Isolation, Structural Modification, and HIV Inhibition of Pentacyclic Lupane-Type Triterpenoids from <i>Cassine xylocarpa</i> and <i>Maytenus cuzcoina</i>

As a part of our investigation into new anti-HIV agents, we report herein the isolation, structure elucidation, and biological activity of six new (<b>1</b>–<b>6</b>) and 20 known (<b>7</b>–<b>26</b>) pentacyclic lupane-type triterpenoids from the stem of <i>Cassine xylocarpa</i> and root bark of <i>Maytenus cuzcoina</i>. Their stereostructures were elucidated on the basis of spectroscopic and spectrometric methods, including 1D and 2D NMR techniques. To gain a more complete understanding of the structural requirements for anti-HIV activity, derivatives <b>27</b>–<b>48</b> were prepared by chemical modification of the main secondary metabolites. Sixteen compounds from this series displayed inhibitory effects of human immunodeficiency virus type 1 replication with IC₅₀ values in the micromolar range, highlighting compounds <b>12</b>, <b>38</b>, and <b>42</b> (IC₅₀ 4.08, 4.18, and 1.70 μM, respectively) as the most promising anti-HIV agents