H-L-Phe(4-NH-Poc)-OH (hydrochloride) is a chemical reagent utilized in the modification of phenylalanine or tyrosine analogues in protein and peptide biosynthesis. It contains an alkyne group, facilitating its role in copper-catalyzed azide-alkyne cycloaddition (CuAAC) with molecules that have azide groups. Commonly abbreviated as Poc or Pryoc, this compound acts as both a conventional click conjugation alkyne component and can be combined with tetrazine linkers in copper-free Diels-Alder type click reactions. Additionally, H-L-Phe(4-NH-Poc)-OH serves as a specialized protective group for amines, hydroxyl, and ester groups. Stable under neat trifluoroacetic acid (TFA), degradation occurs at room temperature using TFA:DCM with Co2(CO)8. Deprotection involving other transition metals such as palladium has also been reported.