Chiral Derivatization Reagent Possessing a Pyridylthiourea Structure

(R)-PyT-C (1), which was developed by Toyo’oka et al., is a useful chiral derivatization reagent possessing a pyridylthiourea structure for the enantiomeric separation and the quantitative determination of chiral amines in LC-ESI-MS/MS. In the presence of 2,2'-dipyridyl disulfide and triphenylphosphine as activation reagents, amines are labeled with 1 to afford the corresponding labeled amines. When enantiomeric mixtures of amines are employed, the diastereomeric labeled amines are given. The formed diastereomers are clearly separated by reversed-phase chromatography using an ODS column. Furthermore, the resulting derivatives show a characteristic product-ion (m/z 137.0) derived from 1, and highly sensitive detection and quantitation are performed from the SRM (selected reaction monitoring) chromatograms. This procedure is also applied to the simultaneous separation and detection of chiral amines. Thus, this analytical procedure is expected to open up a wide range of possibilities for application in the field of metabolomics.

Typical Procedure:
A 10 mM 1 in acetonitrile (20 μL) is reacted at 60 °C for 60 min with chiral amines (10 μM) in the presence of 10 mM triphenylphosphine in acetonitrile (20 μL) and 10 mM 2,2'-dipyridyl disulfide in acetonitrile (20 μL). After removal of the solvent under a gentle nitrogen stream, the residues are re-dissolved in the initial mobile phase, and then an aliquot (2 μL) is subjected to UHPLC-ESI-MS/MS. The separations of the pair of diastereomers for chiral amines are performed by isocratic elution using water/acetonitrile containing 0.1% formic acid. The SRM chromatograms of each pair of diastereomers are obtained from the monitoring ion of m/z 137.0, derived from the MS transition of corresponding protonated-molecular ion, [M+H]⁺.