Directed Evolution improved Biocatalyst Performance in the Enantioselective Baeyer-Villiger Reaction

09 May 2005

Asymmetric Baeyer-Villiger (BV) reactions can be carried out enzymatically but some substrates give poor ee. Whole cell systems rather than isolated enzymes are usually preferred since the oxidation (using O_²) needs cofactors which are already present in the cells. The desymmetrisation of 4-hydroxycyclohexane leads eventually to the five-membered lactone with only 9% ee, using Acinetobacter sp NCIMB 9871. By using genetic engineering, a total of 10,000 mutants were screened of which more than 20 showed enhanced R selectivity, though some showed enhanced S selectivity. Some of the R selective mutants were subjected to a further round of mutation and one mutant had an R selectivity of over 90% (Reetz M T, Angew Chem Int Edn, 2004, 43, 4075).