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Enzymes are exquisite catalysts for chemical and biochemical reactions: They typically display excellent stability and are highly selective both with respect to the substrates used and the products produced. Most enzymes are comprised of a highly potent catalytic center and a surrounding protein superstructure. In contrast to many, or most man-made, catalysts, naturally occurring enzymes tend to rely upon the superstructure, rather than the catalytic site itself, to achieve substrate selectivity. In addition, the superstructure serves to isolate the catalytic center from other reactive centers, thereby enhancing the centers stability and extending its functional lifetime. Here we describe the artificial enzymelike induction of stability and selectivity for a simple epoxidation catalyst by a supramolecular coordination chemistry approach. We further show that the selectivity is tailorable through the supramolecular approach. The tailorability permits, in principle, the rapid and systematic optimization of catalytic selectivity for specific substrates.To demonstrate the utility of the encapsulation concept we targeted the epoxidation of olefins [Eq. (1)] because of its relevancy in biooxidation. [1] We stress that our goal here is to demonstrate the utility of directed supramolecular complex formation in manipulating the properties of conventional catalysts rather than to create a competitive analogue of existing epoxidation catalysts.The baseline for comparing catalyst stability was established by using 1 39, 135; b) O. D. Fox, M.

Anthracene and related compounds function as lifetime-extending cofactors in the (meso-tetraphenylporphine)Mn(III) chloride-catalyzed epoxidation of olefins. An experiment with a chiral porphyrin catalyst shows that enantioselectivity is preserved in the presence of the cofactor. Additional experiments show that (a) turnover number enhancement is greatest for the least reactive substrates, (b) derivatization of anthracene at the 9 and 10 positions largely eliminates the enhancement effect, and (c) anthracene is ultimately converted to anthraquinone. The origin of the observed enhancements is in the reaction of anthracene with the normally unreactive dimeric oxo-bridged form of the catalyst. This reaction, which produces anthraquinone, regenerates the catalytically active monomeric form of the manganese porphyrin.