Boc-N-methyl-L-leucine is the BOC (tert-butyloxycarbonyl) protected N-methylated leucine. The N-methylated amino acid is quite useful in the peptide synthesis, giving a lot of improved properties to peptide. Studies have shown that peptide containing N-methylated amino acids obtain increased proteolytic stability, increased membrane permeability, and altered conformation. The effects of N-methylated amino acids are quite important in the development of therapeutic peptide compound as well as in the assay of biological activity of some modified peptides. BOC group can be easily removed by treatment with strong acids such as trifluoroacetic acid.