Supported Peptide for Asymmetric α-Oxyamination of Aldehydes

asymmetric α-oxyamination - peptide catalysis - aqueous media

Significance

<P>A polystyrene-poly(ethylene glycol) resin supported peptide catalyst bearing terminal five-residue Pro-d-Pro-Aib-Trp-Trp combined with polyleucine was prepared. The polymeric peptide was successfully applied to the asymmetric α-oxyamination of aldehydes with TEMPO in the presence of a catalytic amount of FeCl₂ and NaNO₂ to give the corresponding products under aqueous aerobic conditions with up to 87% yield and 93% ee (5 examples).</P>

Comment

<P>The Kudo group has previously ­reported asymmetric hydrogenation (K. Akagawa et al. Tetrahedron: Asymmetry 2009, 20, 461; K. ­Akagawa et al. Org. Lett. 2008, 10, 2035) and asymmetric Friedel-Crafts alkylation (K. Akagawa et al. Tetrahedron Lett. 2009, 50, 5602) in aqueous media with this catalyst. The polyleucine moiety between the tryptophan and the resin support not only provides a hydrophobic environment, but also effects the stereoselectivity of the reaction.</P>