3,4-Dehydro-L-proline hydrochloride is a non-proteinogenic amino acid derivative, specifically a hydrochloride salt of a dehydrated proline analog. Its chemical structure features a pyrrolidine ring with a double bond between the 3 and 4 positions, which introduces rigidity and alters its conformational properties compared to L-proline. This compound serves as a key chiral building block and intermediate in pharmaceutical research and synthesis. Its primary application lies in the development of peptidomimetics and constrained peptides, where it is incorporated to influence secondary structure, enhance metabolic stability, and modulate biological activity. It is particularly valuable for probing structure-activity relationships (SAR) in drug discovery programs targeting various diseases. As a derivative of a fundamental amino acid, it is also utilized in biochemical studies and as a precursor for more complex bioactive molecules. Handling requires standard precautions for laboratory chemicals.