Studies on the association of 2-thiazolidinecarboxylic acid and antimony potassium tartrate: chiral recognition and prediction of absolute configuration by electrospray ionization mass spectrometry

• Published in: Rapid communications in mass spectrometry Vol. 15; no. 9; pp. 685 - 689
• Main Authors: Arakawa, Ryuichi, Kobayashi, Mako, Fukuo, Tsuyoshi, Shiraiwa, Tadashi
• Format: Journal Article
• Language: English
• Published: Chichester, UK John Wiley & Sons, Ltd 01.01.2001
• ISSN: 0951-4198; 1097-0231
• DOI: 10.1002/rcm.286

Optically active 2‐thiazolidinecarboxylic acid (2‐THC), a substrate for D‐amino acid oxidase in animal kidney, is known to undergo racemization quickly in solution. The association of (+)‐ and (−)‐2‐THC with antimony potassium tartrate K2[Sb2(L or D‐tart)2] was studied by electrospray ionization mass spectrometry (ESI‐MS). We observed that relative intensities of associated ions in acetonitrile/water solution were changing as the racemization progressed. For [Sb2(L‐tart)2]2−, the intensities of the associated ions increased as (+)‐2‐THC underwent racemization to a (−)‐isomer; on the other hand, the intensity of the associated ion decreased as (−)‐2‐THC underwent racemization to a (+)‐isomer. In the case of [Sb2(D‐tart)2]2−, an opposite effect on the intensities of the associated ions was observed. The change in the intensities of associated ions can be used for chiral recognition of (+)‐2‐THC and (−)‐2THC. Stereochemical models of the association of the optical isomers with [Sb2(L‐ or D‐tart)2]2− were constructed from the consideration of both hydrogen bonding of NH‐O functions and HSAB (hard and soft acids and bases) interaction of S and Sb atoms. Comparison of the stereochemical models with the ESI‐MS results enabled us to predict the absolute configurations of the 2‐THC isomers. Copyright © 2001 John Wiley & Sons, Ltd.