Yield:-

Reaction Conditions:

with formic acid;dihydrogen peroxide in methanol;water at 20; for 2 h;

Steps:

6.a

(a) Oxidation of (Cys-Leu)₂ to the Respective Sulfonic Acid Dipeptide; A performic acid solution is freshly prepared by mixing 0.5 ml of H₂O₂ (30% in water) with 9.5 ml of formic acid for 2 hours at room temperature. The oxidized dimeric (Cys-Leu)₂ dipeptide is dissolved in formic acid-methanol (5:1, % by vol.) (40 mg/ml). The 2 solutions are cooled down to 0° C., whereupon the peptide solution is added dropwisely to the performic acid. The solution is then stirred for 2.5 hours at 0° C. In order to stop the reaction, ice is added to the reaction mixture. Thereupon, the solvent is removed by evaporation.

References:

US7064234,2006,B2 Location in patent:Page/Page column 31