Abstract
Cycloeuphoboetirane A (2), a new diterpene with an unprecedented pentacyclic skeleton, has been obtained from lathyrane euphoboetirane A (1). A formal intramolecular [2+2] cycloaddition reaction catalyzed by Sordaria tomento-alba ST1-UCA is involved, providing new evidence for the existence of enzymes capable of catalyzing this reaction. A biomimetic photochemical conversion was also achieved by benzophenone with light-emitting diode irradiation.