Syntheses of 1,2-diamino and 1,2-aminoalcohol derivatives in the piperidine and pyrrolidine series as anti-amnesic agents

Tacrine, one of the drugs available for Alzheimer's disease based on the cholinergic approach, suffers from considerable toxicity. Many analogues of tacrine has been prepared which retain the pharmacologically rich aminopyridine or aminoquinoline motifs. The current research is a continuation of our efforts in the area of 11-aminobenzoquinolizidines (4) and 10-aminobenzoindolizidines (5) (cf. ref 9). A serendipitous discovery led us to the biologically active open chain analogue 9, and we proceeded to elaborate on this molecule. Overall, the compounds we prepared were poor inhibitors of acetylcholinesterase as compared to tacrine. The single exception was compound 20 which exhibited an effect comparable to that of tacrine, but only at a dose in the order of 10^-3 M. However, despite the poor acetylcholinesterase inhibition by 9, this compound was found to be an effective antiamnesic agent. Copyright (C) 1999 Elsevier Science Ltd.