Artificial enzymes, "chemzymes": current state and perspectives.

Enzymes have fascinated scientists since their discovery and, over some decades, one aim in organic chemistry has been the creation of molecules that mimic the active sites of enzymes and promote catalysis. Nevertheless, even today, there are relatively few examples of enzyme models that successfully perform Michaelis-Menten catalysis under enzymatic conditions (i.e., aqueous medium, neutral pH, ambient temperature) and for those that do, very high rate accelerations are seldomly seen. This review will provide a brief summary of the recent developments in artificial enzymes, so called "Chemzymes", based on cyclodextrins and other molecules. Only the chemzymes that have shown enzyme-like activity that has been quantified by different methods will be mentioned. This review will summarize the work done in the field of artificial glycosidases, oxidases, epoxidases, and esterases, as well as chemzymes that catalyze conjugate additions, cycloadditions, and self-replicating processes. The focus will be mainly on cyclodextrin-based chemzymes since they have shown to be good candidate structures to base an enzyme model skeleton on. In addition hereto, other molecules that encompass binding properties will also be presented.