6-Methyluracil Derivatives as Bifunctional Acetylcholinesterase Inhibitors for the Treatment of Alzheimer’s Disease Vyacheslav E. Semenov,* [a] Irina V. Zueva, [a, b] Marat A. Mukhamedyarov, [c] Sofya V. Lushchekina, [a, d] Alexandra D. Kharlamova, [a] Elena O. Petukhova, [c] Anatoly S. Mikhailov, [a] Sergey N. Podyachev, [a] Lilya F. Saifina, [a] Konstantin A. Petrov, [a, b, e] Oksana A. Minnekhanova, [a] Vladimir V. Zobov, [a, b] Evgeny E. Nikolsky, [a, b, c, e] Patrick Masson, [b] and Vladimir S. Reznik [a] Introduction Alzheimer’s disease (AD) is the primary age-related neurodege- nerative disorder. It is characterized by memory loss and pro- gressive cognitive impairment. The brains of AD patients suffer from loss of cholinergic neurons and a decreased number of synapses in specific areas, including the hippocampus, basal forebrain, and cortex areas involved in learning and memory. [1] The pathogenesis of AD is not completely understood, and multiple factors contribute to neuronal cell death to various extents. [2, 3] Most notably, AD is characterized by increased amounts of soluble and insoluble b-amyloid (Ab), predominantly in the forms of Ab 42 in amyloid plaques and Ab 40 in amyloid angiop- athy. The amyloid hypothesis proposes that AD is caused by an imbalance between Ab production and clearance, resulting in increased amounts of Ab in various forms such as monomer, oligomers, insoluble fibrils, and plaques. High levels of Ab then initiate a cascade of events culminating in neuronal death, manifesting as progressive memory impairment. [4, 5] Decreases in Ab production and increased clearance of Ab pathogenic forms are key targets in the development of novel drugs for AD treatment. Unfortunately, only nootropic ap- proaches for the treatment of AD are currently efficient in humans. These approaches focus mainly on the inhibition of brain acetylcholinesterase (AChE) to increase the lifetime of cerebral acetylcholine and slow down patients’ cholinergic de- ficiency. Three AChE inhibitors (donepezil, rivastigmine, and galantamine) have been approved by drug and sanitary agen- cies for palliative treatment of mild to moderately severe AD. These drugs are able to improve memory and cognitive dys- functions, but unfortunately, are unable to slow down neuro- degeneration. [6, 7] Novel 6-methyluracil derivatives with w-(substituted benzyle- thylamino)alkyl chains at the nitrogen atoms of the pyrimidine ring were designed and synthesized. The numbers of methyl- ene groups in the alkyl chains were varied along with the elec- tron-withdrawing substituents on the benzyl rings. The com- pounds are mixed-type reversible inhibitors of cholinesterases, and some of them show remarkable selectivity for human ace- tylcholinesterase (hAChE), with inhibitory potency in the nano- molar range, more than 10 000-fold higher than that for human butyrylcholinesterase (hBuChE). Molecular modeling studies indicate that these compounds are bifunctional AChE inhibitors, spanning the enzyme active site gorge and binding to its peripheral anionic site (PAS). In vivo experiments show that the 6-methyluracil derivatives are able to penetrate the blood–brain barrier (BBB), inhibiting brain-tissue AChE. The most potent AChE inhibitor, 3d (1,3-bis[5-(o-nitrobenzylethyla- mino)pentyl]-6-methyluracil), was found to improve working memory in scopolamine and transgenic APP/PS1 murine models of Alzheimer’s disease, and to significantly decrease the number and area of b-amyloid peptide plaques in the brain. [a] Dr. V. E. Semenov, I.V. Zueva, Dr. S. V. Lushchekina, Dr. A. D. Kharlamova, Dr. A. S. Mikhailov, Dr. S. N. Podyachev, Dr. L. F. Saifina, Dr. K. A. Petrov, O. A. Minnekhanova, Prof. V. V. Zobov, Prof. E. E. Nikolsky, Prof. V.S. Reznik A.E. Arbuzov Institute of Organic & Physical Chemistry Kazan Scientific Center, Russian Academy of Sciences Arbuzov str. 8, Kazan 420088 (Russia) E-mail : sve@iopc.ru [b] I. V. Zueva, Dr. K. A. Petrov, Prof. V. V. Zobov, Prof. E. E. Nikolsky, Prof. P. Masson Kazan Federal University Kremlevskaya str. 18, Kazan 420008 (Russia) [c] Dr. M. A. Mukhamedyarov, E. O. Petukhova, Prof. E. E. Nikolsky Kazan State Medical University Butlerov str. 49, Kazan 420012 (Russia) [d] Dr. S. V. Lushchekina N.M. Emanuel Institute of Biochemical Physics Kosygin str. 4, Moscow 119991 (Russia) [e] Dr. K. A. Petrov, Prof. E. E. Nikolsky Kazan Institute of Biochemistry & Biophysics, Russian Academy of Sciences Lobachevsky str. 2/31, Kazan 420111 (Russia) Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/cmdc.201500334. ChemMedChem 0000, 00,0–0  0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim 1 & These are not the final page numbers! ÞÞ These are not the final page numbers! ÞÞ Full Papers DOI: 10.1002/cmdc.201500334