α -alkyl α-amino acids constitute an interesting class of non proteinogenic amino acids and are used to build new peptidic sequences with enhanced properties in various physiologically active peptides and proteins. The additional alkyl substituent could prevent the free rotation of the residue's side chain leading to unique folding when incorporated into peptides. Peptides containing quaternary α-amino acids also tend to have increased hydrophobicity, as well as an increased stability toward both chemical and metabolic decompositions. Unsaturated a-amino acids have turned out to be especially important building blocks for these studies due to the diverse reactivities of the multiple bonds and their ability to introduce biologically active functionalities. b,c-unsaturated amino acid derivatives have received crucial attention since they are important enzyme inhibitors. a-vinyl glycine is known to inhibit pyridoxal phosphate dependant enzymes in particular decarboxylase. Moreover,a-ethynyl amino acids are described such as potential suicide inhibitors of glutamic acid decarboxylase in particular ethynyl glycine is a well-known natural antibiotic and a suicide substrate for alanine racemase. Given this background, we herein report the synthesis of DL-ethynyl phenylalanine starting from DL-benzylserine in 9 steps.