Visualization of enantiomers using natural abundant (13)C-filtered single and double quantum selective refocusing experiments: Application to small chiral molecules.
The routine use of proton NMR for the visualization of enantiomers, aligned in the chiral liquid crystal solvent poly-gamma-benzyl-l-glutamate (PBLG), is restricted due to severe loss of resolution arising from large number of pair wise interaction of nuclear spins. In the present study, we have designed two experimental techniques for their visualization utilizing the natural abundance (13)C edited selective refocusing of single quantum (CH-SERF) and double quantum (CH-DQSERF) coherences. The methods achieve chiral discrimination and aid in the simultaneous determination of homonuclear couplings between active and passive spins and heteronuclear couplings between the excited protons and the participating (13)C spin. The CH-SERF also overcomes the problem of overlap of central transitions of the methyl selective refocusing (SERF) experiment resulting in better chiral discrimination. Theoretical description of the evolution of magnetization in both the sequences has been discussed using polarization operator formalism.
Nath
Nilamoni
N
NMR Research Centre, Indian Institute of Science, Bangalore 560012, India.
Baishya
Bikash
B
Suryaprakash
N
N
D000480:Alkynes / Q000737:chemistry; D000440:Butanols / Q000737:chemistry; D002247:Carbon Isotopes; D050866:Liquid Crystals; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008968:Molecular Conformation; D011099:Polyglutamic Acid / Q000031:analogs & derivatives / Q000737:chemistry; D011407:Propane / Q000031:analogs & derivatives / Q000737:chemistry; D011422:Propionates / Q000737:chemistry; D011789:Quantum Theory; D012997:Solvents; D013237:Stereoisomerism
C540507:3-butyn-2-ol; D000480:Alkynes; D000440:Butanols; D002247:Carbon Isotopes; D011422:Propionates; D012997:Solvents; C003172:poly-gamma-benzyl-L-glutamate; D011099:Polyglutamic Acid; C045990:propylene carbonate; C007022:3-chloropropionic acid; D011407:Propane