You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
Convert the IUPAC name of a molecule (3R,4R)-3-methoxy-2-[(4-methoxyphenyl)methyl]-4-[(3-methyl-2-oxo-1H-imidazol-4-yl)methyl]-3,4-dihydropyrrolo[1,2-a]pyrazin-1-one into molecular formula.
user
C21H24N4O4
assistant