Protection of thiols, such as cysteine residues in peptide synthesis, as their S-trityl derivatives can be accomplished in high yield in TFA. Cleavage can be effected with HBr in AcOH: J. Chem. Soc. (C), 2683 (1970), with Hg(II) salts, or by oxidation to the disulfide with I2 in MeOH: Helv. Chim. Acta, 51, 2061 (1968).
