Determination of absolute configurations by X-ray crystallography and 1H NMR anisotropy.
To determine the absolute configurations of chiral compounds, many spectroscopic and diffraction methods have been developed. Among them, X-ray crystallographic Bijvoet method, CD exciton chirality method, and the combination of vibrational circular dichroism and quantum mechanical calculations are of nonempirical nature. On the other hand, X-ray crystallography using a chiral internal reference, and 1H NMR spectroscopy using chiral anisotropy reagents are relative and/or empirical methods. In addition to absolute configurational determinations, preparations of enantiopure compounds are strongly desired. As chiral reagents useful for both the preparation of enantiopure compounds by HPLC separation and the simultaneous determination of their absolute configurations, we have developed camphorsultam dichlorophthalic acid (CSDP acid) for X-ray crystallography and 2-methoxy-2-(1-naphthyl)propionic acid (MalphaNP acid) for 1H NMR spectroscopy. In this review, the principles and applications of these X-ray and NMR methods are explained using mostly our own data.
Harada
Nobuyuki
N
Department of Chemistry, Columbia University, New York 10027, USA. nh2212@columbia.edu
D000438:Alcohols / Q000737:chemistry; D016880:Anisotropy; D002264:Carboxylic Acids / Q000737:chemistry; D002851:Chromatography, High Pressure Liquid; D002942:Circular Dichroism / Q000379:methods; D018360:Crystallography, X-Ray / Q000379:methods*; D037741:Fullerenes / Q000737:chemistry; D006859:Hydrogen / Q000737:chemistry; D007202:Indicators and Reagents; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008958:Models, Molecular; D008968:Molecular Conformation; D013237:Stereoisomerism
D000438:Alcohols; D002264:Carboxylic Acids; D037741:Fullerenes; D007202:Indicators and Reagents; D006859:Hydrogen; C069837:fullerene C60