Molecular requirements for antimuscarinic activity in 1,3-oxathiolanes

To study the dimensional and steric requirements of the lipophilic pocket involved in the interaction of the muscarinic receptor with antagonists, we synthetized ten 1,3-oxathiolane derivatives (Scheme 2, compounds 9-18). The pharmacological results show that specific chemical modifications have different effects in the 1,3-oxathiolane series in comparison with the choline diphenylacetic acid esters series, indicating that the two series have different structure-activity relationships. Apart from postulating different binding sites for the two series, such differences can be explained by differences in the ability of the compounds to adopt proper conformations for optimum receptor interaction.