Microbial transformations, 56.: Preparative scale asymmetric Baeyer-Villiger oxidation using a highly productive "two-in-One" resin-based in situ SFPR concept

An efficient preparative scale process for achieving asymmetric Baeyer-Villiger oxidation-a reaction still very difficult to perform using conventional chemistry-is described. This process is based on a biocatalytic whole cells strategy-using a recombinant E. coli strain overexpressing cyclohexanone monooxygenase (CHMO)-combined with a "two-in-one" in situ "substrate feeding and product removal" concept (SFPR) using an adsorbent resin. The most efficient resin out of fourteen tested was used in three types of bioreactors (conventional, recycle and bubble column) that were compared. The best one proved to be the bubble column reactor, where 25 g (0.23 M) of rac-bicyclo[3.2.0]hept-2-en-6-one could be totally transformed using a one-litre vessel with a volumetric productivity of about 1 g L-1 h(-1) (i.e., 7.7 mmol L-1 h(-1)). This led to the production of the two corresponding regioisomeric lactones, which were both obtained in excellent enantiomeric purity (ee > 98%) and high preparative yield (84%). To our knowledge, these results represent the best example of a (highly productive) preparative scale asymmetric Baeyer-Villiger oxidation.