(R)-(-)-O-Acetylmandelic acid

• CAS: 51019-43-3
• Catalog Number: ACM51019433
• Category: Material of Cosmetics
• Molecular Weight: 194.18
• Molecular Formula: C10H10O4
• Synonyms: (−)-O-Acetyl-D-mandelic acid, (R)-(−)-α-Acetoxyphenylacetic acid

Case Study

O-Acetylmandelic Acid for the Determination of Absolute Configuration of Secondary Alcohols via Chiral Anisotropy NMR Analysis

Sureshan KM, et al. Tetrahedron: Asymmetry, 2004, 15(21), 3357-3364.

O-acetylmandelic acid (OAM) is an effective chiral anisotropy reagent for determining the absolute configuration of secondary alcohols. In the reported methodology, O-acetylmandelic acid was experimentally applied as a derivatization reagent to convert alcohol substrates into OAM esters, enabling stereochemical analysis by NMR spectroscopy. Two esterification approaches were employed. In the DCC-mediated method, the alcohol substrate was reacted with O-acetylmandelic acid (1.1 equiv) and dicyclohexylcarbodiimide in dichloromethane at 0 °C for 2-3 h, followed by filtration of dicyclohexylurea and chromatographic purification to afford the corresponding OAM ester. Alternatively, the acid chloride method involved dropwise addition of O-acetyl mandeloyl chloride to the alcohol dissolved in pyridine at 0 °C, followed by aqueous work-up and chromatographic purification. The resulting diastereomeric OAM esters were analyzed by ^1H NMR spectroscopy, and the Δδ values of protons located on both sides of the CH-OAM plane were compared. Using a conformational anisotropy model, the sign and magnitude of Δδ values allowed reliable assignment of the absolute configuration of cyclitol and other secondary alcohols, even in sterically hindered systems.