In the presence of free radicals, such as 2,2,6,6-tetramethyl-1-piperidinyloxyl (TEMPO) and 2,6-di-tert-butyl-a-(3,5-di-tert-butyl-4-oxo-2,5-cyclohexadien-1-ylidene)-p-tolyloxyl (galvinoxyl), flavonols undergo catalytic oxygenation to the corresponding depsides (phenolic carboxylic acid eaters), with concomitant evolution of CO. The oxygenolysis was performed in aprotic solvents (DMF, MeCN) and was followed by Glc. The results of oxygenation of 4 ' -substituted flavonols show that the formation of flavonoxy species is the key step in the activation process of the substrate, and that electron-releasing substituents enhance the reaction rate.