(E)-13-(2-Bromo-phen-yl)micheliolide.

The title compound, C21H23BrO3 [systematic name: (3E,3aS,6Z,9R,9aS,9bS)-3-(2-bromo-benzyl-idene)-9-hy-droxy-6,9-dimethyl-3,3a,4,5,7,8,9,9a-octa-hydro-azuleno[4,5-b]furan-2(9bH)-one] was prepared by the reaction of 1-bromo-2-iodo-benzene with micheliolide [systematic name: (3aS,R,9aS,9bS,Z)-9-hy-droxy-6,9-dimethyl-3-methyl-ene-3,3a,4,5,7,8,9,9a-octa-hydro-azuleno[4,5-b]furan-2(9bH)-one] under Heck reaction conditions. The title compound exhibits intra-molecular O-H⋯O hydrogen bonding between the hy-droxy group and the lactone ring O atom, forming a ring of graph-set motif S(6). The 2-bromo-phenyl group is trans to the lactone ring, indicating that this is the E isomer (geometry of the exocyclic C=C bond). The dihedral angle between the benzene ring of the 2-bromo-phenyl moiety and the mean plane of the lactone ring is 51.68 (7)°.