Coupling chiral homogeneous biocatalytic reactions with benign heterogeneous separation

We describe a method for sustainable biocatalysis in an organic aqueous tunable solvent (OATS) system in which a hydrophobic substrate is transformed with a homogeneous enzymatic catalyst in a single liquid phase. Subsequent CO₂ addition produces a biphasic mixture where the hydrophobic product partitions preferentially into the organic rich phase for separation while the hydrophilic enzyme catalyst partitions into the aqueous rich phase, where it is recyclable. Greater than 99% enantiomeric excess (ee) is shown for catalyzed hydrolysis of rac-1-phenylethyl acetate with Candida antarctica lipase B (CAL B) both before and after CO₂-induced separation. Additionally, processing parameters in OATS systems are discussed. This system combines homogeneous enzymatic reactions with a built-in heterogeneous separation for enantiomerically pure products.