Recombinant Δ 4,5 ‐Steroid 5 β‐Reductases as Biocatalysts for the Reduction of Activated CC‐Double Bonds in Monocyclic and Acyclic Molecules

It was found that Δ 4,5 ‐steroid 5β‐reductases are capable of reducing also small molecules bearing an activated CC double bond such as monocyclic enones and acyclic enoate esters. As preferred Δ 4,5 ‐steroid 5β‐reductase (5β‐StR) for this purpose, 5β‐StR from Arabidopsis thaliana was used. In part, enzyme activities are even higher than that for progesterone. Successful preliminary biotransformations with enzymatic in situ cofactor recycling were also carried out. When using the prochiral compound isophorone as a substrate, a high enantioselective reaction course (>99% ee ) was observed.