Allosteric modulators are able to enhance or decrease the equilibrium binding of orthosteric agonists or antagonists. The treatment of Alzheimer's disease and the organophosphorus poisoning can take advantage of the enhancement of the ligand binding. Prerequisite is the formation of ternary complexes consisting of the receptor protein, the orthosteric ligand, e. g. N-methylscopolamine (NMS), and the alloster optimized for the corresponding orthoster. In this study, heptane-bisammonio compounds were optimized with regard to the orthosteric antagonist NMS. Comparing pairs of compounds characterized by phthalimides, cyclohexanedicarbonic acid imide and succinimides at both ends or a phthalimide at one end and either of the three imides at the other end stressed the importance of an aromatic moiety at both ends of the heptane-bisammonio chain.