<jats:title>Abstract</jats:title><jats:p>Four new diketopiperazine alkaloids, <jats:italic>rel</jats:italic>‐(8<jats:italic>R</jats:italic>)‐9‐hydroxy‐8‐methoxy‐18‐<jats:italic>epi</jats:italic>‐fumitremorgin C (<jats:bold>1</jats:bold>), <jats:italic>rel</jats:italic>‐(8<jats:italic>S</jats:italic>)‐19,20‐dihydro‐9,20‐dihydroxy‐8‐methoxy‐9,18‐di‐<jats:italic>epi</jats:italic>‐fumitremorgin C (<jats:bold>2</jats:bold>), <jats:italic>rel</jats:italic>‐(8<jats:italic>S</jats:italic>,19<jats:italic>S</jats:italic>)‐19,20‐dihydro‐9,19,20‐trihydroxy‐8‐methoxy‐9‐<jats:italic>epi</jats:italic>‐fumitremorgin C (<jats:bold>3</jats:bold>), and (3<jats:italic>S</jats:italic>,8<jats:italic>S</jats:italic>,9<jats:italic>S</jats:italic>,18<jats:italic>S</jats:italic>)‐8,9‐dihydroxyspirotryprostatin A (<jats:bold>4</jats:bold>), together with the eight known compounds <jats:bold>5</jats:bold>–<jats:bold>12</jats:bold>, were isolated from the endophytic fungus <jats:italic>Aspergillus fumigatus.</jats:italic> The structures of the new compounds were determined by extensive spectroscopic methods including HR‐ESI‐MS, NMR, and CD experiments. Compound <jats:bold>12</jats:bold> showed weak inhibitory activity <jats:italic>in vitro</jats:italic> against the release of <jats:italic>β‐</jats:italic>glucuronidase in rat polymorphonuclear leukocytes induced by the platelet‐activating factor. None of the twelve compounds exhibited detectable cytotoxic activities toward five human tumor cell lines (HCT‐8, Bel‐7402, BGC‐823, A549, and A2780) in the MTT assay.