Fmoc-D-3,4-dimethoxyphenylalanine is a non-natural, protected amino acid derivative. Its structure features a D-configuration stereocenter, a 3,4-dimethoxyphenyl side chain, and an N-terminal 9-fluorenylmethoxycarbonyl (Fmoc) protecting group. This compound is a solid under standard conditions and is primarily handled in research and laboratory settings. This amino acid building block is extensively used in solid-phase peptide synthesis (SPPS) employing the Fmoc strategy. The D-configuration and the methoxy-substituted aromatic side chain are key structural features incorporated into synthetic peptides to modulate their biological activity, stability against enzymatic degradation, and physicochemical properties. It serves as a crucial intermediate in the research and development of peptide-based pharmaceuticals, bioactive probes, and tools for studying peptide-receptor interactions. The compound must be stored under appropriate conditions (often at -20°C) to maintain stability. As with many fine chemicals, standard laboratory safety practices should be followed during handling, including the use of personal protective equipment.