N-Me-D-Leu, also known as N-Methyl-D-leucine, is a non-proteinogenic amino acid derivative. It features a D-configuration at the chiral center and a methyl group substitution on the nitrogen atom of the leucine backbone. This specific structural modification imparts distinct physicochemical properties compared to its L-isomer or unmethylated counterpart. This compound serves as a crucial chiral building block in pharmaceutical research and development. Its primary application is as a key intermediate in the synthesis of complex bioactive molecules, particularly peptides and peptidomimetics. The incorporation of N-methylated D-amino acids like N-Me-D-Leu is a common strategy to enhance metabolic stability, modulate conformation, and improve the pharmacokinetic profiles of therapeutic peptides. It is notably used in the synthesis of certain protease inhibitors and other drug candidates. As a specialty chiral synthon, it is available from fine chemical suppliers for research purposes. Handling requires standard precautions for laboratory chemicals, and its use is typically confined to controlled synthetic environments in medicinal chemistry.