Previous structure-activity relationship studies involving a series of lactone-based muscarinic ligands identified a lead compound containing a diphenylmethylpiperazine moiety (4; IC50= 340 nM). The purpose of the present work is to investigate 1, 3- benzodioxoles, 4, 4-diethyl substituted tetrahydrofurans, 5-substituted oxazolidinones and chromones as bioisosteric replacements for the lactone ring in a novel series of ...