Lactic Acid Bacteria as New Whole-Cells Biocatalysts for the Stereoselective Synthesis of Chiral Enantiopure Building Blocks

Biocatalytic processes represent one of the most heavily used green methodologies in preparative chemistry to perform highly chemo-, regio-, and stereoselective organic transformations, which are typically run under very mild reaction conditions (e.g., almost neutral pH buffer solutions, ambient temperature or mild heating, atmospheric pressure)1. Whole-cell microorganisms offer several positive features as biocatalysts with respect to isolated enzymes as they are more accessible, stable and easier to handle. Moreover, the presence of efficient internal cofactors regeneration systems (e.g., NADH or NADPH in reduction reactions) allows for cheap biocatalytic processes to be carried out often using glucose as the sole carbon source2. In this Communication, we discuss the asymmetric bioreduction of aromatic ketones to the corresponding chiral secondary alcohols using lactic acid bacteria (LAB) as new whole-cells biocatalysts. Several strains among LAB and spore-forming bacteria (Bacillus spp.) from the culture collection of the Institute of Sciences of Food Production (CNR-ISPA, Bari) have been screened. Interestingly, among LAB, Weissella strains were found to be the most effective ones for the regioselective bioreduction of aromatic ketones to the corresponding S-alcohols, with high yields and enantiomeric excesses (ees), despite to the known R-stereopreference exhibited by other LAB species as Lactobacilli (Figure)2a,3. Overall, this methodology holds potential to become a promising cheap and environmentally friendly approach for the preparation of chiral nonracemic secondary alcohols and Active Pharmaceutical Ingredients (APIs).3 References: [1] (a) K. Faber, Biotransformations In Organic Chemistry: A Textbook, 6 ed., Springer-Verlag: Berlin/Heidelberg, Germany, 2011; (b) R. C. Simon, F. G. Mutti, W. Kroutil, Drug Discov. Today Technol. 2013, 10, e37-e44; [2] (a) P. Vitale, F. M. Perna, G. Agrimi, A. Scilimati, A. Salomone, C. Cardellicchio, V. Capriati, V. Org. Biomol. Chem. 2016, 14, 11438; (b) P. Vitale, V. M. Abbinante, F. M. Perna, A. Salomone, C. Cardellicchio, V. Capriati, Adv. Synth. Catal. 2017, 359, 1049. [3] P. Vitale, F. M. Perna, G. Agrimi, I. Pisano, F. Mirizzi, R. Capobianco, V. Capriati, Catalysts 2018, 8, 55.