Seven cyclic disulfide peptides (oxytocin, salmon calcitonin 1-10, CTP, crustacean cardioactive peptide, somatostatin 3-14, [C2,6]-β-endorphin 1-6 and endothelin-β 3-11) were synthesized on solid phase and cyclized either on the resin, simultaneously with the cleavage from the resin, or in solution after cleavage, using eight different oxidation methods. The purities of the crude peptides were compared in order to evaluate the efficacy of the different oxidation methods with respect to the peptide sequences.
