![OBC](/sites/default/files/styles/original_ratio_zero/public/2021-07/1045_obc_f2c-900.jpg?itok=rvZVfZal)
The Glaser–Hay diyne coupling proved to be an efficient cyclisation approach towards diyne containing peptidic macrocycles. A variety of tetrapeptide-based macrocyclic 1,3-diynes were obtained from O-propargylated serine or tyrosine residues using Cu(OAc)2·H2O and NiCl2 under an O2-atmosphere. The effect of the linear 1,3-diyne on peptide conformations was studied by NMR and compared with a macrocycle bearing a saturated linker.