This paper shows that it is possible to convert a protected peptide containing djenkolic acid to the corresponding peptide containing cystine. Thus, the tripeptide 8 and the pentapeptide 9 were converted to peptides 10 and 11 respectively by treatment with bromine in anhydrous medium followed by an hydrolysis. The pentapeptides 9 and 11 were then deprotected and purified by filtration through Sephadex G-10 to give respectively the pentapeptide bis-γ-L-glutamyl-L-djenkolyl-bis-glycine (7) and oxidized glutathione (2) with overall respective yields of 57 and 38% from djenkolic acid (1).