Stereocomplementary Asymmetric Reduction of Bulky–Bulky Ketones by Biocatalytic Hydrogen Transfer

✍ Scribed by Iván Lavandera; Gustav Oberdorfer; Johannes Gross; Stefaan de Wildeman; Wolfgang Kroutil

• Publisher: John Wiley and Sons
• Year: 2008
• Tongue: English
• Weight: 136 KB
• Volume: 2008
• Category: Article
• ISSN: 1434-193X
• DOI: 10.1002/ejoc.200800103

✦ Synopsis

Abstract

Biocatalysts suitable for the reduction of ketones bearing two sterically demanding substituents (bulky–bulky ketones) at elevated substrate concentration (10 g L^–1^) were identified. The biocatalysts can be employed in a substrate‐coupled approach; thus, a simple alcohol such as ethanol or 2‐propanol serves as a hydrogen donor. Both enantiomers are accessible by using either Rhodococcus ruber DSM 44541 and ethanol or Ralstonia sp. DSM 6428 and Sphingobium yanoikuyae DSM 6900 and ethanol or 2‐propanol as the hydrogen source. For Rhodococcus ruber DSM 44541, it was found that bulky–bulky ketones were only transformed when ethanol was used as a hydrogen source, whereas no conversion was observed when 2‐propanol was employed. From the substrate spectrum, as well as from the cosubstrate preference, it became clear that a different alcohol dehydrogenase than the previously described ADH‐“A” is active in the presence of ethanol in Rhodococcus ruber.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)