O-tert-Butyl-N-[(9H-fluoren-9-ylmethoxy)carbonyl]-N-methyl-L-tyrosine, commonly abbreviated as Fmoc-N-Me-Tyr(tBu)-OH, is a protected, N-methylated derivative of the amino acid tyrosine. It features an Fmoc (9-fluorenylmethoxycarbonyl) protecting group on the amine, a tert-butyl (tBu) ether protecting group on the phenolic hydroxyl side chain, and a methyl group on the amide nitrogen. This specific combination of protecting groups and modifications makes it a non-natural, specialty amino acid building block. Its primary and definitive application is in the field of solid-phase peptide synthesis (SPPS), particularly using the Fmoc strategy. The Fmoc group is base-labile and allows for orthogonal deprotection during peptide chain assembly. The N-methylation introduces conformational constraints and can enhance metabolic stability, protease resistance, and membrane permeability of the resulting synthetic peptides. It is therefore a critical reagent for medicinal chemists and peptide researchers aiming to develop novel peptide-based therapeutics, peptidomimetics, and probes with improved pharmacological properties. This compound is not a general-purpose synthesis reagent but a highly specialized, application-driven intermediate. It is supplied as a high-purity white powder for research and development use in pharmaceutical and biotechnology laboratories.