<jats:title>Abstract</jats:title><jats:p>A new fungus‐derived benzodiazepine analogue, 2‐hydroxycircumdatin C (<jats:bold>1</jats:bold>), and a compound which has been isolated from a natural resource for the first time, but has been previously synthesized, namely (11a<jats:italic>S</jats:italic>)‐2,3‐dihydro‐7‐methoxy‐1<jats:italic>H</jats:italic>‐pyrrolo[2,1‐<jats:italic>c</jats:italic>][1,4]benzodiazepine‐5,11(10<jats:italic>H</jats:italic>,11a<jats:italic>H</jats:italic>)‐dione (<jats:bold>2</jats:bold>), along with five structurally related known alkaloids (<jats:bold>3</jats:bold>–<jats:bold>7</jats:bold>), were isolated from <jats:italic>Aspergillus ochraceus</jats:italic>, an endophytic fungus derived from the marine brown alga <jats:italic>Sargassum kjellmanianum.</jats:italic> Their structures were established on the basis of spectroscopic methods. The absolute configuration of <jats:bold>1</jats:bold> was determined through CD evidence. Compound <jats:bold>1</jats:bold> displayed significant DPPH radical‐scavenging activity with an <jats:italic>IC</jats:italic><jats:sub>50</jats:sub> value of 9.9 μ<jats:sc>M</jats:sc>, which is 8.9‐fold more potent than that of butylated hydroxytoluene (BHT), a well‐known synthetic positive control.