Conformational analysis of an isoquinolinium hydrochloride in water using residual dipolar couplings.

The use of the cetylpyridinium chloride (CPCL)/NaCl/hexanol liquid crystal allowed the measurement of (1)D(CH) residual dipolar couplings of the isoquinoline alkaloid salsolidine in its protonated state. Populations of its two half-chair forms were determined by using the single alignment tensor approximation combined with global superposition of conformers. These populations were in good agreement with the DFT-computed energies for both conformers.