Tuning the outcome of enzyme-mediated dynamic cyclodextrin libraries to enhance template effects

Enzyme-mediated dynamic combinatorial chemistry combines the concept of thermodynamically controlled covalent self-assembly with the inherent biological relevance of enzymatic transformations. We explore a system of interconverting cyclodextrins wherein the glycosidic linkage is rendered dynamic by the action of cyclodextrin glucanotransferase (CGTase). We report that external factors, such as pH, temperature, solvent, and salinity can be modulated to influence the composition of the dynamic cyclodextrin library. Dynamic libraries of cyclodextrins (CDs) could be obtained in wide ranges of pH (5.0 -  9.0), temperature (5 - 37 ºC), and salinity (up to 7.5 M NaNO 3 ), and with high organic solvent content (50% by volume of ethanol), showing that enzyme-mediated dynamic systems can be robust and not limited to physiological conditions. Furthermore, we demonstrate how strategic choice of reaction conditions can enhance template effects, in this case, to achieve highly selective production α-CD, an otherwise challenging target due to competition from the structurally similar β-CD.