methanesulfonic acid; methanesulfonic acid in trifluoroacetic acid-thioanisole; trifluoroacetic acid T=20°C; 2 h; effect of the concentration of methanesulfonic acid; deprotection of the Mtr group with various deprotecting agents (TFA-thioanisole, HF-thioanisole, TFA, methanesulfonic acid-thioanisole); Product distribution;