<jats:title>Abstract</jats:title><jats:p>The structure and absolute configuration of pseurotin (<jats:bold>1</jats:bold>), a new metabolite, isolated from culture filtrates of <jats:italic>Pseudeurotium ovalis</jats:italic> S<jats:sc>TOLK</jats:sc> (<jats:italic>Ascomycetes</jats:italic>), has been shown to be 2‐[1′(S), 2′ (S)‐dihydroxhex‐3′‐ene‐yl]‐3‐methyl‐8(S)‐methoxy‐8‐benzoyl‐9(R)‐hydroxy‐(5S)‐1‐oxa‐7‐aza‐spiro[4.4]non‐2‐ene‐4, 6‐dione (<jats:bold>1</jats:bold>), by spectral data and chemical transformations, and by X‐ray analysis of its dibromo derivative <jats:bold>2</jats:bold> [1].