N3-D-Orn(Boc)-OH is a Boc-protected pentanoic amino acid derivative, can be used as a click chemistry reagent and has been used to synthesis antibody-drug conjugates (ADC). It contains an azide group and can undergo copper-catalyzed azide-alkyne cycloaddition (CuAAc) with molecules containing alkyne groups. It can also undergo ring strain-promoted alkyne-azide cycloaddition (SPAAC) with molecules containing DBCO or BCN groups.