1-picrylhydrazyl and superoxide radical was studied. The effect of the synthesized compounds on xanthineoxidase activity was also found. 5,7-Dihydroxy-4-methylcoumarin-3-ylacetic acid (2) that was required for subsequent transformations was prepared by saponification of the ester in 5,7-dihydroxy-4-methylcoumarin (1) by NaOH in aqueous propan-2-ol with subsequent acidolysis of the reaction mixture. Coumarin 1 was synthesized by condensation of phloroglucinol dihydrate and dimethylacetylsuccinate in the presence of dry HCl.Amides of 2 were prepared by two methods. The first used N-acylation based on the activated ester method that is used commonly in peptide synthesis [6]. The carboxylic acid was activated using a highly reactive N-hydroxysuccinimide ester [7]. The activated ester was prepared by reacting 2 and N-hydroxysuccinimide (SuOH) in absolute dioxane using diisopropylcarbodiimide (DIC) as the condensing agent. Condensation of the resulting activated ester with amines in dioxane at room temperature formed amides...