The sustainable synthesis of levetiracetam by an enzymatic dynamic kinetic resolution and an ex-cell anodic oxidation

Levetiracetam is an active pharmaceutical ingredient widely used to treat epilepsy. We describe a new synthesis of levetiracetam by a dynamic kinetic resolution and a ruthenium-catalysed ex-cell anodic oxidation. For the enzymatic resolution, we tailored a high throughput screening method to identify Comamonas testosteroni nitrile hydratase variants with high ( S )-selectivity and activity. Racemic nitrile was applied in a fed-batch reaction and was hydrated to ( S )-(pyrrolidine-1-yl)butaneamide. For the subsequent oxidation to levetiracetam, we developed a ligand-free ruthenium-catalysed method at a low catalyst loading. The oxidant was electrochemically generated in 86% yield. This route provides a significantly more sustainable access to levetiracetam than existing routes.