Selectively Activatable Latent Thiol and Selenolesters Simplify the Access to Cyclic or Branched Peptide Scaffolds

The cyclic dichalcogenides based on the bis­(2-chalcogenoethyl)­amide structure are latent N,S (SEA, chalcogen = S) or N,Se (SeEA, chalcogen = Se) acyl shift systems. The large difference in the reducing potential between SEA and SeEA dichalcogenides allows their sequential and selective activation by reduction. Based on these concepts, one-pot three or four peptide segment assembly processes were designed, facilitating access to branched or cyclic peptide scaffolds.