3-(Tritylthio)propionic acid is used as a protected thiol building block in organic synthesis, particularly in peptide, nucleotide, and bioconjugate synthesis. The trityl (Trt) group provides steric protection to the thiol functionality, ensuring stability under basic and neutral conditions, while the free carboxylic acid enables straightforward coupling to amines or resins in solid-phase synthesis. It facilitates the introduction of a -CH₂CH₂SH linker, which is valuable for creating thiol-containing peptides, polymers, and conjugates. The Trt protecting group is orthogonally removable under mild acidic conditions (e.g., TFA), allowing selective deprotection without disrupting other functionalities, thereby improving yield, purity, and control in multistep assemblies.