Holtje_1983_Arzneimittelforschung_33_190

In the course of investigations of structure- and conformation-activity relationships of heterocyclic acetylcholine analogues, both the methyl esters of the tertiary and quaternary isoarecaidine and the sulfoisoarecoline were tested for their cholinergic properties. The electronic structures and the conformational behaviour of these cholinergics were investigated by quantum chemical calculations using Extended Huckel Theory (EHT) and Complete Neglect of Differential Overlap (CNDO/2)MO methods. The results show that the muscarinic potency of the heterocyclic compounds is dependent on structure and conformational behaviour of the onium center. The divergent charge distribution around the cationic heads of the ammonium and sulfonium derivatives, respectively, as well as differences in the dimensions of the two heterocyclic systems, can not be utilized to explain the differences in muscarinic potency of the isoarecaidine and sulfoisoarecaidine methyl esters.