Synthesis and in vivo antimalarial activity of novel naphthoquine derivatives with linear/cyclic structured pendants

Aim: Naphthoquine (NQ) was discovered by our institute as an antimalarial candidate in 1980s, and currently employed as an artemisinin-based combination therapy partner drug. Resistance to NQ was found in mouse model in laboratory, and might emerge in future as widely used. Methodology: We herein report the design and synthesis of NQ derivatives by replacing t-butyl moiety with linear/cyclic structured pendants. All the target compounds 6a-l and intermediates 5a-h were tested for their in vivo antimalarial activity against Plasmodium berghei K173 strain in mice. Results: Compounds 6a and 6j were found to have a comparable or slightly more potent activity (the 50% effective dose [ED50], which is required to decrease parasitemia by 50%: 0.38–0.43 mg/kg) than NQ (ED50: 0.48 mg/kg). Conclusion: The newly designed compounds 6a and 6j might be promising antimalarial candidates for further research.