First Chemical Synthesis of Three Natural Depsides Involved in Flavonol Catabolism and Related to Quercetinase Catalysis

We report here the first chemical synthesis of three depsides related to quercetinase-catalyzed degradation of kaempferol, quercetin, and myricetin. The three depsides were constructed through the coupling of suitably protected phloroglucinol carboxylic acid and hydroxy-perbenzylated, derivatives of gallic, protocatechuic, and 4-hydroxy benzoic acids. The three synthesized target compounds proved to be identical to their natural counterparts, arising from quercetinase action on corresponding flavonols.