Used in solid-phase peptide synthesis as a chiral building block for introducing a side chain with a terminal alkene functionality. The Fmoc group allows for orthogonal protection, enabling stepwise assembly of peptides under mild basic conditions. The pentenyl side chain serves as a handle for post-assembly modifications, such as thiol-ene coupling or metathesis reactions, useful in peptide cyclization, bioconjugation, or attachment to surfaces and polymers. Commonly applied in the development of peptide-based therapeutics, probes, and biomaterials.