Asymmetric oxidation catalyzed by myoglobin mutants

The sperm whale myoglobin active site mutants (L29H/H64L and F43H/H64L Mb) have been shown to catalyze the asymmetric oxidation of sulfides and olefin s. Thioanisole, ethyl phenyl sulfide, and cis-beta-methylstyrene are oxidiz ed by L29H/H64L Mb with more than 95% enantiomeric excess (% ee). On the ot her hand, the F43H/H64L mutant transforms trans-beta-methylstyrene into the trans-epoxide with 96% ee. The dominant sulfoxide product in the incubatio n of alkyl phenyl thioethers is the R isomer; however, the mutants afford d ominantly the S isomer of aromatic bicyclic sulfoxides. The results help us to rationalize the difference in the preferred stereochemistry of the Mb m utant-catalyzed reactions. Furthermore, the Mb mutants exhibit an improveme nt in the oxidation rate up to 300-fold with respect to wild type. (C) 1999 Elsevier Science Ltd. All rights reserved.