in DCM with a final concentration of 50 mM. Subsequently, TFA (10 eq) was added and the reaction was stirred at room temperature for 1-3 hours, until full deprotection was indicated by TLC. The pH was adjusted to 11 with aqueous NaOH solution and the organic layer was separated. Afterwards, the organic layer was washed with saturated NaHCO3 solution (aq., 10 mL) and the aqueous layer was extracted with DCM (10 mL, 3×). The combined organic layers were dried over Na2SO4, filtered and the solvent was removed under reduced pressure.