You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
Convert the IUPAC name of a molecule 2-methoxy-1-[2-[(2-methyl-1,3-thiazol-4-yl)methyl]-1,1-dioxospiro[1,2-benzothiazole-3,3'-pyrrolidine]-1'-yl]ethanone into molecular formula.
user
C18H21N3O4S2
assistant