The molecule is a butenolide that is furan-2(5H)-one which is substituted by a hydroxymethyl group at position 4 and a 2-hydroxyethylidene group at position 5 (the 5E isomer). A direct precursor of patulin in cell-free preparations of Penicillium urticae patulin-minus mutants J1 and S11, but not S15. It has a role as a mycotoxin. It is a butenolide and a primary allylic alcohol.
(5E)-5-(2-hydroxyethylidene)-4-(hydroxymethyl)furan-2-one