You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
4-[(2S,3E)-3-[hydroxy(phenyl)methylidene]-2-(3-methoxyphenyl)-4,5-dioxopyrrolidin-1-yl]butanoic acid is the IUPAC name of a molecule. Please give its molecular formula.
user
C22H21NO6
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