N^α-Fmoc-L-threonine tert-butyl ester is a protected derivative of L-threonine widely used in peptide synthesis, particularly solution-phase methods and fragment condensation strategies. The Fmoc (9-fluorenylmethoxycarbonyl) group protects the α-amino group, and the tert-butyl ester protects the α-carboxyl group, leaving the β-hydroxyl side chain unprotected. This orthogonal protection strategy enables selective deprotection and coupling reactions, preventing unwanted side reactions during peptide assembly. It is valuable for synthesizing complex peptide esters for research in biochemistry, pharmaceuticals, and biotechnology. Its stability, solubility in organic solvents, and ease of deprotection (piperidine for Fmoc, TFA for tBu) contribute to high purity and yield.