From theozymes to artificial enzymes:: Enzyme-like receptors for Michael additions with oxyanion holes and active amino groups

Different artificial enzymes, based on the theozyme concept, have been designed for Michael additions of pyrrolidine to alpha,beta-unsaturated lactams. These molecules each have skeleton able to mimic a structure called an oxyanion hole, as is present in many enzymes. Amine groups are also responsible for the catalytic activities of these receptors, since they support the important proton -transport step. The requirement for the amine groups was established from the reaction mechanism and from theoretical calculations. The catalytic activities of the receptors are discussed, taking into account their relative association constants with the substrate: k(cat)/ k(uncat) values of up to 10(4) were obtained. The catalytic activities of the receptors are compared with those found in natural enzymes and catalytic antibodies.