1. D-Amino Acid
  2. Aib, Abu, Ahx, Abz,β-Ala, Cit, Cha, Chg, Dab, Hyp, Har, Nle, Nva, Nal, Pyr, Orn, Phg, Sar
  3. Cys(tBu), Cys(Acm), Lys(Ac), Lys(Biotin), Lys(TFA)
  4. Seleno-Met