Premium
Iron‐Catalyzed C2C3 Bond Cleavage of Phenylpyruvate with O 2 : Insight into Aliphatic CC Bond‐Cleaving Dioxygenases
Author(s) -
Paine Tapan Kanti,
England Jason,
Que Lawrence
Publication year - 2007
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200601844
Subject(s) - chemistry , bond cleavage , moiety , ligand (biochemistry) , stereochemistry , denticity , amine gas treating , catalysis , oxalate , medicinal chemistry , dioxygenase , crystal structure , crystallography , organic chemistry , enzyme , biochemistry , receptor
Iron(II)‐phenylpyruvate complexes of tetradentate tris(6‐methyl‐2‐pyridylmethyl)amine (6‐Me 3 ‐TPA) and tridentate benzyl bis(2‐quinolinylmethyl)amine (Bn‐BQA) were prepared to gain insight into CC bond cleavage catalyzed by dioxygenase enzymes. The complexes we have prepared and characterized are [Fe(6‐Me 3 ‐tpa)(prv)][BPh 4 ] ( 1 ), [Fe 2 (6‐Me 3 ‐tpa) 2 (pp)][(BPh 4 ) 2 ] ( 2 ), and [Fe 2 (6‐Me 3 ‐tpa) 2 (2′‐NO 2 ‐pp)][(BPh 4 ) 2 ] ( 3 ), [Fe(6‐Me 3 ‐tpa)(pp‐Me)][BPh 4 ] ( 4 ), [Fe(6‐Me 3 ‐tpa)(CN‐pp‐Et)][BPh 4 ] ( 5 ), and [Fe(Bn‐bqa)(pp)] ( 8 ), in which PRV is pyruvate, PP is the enolate form of phenylpyruvate, 2′‐NO 2 ‐PP is the enolate form of 2′‐nitrophenylpyruvate, PP‐Me is the enolate form of methyl phenylpyruvate, and CN‐PP‐Et is the enolate form of ethyl‐3‐cyanophenylpyruvate. The structures of mononuclear complexes 1 and 5 were determined by single‐crystal X‐ray diffraction. Both the PRV ligand in 1 and the CN‐PP‐Et ligand in 5 bind to the iron(II) center in a bidentate manner and form 5‐membered chelate rings, but the α‐keto moiety is in the enolate form in 5 with concomitant loss of a CH β proton. The PP ligands of 2 , 3 , 4 , and 8 react with dioxygen to form benzaldehyde and oxalate products, which indicates that the C2C3 PP bond is cleaved, in contrast to cleavage of the C1C2 bond previously observed for complexes that do not contain α‐ketocarboxylate ligands in the enolate form. These reactions serve as models for metal‐containing dioxygenase enzymes that catalyze the cleavage of aliphatic CC bonds.