A One-Pot Two-Step Enzymatic Pathway for the Synthesis of Enantiomerically Enriched Vicinal Diols

Enantiomerically enriched 1,2-diols are prominent compounds that find numerous applications in organic chemistry. They are privileged building blocks for the synthesis of APIs (Active Pharmaceutical Ingredients), broadly used as chiral ligands in asymmetric catalysis, and efficient auxiliaries employed to control the stereochemical outcome of total synthesis. Among the number of strategies developed for the preparation of these molecules, enzyme mediated reactions have gained a crucial role in the toolbox of organic chemists for their high efficiency and sustainability. Herein we describe a one-pot two-step protocol designed by combining a thiamine diphosphate (ThDP)-dependent lyase and a NADH-dependent reductase. The ThDP-dependent acetoin:dichlorophenolindophenol oxidoreductase (Ao : DCPIP OR) is exploited to produce enantioenriched α-hydroxyketones through the benzoin-type condensation of methylacetoin with either aldehydes or activated ketones. The enantioenriched α-hydroxyketones undergo the selective reduction into the corresponding 1,2-diols in the same reaction mixture due to the addition of NAD+ and of the NADH-dependent acetylacetoin reductase (AAR). Sodium formate was selected as the sacrificial reductive reactant to generate and recycle in situ the precious NADH by formate-dehydrogenase. Unprecedented reported details on the cloning and expression of the AAR are reported as well.