SYNTHESIS AND EVALUATION OF TACRINE-RELATED COMPOUNDS FOR THE TREATMENT OF ALZHEIMERS-DISEASE

A number of polycyclic compounds related to tacrine have been prepared by condensation of ortho-aminobenzonitriles and 2-aminocyclopentenecarbonitrile with several C2v-symmetric diketones under AlCl3 or ZnCl2 catalysis. Monocondensation products 8 together with syn- and anti-dicondensation products 9 and 10, respectively, were formed in different proportions depending mainly on the starting diketone. These compounds were separated by column chromatography, fully characterized by spectroscopic and elemental analyses and tested as acetylcholinesterase (AchE) inhibitors. Syn- and anti-compounds 9 and 10, derived from diketones 7y and 7z, have significant anti-AchE activity although compounds 8 and derivatives of diketones 7v, 7w and 7x were inactive in the range of concentrations studied. Compound 9ay was the mdst potent of the group, being 4.4-fold less active than tacrine as anti-AchE in biochemical assays, but only slightly less potent in biological studies and 3-fold less toxic. Compound 9ay was also able to reverse cognitive deficits in middle-aged rats.