A convenient preparation of dityrosine via Mn(III)-mediated oxidation of tyrosine

A simple method to rapidly and conveniently prepare dityrosine from l-tyrosine was developed using Mn(III) as an oxidizing agent. The best yield of the reaction was obtained from the 1 min equimolar reaction of l-tyrosine with Mn(III) acetate in 0.2 M sodium phosphate solution (pH 2.1) at 25 °C. Phosphate was removed by precipitation in ammonia water. The remaining tyrosine was mostly eliminated by precipitation in cold acidic water. Dityrosine was then further purified by HPLC, and its chemical structure was identified by NMR spectroscopy. Even though the yield was only 15.8%, this one-step Mn(III)-mediated oxidation of tyrosine allows dityrosine to be prepared without the need for complicated multi-step organic reactions.