Design, synthesis and biological activity of some 4-DAMP- related compounds

Two constrained analogues (4a and 4b) of both 4-DAMP (1) and spiro-DAMP (2) were designed, and their biological profiles at muscarinic receptor subtypes were assessed by functional and binding assays. It turned out that these constrained analogues display a modest, if any, M2/M3 selectivity ratio. However, most interestingly, they proved to be highly selective for muscarinic M1 receptors.