名称:
                                Muscarinic cholinergic agonists and antagonists of the 3-(3-alkyl-1,2,4-oxadiazol-5-yl)-1,2,5,6-tetrahydropyridine type. Synthesis and structure-activity relationships
                             
                            
                                摘要:
                                A series of 3-(3-alkyl-1,2,4-oxadiazol-5-yl)-1,2,5,6-tetrahydro-1-methylpyridines (2a-q) were synthesized and tested for central muscarinic cholinergic receptor binding affinity by using [H-3]oxotremorine-M and [H-3]QNB as ligands and in a functional assay using guinea pig ileum.  The analogues with unbranched C1-8-alkyl substituents (2a-g) were agonist, whereas the compounds with branched or cyclic substituents (2h-m) were antagonists.  The alkyl ether analogues (2o-q) were also agonists but had lower receptor binding affinity than the corresponding alkyl analogues.  The 3-(5-alkyl-1,2,4-oxadiazol-3-yl)-1,2,5,6-tetrahydro-1-methylpyridine analogues had only very low affinity for the central muscarinic receptors and were weak antagonists in the ileum assay.  A few 3-(3-butyl-1,2,4-oxadiazol-5-yl)-1,2,5,6-tetrahydro-1-methylpyridines substituted with methyl or hydrogen in the 1-, 5-, or 6-position were synthesized and tested.  N-Desmethyl analogue 7 was a potent muscarinic agonist, whereas N-desmethyl-5-methyl analogue 11 and N-methyl-6-methyl analogue 13 both were antagonists with lower muscarinic receptor affinity.  The 3-(3-butyl-1,2,4-oxadiazol-5-yl)quinuclidine (17) and tropane (15) analogues were both very potent antagonists with high affinity for central muscarinic receptors.  The ratio [IC50(QNB)/IC50(Oxo-M)] x 0.162 proved to be a good indicator of the efficacy of the compounds in the guinea pig ileum assay.