Phenylalanine

Phenylalanine is an essential amino acid and it is classified as nonpolar because of the hydrophobic nature of the benzyl side chain. Phenylalanine can also be converted into L-tyrosine, which can be converted into L-DOPA, which is further converted into dopamine, norepinephrine (noradrenaline), and epinephrine (adrenaline).