Sequential Intermolecular Radical Addition and Reductive Radical Cyclization of Tyrosine and Phenylalanine Derivatives with Alkenes via Photoinduced Decarboxylation: Access to Ring-Constrained γ‑Amino Acids

Sequential
radical addition to alkenes and reductive radical cyclization
of phenylalanine and tyrosine derivatives via photoinduced decarboxylation
furnished ring-constrained γ-amino acids under mild conditions.
A variety of alkenes such as acrylamides and acrylic esters could
be employed in the photoinduced radical cascade cyclization. The yields
of the ring-constrained γ-amino acids are dependent on the electron-accepting
ability and steric hindrance of the alkene used. The proposed sequential
reaction can also be applied for direct tethering of dipeptides to
yield unique ring-constrained tetrapeptides.