Photoinduced Intramolecular Macrocyclization Reaction between a Bpa and a Met Residue in a Helical Peptide: 3D-Structures of the Diastereomeric Products.

The first photoinduced intramolecular macrocyclization reaction in a helical peptide, containing a Bpa and a Met residue incorporated one on top of the other after a complete turn of the helix, has been performed. The photochemical remote functionalization and subsequent intramolecular cross-linking are strictly regioselective, involving exclusively the original Met side-chain epislon-CH3 group and generating two diastereomeric macrocyclized peptides.