Fmoc-O-(tert-butyldimethylsilyl)-L-threonine is a protected derivative of the amino acid L-threonine. It features two orthogonal protecting groups: the base-labile 9-fluorenylmethoxycarbonyl (Fmoc) group on the α-amino function and the acid-labile tert-butyldimethylsilyl (TBDMS) group on the β-hydroxyl side chain. This specific protection scheme is critical for its primary application. This compound is a fundamental building block in solid-phase peptide synthesis (SPPS) employing the Fmoc strategy. The TBDMS protection of the threonine side chain prevents undesired side reactions, such as β-elimination or aspartimide formation, during the repetitive cycles of deprotection and coupling. It ensures the integrity and high yield of peptides containing threonine or serine residues. It is therefore an essential specialty reagent for the synthesis of complex peptides, including therapeutic peptides and research tools in biochemistry and pharmaceutical development. While its primary and defining use is in peptide synthesis, its well-defined structure with orthogonal protecting groups also makes it a valuable chiral synthon in specialized organic synthesis contexts, particularly where the introduction of a protected threonine moiety is required.