Remisporine B, a novel dimeric chromenone derived from spontaneous Diels–Alder reaction of remisporine A

A novel cyclopentachromenone, remisporine A, has been isolated from liquid culture of the marine fungus Remispora maritima. Remisporine A is not stable under normal conditions and autocatalytically dimerizes to give rise to a stereospecific product remisporine B via Diels–Alder reaction. The structure of remisporine B was elucidated by spectroscopic analyses including 2D-NMR and HRMS data.