N-[(9H-Fluoren-9-ylmethoxy)carbonyl]-O-methyl-D-threonine is a specialized building block in peptide synthesis, featuring an Fmoc-protected N-terminus on O-methyl-D-threonine. The fluorenylmethoxycarbonyl (Fmoc) group safeguards the amino group against unwanted reactions during peptide bond formation, while the O-methyl modification on the threonine side chain provides a permanent ether protection or structural alteration. This compound is particularly suited for solid-phase peptide synthesis (SPPS), where the Fmoc can be orthogonally deprotected under mild basic conditions (e.g., with piperidine) without impacting other functionalities. It enables the precise incorporation of modified D-threonine residues into peptides and proteins, supporting advanced research in biochemistry, drug discovery, and therapeutic peptide development.