Mosher's acid explained
Mosher's acid, or α-methoxy-α-trifluoromethylphenylacetic acid (MTPA) is a carboxylic acid which was first used by Harry Stone Mosher as a chiral derivatizing agent.[1] [2] [3] [4] It is a chiral molecule, consisting of R and S enantiomers.
Applications
As a chiral derivatizing agent, it reacts with an alcohol or amine[5] of unknown stereochemistry to form an ester or amide. The absolute configuration of the ester or amide is then determined by proton and/or 19F NMR spectroscopy.
Mosher's acid chloride, the acid chloride form, is sometimes used because it has better reactivity.[6]
See also
Notes and References
- J. A. Dale . D. L. Dull . H. S. Mosher . α-Methoxy-α-trifluoromethylphenylacetic acid, a versatile reagent for the determination of enantiomeric composition of alcohols and amines. Journal of Organic Chemistry. 1969. 34. 9. 2543–2549. 10.1021/jo01261a013.
- J. A. Dale . H. S. Mosher . Nuclear magnetic resonance enantiomer regents. Configurational correlations via nuclear magnetic resonance chemical shifts of diastereomeric mandelate, O-methylmandelate, and α-methoxy-α-trifluoromethylphenylacetate (MTPA) esters. Journal of the American Chemical Society. 1973. 95. 2. 512–519. 10.1021/ja00783a034.
- Y. Goldberg . H. Alper . A new and simple synthesis of Mosher's acid. Journal of Organic Chemistry. 1992. 57. 13. 3731–3732. 10.1021/jo00039a043.
- D. L. Dull . H. S. Mosher . Aberrant rotatory dispersion curves of α-hydroxy- and α-methoxy-α-trifluoromethylphenylacetic acids. Journal of the American Chemical Society. 1967. 89. 16. 4230. 10.1021/ja00992a053.
- See for example: Mosher Amides: Determining the Absolute Stereochemistry of Optically-Active Amines Allen, Damian A.; Tomaso, Anthony E., Jr.; Priest, Owen P.; Hindson, David F.; Hurlburt, Jamie L. J. Chem. Educ. 2008, 85, 698. Abstract
- D. E. Ward . C. K. Rhee . A simple method for the microscale preparation of Mosher's acid chloride. Tetrahedron Letters. 1991. 32. 49. 7165–7166. 10.1016/0040-4039(91)80466-J.
