Error analysis of solution state three-dimensional structures determined using residual dipolar coupling NMR

Abstract

When mols. in soln. are placed in an anisotropic environment, residual dipolar couplings (RDCs) can be obsd. in a NMR spectrum. [1] Using the magnitude of the measured RDCs, the angle and distance between two nuclei can be detd. [1] As previously reported, RDC NMR has been used to det. the stereochem. of small org. mols. [3] Previous studies have focused on detd. one stereoisomer from many theor. options. [1,2,3] One limitation of using RDCs to det. the structures of mols. is that they cannot provide a measure of the error in the three-dimensional structure coordinates detd. as is done in X-ray crystallog.[4] This research will compare the RDCs of many stereoisomers of steroid compds. and det. how well the methodol. can distinguish their stereochem. The percent error in assignment of the stereocenters in the steroids will be compared to the percent error in the measured RDCs to det. an acceptable std. for the confidence of structures detd. by RDCs.