12i dual-site binding strategy with two 4-Aminopyridine with tether length of 10 methylene units .(AChE IC50=152+/-30 nM) is at least 3000 times more potent than the corresponding monomer, and is even more potent than tacrine
Title: Dual-site binding of bivalent 4-aminopyridine- and 4-aminoquinoline-based AChE inhibitors: contribution of the hydrophobic alkylene tether to monomer and dimer affinities Han YF, Li CP, Chow E, Wang H, Pang YP, Carlier PR Ref: Bioorganic & Medicinal Chemistry, 7:2569, 1999 : PubMed
Three series of 4-aminopyridine-and 4-aminoquinoline based symmetrical bivalent acetylcholinesterase (AChE) inhibitors were prepared and compared to previously synthesized dimers of 9-amino-1,2,3,4-tetrahydroacridine (tacrine). In each case significant, tether length-dependent increases in AChE inhibition potency and selectivity (up to 3000-fold) were observed relative to the corresponding monomer, indicating dual-site binding of these inhibitors to AChE. Assay of the corresponding alkylated monomers revealed that the alkylene tether played at least two complementary roles in the dimer series. In addition to reducing the entropy loss that occurs on binding both monomeric units of the dimer, the alkylene tether can also significantly improve potency through hydrophobic effects.
