hydrogen fluoride; ethane-1,2-dithiol; methoxybenzene T=0°C; 1 h; Effect of the Nin-tryptophan protecting groups (Tos, Mbs, Dmb, Mtb, Mtr) on the removing of the protecting groups and the recovery of tryptophan; other reagent: methanesulfonic acid/1,2-ethanedithiol/thioanisole; Product distribution;