O-methyl-DS-threonine, also known as (2R,3S)-2-amino-3-methoxybutanoic acid, is a non-proteinogenic amino acid derivative. It is a structural analog of threonine where the hydroxyl group is replaced by a methoxy group, and it possesses a specific (2R,3S) stereochemistry. This compound is a chiral building block with a defined configuration. Its primary application is in pharmaceutical research and development as a key chiral intermediate. It is notably used in the synthesis of complex bioactive molecules, including peptide-based drugs and other therapeutic agents where the introduction of a methoxy-substituted amino acid moiety is crucial for modulating biological activity, stability, or pharmacokinetic properties. The defined stereochemistry is essential for achieving the desired interaction with biological targets. As a specialty amino acid derivative, it serves as a valuable tool in medicinal chemistry for structure-activity relationship (SAR) studies and the construction of novel peptide mimetics. It is typically used in laboratory-scale synthesis rather than as a bulk commodity.