Scheme 5. Synthesis of cyclic peptide amide-28 using the optimized KAHA cyclization process. Analytical HPLC traces at 220 nm: (a) crude linear peptide 27 after cleavage from resin. (b) Crude cyclic peptide depsi-28 after 18 h at 50 °C. (c) Crude cyclic peptide amide-28 3 h after the addition of 1.6 M aq NH3. [DODT = 3,6-dioxa-1,8-octanedithiol].28 .
