<jats:title>Abstract</jats:title><jats:p>Seven new alkaloids including tryptoquivaline K (<jats:bold>1</jats:bold>) and fumiquinazolines K–P (<jats:bold>2–7</jats:bold>), bearing a rare 1‐aminocyclopropane‐1‐carboxylic acid residue, together with six known compounds (<jats:bold>8–13</jats:bold>), were isolated from the fungus <jats:italic>Aspergillus</jats:italic> sp. obtained from the Mediterranean sponge <jats:italic>Tethya aurantium</jats:italic>. The structures of the new compounds were determined by extensive analysis by 1D and 2D NMR spectroscopy and mass spectrometry. The absolute configurations of tryptoquivaline K (<jats:bold>1</jats:bold>) and fumiquinazolines K and L (<jats:bold>2</jats:bold>, <jats:bold>3</jats:bold>) were determined by TDDFT ECD calculations of their solution conformers, and the configurational assignment of the related fumiquinazolines M–P (<jats:bold>4–7</jats:bold>) was achieved by comparison of their ECD spectra with those of compounds <jats:bold>2</jats:bold> and <jats:bold>3</jats:bold>. All compounds were evaluated for their cytotoxic activity by the MTT method. Compound <jats:bold>8</jats:bold> exhibited pronounced cytotoxicity against the mouse lymphoma cell line (L5178Y) with an IC<jats:sub>50</jats:sub> value of 3.6 μ<jats:sc>M</jats:sc>, but only moderate activity was observed against human ovarian cancer (A2780) and human Philadelphia chromosome‐positive chronic myelogenous leukemia (K562) cell lines with IC<jats:sub>50</jats:sub> values of 18.5 and 15.0 μ<jats:sc>M</jats:sc>, respectively.