Neonectrolide A, a New Oxaphenalenone Spiroketal from the Fungus <i>Neonectria</i> sp.

Neonectrolide A (<b>1</b>), an oxaphenalenone spiroketal with the previously undescribed (5,8′-dimethyl-5′-oxo-3a′,4,5,5′-tetrahydro-3<i>H</i>,3′<i>H</i>-spiro[furan-2,2′-isochromeno[3,4,5-<i>def</i>]chromene]-3′-yl)but-3-enoic acid skeleton, was isolated from cultures of the fungus <i>Neonectria</i> sp. Its absolute configuration was assigned by electronic circular dichroism (ECD) calculations. The skeleton of an oxaphenalenone fused with a 1,6-dioxaspiro[4.5]decane moiety in <b>1</b> could be derived from the coisolated putative precursors, corymbiferan lactone E (<b>2</b>) and 3-dehydroxy-4-<i>O</i>-acetylcephalosporolide C (<b>3</b>).