Catalytic hydrogenation of vinylogous peptides: a route towards γ-peptide foldamers

Catalytic hydrogenation over Pd/C of vinylogous aminoacids and aminoamides has been studied. The configuration of the ethylenic bond has an important effect on the diastereoselectivity. The higher selectivity is observed with the E-vinylogous aminoamides. The conformational preferences of the α,γ-disubstituted γ-peptides have been determined. The 2S,4S-γ-peptide moiety induces a β-like folded structure stabilized by an intramolecular hydrogen bond, whereas the 2S,4R-diastereomer assumes an open structure.