Fig. 4: Furan-thiol-amine (FuTine) multicomponent reaction (MCR) for chemoselective modification and cyclization of peptides.

a Chemoselective modification of lysine or cysteine to form N-pyrrole on peptides without modification of any reactive amino acids. b Chemoselective modification of 2-furylalanine to form N-pyrrole on peptides. c Synthesis of peptide macrocycles of varying ring sizes between Cys and Lys side chains by the addition of oxidized furan. d Macrocyclization showed no preference for a ring size, N-terminus, and reactive lysine residue. e Stapling of peptides between two cysteine or two lysine residues on peptides by the addition of diamine or dithiol and oxidized furan.