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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.
Mague et al. (Sat,) studied this question.