This compound, (4S,5R)-3-[(2S)-2-{[(9H-fluoren-9-ylmethoxy)carbonyl]amino}-3-methylbutanoyl]-2,2,5-trimethyloxazolidine-4-carboxylic acid, is a chiral auxiliary complex featuring an Fmoc-protected L-valine residue acylated onto a valinol-derived oxazolidine. The Fmoc group protects the amino functionality during synthesis, while the oxazolidine auxiliary enables highly stereoselective enolate reactions, such as Evans aldol additions, for constructing modified amino acid derivatives with precise stereocontrol. Post-reaction, the auxiliary is cleaved to yield the free acid, and Fmoc is orthogonally deprotected under mild conditions. It is invaluable for synthesizing unnatural amino acids, peptide precursors, and bioactive molecules in pharmaceutical research and biochemistry.