Antimalarial candidates possessing novel mechanisms of action are needed to control drug resistant Plasmodium falciparum. We were drawn to Malaria Box compound 1 (MMV665831) by virtue of its excellent in vitro potency, and twelve analogs were prepared to probe its structure–activity relationship. Modulation of the diethyl amino group was fruitful, producing compound 25, which was twice as potent as 1 against cultured parasites. Efforts were made to modify the phenolic Mannich base functionality of 1, to prevent formation of a reactive quinone methide. Homologated analog 28 had reduced potency relative to 1, but still inhibited growth with EC₅₀ ≤ 200 nM. Thus, the antimalarial activity of 1 does not derive from quinone methide formation. Chemical stability studies on dimethyl analog 2 showed remarkable hydrolytic stability of both the phenolic Mannich base and ethyl ester moieties, and 1 was evaluated for in vivo efficacy in P. berghei-infected mice (40 mg/kg, oral). Unfortunately, no reduction in parasitemia was seen relative to control. These results are discussed in the context of measured plasma and hepatocyte stabilities, with reference to structurally-related, orally-efficacious antimalarials.

需要具有新作用机制的抗疟候选物来控制耐药性恶性疟原虫。我们被 Malaria Box 化合物1 (MMV665831) 所吸引，因为它具有出色的体外效力，并准备了 12 种类似物来探索其结构-活性关系。二乙基氨基的调节是卓有成效的，产生了化合物25，其对抗培养的寄生虫的效力是1 的两倍。已作出努力，以修改的酚曼尼希碱官能度1，以防止形成的反应性醌甲基化物的。与1相比，同源类似物28 的效力降低，但仍抑制生长，EC ₅₀  ≤ 200 nM。因此，抗疟活性1并没有从醌甲基化物的形成派生。对二甲基类似物2 的化学稳定性研究表明，酚类曼尼希碱和乙酯部分具有显着的水解稳定性，并且在伯氏疟原虫感染的小鼠（40 毫克/千克，口服）中评估了1 的体内功效。不幸的是，与对照相比，没有看到寄生虫血症的减少。这些结果在测量的血浆和肝细胞稳定性的背景下讨论，参考结构相关、口服有效的抗疟药。