An improved method for determining enantiomeric excess by (13)C-NMR in chiral liquid crystal media.
By using a combination of inverse gated (1)H decoupled (13)C-NMR experiments1 with short acquisition times and NMR Cryo-probe technology, the sample requirements and experimental times necessary to accurately measure enantiomeric excess of small chiral molecules has been reduced 16-fold. Quality (13)C-NMR spectra can now be obtained from a 1 to 5 mg sample in 12 minutes. The enantiomeric excess determination achieved from the average integration of all the (13)C-resonances in the spectrum is comparable to enantiomeric excess measured by chiral SFC. The advantage of the NMR method is that enantiomeric excess can rapidly be measured in situ on practical amounts of enantioselective reaction products without the need for chromatographic separation or chemical modification and with substantially less solvent waste.
Marathias
Vasilios M
VM
Pfizer Global Research, Analytical Chemistry, Inflammation / Immunology Research Unit, Cambridge, Massachusetts, USA. marathv@wyeth.com
Tate
Peter A
PA
Papaioannou
Nikolaos
N
Massefski
Walter
W
D050866:Liquid Crystals / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D013237:Stereoisomerism; D013997:Time Factors