Used in peptide synthesis as a protected N-methyl-D-amino acid building block. The Fmoc group provides temporary protection for the N-methyl amine functionality, enabling selective coupling reactions in solid-phase and solution-phase peptide synthesis. The N-methyl substitution on the alpha-nitrogen increases peptide backbone rigidity, resistance to enzymatic degradation, and alters conformational properties, making it valuable for designing bioactive peptides and peptidomimetics. The D-methionine enantiomer introduces specific stereochemical control, while the methionine side chain (with its thioether methyl group) contributes to side-chain reactivity and stability under mild conditions. Commonly applied in the preparation of structured peptides, bioactive analogs, pharmaceutical intermediates, and drug discovery efforts targeting N-methylated sequences.