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Note | Regular issue | Vol 51, No. 1, 1999, pp.183-184
Published online, 1st January, 1970
DOI: 10.3987/COM-98-8361
■ A Cautionary Note on the Use of Commercial (R)-MTPA-Cl and (S)-MTPA-Cl in Determination of Absolute Configuration by Mosher Ester Analysis

Balawant S. Joshi* and S. William Pelletier

*Department of Chemistry, Institute for Natural Products Research, The University of Georgia, Chemistry Building, Athens, Georgia 30602-2556, U.S.A.

Abstract

While the absolute configuration of a Mosher ester derivative (MTPAOR) is identical with that of the Mosher acid (MTPAOH) precursor, it is opposite that of the Mosher acid chloride (MTPA-Cl). Since (R)-MTPA-Cl and (S)-MTPA-Cl are now commercially available, incorrect conclusions may be drawn in deriving the absolute configuration, if this fact is overlooked. The absolute configuration of (-)-vasicinone (1) derived by Mosher ester analysis (Tetrahedron Asymmetry, 1996, 7, 25) has been revised as 3S. Masher ester analysis of (-)-vasicine (2) confirmed a 3S configuration for this alkloid.