Separation of 4-substituted 5-methylpiracetam stereoisomers on polysaccharide-based chiral stationary phases

Abstract

Monitoring of stereoisomer content in samples containing chiral compounds with multiple chiral centers is an important and challenging task in chiral liquid chromatography. 4-Phenyl-5-methylpiracetam, containing two chiral centers, was used as model compound to explore the stereorecognition ability of polysaccharide-based chiral selectors. Initially, the chromatographic behavior of racemic 4-phenyl-5-methylpiracetam on nineteen commercially available polysaccharide-based chiral columns was tested with a mobile phase, consisting of a mixture of ethanol and n-hexane. The obtained results were analysed, and nine chiral phases were selected for further investigation of seven newly synthesized 4-substituted 5-methylpiracetam chiral separations. Our subsequent studies showed that chiral stationary phases based on amylose tris(5-chloro-2-methylphenylcarbamate) and amylose tris[(S)-α-methylbenzylcarbamate] posess higher ability for chiral recognition of stereoisomers of the studied analytes.

Keywords

• Column liquid chromatography
• 4,5-disubstituted piracetam derivatives
• Separation of stereoisomers
• Polysaccharide-based chiral stationary phase
• Normal-phase mode