The Synthesis of Chiral Gamma-Lactones by Merging Decatungstate Photocatalysis with Biocatalysis

The implementation of light-driven catalytic processes in biocatalysis opens a golden window of opportunities. We hereby report the merging of photocatalytic C-C bond formation with enzymatic asymmetric reduction for the direct conversion of simple aldehydes and acrylates or unsaturated carboxylic acids into chiral ?-lactones. Tetrabutylammonium decatungstate (TBADT) is employed as the photocatalyst to trigger the hydroacylation of the starting olefins, yielding the corresponding keto esters/acids. Subsequently, an alcohol dehydrogenase converts the intermediate to the chiral alcohol, which undergoes lactonization to the desired ?-lactone. The photochemoenzymatic synthesis of aliphatic and aromatic ?-lactones was thereby achieved with up to >99 % ee  and >99 % yield. This synthesis highlights the power of building molecular complexity by merging photocatalysis with biocatalysis to access high-value added chiral compounds from simple, cheap and largely available starting materials.