Design, synthesis and anti-P. falciparum activity of pyrazolopyridine–sulfonamide derivatives

Ten 1-phenyl-1H-pyrazolo[3,4-b]pyridine derivatives connected by a linker group to benzenesulfonamide moieties with different substituents in the 4-position were synthesized and assayed against Plasmodium falciparum. These ten compounds exhibited activity in vitro against the chloroquine-resistant clone W2 with IC50 values ranging from 3.46 to 9.30 μM. The most active derivatives with substituent R2 = Cl or CH3 at the benzenesulfonamide moiety exhibited the lowest IC50. Compounds with an R1 = CO2Et substituent at the 5-position of the 1H-pyrazolo[3,4-b]pyridine ring presented lower activity than those with a CN substituent. The 1H-pyrazolo[3,4-b]pyridine system appears to be promising for further studies as an antimalarial for overcoming the burden of resistance in P. falciparum.