You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
For the molecule named 2-(1,1,3-trioxo-1,2-benzothiazol-2-yl)ethyl 1-(5-chloro-2-methoxyphenyl)-5-oxopyrrolidine-3-carboxylate by IUPAC nomenclature, provide its molecular formula.
user
C21H19ClN2O7S
assistant