Tyrosinase reactivity in a model complex: An alternative hydroxylation mechanism

INOR 69

Liviu M. Mirica, liviu@berkeley.edu, Department of Chemistry, University of California, Berkeley, CA 94720-1460 and T. Daniel. P. Stack, stack@leland.stanford.edu, Department of Chemistry, Stanford University, Stanford, CA 94305-5080.
The ubiquitous binuclear copper enzyme tyrosinase activates O2 to form a m-h2:h2-peroxodicopper(II) complex, which oxidizes phenols to catechols. A synthetic, spectroscopically faithful m-h2:h2-peroxodicopper(II) complex, capable of aromatic hydroxylation at –80 °C, forms a reactive intermediate upon phenolate addition at extreme temperature in solution (–120 °C). Detailed spectroscopic characterization supports a bis-m-oxodicopper(III)-phenolate complex, in which the O–O bond is cleaved. The subsequent hydroxylation step has the hallmarks of an electrophilic aromatic substitution, similar to tyrosinase. Density functional theory calculations on this system strongly support that the bis-m-oxodicopper(III) species can serve as an electrophilic agent. Overall, in this synthetic complex, the evidence for sequential O–O bond cleavage and C–O bond formation suggests an alternative intimate mechanism for phenol hydroxylation, as compared to that generally accepted for tyrosinase.
 

Young Investigator Symposium
1:30 PM-5:30 PM, Sunday, 10 September 2006 Moscone Center -- Room 303, Oral

Division of Inorganic Chemistry

The 232nd ACS National Meeting, San Francisco, CA, September 10-14, 2006