A new method proposed for the determination of absolute configurations of α-amino acids

✍ Scribed by Edison Díaz Gómez; Helmut Duddeck

• Publisher: John Wiley and Sons
• Year: 2009
• Tongue: English
• Weight: 175 KB
• Volume: 47
• Category: Article
• ISSN: 0749-1581
• DOI: 10.1002/mrc.2374

✦ Synopsis

Abstract

Enantiopure α‐amino acids were converted to 4‐substituted 2‐aryl‐ and 2‐alkyl‐5(4__H__)‐oxazolones under partial racemization. These nonracemic mixtures were dissolved in CDCl~3~, an equimolar amount of the chiral dirhodium complex $Rh^{\rm (II)}_{2}$[(R)− (+)− MTPA]~4~ (MTPA‐H = Mosher's acid) was added, and the ^1^H NMR spectra of the resulting samples were recorded (dirhodium method). The relative intensities of ^1^H signals dispersed by the formation of diastereomeric adducts allow to determine the absolute configuration (AC) of the starting α‐amino acids. Binding atoms in the adducts were identified by comparing the ^1^H and ^13^C chemical shifts of the oxazolones in the absence and presence of $Rh^{\rm (II)}_{2}$[(R)− (+)− MTPA]~4~. Thereby, information about the scope and limits of this method can be extracted. A protocol how to use this method is presented. Copyright © 2008 John Wiley & Sons, Ltd.