Synthesis and biological assessment of diversely substituted furo[2,3-b]quinolin-4-amine and pyrrolo[2,3-b]quinolin-4-amine derivatives, as novel tacrine analogues

Eur J Med Chem. 2011 Dec;46(12):6119-30. doi: 10.1016/j.ejmech.2011.09.038. Epub 2011 Sep 29.


The synthesis and pharmacological analyses of a number of furo[2,3-b]quinolin-4-amine, and pyrrolo[2,3-b]quinolin-4-amine derivatives are reported. Thus, we synthesized diversely substituted tacrine analogues 1-11 and 12-16 by Friedländer-type reaction of readily available o-amino(furano/pyrrolo)nitriles with suitable and selected cycloalkanones. The biological evaluation of furanotacrines1-11 and pyrrolotacrine13 showed that these are good, in the micromolar range, and highly selective inhibitors of BuChE. In the furanotacrine group, the most interesting inhibitor was 2-(p-tolyl)-5,6,7,8-tetrahydrofuro[2,3-b]quinolin-4-amine (3) [IC(50) (eqBuChE)=2.9 ± 0.4 μM; IC(50) (hBuChE)=119 ± 15 μM]. Conversely, pyrrolotacrines 12 and 14 proved moderately equipotent for both cholinesterases, being 1,2-diphenyl-5,6,7,8-tetrahydro-1H-pyrrolo[2,3-b]quinolin-4-amine (12) the most potent for the inhibition of both enzymes [IC(50) (EeAChE)=0.61 ± 0.04 μM; IC(50) (eqBuChE)=0.074 ± 0.009 μM]. Moreover, pyrrolotacrine 12, at concentrations as low as 300 nM can afford significant neuroprotective effects against Aβ-induced toxicity. Docking studies show that compounds 3 and 12 bind in the middle of the AChE active site gorge, but are buried deeper inside BuChE active site gorge, as a consequence of larger BuChE gorge void. All these data suggest that these new tacrine analogues could be used for the potential treatment of Alzheimer's disease.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Acetylcholinesterase / metabolism
  • Alzheimer Disease / drug therapy
  • Alzheimer Disease / enzymology
  • Aminoquinolines / chemical synthesis
  • Aminoquinolines / chemistry*
  • Aminoquinolines / pharmacology*
  • Butyrylcholinesterase / metabolism
  • Cholinesterase Inhibitors / chemical synthesis
  • Cholinesterase Inhibitors / chemistry*
  • Cholinesterase Inhibitors / pharmacology*
  • Humans
  • Models, Molecular
  • Tacrine / analogs & derivatives*


  • Aminoquinolines
  • Cholinesterase Inhibitors
  • Tacrine
  • Acetylcholinesterase
  • Butyrylcholinesterase