Synthesis of conformationally constrained adamantane imidazolines with trypanocidal activity

Aiming at the development of new adamantano building blocks for treating African trypanosomiasis, we report on the synthesis of spiro adamantane 2-imidazolines 8a-f and 9a-c, and their congeneric 5-(1-adamantyl)imidazolines 14 and 15. The potency of these compounds against Trypanosoma brucei was compared to that of rimantadine and found, in the case of compound 14e, to be three fold higher. Together with the other active compounds, 14b and 15b, which were equipotent to rimantadine, the new molecules illustrate the synergistic effect of the lipophilic character of adamantane and the C1 amidine functionality on trypanocidal activity.