Fmoc-Phe-Lys(Boc)-PAB is a Phe-Lys dipeptide featuring an Fmoc-protected N-terminal, a Boc-protected ε-amine on the lysine, and a p-aminobenzyl (PAB) group. The benzylic alcohol on the PAB can be used to attach with reactive groups such as PNP for conjugation with drug payloads. The Fmoc protecting group may be removed by piperidine to allow the N-terminal to couple with carboxylic acids, while the Boc protecting group may be removed by acid towards the same ends. The Phe-Lys dipeptide may be cleaved by proteases to release a given drug payload via an elimination mechanism within the PAB group.
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