Methods are provided for making pharmaceutical-grade cis-2-methylspiro(1,3- oxathiolane-5,3)quinuclidine and pharmaceutically acceptable salts thereof by isomerizing racemic 2-methylspiro(1,3-oxathiolane-5,3)quinuclidine to cis-2-methylspiro(1,3-oxathiolane- 5,3)quinuclidine and subsequent purification of the C-MSOQ by salt formation with inexpensive and commercially available material such as sulfuric acid. Purification methods are disclosed which employ an organic solvent/water system and recrystallization with an organic solvent such as acetone.
