Dioxane and Oxathiane Nuclei: Suitable Substructures for Muscarinic Agonists

Muscarinic agonists, bearing 1,4-dioxane and 1,4-oxathiane nuclei, were synthesized and tested to evaluate their potency at M1-M4 muscarinic receptor subtypes. The stereochemical relationship between the 2-side chain and the 6-methyl group plays an important role in drug-receptor interaction, since the cis isomers are more potent than the corresponding trans isomers. However, the latter are able to discriminate between the muscarinic receptor subtypes. Among them compound 5b proves particularly interesting, since it selectively activates the ileal M3 receptor subtype and is devoid of agonist activity at the others.