You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
2-[(4S)-3-[(3-bromo-4-methoxyphenyl)methyl]-2,5-dioxo-1-(2-phenylethyl)imidazolidin-4-yl]acetic acid The above is the IUPAC name of a molecule. Write its molecular formula.
user
C21H21BrN2O5
assistant