A slight modification of reported gel synthesis procedure enabled acquisition of high‐quality 1 H nuclear magnetic resonance (NMR) spectrum of partially aligned strychnine. For the first time, the narrow line width in compressed PMMA gel, comparable to that of liquid samples, allowed direct access to nearly 40 1 H– 1 H couplings constants. Using a novel approach to determine their relative signs, half of them could be readily converted to residual dipolar couplings (RDCs) without the need for additional measurements. The remaining couplings were evaluated through back‐prediction. With the inclusion of the 1 H– 1 H RDCs, remarkably clear stereochemical discrimination between strychnine and its 12‐ epi isomer—an outcome unattainable using solely the one‐bond 1 H– 13 C RDCs—was successfully achieved.
Szigetvári et al. (Sun,) studied this question.