Bisguanidine, bis(2-aminoimidazoline), and polyamine derivatives as potent and selective chemotherapeutic agents against Trypanosoma brucei rhodesiense.: Synthesis and in vitro evaluation

The in vitro screening for trypanocidal activity against Trypanosoma brucei rhodesiense of an in-house library of 62 compounds [i.e. alkane, diphenyl, and azaalkane bisguanidines and his(2-aminoimidazolines)], which were chosen for their structural similarity to the trypanocidal agents synthalin (1,10-decanediguanidine) and 4,4'-diguanidinodiphenylmethane and the polyamine N-1-(3-amino-propyl)propane-1,3-diamine, respectively, is reported. The original synthetic procedure for the preparation of 21 of these compounds is also reported. Most compounds displayed low micromolar antitrypanosomal activity, with five of them presenting a nanomolar inhibitory action on the parasite: 1,9-nonanediguanidine (1c), 1,12-dodecanediguanidine (1d), 4,4'-bis[1,3-bis(tert-butoxycarbonyl)-2-imidazolidinyliminoldiphenylamine (28a), 4,4'-bis(4,5-dihydro-1H-2-imidazolylamino)diphenylamine (28b), and 4,4'-diguanidino-diphenylamine (32b). Those molecules that showed an excellent in vitro activity as well as high selectivity for the parasite [e.g. 1c (IC50 = 49 nM; SI > 5294), 28b (IC50 = 69 nM; SI = 3072), 32b (IC50 = 22 nM; SI = 29.5), 41b (IC50 = 118 nM; SI = 881)] represent new antitrypanosomal lead compounds.