Combinatorial evolution of site- and enantioselective catalysts for polyene epoxidation

Abstract

Selectivity in the catalytic functionalization of complex molecules is a major challenge in chemical synthesis. The problem is magnified when there are several possible stereochemical outcomes and when similar functional groups occur repeatedly within the same molecule. Selective polyene oxidation provides an archetypical example of this challenge. Historically, enzymatic catalysis has provided the only precedents. Although non-enzymatic catalysts that meet some of these challenges became known, a comprehensive solution has remained elusive. Here, we describe low molecular weight peptide-based catalysts, discovered through a combinatorial synthesis and screening protocol, that exhibit site- and enantioselective oxidation of certain positions of various isoprenols. This diversity-based approach, which exhibits features reminiscent of the directed evolution of enzymes, delivers catalysts that compare favourably to the state-of-the-art for the asymmetric oxidation of these compounds. Moreover, the approach culminated in catalysts that exhibit alternative-site selectivity in comparison to oxidation catalysts previously described. Aspartic acid-based catalysts that are selective for oxidation of either the 2,3 position or the 6,7 position of certain isoprenols have been discovered. The catalysts emerged from a diversity-based approach employing the one-bead-one-compound libraries. The site-selectivity of the catalysis seems to derive from the hydroxyl group in the substrate, although the details of this are not yet known.

Cite this article

Lichtor, P., Miller, S. Combinatorial evolution of site- and enantioselective catalysts for polyene epoxidation. Nature Chem 4, 990–995 (2012). https://doi.org/10.1038/nchem.1469

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