D-Leucine is a non-proteinogenic amino acid used primarily in pharmaceutical research and development as a chiral building block for the synthesis of peptides and proteins. It is particularly valuable in creating therapeutic compounds with enhanced stability against enzymatic degradation, improving drug efficacy and specificity. In biochemical research, it aids in studying metabolic pathways, enzyme inhibition, and stereospecific interactions. Unlike its L-enantiomer, D-Leucine has limited applications in nutritional supplements or food, but emerging studies explore its potential in neuroscience and antimicrobial peptide design.