title: Homodimeric tacrine congeners as acetylcholinesterase inhibitors.
abstract: In the search for highly selective and potent derivatives of tacrine (1a), a number of homodimeric tacrine congeners were synthesized and conducted for their effects on rat acetylcholinesterase (AChE) and human butyrylcholinesterase (BChE) inhibitions. Heptylene-linked bis-(6-chloro)tacrine (3h) was found up to 3000- and 3-fold more potent in inhibiting rat AChE than tacrine and the unsubstituted bis-tacrine 3b, respectively. Changes in the size of the carbocyclic ring of the dimeric tacrine reduced both the selectivity and the potency of AChE inhibition as compared to 3b. Inserting an aza into the tacrine nucleus as the desired isosteres 3j-m resulted in moderate potency but tended to be detrimental to selectivity. The pronounced enhancement of AChE inhibition potency and AChE/BChE selectivity was achieved with incorporation of a halogen at the 6-position of homodimeric tacrines. The assay results of 3a-m also provided evidence that the 7-methylene tether tended to be optimal to AChE inhibition potency.
authors.affiliation: School of Pharmacy and Department of Pharmacology, National Defense Medical Center, 161 Section 6, Minchuan East Road Taipei, Taiwan 114, Republic of China. hmk@ndmctsgh.edu.tw
authors.forename: Ming-Kuan
authors.initials: MK
authors.lastname: Hu
authors.forename: Li-Ju
authors.initials: LJ
authors.lastname: Wu
authors.forename: George
authors.initials: G
authors.lastname: Hsiao
authors.forename: Mao-Hsiung
authors.initials: MH
authors.lastname: Yen
mesh_terms: D000110:Acetylcholinesterase / Q000378:metabolism*; D000818:Animals; D001921:Brain / Q000201:enzymology; D002091:Butyrylcholinesterase / Q000378:metabolism; D002800:Cholinesterase Inhibitors / Q000138:chemical synthesis* / Q000737:chemistry / Q000494:pharmacology; D019281:Dimerization; D006801:Humans; D066298:In Vitro Techniques; D051381:Rats; D013329:Structure-Activity Relationship; D013619:Tacrine / Q000138:chemical synthesis* / Q000737:chemistry / Q000494:pharmacology
chemical_list: D002800:Cholinesterase Inhibitors; D013619:Tacrine; D000110:Acetylcholinesterase; D002091:Butyrylcholinesterase