Optically active N-Me-N-benzyl quaternary derivatives of (1S,2S)-2-oxa-5-azabicyclo[2.2.1]heptane were synthesized in order to investigate the effect of an asymmetric quaternary N on anticholinergic activity. Nmr studies indicate that the N-substituted bicyclic system undergoes highly stereoselective quaternization. Configurations have been tentatively assigned to the N epimers. The exo-5-methyl-crido-5-benzyl and ero-5-benzyl-endo-5-methyl N epimers possess comparable antagonistic activities on the guinea pig ileum. The possible implications of the biological data are discussed.