You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
Provide the molecular formula for the IUPAC named substance (2S)-2-[[(2S)-2-[[4-[4-[(E)-2-nitroethenyl]phenoxy]sulfonylbenzoyl]amino]propanoyl]amino]propanoic acid .
user
C21H21N3O9S
assistant