The primary aim of this project is to substantially expand the frontiers of current benchmark organocatalytic technology by the design, preparation and evaluation of the first class of thiol-based nucleophilic catalyst capable of emulating the action of NAD+-dependant enzymes such as aldehyde dehydrogenases, which promote the chemoselective oxidation/reduction of aldehyde substrates under mild conditions in aqueous media. The proposed artificial enzymes are designed biomimetically (in the true sense of the word) – only careful examination of the core enzyme competencies, modes-of-action and active sites has guided the design process. One of the key issues which this proposal addresses is the inherent difficulty associated with the design of artificial cofactor-dependent enzymes due to the requirement for a) efficient recognition by the catalyst of both the substrate and the cofactor, and b) the exertion of control over their encounter in the active site. We intend to tackle this challenge by covalently attaching groups functionally equivalent to the catalytically active residues of aldehyde dehydrogenases to a rigid NAD+ analogue in a manner which allows for their synergistic and biomimetic cooperation. Structure determination/mechanistic studies and the application of these new catalysts in a range of oxidations/reductions (we envisage that this project will result in the first organocatalyst able to demonstrably promote either - depending on the reaction conditions), (dynamic) kinetic resolutions, desymmetrisations, and ligations) will be undertaken and the development of catalytic processes for reactions currently outside the scope of any catalytic methodology is a clear long-term goal. We also wish to pursue the application of this potentially groundbreaking nucleophilic catalytic technology (for which no efficient organocatalysts have been thus far reported) toward the selective synthesis of enantiopure building blocks and pharmaceutically relevant molecules.