Eurifoloids A–R, Structurally Diverse Diterpenoids from <i>Euphorbia neriifolia</i>

Eighteen new diterpenoids, named eurifoloids A–R (<b>1</b>–<b>18</b>), including ingenane (<b>1</b> and <b>2</b>), abietane (<b>3</b>–<b>7</b>), isopimarane (<b>8</b>–<b>12</b>), and <i>ent</i>-atisane (<b>13</b>–<b>18</b>) types, along with four known analogues were isolated from <i>Euphorbia neriifolia</i>. Eurifoloid M (<b>13</b>) represents a rare class of <i>ent</i>-atisane-type norditerpenoid. Eurifoloids E (<b>5</b>) and F (<b>6</b>) exhibited significant anti-HIV activities, with EC₅₀ values of 3.58 ± 0.31 (SI = 8.6) and 7.40 ± 0.94 μM (SI = 10.3), respectively