Used as a thiol-containing building block in organic synthesis, particularly in peptide and heterocyclic chemistry. The tert-butyl carbamate (Boc) group protects the pyrrolidine nitrogen, providing stability and selectivity during multi-step reactions, while the free thiol group at the 3-position allows for direct conjugation or subsequent protection/deprotection, such as in the formation of disulfide bonds or thioether linkages. Commonly employed in pharmaceutical development for modifying bioactive molecules, enhancing stability, or enabling site-specific modifications in drug design. Also useful in the preparation of cysteine analogs and in chemoselective ligation strategies.