You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
(3-methyl-5-oxo-[1,3]thiazolo[3,2-a]pyrimidin-7-yl)methyl 4-(3-methylbutanoylamino)benzoate is the IUPAC name of a molecule. Please give its molecular formula.
user
C20H21N3O4S
assistant