Diterpenoids of the Cassane Type from <i>Caesalpinia decapetala</i>

Eighteen compounds, including eight new cassane-type furanoditerpenoids, 3β-hydroxyphanginin H (<b>1</b>), 3β-acetoxyphanginin H (<b>2</b>), 7β-acetoxyphanginin H (<b>3</b>), 7β-hydroxyphanginin H (<b>4</b>), 4-<i>epi</i>-3β-hydroxycaesalpinilinn (<b>5</b>), 4-<i>epi</i>-3β-acetoxycaesalpinilinn (<b>6</b>), 20-acetoxytaepeenin D (<b>7</b>), and tomocin E (<b>8</b>), along with 10 known compounds (<b>9</b>–<b>18</b>) were isolated from the roots of <i>Caesalpinia decapetala</i>. Compounds <b>1</b>–<b>13</b> were isolated from <i>C. decapetala</i> for the first time. The new compounds with their absolute configurations were determined by extensive spectroscopic analysis, single-crystal X-ray diffraction, and electronic circular dichroism calculations. Compounds <b>1</b>, <b>4</b>, <b>5</b>, <b>7</b>, and <b>11</b> exhibited inhibitory activities against the SW1990 human pancreatic cancer cell line with IC₅₀ values ranging from 2.9 to 8.9 μM