It is used in peptide synthesis as an unnatural amino acid building block in biochemical research for enzyme purification (e.g. peptide synthetases in pristinamycin biosynthesis) and as a metabolic intermediate or probe in medicinal chemistry.

Its primary purpose is to introduce an aromatic amine functionality into peptides for selective modification receptor binding studies or affinity chromatography due to the reactive para-NH group.

4-Amino-L-phenylalanine is the L-enantiomer of a non-proteinogenic amino acid with formula CHNO a white to off-white crystalline solid featuring a phenyl ring with a para-amino group substitution on the -carbon of alanine molecular weight 180.2 gmol and high water solubility.