NMR studies of dextromethorphan in both isotropic and anisotropic states

Herein, we present the solution-state NMR studies on dextromethorphan (1) under both isotropic and anisotropic conditions. From the measurement of 22 residual dipolar couplings using a stretched polystyrene gel (PS), we show that accurate and detailed structural information is readily determined including the relative stereochemical assignments of chiral centers, validation of diastereomer configuration, and the stereospecific assignment of the seven pairs of prochiral protons. This utility of PS gels is thus showcased to obtain rapid, accurate conformational, and relative configuration information in this important class of compounds without recourse to X-ray analysis.