(S)-(-)-Methyl 2-hydroxy-2-phenylacetate, commonly known as (S)-(-)-Methyl mandelate, is a chiral α-hydroxy ester. It is a white to off-white crystalline solid with the molecular formula C9H10O3 and a molecular weight of 166.17 g/mol. This compound is characterized by its specific optical rotation, [α]D = -150° to -155° (c=1 in methanol), indicating its high enantiomeric purity in the (S)-configuration. Its primary and most significant application is as a versatile chiral building block and resolving agent in the pharmaceutical industry. It serves as a key chiral intermediate in the synthesis of various active pharmaceutical ingredients (APIs), particularly those requiring the (S)-mandelic acid moiety. It is instrumental in the production of drugs such as cilostazol (a vasodilator and antiplatelet agent) and other cardiovascular or neurological therapeutics. The compound is also employed in asymmetric synthesis and as a chiral auxiliary or ligand precursor in catalytic reactions. Beyond pharmaceutical synthesis, (S)-(-)-Methyl mandelate finds use in organic chemistry research as a model substrate for studying enzymatic resolutions (e.g., using lipases or esterases) and for preparing other chiral derivatives. It should be handled with standard laboratory precautions, as it may cause skin and eye irritation.