Bio-inspired flavonol and quinolone dioxygenation by a non-heme iron catalyst modeling the action of flavonol and 3-hydroxy-4(1H)-quinolone 2,4-dioxygenases

The mononuclear complex, FeIII(O-bs)(salen) (salenH2 = 1,6-bis(2-hydroxyphenyl)-2,5-diaza-hexa-1,5-diene; O-bsH = O-benzoylsalicylic acid) was synthesized as synthetic enzyme-depside complex, and characterized by spectroscopic methods and X-ray crystal analysis. The dioxygenation of flavonol (flaH) and 3-hydroxy-4-quinolone (quinH2) derivatives in the presence of catalytic amounts of FeIII(O-bs)(salen) results in the oxidative cleavage of the heterocyclic ring to give the corresponding O-benzoylsalicylic and anthranilic acid derivatives with concomitant release of carbon monoxide. These reactions can be regarded as biomimetic functional models with relevance to the iron-containing flavonol and the cofactor-independent 3-hydroxy-4(1H)-quinolone 2,4-dioxygenases.

Graphical abstractFeIII(O-bs)(salen) as an iron-containing enzyme-depside model, highly selectively and efficiently catalyzes the dioxygenolytic cleavage of the heterocycle ring of flavonols and 3-hydroxy-4(1H)-quinolone derivatives to give the corresponding O-benzoylsalicylic and anthranilic acid derivatives with concomitant release of carbon monoxide.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► O-Benzoylsalicylatoferric complex with Salen was isolated as enzyme-depside model. ► Substrates reacted with O2 in presence of the complex to give enzyme-like products and CO. ► The system is a catalytic model for flavonol and hydroxyquinolone dioxygenases.