Arakawa R, Kobayashi M, Fukuo T, Shiraiwa T
Department of Applied Chemistry, Kansai University, Suita, Osaka 564-8680, Japan.
Rapid Commun Mass Spectrom. 2001;15(9):685-9. 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 K(2)[Sb(2)(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 Sb(2)(L-tart)(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 Sb(2)(D-tart)(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 Sb(2)(L- or D-tart)(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.
光学活性的2-噻唑烷羧酸（2-THC）是动物肾脏中D-氨基酸氧化酶的底物，已知其在溶液中会迅速发生外消旋化。通过电喷雾电离质谱（ESI-MS）研究了（+）-和（-）-2-THC与酒石酸锑钾K₂[Sb₂（L或D-酒石酸）₂]的缔合。我们观察到，随着外消旋化的进行，乙腈/水溶液中缔合离子的相对强度在发生变化。对于[Sb₂（L-酒石酸）₂]²⁻，随着（+）-2-THC外消旋化为（-）-异构体，缔合离子的强度增加；另一方面，随着（-）-2-THC外消旋化为（+）-异构体，缔合离子的强度降低。在[Sb₂（D-酒石酸）₂]²⁻的情况下，观察到对缔合离子强度的相反影响。缔合离子强度的变化可用于对（+）-2-THC和（-）-2-THC进行手性识别。从NH-O官能团的氢键以及S和Sb原子的HSAB（硬软酸碱）相互作用两方面考虑，构建了光学异构体与[Sb₂（L-或D-酒石酸）₂]²⁻缔合的立体化学模型。将立体化学模型与ESI-MS结果进行比较，使我们能够预测2-THC异构体的确切构型。
