Cleavage of the phosphoramidate group in Uaa 1

To a solution of 1 (1 mg mL⁻¹) in water was added hydrochloric acid to reach a final concentration of 0.04 M HCl (pH~2). The reaction mixture was incubated at 25°C and the reaction was followed over time by successive LC-MS measurements at 1 h, 18 h and 36 h. After 36 h, ~95% of pTyr 2 had been formed confirming that even very low hydrochloric acid concentrations allowed cleaving the phosphoramidate group in 1.