This compound, (S)-1-(((9H-fluoren-9-yl)methoxy)carbonyl)-2-methylpyrrolidine-2-carboxylic acid, also known as Fmoc-(S)-2-methylproline, is a protected derivative of the non-natural amino acid (S)-2-methylproline. It serves as a key building block in solid-phase peptide synthesis (SPPS), where the fluorenylmethoxycarbonyl (Fmoc) group protects the nitrogen of the pyrrolidine ring. This protection allows for orthogonal deprotection under mild basic conditions, facilitating the controlled, stepwise elongation of peptide chains. The (S)-chirality and 2-methyl substitution introduce specific steric effects that can modulate peptide conformation, stability, and biological activity. It is particularly valuable in the synthesis of enantiomerically pure peptides, peptidomimetics, and complex biomolecules for pharmaceutical research, drug development, and biotechnological applications.