γ- and δ‑Lactams from the Leaves of <i>Clausena lansium</i>

Eight new clausenamides, including three γ-lactams (<b>1</b>–<b>3</b>), four δ-lactams (<b>4</b>–<b>7</b>), and an amide (<b>8</b>), and seven known lactams, including compounds <b>9</b>–<b>11</b>, which were purified from natural sources for the first time, were characterized from the leaves of <i>Clausena lansium</i>. Their structures were elucidated using spectroscopic methods, and the absolute configurations were determined using electronic circular dichroism and single-crystal X-ray diffraction analyses with Cu Kα radiation. Compound <b>2</b> (50 μM) protected 22.24% of cortical neurons against Aβ_25–35-induced cell death