title: Synthesis of novel purine nucleosides towards a selective inhibition of human butyrylcholinesterase.
abstract: The search for new and potent cholinesterase inhibitors is an ongoing quest mobilizing many organic chemistry groups around the world as these molecules have been shown to treat the late symptoms of Alzheimer's disease as well as to act as neuroprotecting agents. In this work, we disclose the synthesis of novel 2-acetamidopurine nucleosides and, for the first time, regioselective N(7)-glycosylation with 2-acetamido-6-chloropurine, promoted by trimethylsilyl triflate, was accomplished by tuning the reaction conditions (acetonitrile as solvent, 65 degrees C, 5h) starting from 1-acetoxy bicyclic glycosyl donors, or by direct coupling of a methyl glucopyranoside with the nucleobase to obtain only N(7) nucleosides in reasonable yield (55-60%). The nucleosides as well as their sugar precursors were screened for acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) inhibition. While none of the compounds tested inhibited AChE, remarkably, some of the N(7) nucleosides and sugar bicyclic derivatives showed potent inhibition towards BChE. Nanomolar inhibition was obtained for one compound competing well with rivastigmine, a drug currently in use for the treatment of Alzheimer's disease. Experimental results showed that the presence of benzyl groups on the carbohydrate scaffold and the N(7)-linked purine nucleobase were necessary for strong BChE inactivation. A preliminary evaluation of the acute cytotoxicity of the elongated bicyclic sugar precursors and nucleosides was performed indicating low values, in the same order of magnitude as those of rivastigmine.
authors.affiliation: Carbohydrate Chemistry Group, CQB-FCUL, Departamento de Química e Bioquímica, Faculdade de Ciências da Universidade de Lisboa, Campo Grande, Ed. C8, 5 degrees Piso, Campo Grande, 1749-016 Lisboa, Portugal.
authors.forename: Filipa
authors.initials: F
authors.lastname: Marcelo
authors.forename: Filipa V M
authors.initials: FV
authors.lastname: Silva
authors.forename: Margarida
authors.initials: M
authors.lastname: Goulart
authors.forename: Jorge
authors.initials: J
authors.lastname: Justino
authors.forename: Pierre
authors.initials: P
authors.lastname: Sinaÿ
authors.forename: Yves
authors.initials: Y
authors.lastname: Blériot
authors.forename: Amélia P
authors.initials: AP
authors.lastname: Rauter
mesh_terms: D000544:Alzheimer Disease / Q000188:drug therapy*; D002091:Butyrylcholinesterase / Q000378:metabolism*; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D002800:Cholinesterase Inhibitors / Q000138:chemical synthesis / Q000737:chemistry* / Q000494:pharmacology* / Q000633:toxicity; D005347:Fibroblasts / Q000187:drug effects; D006031:Glycosylation; D006801:Humans; D011684:Purine Nucleosides / Q000138:chemical synthesis / Q000737:chemistry* / Q000494:pharmacology* / Q000633:toxicity; D013237:Stereoisomerism
chemical_list: D002800:Cholinesterase Inhibitors; D011684:Purine Nucleosides; D002091:Butyrylcholinesterase