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Dioxygenation of Flavonol Catalyzed by Copper(II) Complexes Supported by Carboxylate‐Containing Ligands: Structural and Functional Models of Quercetin 2,4‐Dioxygenase
Author(s) -
Sun YingJi,
Li Pei,
Huang QianQian,
Zhang JianJun,
Itoh Shinobu
Publication year - 2017
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/ejic.201601371
Subject(s) - chemistry , carboxylate , benzoic acid , stereochemistry , medicinal chemistry , catalysis , copper , reactivity (psychology) , ternary operation , organic chemistry , computer science , programming language , medicine , alternative medicine , pathology
To obtain insights into the role of the carboxylate group of Glu73 in the active site of quercetin 2,4‐dioxygenase (2,4‐QD), the copper(II) complexes [Cu II L n (AcO)] [ 1 (L n = L1 ), 2 (L n = L2 ), 3 (L n = L3 ), and 4 (L n = L4 )] supported by a series of carboxylate‐containing ligands [ L1 H = 2‐{[bis(pyridin‐2‐ylmethyl)amino]methyl}benzoic acid; L2 H = 3‐{[bis(pyridin‐2‐ylmethyl)amino]methyl}benzoic acid,; L3 H = 2‐({bis[2‐(pyridin‐2‐yl)ethyl]amino}methyl)benzoic acid; L4 H = 3‐({bis[2‐(pyridin‐2‐yl)ethyl]amino}methyl)benzoic acid] as well as the ternary Cu II flavonolate (fla – ) complexes [Cu II L n (fla)] [ 5 (L n = L1 ), 6 (L n = L2 ), 7 (L n = L3 ), and 8 (L n = L4 )] were synthesized and characterized as structural and functional models for the active site of 2,4‐QD. The ternary complexes [Cu II L n (fla)] showed different reactivities in the dioxygenation of bound flavonolate to benzoic acid, salicylic acid, and N , N ‐dimethylbenzamide at 75–90 °C (single‐turnover reaction) in the order 5 >> 7 > 8 ≈ 6 . A similar reactivity tendency was found in the catalytic dioxygenation of the substrate flavonol (multiturnover reaction) by the binary complexes. The different reactivities of the copper complexes could be attributed to the different Lewis acidities of the copper(II) ions induced by the different coordination environments of the ligands. The results will provide important insights into the pivotal catalytic role of the carboxylate group of Glu73 in 2,4‐QD.