Anti-AIDS Agents 78 . Design, Synthesis, Metabolic Stability Assessment, and Antiviral Evaluation of Novel Betulinic Acid Derivatives as Potent Anti-Human Immunodeficiency Virus (HIV) Agents

In a continuing study of potent anti-HIV agents, seventeen 28,30-disubstituted betulinic acid (BA, 1) derivatives and seven novel 3,28-disubstituted BA analogues were designed, synthesized, and evaluated for in vitro antiviral activity. Among them, compound 21 showed an improved solubility and equal anti-HIV potency (EC50 = 0.09 μM) when compared to HIV entry inhibitors 3b (IC9564, (3R,4S)-N′-[N-[3β-hydroxy-lup-20(29)-en-28-oyl]-8-aminooctanoyl]-4-amino-3-hydroxy-6-methylheptanoic acid) and 4 (A43-D, [[N-[3β-O-(3′,3′-dimethylsuccinyl)-lup-20(29)-en-28-oyl]-7-aminoheptyl]carbamoyl]methane). Using a cyclic secondary amine to form the C-28 amide bond increased the metabolic stability of the derivatives significantly in pooled human liver microsomes. The most potent compounds 47 and 48 displayed potent anti-HIV activity with EC50 values of 0.007 and 0.006 μM, respectively. These results are slightly better than that of bevirimat (2, 3′,3′-dimethylsuccinylbetulinic acid), which is currently in phase IIb clinic...