Herein, we describe a chemoenzymatic synthesis of the bicyclic fragment of Darunavir. A ketoreductase was identified using metagenomic mining to catalyze a highly enantio- and diastereoselective dynamic kinetic resolution of a β-ketolactone. Subsequent lactone reduction with diisobutylaluminum hydride and phase transfer cyclization affords the bicyclic acetal fragment in 39% yield over four steps.