Abstract: The present invention provides a method of making an enantiomerically enriched tertiary or quaternary ammonium salt, and the use of a non-racemic chiral compound in the synthesis of an enantiomerically enriched tertiary or quaternary ammonium salt. The control of nitrogen-based chirality, achieved via the method of the invention, is useful where a specific tertiary or quaternary ammonium enantiomer is preferred over the other enantiomer, for example where a specific tertiary or quaternary ammonium enantiomer is more effective than the other enantiomer in treating a specific medical condition.