ChemCatChem

Cover image for Vol. 6 Issue 4

Editor: Michael Rowan

Impact Factor: 5.181

ISI Journal Citation Reports © Ranking: 2012: 26/135 (Chemistry Physical)

Online ISSN: 1867-3899

Associated Title(s): Advanced Synthesis & Catalysis, Angewandte Chemie International Edition, Chemistry - A European Journal, ChemBioChem, ChemElectroChem, ChemPhysChem, ChemSusChem

4_03/2012Cover Picture: The l-Leu Hexamer, a Short and Highly Enantioselective Peptide Catalyst for the Juliá–Colonna Epoxidation: Stabilization of a Helical Conformation in DMSO (ChemCatChem 3/2012)

Peptide catalyzed asymmetric epoxidation In the Juliá–Colonna epoxidation—discovered in the early 1980s—a homo-polymeric peptide such as poly-Leu catalyzes the highly enantioselective oxygen transfer from hydrogen peroxide to enones, mostly chalcones. Mechanistic proposals for this intriguing organocatalytic epoxidation involve a helical conformation of the peptide catalyst, and the N-terminus as the active site. It was shown later that even short peptides can be similarly effective—as little as five amino acid residues are sufficient to induce high enantioselectivity. However, a conformational analysis of such peptide catalysts in solution by using NMR spectroscopy has been missing. On p. 337 ff. of this issue, Berkessel, Schlörer, Díaz et al. provide evidence that the l-Leu hexamer, in DMSO solution, indeed forms the depicted one-turn 310-helix to a significant extent. Computational docking experiments of this helical structure with the proposed α-hydroperoxyenolate intermediate of the Juliá–Colonna epoxidation are in accord with the experimentally observed sense of induction. And yes indeed, the balcony shown is Julia's balcony in Verona.

Read Full Text  | Table of Contents

SEARCH

SEARCH BY CITATION