Synthesis and Antiprotozoal Activity of Azabicyclo-Nonane Pyrimidine Hybrids

Abstract

2,4-Diaminopyrimidines and (dialkylamino)azabicyclo-nonanes possess activity against protozoan parasites. A series of fused hybrids were synthesized and tested in vitro against pathogens of malaria tropica and sleeping sickness. The activities and selectivities of compounds strongly depended on the substitution pattern of both ring systems as well as on the position of the nitrogen atom in the bicycles. The most promising hybrids of 3-azabicyclo-nonane with 2-aminopyrimidine showed activity against P. falciparum NF54 in submicromolar concentration and high selectivity. A hybrid with pyrrolidino substitution of the 2-azabicyclo-nonane as well as of the pyrimidine moiety exhibited promising activity against the multiresistant K1 strain of P. falciparum. A couple of hybrids of 2-azabicyclo-nonanes with 2-(dialkylamino)pyrimidines possessed high activity against Trypanosoma brucei rhodesiense STIB900 and good selectivity.

Keywords: Plasmodium falciparum; Trypanosoma brucei rhodesiense; azabicyclo-nonanes; hybrids; pyrimidine.

Figure 1

Pyrimethamine, 2-azabicyclo[3.2.2]nonanes and 3-azabicyclo[3.2.2]nonanes.

Scheme 1

Preparation of compounds 5–24. Reagents and conditions: (a) corresp. 4-chloropyrimidine, DIPEA, 1-BuOH, 145 °C, 48h; (b) 2,4-dichloro-6-methylpyrimidine, DIPEA, EtOH, 0 °C→RT, 44–188 h; (c) sec. amine, DIPEA, ACN, 105 °C, 20–48h.

Figure 2

Most active compounds.