Curcumin and derivatives

The title compound, 4-[7-(4-acetoxy-3-methoxy­phenyl)-5-hydroxy-3-oxohepta-1,4,6-trienyl]-2-methoxy­phenyl acetate [or bis­(acetoxy)curcumin, C₂₅H₂₄O₈], is shown unequivocally to exist in the keto–enol form, with only intramolecular hydrogen bonding. A redetermination of the structure of curcumin itself confirms the results of a previous report that it also exists in the keto–enol form.