Olefinic alpha-methyl amino acid for peptide stapling. Upon incorporation of this amino acid into a peptide, along with another of the same or derivative with a different length of the olefinic side chain, the two can be ′stapled′ via a ring closing metathesis reaction with Grubb′s catalyst (product # 579726). The resulting stapled peptide macrocycle has been shown to stabilize the alpha-helical structure of peptides, which can lead to favorable biological characteristics such as increased proteolytic stability and cellular uptake.