Development of an organo-and enzyme-catalysed cascade reaction

This thesis describes the development of a novel one-pot reaction (Scheme 1). The reaction combines organo- and enzyme-catalysis in an aldol/aldol cascade for the first time. The bicatalytic, three-component assembly involves two aldol reactions: an organocatalysed reaction and an aldol reaction catalysed by an aldolase.

The feasibility of the one-pot reaction was evaluated by testing whether the aldol intermediates 3 were substrates for the E192N aldolase variant of Nacetylneuraminic
acid lyase. A range of compounds was selected as potential
substrates for the enzyme. The synthesis of the compounds, and their characterisation as substrates for the aldolase variant, is described.

The development of common conditions under which both organo- and enzyme-catalysis could occur was then investigated. To do so, a number of potential organocatalysts suitable for the one-pot reaction were prepared. The catalysts were evaluated in a screening reaction which yielded optimal conditions for the organocatalysed reaction. The organocatalytic conditions were tested for compatibility with the E192N aldolase variant using an appropriate enzyme assay. The optimised process was a sequential one-pot reaction in which the
organocatalysed reaction was conducted before the addition of the variant enzyme. The scope of the optimal process was determined and a range of novel acids of general structure 4, were prepared.