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 (E)-4-[4-[1-(4-chloro-2-methoxy-5-methylanilino)-1-oxopropan-2-yl]sulfanylanilino]-4-oxobut-2-enoic acid .
user
C21H21ClN2O5S
assistant