Fmoc-cyclopropyl-L-glycine is a non-proteinogenic, conformationally constrained amino acid derivative. It features a cyclopropyl side chain and is protected at the N-terminus with a 9-fluorenylmethoxycarbonyl (Fmoc) group, making it a standard building block for solid-phase peptide synthesis (SPPS) using the Fmoc strategy. This compound is primarily used in peptide chemistry and medicinal chemistry research. The cyclopropyl group introduces significant conformational rigidity into the peptide backbone, which is a valuable strategy for probing structure-activity relationships (SAR), enhancing metabolic stability, and improving the bioavailability of peptide-based drug candidates. It serves as a key synthetic intermediate for the preparation of modified peptides and peptidomimetics. As a specialized, protected amino acid, its primary application is highly focused on the synthesis of bioactive peptides and potential therapeutic agents. It is a standard reagent in the toolkit for peptide chemists and is commercially available from suppliers specializing in peptide synthesis materials and advanced pharmaceutical intermediates.