Investigation of the dimethylsulfoxide-trifluoroacetic acid oxidation system for the synthesis of cystine-containing peptides.

Disulfide bonds of peptides were effectively established between S-protected cysteine residues as well as free cysteine residues by the action of dimethylsulfoxide in trifluoroacetic acid. Oxytocin and alpha-human calcitonin gene-related peptide were synthesized using this oxidation system. The feasibility of this method for the formation of two disulfide bridges of apamin was also examined.