Isolation and Structure of Pseurotin A, a Microbial Metabolite of Pseudeurotium ovalis S TOLK with an Unusual Heterospirocyclic System

The structure and absolute configuration of pseurotin A, a new metabolite, isolated from culture filtrates of Pseudeurotium ovalis STOLK (Ascomycetes) has been shown to be (1′S, 2′S, 5S, 8S, 9R, 3′Z)‐8‐benzoyl‐2 (1′,2‐dihydroxy‐3′‐hexenyl)‐9‐hydroxy‐8‐methoxy‐3‐methyl‐1‐oxa‐7‐azaspiro [4,4]non‐2‐ene‐4,6‐dione (1).