Characterization of stereochemistry and molecular conformation using solid-state NMR tensors

A solid-state NMR technique is described for establishing stereochemistry u sing the natural product terrein as a model compound. This method involves comparison of experimental C-13 tensor principal values with ab initio comp uted values for all possible computer-generated stereoisomers. In terrein t he relative stereochemistry is confirmed by NMR to be 2R*,3S* with high sta tistical probability (>99.5%). The proposed approach also simultaneously ve rifies the molecular conformation of the two hydroxy groups in terrein esta blished by X-ray data. It is sufficient to use only shift tensor values at carbons 2 and 3, the stereocenters, to characterize both the stereochemistr y and molecular conformations. The solid-state NMR method appears to be esp ecially useful for determining relative stereochemistry of compounds or the ir derivatives that are difficult to crystallize.