Fmoc-N-methyl-L-isoleucine is primarily used in peptide synthesis, particularly in solid-phase peptide synthesis (SPPS). Its Fmoc (fluorenylmethyloxycarbonyl) protecting group allows for the selective deprotection of the amino group, enabling the stepwise construction of peptides. The N-methyl modification enhances the peptide's stability and resistance to enzymatic degradation, making it valuable in the development of therapeutic peptides and peptidomimetics. This compound is also utilized in research to study peptide structure-activity relationships, as the N-methylation can influence the peptide's conformation and biological activity. Additionally, it finds application in the synthesis of modified peptides for drug discovery, where the incorporation of N-methyl amino acids can improve pharmacokinetic properties such as bioavailability and metabolic stability.