Chemoenzymatic Synthesis of Sertraline

A chemoenzymatic approach has been developed for the preparation of sertraline, an established anti‐depressant drug. Ketoreductases (KREDs) were employed to yield a key chiral precursor. The bioreduction of the racemic tetralone exhibited excellent enantioselectivity (>99 % ee ) and diastereomeric ratio (99:1) at 29 % conversion (the maximum theoretical yield is 50 %) after 7 hours. The resulting ( S , S )‐alcohol was efficiently oxidized to an enantiopure ( S )‐ketone, an immediate precursor of sertraline, by using sodium hypochlorite as oxidant and 2‐azaadamantane N ‐oxyl (AZADO) as organocatalyst. Alternative routes aiming at the direct biocatalytic amination using imine reductases and transaminases were unsuccessful.