You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
Convert the IUPAC name of a molecule (3S)-4-[[(2S)-1-methoxy-1-oxo-3-phenylpropan-2-yl]amino]-3-[(4-nitrophenyl)carbamothioylamino]-4-oxobutanoic acid into molecular formula.
user
C21H22N4O7S
assistant