Pepsin-Catalyzed Asymmetric Cross Aldol Reaction Promoted by Ionic Liquids and Deep Eutectic Solvents

Abstract Pepsin was found to catalyze asymmetric cross aldol reactions of aromatic and polycyclicaromatic aldehydes with cyclic ketones in ionic liquids and deep eutectic solvents for the first time. Pepsin exhibited high catalytic activity and excellent stereoselectivity in ionic liquids and deep eutectic solvents in the presence of moderate water. High yields of up to 93.1%, excellent enantioselectivities of up to 96% ee, and good diastereoselectivities of up to 5:95 dr were achieved. Graphic Abstract