Biocatalytic Asymmetric Oxidations with Oxygen

Oxidahon reactions in flammable solvents are crihcal to exothermic, fire, and explosion events. The simultaneous presence of reachve oxidants and flammable organic solvents represent operating conditions that require substanhal safety precautions and have the disadvantage of generating stoichiometric amounts of waste from the oxidant. Therefore the replacement of solvents, oxidants, and reac-hon methodology by environmentally compatible and safe reagents is of prime 

Modem Biocatalysis Stereoselective and Environmentally Friendly Reactions. Edited by Wolf-Dieter Fessner and Thorleif Anthonsen Copyright 2009 WILEY-VCH Verlag GmbH Co. KGaA, Weinheim ISBN 978-3-527-32071-4 

Immobilized o-amino acid oxidase from T.variabilis 

The focus is on proteins with redox functionalities hke oxidases, mono- and dioxygenases, and other enzymes able to utilize molecular oxygen as an oxidant, but dehydrogenases and peroxidases will also be discussed. The use of common proteins such as bovine serum albumin with no distinctive redox functionalities as chiral templates for asymmetric oxidations has been reviewed elsewhere [16]. As the oxidations require the transfer of electrons from a substrate to an electron 

Enantioselective oxidation of racemic 0-methyl-N-hydroxycyclohexylethylamine using monoamine oxidase N from Aspergillus niger yields unreacted (R)-enantio-mer together with the oxime exclusively in the ( )-configuration [23]. 

---

Figure 20.2 Historical industrial examples of biocatalytic asymmetric oxidations with oxygen.

J341 20 Biocatalytic Asymmetric Oxidations with Oxygen... 

Biocatalytic asymmetric oxidation of 2,3-dihydrobenzo[. ]thiophene to (—)-(lJ)-sulfoxide in excellent yield has been reported. The enzyme used is a chloroperoxidase from the marine fungus Caldariomycesfumago. This enzyme is relatively stable and does not require any cofactor. Hydrogen peroxide was the oxygen source. Using this system, 2,3-dihydro-benzo[. ]thiophene was converted to the (—)-(i )-sulfoxide in 99.5% yield, with an ee of 99%. Similarly, 1,3-dihydro-benzo[f]thiophene could be oxidized to the corresponding sulfoxide in 80% yield <1998CH246>. 

---