Used in peptide synthesis, particularly in solid-phase peptide synthesis (SPPS) as a building block. It is employed to introduce deuterium-labeled leucine residues into peptides, which is useful for studies involving nuclear magnetic resonance (NMR) spectroscopy or mass spectrometry. The deuterium labeling allows for enhanced tracking and analysis of peptide behavior, structure, and interactions in various biochemical and pharmaceutical research applications. Its Fmoc (fluorenylmethyloxycarbonyl) protecting group ensures compatibility with standard SPPS protocols, enabling efficient and selective deprotection during synthesis. This compound is valuable in the development of labeled peptides for drug discovery, metabolic studies, and protein engineering.