1,4-dioxane, a suitable scaffold for the development of novel M₃ muscarinic receptor antagonists.

In this study the modulation of the pharmacological profile from agonist to antagonist was successfully obtained by replacing the methyl group in position 6 of the 1,4-dioxane scaffold of the potent M(2)/M(3) muscarinic agonist 1 with bulkier groups. In particular, the 6,6-diphenyl substitution provided the potent M(3) preferring antagonist (±)-17, which in in vivo study proved to be effective in reducing the volume-induced contractions of rat urinary bladder and was devoid of cardiovascular effects.